Random Wisdom

Bash process substitution

2008-10-03T15:09:00.008+02:00

"Piping the stdout of a command into the stdin of another is a powerful technique. But, what if you need to pipe the stdout of multiple commands? This is where process substitution comes in.

Process substitution feeds the output of a process (or processes) into the stdin of another process."

The syntax is:


 >(cmd_list)
 <(cmd_list)

Example: comparing the head of two files using diff


$ diff -u <(head -n3 /var/log/dmesg) <(head -n3 /tmp/dmesg)
--- /proc/self/fd/63 2009-05-26 19:52:45.144544140 +0100
+++ /proc/self/fd/62 2009-05-26 19:52:45.149544007 +0100
@@ -1,3 +1,3 @@
-Initializing cgroup subsys cpuset
-Initializing cgroup subsys cpu
-Linux version 2.6.27.21-170.2.56.fc10.i686 (mockbuild@xenbuilder2.fedora.redhat.com)
 (gcc version 4.3.2 20081105 (Red Hat 4.3.2-7) (GCC) )
 #1 SMP Mon Mar 23 23:37:54 EDT 2009
+Linux version 2.6.22.9-61.fc6 (brewbuilder@hs20-bc2-4.build.redhat.com)
 (gcc version 4.1.2 20070626 (Red Hat 4.1.2-13))
 #1 SMP Thu Sep 27 18:48:03 EDT 2007
+BIOS-provided physical RAM map:
+ BIOS-e820: 0000000000000000 - 000000000009f000 (usable)

The diff header clearly shows that file descriptors are used as the underlying mechanism.

Embedding fonts in a PDF document

2008-10-03T15:08:00.005+02:00

It is often a good idea (or a requirement) to embed the used font faces in a PDF document. This is easily accomplished using ps2pdf during the final stage of conversion of a document from PS to PDF:


$ ps2pdf -sPAPERSIZE=a4 -dPDFSETTINGS=/printer -dCompatibilityLevel=1.3 \
         -dMaxSubsetPct=100 -dSubsetFonts=true -dEmbedAllFonts=true \
         'input_file.ps' 'output_file.pdf'

An explanation of the command options can be found in the Ps2pdf.htm file in the Ghostscript documentations (or here).

[Source]

Re-encoding MP3 Files using LAME

2008-06-06T16:41:00.003+02:00

I have some MP3 files encoded at a constant bitrate of 320kbps that my phone seems to have trouble playing smoothly. So, I looked into LAME.

The files I had were named using the following scheme:


01 - Title of track 01.mp3
02 - Title of track 02.mp3
...

I used the BASH for-loop construct to process the files:


$ for A in *.mp3;\              # Process one mp3 at a time
  do B=${A%.mp3};\              # Extract track number and title
     C=${B#?? -};\              # Extract the title
     D=${B%% - *};\             # Extract the track number
     lame --vbr-new -V0 -q0\    # Variable-bitrate, high-quality
          --mp3input\           # Inputs are MP3 files
          --tt "$C"\            # ID3v2 tags: title
          --ta 'Artist Name'\   # ID3v2 tags: artist
          --tl 'Album Title'\   # ID3v2 tags: album
          --ty 2007\            # ID3v2 tags: year
          --tn "$D"\            # ID3v2 tags: track no.
          --tg 'GENRE'\         # ID3v2 tags: genre
          "$A" processed/"$A";\ # Keep filename and save in ./processed/
  done

Since no bit-rate bounds are explicitly provided, the re-encoded files can contain anything between 32kbps and 320kbps. The LAME man-page provides an extensive list of options and their meanings.

Processing files using 'find'

2008-03-26T16:32:00.003+01:00

In its most basic form, find is often used to locate files that are subsequently piped through a complex set of commands for processing. However, this particular method is easily broken by files that contain spaces in their names.

This is where the 'exec' option provided by find comes in handy. From the man-page:


-exec command ;
       Execute  command;  true  if 0 status is returned.  All following
       arguments to find are taken to be arguments to the command until
       an  argument  consisting of ‘;’ is encountered.  The string ‘{}’
       is replaced by the current file name being processed  everywhere
       it occurs in the arguments to the command, not just in arguments
       where it is alone, as in some versions of find.  Both  of  these
       constructions might need to be escaped (with a ‘\’) or quoted to
       protect them from expansion by the shell.  See the EXAMPLES sec-
       tion  for examples of the use of the ‘-exec’ option.  The speci-
       fied command is run once for each matched file.  The command  is
       executed  in  the  starting  directory.    There are unavoidable
       security problems surrounding  use  of  the  -exec  option;  you
       should use the -execdir option instead.

An example that recursively removes all *.doc files from the current directory would be:


$ find . -name \*.doc -exec rm {} \;

Saving Power with Linux

2007-12-03T19:45:00.000+01:00

An interesting site with numerous tips and tricks on power efficient computing using Linux:

LessWatts

It is also home to the rather useful "PowerTOP" tool. If the testimonials are anything to go by, everyone running a recent release of Linux should give this a try.

Embedded multimedia in LateX/Prosper

2007-12-01T15:29:00.000+01:00

The movie15 package by Alexander Grahn is useful for this purpose. The movies embedded, however, cannot be viewed with any PDF reader on Linux.

Extracting Audio/Video

2007-12-01T15:24:00.000+01:00

It's really easy to extract either audio or video from a multimedia file using 'ffmpeg'. To extract audio only:


$ ffmpeg -i inputfile -vn -acodec copy outputfile

And for video only, replace '-vn' with '-an' and '-acodec' with '-vcodec'.

ffmpeg is also commonly used as a transcoding tool.

SSH Blacklisting

2007-11-29T19:27:00.000+01:00

After getting around 1500 failed ssh login attempts a day for a while on a server I manage, I decided to look into tools that automatically blacklist offending IPs.

Sshblack fits the bill perfectly. A HOWTO (including an init-script) for REDHAT-like systems is available from the OSS Watch Wiki.

Logo in a LaTeX document header/footer

2007-10-22T17:47:00.000+02:00

Easily accomplished using the 'fancyhdr' package:


\usepackage{fancyhdr}
\renewcommand{\headheight}{0.6in}
\setlength{\headwidth}{\textwidth}
\fancyhead[L]{}% empty left
\fancyhead[R]{ % right
   \includegraphics[height=0.53in]{img-file}
}
\pagestyle{fancy}

All of that goes into the preamble of the document.

Duplicate identifiers with hyperref in pdflatex

2007-10-01T14:07:00.000+02:00

The following warning is fairly common when hyperref is used with PDFLaTeX:


! pdfTeX warning (ext4): destination with the same identifier (name{page.1}) ha
s been already used, duplicate ignored

The solution is to use the 'plainpages=false' option with hyperref.

However, this appears to be insufficient for the article class with the 'titlepage' option. To remedy the warning the following is additionally needed around the \maketitle in the body of the document:


\renewcommand{\thepage}{\roman{page}}
\maketitle
\renewcommand{\thepage}{\arabic{page}}

By switching the style of page counter before and after the title page, any ambiguity regarding page numbers is resolved (title page is logically page 1 but LaTex re-initiates the counter on the actual page 1 - leading to 2 successive page 1s).

User installation of additional TeX/LaTeX classes and styles

2007-08-10T00:04:00.002+02:00

When you are the sysadmin, you can simply drop the new class/style files under the system TeX path (e.g. /usr/share/texmf/tex/) and run 'texhash' to have them automatically picked up. But what do you do when you are just a regular user?

TeX/LaTeX looks at the TEXINPUTS environment variable to look for additional locations to search for included/referenced files. Therefore, new classes/styles can be easily added as follows:

Create a directory for the files:
```
$ mkdir -p $HOME/tex/latex
```

Place the new class files into that folder (each class can be in its own directory and contain subdirectories):
```
$ cp -a fancy-class $HOME/tex/latex/
```

Export the TEXINPUTS variable and also add it to your $HOME/.bash_profile:
```
$ export TEXINPUTS=.:$HOME/tex/latex//:$TEXINPUTS
```

The '.' ensures that the working directory is included in the search path. The double-'//' tells bash to also include files in subdirectories of '$HOME/tex' recursively.

New BibTeX files can also be added locally in a similar fashion. The variables to set are then BSTINPUTS and BIBINPUTS.

The environment variable to set for MakeIndex styles is: INDEXSTYLE.

Source: AstroNat - Installation at The Smithsonian/NASA Astrophysics Data System

UPDATE [16 July 2009] The Kpathsea manual provides a wealth of information about usable environment variables.

Network Security

2007-08-10T00:00:00.000+02:00

A list of very interesting articles:

http://backtrack.offensive-security.com/index.php?title=ExternalHowto

Joining PDF Documents

2007-08-03T17:41:00.000+02:00

A quick search on the web reveals that the simplest (and most available) command to do so is:


$ gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=finished.pdf file1.pdf file2.pdf

Source: Putting together PDF files by Scott Nesbitt on NewsForge

Named Pipes (FIFOs)

2007-05-22T10:13:00.000+02:00

A named pipe is a special kind of file on *nix systems that can be used for inter-process communication. They behave like FIFOs and are created using the command "mkfifo":


$ mkfifo mypipe
$ ls -l mypipe 
prw-rw-r-- 1 xxx xxx 0 May 22 10:18 mypipe

The "p" in the attributes list indicates that this is indeed a pipe.

A trivial example of its use may be to redirect the output of a command on a remote server to a pipe and then reading from that pipe from another host via ssh.

Software Keyboard and Mouse (KM) Switcher

2007-05-15T18:00:00.000+02:00

Stumbled across this great tool a few days ago:

Synergy

Description from the project homepage:

Synergy lets you easily share a single mouse and keyboard between multiple computers with different operating systems, each with its own display, without special hardware. It's intended for users with multiple computers on their desk since each system uses its own monitor(s).

Redirecting the mouse and keyboard is as simple as moving the mouse off the edge of your screen. Synergy also merges the clipboards of all the systems into one, allowing cut-and-paste between systems. Furthermore, it synchronizes screen savers so they all start and stop together and, if screen locking is enabled, only one screen requires a password to unlock them all.

Mass conversion of images

2007-05-08T00:00:00.000+02:00

The following "one-liner" can be used to mass convert a given image format into another using the convert (part of ImageMagick) and basename tools:


$ for A in $(ls *.$SRC_TYPE); do convert $A $(basename $A .$SRC_TYPE).$DST_TYPE; done

where $SRC_TYPE is the file suffix of the original images (e.g. png) and $DST_TYPE is the file suffix of the type desired (e.g. eps).

Linux and DVD Regions

2007-04-12T19:52:00.000+02:00

Typically, Linux DVD playback software are capable of decrypting (libdvdcss must be installed) and playing back DVDs from any region, irrespective of the region code of the drive. Therefore, there should be no need to change the region code of the drive to watch discs from a different region. Regardless, there exists a very handy program that allows the user to change the region code and view other relevant information such as the number of changes remaining. It is called "regionset" and is available for Fedora from the Extras repository. The project website is:

http://linvdr.org/projects/regionset/

There is also a useful article on Linux.com about DVD playback:

DVD Playback HOWTO

Gnome automount options

2007-03-15T10:32:00.000+01:00

On a default Fedora installation, Gnome will automatically mount (with some default options) any recognized volumes as soon as an external storage device is plugged in. While the defaults might be fine in general, sometimes it is necessary to supply some more options.

The tool responsible for automating the mount (gnome-volume-manager) gets additional options from the /system/storage/default_options/$fstype$/mount_options key of gconf -- the Gnome "system registry". One can check/modify existing entries (one a per user basis) by running:


$ gconf-editor /system/storage/default_options &

This should launch the graphical configuration editor with the default_options key selected. Under this key are the entries for different filesystems. Default mount options can then be changed by selecting the desired filesystem and editing the mount_options key.

If a required filesystem type is not listed, then it can be added by using the gconftool-2 utility. E.g. if we wanted to add the ext3 filesystem to the configuration database with the options "sync" and "uid=", we would run the command:


$ gconftool-2 -t list --list-type string -s /system/storage/default_options/ext3/mount_options "[sync,uid=]"

Next time an external volume is plugged in, it will be mounted with the additional options specified! It should be noted that regardless of the options supplied via gconf, some mount options are always present: r(o|w),noexec,nosuid,nodev. At the moment I do not know how to change them.

The main motivation for finding out about the defaults is that I wanted to add "sync" as a default option. This causes data to be written immediately to the device, instead of being buffered first -- a useful option to have for external devices. It should minimized data loss in case of an accidental removal (without running umount first). However, it should also be noted that for solid state drives (e.g. flash), this may result in a shortening of service life and poorer performance.

Update [Sun Mar 18, 2007]:
I've done some rudimentary throughput performance testing with both the sync and async modes and the performance hit with sync appears to be quite severe (at least 20 times slower than async) -- even with a high performance HDD as the target. In light of this, I am removing sync from the list of default options. Given the type of data I'm likely to store on the device, speed is certainly more valuable than data integrity.

Test results:
Testing was carried out on a FAT32 volume. For each mode, both the transfer time and the subsequent un-mount time (indicating the time needed to flush the buffer) are shown.

async:


$ time dd if=/dev/zero of=/tmp/usb/dummy bs=8k count=130000 && time sudo umount /tmp/usb/
130000+0 records in
130000+0 records out
1064960000 bytes (1.1 GB) copied, 45.9035 seconds, 23.2 MB/s

real    0m46.026s
user    0m0.035s
sys     0m2.915s

real    0m11.680s
user    0m0.003s
sys     0m0.263s

sync:


$ time dd if=/dev/zero of=/tmp/usb/dummy bs=8k count=130000 && time sudo umount /tmp/usb/
130000+0 records in
130000+0 records out
1064960000 bytes (1.1 GB) copied, 969.384 seconds, 1.1 MB/s

real    16m13.525s
user    0m0.048s
sys     0m12.156s

real    0m0.842s
user    0m0.004s
sys     0m0.199s

Streaming TV!!

2007-03-13T21:16:00.000+01:00

I'm sorry if this is illegal - but being stuck in Germany, I had to do something about not being able to watch the Cricket World Cup and I am happy to say I found a solution!

Here's what you need to do:

Download "sopcast" from here and put it in a suitable place
Download the stdc++5 library also from here
Extract the files from the library as explained in the README

Now you're more-or-less done. To see a list of available channels, go here. As you can see, the sky is the limit. If you want to view a particular channel, let's say ESPN, copy the ID number of the channel (which at the time of writing this post was 6003). Now navigate to the place you extracted the sp-sc and execute


$ ./sp-sc sop://broker.sopcast.com:3912/$channel_id$ 3908 8908 > /dev/null &

Here, the 3912 might vary, so check the URL of the channel anyway. Replace $channel_id$ with the channel ID. Here 3908 is the local port and 8908 is the player port. Now fire up VLC or any player capable of opening a network stream and open the http url http://localhost:8908/tv.asf.

That's it. Enjoy your show. Oh, if you want to "change" the channel, I can't think of any other way other than doing "killall -9 sp-sc" before repeating the process.

Using screen

2007-03-08T22:19:00.000+01:00

My God! I can't believe I didn't put more effort into looking into screen earlier. This is such a wonderful utility. Just imagine ssh-ing to a machine and having your work go on even if you face a network disconnection. Wonderful stuff!
To start a screen, type "screen" at the prompt.
You have now opened a screen. It can support multiple windows. So if you have multiple tasks, you need not open many different terminals. Try it out. Run top in the current screen. Now, open a new window by the key sequence "ctrl-a" "c". Each window can support a task as a normal shell would. To scroll through the windows, use "ctrl-a" "p" for the previous window or "ctrl-a" "n" for the next one. If you go back to the first window, you'll see top still running.
If you desire, you can also open several screens. In case you have ssh-ed to a machine and you'd like to log out but still keep your process running, you need to detach the screen before logging out. In order to detach a screen, use the key sequence "ctrl-a" "d". You will now be returned to the shell. To see the status of all the screens, do "screen -ls". The output looks something like:


[silverstreak@silverstreak Desktop]$ screen -ls
There are screens on:
       22077.pts-0.silverstreak        (Detached)
       22153.pts-0.silverstreak        (Detached)
2 Sockets in /var/run/screen/S-silverstreak.

Since both screens are detached, it's ok to log off without losing any work. When you log back on, the screens will still remain detached. In order to re-attach a screen (let's say we want to re-attach the first one in the list), do "screen -r 22077.pts-0.silverstreak". Very simple and very handy!

Printing man pages

2007-03-08T15:18:00.000+01:00

I never did this because I was too afraid about how many commands it would involve. Actually, it's extremely simple!

Let's say you have a printer installed by the name of "printer_1". If you want to print the contents of the man page related to chmod on this printer, do the following:


$ man -t chmod | lpr -P printer_1

Here, you are piping the contents of the chmod man page through lpr to the installed printer. If you don't use a printer name, the default printer will be used.

If instead of printing the contents out, you want to make a pdf file out of them, simply do


$ man -t chmod > chmod.ps && ps2pdf chmod.ps && rm chmod.ps

MATLAB - Interrupting function execution

2007-03-02T16:39:00.000+01:00

MATLAB itself does not provide any way of arbitrarily interrupting/pausing a function at mid-execution to examine the internal function stack/variables. It is a pity since such a mechanism would be an extremely valuable debugging tool.

Finally, I realized that this is not as impossible as it seems. In fact, it is EXTREMELY simple! All that is required are four lines of code in any script/function:


[statcode, result] = system('ls sometoken');
if statcode == 0
   keyboard
end

The system command is used to run system console commands. Here, a simple check is made for the existence of the file 'sometoken' in the current directory. If the file exists, statcode is set to zero and the if condition is satisfied. The keyboard command is then executed which causes MATLAB to pause execution and return control to the command line! In order to continue execution, 'sometoken' must be deleted/removed from the current directory and the command return must be issued.

The best place for this code is perhaps in any loop that might exist in the MATLAB script/function. Then, to cause execution to pause, one simply needs to create a file 'sometoken' in the current directory.

Linux NFSv4 Howto

2007-02-27T19:31:00.000+01:00

NFS is commonly used to share files on Linux. NFSv4 is the latest protocol and circumvents firewall related complications experienced with NFSv3 by requiring only ONE fixed tcp port open on the server side. It is surprisingly easy to set up:

Server side:

Edit /etc/exports and add directories to be exported (fsid=0 is a mandatory option for nfs4) and authorized clients (check the exports manpage)

Open up tcp port 2049 on the firewall

# /etc/init.d/nfs restart

# chkconfig --level 345 nfs on

Client side:

# mount -t nfs4 -o rw,intr,hard server:/ /mount/point

It is not necessary to specify the exact path on the "server:/" with NFSv4.

Useful sites:

Learning NFSv4 with Fedora Core 2
RHEL4 NFS manual
Linux NFS-HOWTO

Linux - Disable Shutdown For Normal Users

2007-02-27T13:11:00.000+01:00

Very useful for servers/shared machines:

Disable Shutdown For Normal Users

Addendum:

Setting file mode for /etc/acpi/events/power.conf to "0000" is not sufficient to disable the power button. It's better to:

Uninstall gnome-power-manager

Leave file permissions for power.conf unchanged and simply set the action= line to an empty string

It is also advisable to set the local login screen style to plain in gdmsetup.

Linux authentication using LDAP

2007-02-27T11:07:00.000+01:00

There's a lot of information out there but none really provide a step-by-step guide that would be useful to a novice:

RHEL4 LDAP manual

LDAP Howto from TLDP

OpenLDAP Quickstart Guide

OpenLDAP 2.3 Admin Guide

This one however, sheds some light on the bigger picture:

LDAP Authentication In Linux

Once the initial configuration of the server is complete, LDAP Browser/Editor serves as a very useful client/admin tool.

Replacing broken laptop displays

2007-02-02T15:50:00.000+01:00

Notebook LCD replacement need not be a costly affair:

How To Replace A Broken Laptop or Notebook Display

ScreenTek is apparently a leading manufacturer.

More LaTeX Resources

2007-01-25T11:01:00.000+01:00

http://myitcv.org.uk/latex/

Cross-platform filesystem access

2006-11-21T10:01:00.000+01:00

Looks like the ntfs-3g driver has already gained a lot of popularity and is quite easy to use:

NTFS-3G Read/Write Driver

The driver itself is supposedly available from the Fedora Extras repository for FC6 onwards. Completely safe read/write access to NTFS drives from Linux -- now that's a dream come true!

In the meanwhile, it looks like there's also a windows Ext2 file-system driver that allows full read/write access to Ext2/3 volumes:

Ext2 Installable File System For Windows

Of course, one of the drawbacks here is that the Ext3 volume is mounted as Ext2 -- so there is no journaling support. In case of a 'dirty' unmount e2fsck will have to be run. The other drawback is the fact that is won't work with LVM.

So, these drivers really open up a lot of choices. But I guess the best option is to have the shared drive as NTFS since the ntfs-3g driver takes care of journaling.

BASH as a simple calculator

2006-09-25T11:27:00.000+02:00

As long as you are satisfied with integer results:


[darkknight@darkworld ~]$ echo $[32 * 98]
3136
[darkknight@darkworld ~]$ echo $[332 / 98]
3
[darkknight@darkworld ~]$ echo $[29 + 56]
85
[darkknight@darkworld ~]$ echo $[29 - 156]
-127

The Comprehensive LaTeX Symbol List

2006-08-22T12:46:00.000+02:00

A handy document listing all the symbols possible with latex:

CTAN Page

A copy is also available here.

Cropping a PDF Document

2006-07-31T22:29:00.005+02:00

Easily accomplished using pdftops:


$ pdftops -paperw WIDTH  -paperh HEIGHT -noshrink -expand document.pdf && ps2pdf document.ps

WIDTH and HEIGHT are in points -- they basically specify the dimensions of the image to be cropped.

Content is extracted from the center of the page. This technique is specially useful as a bypass for using psfrag with pdfLatex:

Save EPS figure with TAGS

Create a very simple tex document that simply includes the figure (centered) with psfrag replacements and run latex -> dvips -> ps2pdf

Follow the step above to crop out the figure.

The cropped out figure will have the TAGS replaced and be in PDF format -- ready to be used with pdfLatex!

UPDATE [16 July 2009] It looks like pdfcrop might actually be a better option:


$ pdfcrop --help
PDFCROP 1.5, 2004/06/24 - Copyright (c) 2002, 2004 by Heiko Oberdiek.
Syntax:   pdfcrop [options] <input[.pdf]> [output file]
Function: Margins are calculated and removed for each page in the file.
Options:                                                    (defaults:)
  --help              print usage
  --(no)verbose       verbose printing                      (false)
  --(no)debug         debug informations                    (false)
  --gscmd <name>      call of ghostscript                   (gs)
  --pdftexcmd <name>  call of pdfTeX                        (pdftex)
  --margins "<left> <top> <right> <bottom>"                 (0 0 0 0)
                      add extra margins, unit is bp. If only one number is
                      given, then it is used for all margins, in the case
                      of two numbers they are also used for right and bottom.
  --(no)clip          clipping support, if margins are set  (false)
  --(no)hires         using `%%HiResBoundingBox'            (false)
                      instead of `%%BoundingBox'
  --papersize <foo>   parameter for gs's -sPAPERSIZE=<foo>,
                      use only with older gs versions <7.32 ()
Examples:
  pdfcrop --margins 10 input.pdf output.pdf
  pdfcrop --margins '5 10 5 20' --clip input.pdf output.pdf

The tool comes as a part of the 'tetex' package.

Finally, NTFS write support!

2006-07-16T18:19:00.000+02:00

Slashdot ran a story yesterday about the new fully open source NTFS driver that has full read and write support for NTFS volumes. Although still in BETA phase it looks really promising. Too bad it doesn't work on 64-bit systems yet. I'm definitely keeping my eyes peeled for this one ..

More details and download links here:

[announcement] ntfs-3g: open source read-write driver

Creating directory hierarchies in bash

2006-07-16T17:59:00.000+02:00

The BASH 'brace expansion' feature can be used to create whole directory trees using a single command. From the man page for BASH:


Brace Expansion
       Brace expansion is a mechanism by which arbitrary strings may be gener‐
       ated.   This  mechanism is similar to pathname expansion, but the file‐
       names generated need not exist.  Patterns to be brace expanded take the
       form of an optional preamble, followed by either a series of comma-sep‐
       arated strings or a sequence expression between a pair of braces,  fol‐
       lowed  by  an  optional  postscript.   The preamble is prefixed to each
       string contained within the braces, and the postscript is then appended
       to each resulting string, expanding left to right.

       Brace  expansions  may  be nested.  The results of each expanded string
       are not sorted;  left  to  right  order  is  preserved.   For  example,
       a{d,c,b}e expands into `ade ace abe'.

       A  sequence  expression takes the form {x..y}, where x and y are either
       integers or single characters.  When integers are supplied, the expres‐
       sion  expands  to each number between x and y, inclusive.  When charac‐
       ters are supplied, the expression expands  to  each  character  lexico‐
       graphically between x and y, inclusive.  Note that both x and y must be
       of the same type.

       Brace expansion is performed before any other expansions, and any char‐
       acters  special to other expansions are preserved in the result.  It is
       strictly textual.  Bash does not apply any syntactic interpretation  to
       the context of the expansion or the text between the braces.

       A  correctly-formed  brace  expansion must contain unquoted opening and
       closing braces, and at least one unquoted comma  or  a  valid  sequence
       expression.   Any incorrectly formed brace expansion is left unchanged.
       A { or , may be quoted with a backslash to prevent its being considered
       part  of  a brace expression.  To avoid conflicts with parameter expan‐
       sion, the string ${ is not considered eligible for brace expansion.

       This construct is typically used as shorthand when the common prefix of
       the strings to be generated is longer than in the above example:

              mkdir /usr/local/src/bash/{old,new,dist,bugs}
       or
              chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}

       Brace  expansion  introduces  a  slight incompatibility with historical
       versions of sh.  sh does not treat opening or closing braces  specially
       when  they  appear as part of a word, and preserves them in the output.
       Bash removes braces from words as a  consequence  of  brace  expansion.
       For  example,  a word entered to sh as file{1,2} appears identically in
       the output.  The same word is output as file1 file2 after expansion  by
       bash.   If strict compatibility with sh is desired, start bash with the
       +B option or disable brace expansion with the +B option to the set com‐
       mand (see SHELL BUILTIN COMMANDS below).

So, for example:


$ mkdir -p root/{1/{1.1,1.2,1.3},2,3/{3.1,3.2/{3.2.1,3.2.2}}}

$ tree
.
`-- root
    |-- 1
    |   |-- 1.1
    |   |-- 1.2
    |   `-- 1.3
    |-- 2
    `-- 3
        |-- 3.1
        `-- 3.2
            |-- 3.2.1
            `-- 3.2.2

11 directories, 0 files

The '-p' option to mkdir makes it create the parent directories if they do not exist.

Working with LaTeX & KPDF

2006-07-11T19:57:00.000+02:00

KPDF is particularly handy in "watch file" mode. To activate, go to:

Settings -> Configure KPDF...

and check "Watch file" in the General section.

This causes KPDF to watch the file for changes and reload it automatically. Really handy when you don't want to keep navigating to the old page after an edit and reload ..

Create a matrix with specific diagonal elements in MATLAB

2006-06-20T11:46:00.000+02:00

Stupid, but lest I forget how to do this once again:

For a 4x4 matrix with uniformly distributed random elements with infinity on the diagonal.


>> A=diag(inf(4,1))+rand(4,4)

Installing MS TrueType core fonts on Linux

2006-05-31T17:24:00.000+02:00

Instructions obtained from:
http://corefonts.sourceforge.net/

Install cabextract and fedora-rpmdevtools:

$ sudo yum install cabextract fedora-rpmdevtools

Create the build tree:
```
 $ fedora-buildrpmtree 
```

Get the SPEC file:

 $ cd ~/rpmbuild/SPEC && wget http://corefonts.sourceforge.net/msttcorefonts-2.0-1.spec

Get the fonts and create the RPM package:

 $ rpmbuild -bb msttcorefonts-2.0-1.spec

Install the fonts package:

 $ sudo rpm -ivh ../RPMS/noarch/msttcorefonts-2.0-1.noarch.rpm

Restart any running application to use the new fonts.

Making slides in LaTeX using the Beamer package

2006-05-16T00:41:00.000+02:00

Prosper is excellent - no doubt about that. But this package also has some promising features and a very, very slick look and feel. Take a looksie at the samples and tutorial here. It also works with pdflatex.

Using LaTeX expressions in Xfig

2006-05-14T21:36:00.000+02:00

This is a really cool method to get those awesome LaTeX expressions working with Xfig figures.

Before you enter a mathematical expression, make sure to turn "Special Flags" to "special" under "Text Flags".

Complete your figure with the drawings and don't forget to enter your expressions in math mode (i.e. $...$).

Save the figure as a *.fig file.

Now, export the figure using the "combined PS/LaTeX (both parts)" language.

Next, make a file name_of_fig.tex and put this in it:


\documentclass{article}
\usepackage{epsfig}
\usepackage{color}
\setlength{\textwidth}{100cm}
\setlength{\textheight}{100cm}
\begin{document}
\pagestyle{empty}
\input{name_of_file.pstex_t}
\end{document}

Run LaTeX.

You will have a name_of_fig.dvi file.

Run the following to convert to *.eps:


[silverstreak@localhost]$ dvips -E name_of_file.dvi -o name_of_file.eps

You can now include this in your LaTeX document using the usual method.

Installing RPMs as a regular user

2006-04-20T10:03:00.000+02:00

A while back I needed some packages on a machine that I don't have admin rights to. Grabbing the source and recompiling would have been a pain the a** so I decided to read the rpm man pages and look for a way to install packages in the user home directory. Since it's such a nice package manager, it comes with options that allows me to do just that. The command needed is:


$ rpm -ivh --relocate OLDPATH1=NEWPATH1 [--relocate OLDPATH2=NEWPATH2 ...] --badreloc package.rpm

where OLDPATH is the path in the package; and NEWPATH is something like /home/user/userroot/usr, etc.

It's best to run


$ rpm -qpl package.rpm

to see exactly which paths are going to be used by the package. For example, if the package foo.rpm produces:


$ rpm -qpl foo.rpm
/usr/bin/foo
/usr/lib/foo.so.0.0
/usr/lib/foo.so.0
/usr/share/doc/foo/README

then the steps needed are:


$ mkdir -p ~/myroot/usr/bin ~/myroot/usr/lib ~/myroot/usr/share/doc
$ rpm -ivh --relocate /usr=/home/$USER/myroot/usr --badreloc foo.rpm

That'll install the package under the hierarchy ~/myroot. There will some errors from rpmdb but this is fine since the rpmdb is in a filesystem that we do not have write access to. The only repercussion is that rpm will have no record of the package foo being installed (so packages will have to be removed by hand); but that's okay since we cannot possibly mess up the system while installing stuff under our own home dirs.

The only steps remaining are to add the new paths to the binary and library search paths. To so this, add the following lines to ~/.bash_profile


        PATH=$PATH:$HOME/myroot/usr/bin
        LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HOME/myroot/usr/lib

        export PATH LD_LIBRARY_PATH

This is only efficient as long as the package does not have too many unmet dependencies -- since you will need to grab and install all missing dependencies along with the package itself. And even if you had installed some of the dependencies earlier using this method, rpm will not know about it since there will be no entry in the system rpmdb.

FC kernel rebuild HOWTO

2006-04-20T09:57:00.000+02:00

Paul Howarth has a very nice article here:

http://www.city-fan.org/tips/TweakKernelPackage

The main benefit is that you can use rpmbuild to generate kernel RPMs using the same SPEC file as the distribution itself -- resulting in packages that are as easy to handle as those from FC itself.

Write algorithms with LaTeX

2006-04-15T16:26:00.000+02:00

Clicky

Click on the link in "Algorithms with LaTeX" and download the package. The manual is extremely useful and the pseudocode looks wonderful!

By the way, I would suggest to anyone reading this to turn on Google's personalized search. I knew that I needed this package but I'd lost it after I moved to FC5. Every search I performed for ALgo in Google turned up something else. I had obviously used a different search phrase when I first found this package. Out of desperation, I searched my search history for ALgo and viola - it turned up right there! I had last searched for this package and successfully found it on Jan. 23, 2006. I think Google is a lifesaver and a timesaver! Thanks Larry and Sergey!

Mounting fat32 partition/hard disk

2006-03-25T16:21:00.000+01:00

I found this easy method somewhere online:

First find out what the partition is labelled as by performing fdisk -l


[root@localhost /]# fdisk -l

Disk /dev/sda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        2611    20972826    7  HPFS/NTFS
/dev/sda2            2612        3886    10241437+  83  Linux
/dev/sda3            3887        5161    10241437+  83  Linux
/dev/sda4            5162       14593    75762540    5  Extended
/dev/sda5            5162        8221    24579418+   b  W95 FAT32
/dev/sda6            8222       11281    24579418+   b  W95 FAT32
/dev/sda7           11282       14593    26603608+   b  W95 FAT32

So sda5, 6 and 7 are my fat32 partitions. I need to mount those so that I can make use of them. The following method also mounts them at reboot so you only need to do this once.

Open /etc/fstab in any convenient editor.

In my case, I had to append the following at the end of the file:


/dev/sda5 /mnt/academics vfat users,owner,rw,umask=000 0 0
/dev/sda6 /mnt/media vfat users,owner,rw,umask=000 0 0
/dev/sda7 /mnt/storage vfat users,owner,rw,umask=000 0 0

This gives all users read/write access to the three paritions. I decided to name them academics, media and storage. If you want only read access and no write access, change the "rw" to "ro".

Save the fstab file.

Next, you would like to create mount points for these partitions. I decided to have them under "/mnt". So:


[root@localhost /]# mkdir /mnt/academics
[root@localhost /]# mkdir /mnt/media
[root@localhost /]# mkdir /mnt/storage

And finally, automount:


[root@localhost /]# mount -a

The drives should be accessible now. Furthermore, they stay accessible after reboot. Enjoy.

SSH automatic reconnect on timeout

2006-03-15T09:36:00.000+01:00

There may already be some builtin option that allows a client to reconnect when a timeout occurs but I was too lazy to look through the man pages. So I came up with line of bash commands that will do just that:


$ while [ 1 ]; do ssh user@host.domain; sleep 120; done

This will keep reconnecting to the host 120 seconds after a connection drops out for whatever reason. This is specially handy to make sure that a remote tunnel stays open. Right now I use it to reach a single host (A,http) on a remote private network from home (B) via another machine in the private network (C) and an intermediate SSH server (D):

[user@C ~]$ while [ 1 ]; do ssh -R someport:A:80 user@D; sleep 120; done

[user@B ~]$ ssh -L 80:localhost:someport user@D

[root@B ~]# echo "127.0.0.1    A" >> /etc/hosts

Now it is possible to type "http://A" and visit the site from B as easily as from within the remote private network.

Prosper & PDF Output

2006-02-24T13:33:00.000+01:00

Prosper cannot be used with PDFTeX and hence PDF files must be obtained via the DVI -> PS -> PDF route. The default ps2pdf conversion, however, generates a PDF with pages that are a bit too narrow. This is easily remedied by specifying the size of the output desired to the ps2pdf program:


$ ps2pdf -dDEVICEWIDTHPOINTS=x -dDEVICEHEIGHTPOINTS=y somefile.ps

Where 'x' is the width in and 'y' is the height in 1/72" units. So, for an approximately A4 size output, 'x'=595 & 'y'=842.

Important locations in Linux

2006-02-16T17:46:00.000+01:00

For a beginner migrating from Windoz, this is pretty confusing. So, I'm just going to put some information here that comes from a December 2, 2005 mail to the Fedora list.

Basic executables: /bin

Userland executables: /usr/bin

System executables: /sbin and /usr/sbin

Personal programs: ~/bin

Some programs end up in /usr/local/bin or /opt/bin.

Few are hidden in /lib and /usr/lib and some other places.

To find where a command resides, do:


type commandname

A list of the commands built into the shell can be gotten by typing "help" to the command prompt.

Non-builtin commands documentation is available by typing "man commandname".

The Linux Documentation Project (TDLP in short) provides a lot of information - especially for users migrating from Windoz to Linux.

BASH Commands

2006-02-14T13:07:00.000+01:00

Here's a nice list:

http://www.ss64.com/bash/index.html

Removing old kernels using yum

2006-02-09T20:31:00.000+01:00

I found this neat and tidy method of removing old kernels. Before, I used to do this:


[root@localhost ~]# rpm -e kernel_name

But I have just come across a way of doing the same using yum. That way, you save time because you don't have to remove each one manually. It also prevents you from making mistakes and leaves the latest two kernels intact. First, you need to get "yum-utils".


[root@localhost ~]# yum install yum-utils

Then, simply remove all your old kernels!


[root@localhost ~]# package-cleanup --oldkernels

And you're done already! To check which kernels your system still retains, do:


[root@localhost ~]# rpm -qa | grep kernel

Nice, no?

Tesselated Cells

2006-02-03T11:05:00.000+01:00

Finally .. a script that will generate a square field of tesselated cells in MATLAB. The script take as input the desired cell radius and the dimension of the square field.

Generating a cell is simple enough. The corners are simply R*exp(j*(-pi:pi/3:pi)+pi/6)/cos(pi/6). The additional pi/6 is needed to rotate the resulting hexagon. The real challenge is in the tesselation. In order to achieve that, two base vectors that govern the tesselation must be defined:


vi = 2*R;
vj = 2*R*(cos(pi/3) + j*sin(pi/3))

Using these base vectors, the centers of every cell in the tesselation can be defined:


for a = 1:x
    for b = 1:x
        centr(a,b) = a*vi+b*vj;
    end
end

One we have the centers, use the MATLAB repmat function to replicate the corners around each of the centers to get the tesselated cells:


cells = repmat(corners.', 1,...
               numel(centr))+repmat(reshape(centr.',1,...
               numel(centr)),length(corners), 1);

A plot of the cells can be achieved using:


plot(real(cells),imag(cells));

This will however, generate a tesselation that is skewed. The linked *.m file takes care of that issue to generate a square tesselated field.

Generate BibTeX Entry from IEEEXplore Citations

2006-01-30T12:18:00.000+01:00

Very useful:

BibConverter v 1.5.3

[edited Aug 20, 2006]:
The link now redirects to:

BibConverter v. 3.0beta

HTTP Access Control

2006-01-25T16:51:00.000+01:00

Finally figured out how to password protect individual directories on the server:

Authentication, Authorization and Access Control

It's a simple 2-step process:

1. Create a passwords file for the users using "htpasswd":


jsmith@server:~/public_html/db$ htpasswd -c ~/htpasswds jdoe
New password:
Re-type new password:
Adding password for user jdoe
jsmith@server:~/public_html/db$

2. Create a file ".htaccess" in the directory to be protected:


jsmith@server:~/public_html/db$ cat .htaccess
AuthType Basic
AuthName "db"
AuthUserFile /home/jsmith/htpasswds
Require user jdoe

Proxy tools

2006-01-25T13:10:00.000+01:00

There's a very nice list of servers here:

Proxyz.net

This Firefox extension is handy for changing Proxies quickly: SwitchProxy

coLinux

2006-01-19T18:19:00.000+01:00

Recently, I needed to use Umbrello but didn't have access to a workstation that had it installed. And since I'm stuck with a Windows PC, I thought I'd take a look at the KDE-Cygwin project. It seems that they've stopped working on the project since there is a better alternative: Cooperative Linux. It's basically a modified Linux 2.6.10 kernel that runs on Windows -- kind of a like a virtual machine but it's different -- it's definitely a lot faster. Here's a snippet from the coLinux homepage:

Cooperative Linux is the first working free and open source method for optimally running Linux on Microsoft Windows natively. More generally, Cooperative Linux (short-named coLinux) is a port of the Linux kernel that allows it to run cooperatively alongside another operating system on a single machine. For instance, it allows one to freely run Linux on Windows 2000/XP, without using a commercial PC virtualization software such as VMware, in a way which is much more optimal than using any general purpose PC virtualization software.

The project page had a preconfigured Debian image and so that's what I'm using at the moment. The native X server does not work though -- so the Cygwin based X server is needed to diplay all the GUI stuff.

Getting it installed was a piece of cake. The Wiki site for coLinux has a lot of helpful info.

Once the basic text-mode linux is up and running (must be able to reach the host via the network), we need to run some commands from the cygwin shell. First run


$ cygserver-config

to configure the cygwin server and then start the server with:


$ cygrunserver -S cygserver

Then, we need to set


$ export CYGWIN=server

And then start the X server in rootless mode. The easiest way is to just make a copy of the startxwin.bat file and then edit it to change the options to XWin.

Once the X server is running, we need to run "xhost +" from the xterm that had popped up. Then, we switch over to the coLinux console and run:


$ export DISPLAY=<ip of windows host>:0

And that's it! Now you have a fully functional linux distro! I would have gone for a Fedora install but couldn't find a proper image.

PSfrag for EPS Graphichs Text Manipulation

2006-01-17T12:20:00.000+01:00

There's a nice package called psfrag that allows you to insert LaTeX constructs into EPS figures. This is specially useful with EPS files saved from MATLAB plots. The way it works is by replacing a given tag in the text of the EPS file with the LaTeX construct.

E.g. label the x-axis of of the plot as XLABEL and save the plot as an EPS file. Then, when you include that file, just put in the \psfrag{}{} tag:


\psfrag{XLABEL}{$\frac{\tau}{\sigma}$}
\includegraphics{file}

The most obvious disadvantage is that it only works with EPS figures -- so no PdfLaTeX. So, to compile a document to PDF, you'll need to go the old latex -> dvi2ps -> ps2pdf way.

More details can be found on CTAN.

Return of DARKWORLD

2006-01-15T20:22:00.000+01:00

Yup! My favorite PC just regained Net connectivity today. I moved into the new apartment this morning and was up and running by the evening. The guy who I share the place with wasn't around and so I would have had to wait till I got the info about the wireless network. So, instead of waiting, I just decided to see what kind of a WLAN he has ... and oh my oh my ... there were 5 freakin' access points around -- and 3 of them completely unsecured! As it turned out, one belonged to the dude I share the place with ...

Anyway, then I decided to catch up on my TV eps (Stargate SG1/Atlantis, Threshold, Supernatural, Doctor Who) and f*** the speed sux! It's a bloody T-Online DSL1000 Flat deal. Anyway, the IP I got was "192.168.0.5", so I deduced that the router should be at "192.168.0.1" or "192.168.0.254". And sure enough there it was in the first address. Obviously, it asked me for a password that I didn't know. So, I just tried "admin:1234" .. and nope, no go .. Then I thought I'd just do a little net search. The router was NETGEAR (deduced from the WLAN SSID), so I just googled "netgear default password" and the 4th hit came up with "admin:password". Turns out the guy didn't even change that password :D So, I got in, fiddled around with the NAT settings and Azureus was NAT free in no time. This has got to be the prime example of an unsecured network ...

Anyway, once the guy got back, I explained everything to him and changed the router password and setup a WEP-key. It seems there was a machine leeching off of this net and things improved a little once that dude got kicked out. It turns out DSL6000 costs just as much as he pays right now -- but he has no use for so much bandwidth when I'm gone -- so we'll just change to DSL2000 with 384k upload for now. That should be enough for me to download the occasional SG1 / Doctor Who episode :D

Monkeys!

2006-01-10T15:51:00.000+01:00

I know that this is all over the web but it just never gets old. Just putting it here so that I know where to find some instant laughter:

I LIKE MONKEYS

Proxy Bypass

2006-01-10T14:37:00.000+01:00

I guess it's usual for every institution to have a central firewall/proxy that all internal traffic must go through to reach the outside world. I am by no means paranoid about security/privacy but it got me thinking.

... And once again, SSH to the rescue! It almost feels like the possibilites of a SSH tunnel with Local port forwarding are limitless :D

I just picked up a public German proxy from this page:

http://www.publicproxyservers.com/index.html

And then setup a SSH connection to forward local port 8080 to proxy:port. Then for the browser I just set localhost:8080 as the proxy.

Well, the speed is a little short of astounding but it's very much usable :D Now all that the central firewall/proxy should be seeing is a bunch of encrypted traffic.

Embedded IE for Firefox

2006-01-09T13:10:00.000+01:00

While customizing firefox, I came across this extension: ietab

It doesn't really kill that IE dependence but it's not a bad extension to have around.

First day at DoCoMo

2006-01-09T11:07:00.000+01:00

Thus starts my first day at work. I've already got 2 papers to read and a meeting scheduled for later today. Got a brand new computer (HP Compaq DC5100) running only Win XP :(. For the kind of work I'll be doing (software development), I would have liked a *nix based machine. Apparently the simulation workstations are *nix so I'll have to make do with Xwin32 for the next 6 months.

Well .. at least I still have my own PC which should become net active again sometime after next weekend.

Alright then, back to my reading. Good luck to me! :)

2006

2006-01-01T00:05:00.000+01:00

A great big Happy New Year to everyone out there!

Bash scripting guides

2005-12-30T13:31:00.000+01:00

Here's a modest list:

http://www.tldp.org/LDP/Bash-Beginners-Guide/html/
http://www.opengroup.org/onlinepubs/009695399/toc.htm
http://cfaj.freeshell.org/shell/
http://www.shelldorado.com/
http://home.comcast.net/~j.p.h/cus-faq.html
http://sed.sourceforge.net/sed1line.txt
http://www.student.northpark.edu/pemente/sed/sedfaq.html
http://www.faqs.org/faqs/unix-faq/faq/part1/
http://www.shelldorado.com/goodcoding/cmdargs.html
http://www.macobserver.com/tips/macosxcl101/
http://www.wagoneers.com/UNIX/FIND/find-usage.html
http://cnswww.cns.cwru.edu/~chet/bash/bashref.html
http://www.tldp.org/LDP/abs/html/

Got the links from a post by Charles Howse on the 30th of December 2005 to the thread Why questions don't get answered, or "No, I've already RTFM, tell me the answer!" on fedora-list.

Command line search utility

2005-12-27T12:34:00.000+01:00

While studying for one of the finals this year, I felt the need for a CLI search utility that would search on Google, Wikipedia, Google Images, etc. I didn't know of any tools that would already do this so I decided to write my own little bash script:


#!/bin/bash
#Needs the htmlview package

opt="$1"
str="$2"


#Create the search string
until [ -z "$3" ]
do
  str="$str+$3"
  shift
done

case "$opt" in
    "google"  )
    htmlview http://www.google.com/search?hl=en\&q="$str"&btnG=Google+Search &
    ;;

    "image"   )
    htmlview http://images.google.com/images?q="$str"\&safe=off &
    ;;

    "wpedia"  )
    htmlview http://en.wikipedia.org/wiki/Special:Search?search="$str" &
    ;;

    "scholar" )
    htmlview http://scholar.google.com/scholar?q="$str"\&ie=UTF-8\&oe=UTF-8\&hl=en\&btnG=Search &
    ;;

    "ieee"    )
    htmlview http://ieeexplore.ieee.org/search/searchresult.jsp?queryText=\%28\%28"$str"\%29\%3Cin\%3Emetadata\%29 &
    ;;

    *         )
    echo "Usage: search engine searchterm [searchterms]"
    echo
    echo "Engines: google    Basic Google websearch"
    echo "         image     Unfiltered Google image search"
    echo "         wpedia    Wikipedia (English)"
    echo "         scholar   Google Scholar"
    echo "         ieee      IEEE Xplore (needs subscription)"
    echo
    echo "Example: search image batman"
    ;;
esac

echo

exit 0

It makes use of the htmlview package to discover the default browser and display the results. The use of the script is quite straightforward:


[darkknight@darkworld bin]$ search image batman begins

As is, it considers all search terms. Fancy things like Boolean expressions are not supported (yet :)). A copy of the script can be found here.

Time synchronization using NTP

2005-12-27T12:22:00.000+01:00

I've been having some trouble getting the system clock to sync. with time servers using ntpd. The method that works at the moment is the use of the CLI utility ntpdate:


[darkknight@darkworld ~]$ sudo su -
[root@darkworld ~]# ntpdate time.nist.gov
27 Dec 12:25:17 ntpdate[5743]: adjust time server 192.43.244.18 offset 0.002806 sec
[root@darkworld ~]#

Unfortunately, the man page of ntpdate says that it's set to be removed from the distro. -- hopefully ntpd will work again once that happens.

[Update] It seems the ntpd daemon was missing. The RPM was installed but the daemon was no longer in /usr/sbin/. So, I reinstalled the ntp package and now time sync. works as is should.

Picture of the Moon

2005-12-18T16:10:00.000+01:00

For a while now I've been thinking of photographing the moon. It was a clear night and I finally got around to doing exactly that:

I used my Fujifilm FinePix S5100 (Black&White mode, ISO 200) at a combined maximum zoom of 360x. Then I used Photoshop to increase the contrast a little. I'm quite surprised with the result -- didn't expect this from a consumer grade digicam.

Adding style files to LaTeX

2005-11-13T16:40:00.000+01:00

Lest I forget how to do this once more, I'm going to jot it down here for eternity:

If you want to use a non-standard style file for LaTeX, you have to first put it in the LaTeX tree and then compile it so that it is recognized.

So, first I downloaded the style files from here.

Next, I unzipped them to my desktop. There were three files:


bare_conf.tex  
bare_jrnl.tex  
IEEEtran.cls

These were then copied (as root) to the directory


/usr/share/texmf/tex/latex/misc/ieeetran

The folder "ieeetran" was created to avoid confusion.

Finally, I had to run the "mktexlsr" command so that these new files were "compiled" and read as part of the path. This was done as:


[zubin@localhost ieeetran]$ sudo mktexlsr

Console based MSN client

2005-11-04T12:49:00.000+01:00

Earlier today I stumbled across a client for MSN Messenger that runs in a terminal! It's called tmsnc.

The RPM had some dependencies that I could not solve so I decided to compile from source. Apart from a few minor issues, it looks great! There are some screenshots available here.

You might wonder why you need a text based MSN client; well, one can never have too many tools :)

The wonders of gdmflexiserver

2005-10-31T17:17:00.000+01:00

If you're using GDM, this is the easiest way to get the "Fast User Switching" seen on Windows XP. All you have to do is type:


[darkknight@darkknight ~]$ gdmflexiserver

and you get a brand new login on Virtual Terminal (VT) #8. Successive runs of gdmflexiserver will open up logins on VT#9, VT#10 and so on. Just in case you don't know how to switch VTs, its done through the Ctrl+Alt+F<1-12> key combinations. The main login is on VT#7. Once you exit/logout from any of the sessions on VT#<8-12>, it will simply close. If you're not automatically returned to the original session, just switch back manually using Ctrl+Alt+F7.

One useful option of gdmflexiserver is the ability to run in a nested X server. The command in that case is:


[darkknight@darkknight ~]$ gdmflexiserver -n

Now, instead of opening up a login in a brand-new VT, it will just open up a Xnest window with the login. The new X-Server is then a nested (child) server under the main X server on VT#7.

By default the Xnest window opened has a geometry of 1024x768 pixels. This can be changed by adding the -geometry option to the Xnest command in /etc/X11/gdm/gdm.conf :


...
# the X nest command
Xnest=/usr/X11R6/bin/Xnest -audit 0 -name Xnest -geometry 1280x1024+0+0
# Automatic VT allocation.  Right now only works on Linux.  This way
...

The geometry is specified as WidthxHeight+XCoord.+YCoord. After saving the modified gdm.conf, gdm must be restarted for the changes to take effect. This is done by logging in as root into one of the text VTs (VT#<1-6>) and issuing the commands:


[root@darkknight ~]# telinit 3; telinit 5; exit

New GDM Theme

2005-10-31T09:31:00.000+01:00

Just designed my very first GDM theme. It's based on the "Pixel Girl" theme and uses the "Blue Turbulence" wallpaper. Here's a screenshot:

It can be downloaded from GNOME-Look.org or here.

To install and use, run the gdmsetup tool as root and look under "Graphical greeter"

Addendum to VLC post

2005-10-29T20:22:00.000+02:00

One thing to note is that after installing an older, more stable version of VLC on your 32 bit system, you will get an error while running "sudo yum update". The problem is that the Livna repository has a newer version of "libdvbpsi" than the one required by the VLC player. So to avoid conficts, do this:


sudo yum --exclude=libdvbpsi update

Using sudo - for the layman

2005-10-28T00:29:00.000+02:00

Are you tired of becoming the root user just to perform updates? Well, you don't have to. Using sudo, you can perform all those restricted tasks without having to be the super user.

To do this, one has to edit the sudoers file.

The configuration of sudo is in /etc/sudoers. sudo is a setuid binary. Since sudo is owned by root, your effective id becomes root.

To edit the sudoers file, log on as root and change to /etc and:


[root@localhost etc]# visudo

This prevents multiple users from editing the same file at the same time because that would make things rather messy, don't you think?

Anyway, if you want to give yourself full permission to perform root tasks, edit the file as follows:


...
# User privilege specification
root    ALL=(ALL) ALL
zubin   ALL=(ALL)
...

Note that doing this does not give "zubin" root's PATH. If I want to run lpc, I'd have to do:


[zubin@localhost ~]$ sudo /usr/sbin/lpc

In this case, I'd have to provide my own login password to get sudo to work. sudo remembers the password for 5 minutes by default.

Now, if we modify the file like this:


...
# Defaults specification
Defaults:zubin timestamp_timeout=0, runaspw, passwd_tries=1
...

This means that the password will not be remembered. Setting it to -1 means that it will never be forgotten. The "runaspw" means that the user needs to have root's password to run sudo. "passwd_tries=1" means that zubin only gets one shot at getting the password correct. In general, many users can be added, each having a different default. If there is no ":" after Defaults, it is assumed to be global.

If we simply don't want to enter any password, then we'd have to do this:


# User privilege specification
root    ALL=(ALL) ALL
zubin   ALL=(ALL)               NOPASSWD: ALL

sudo logs authentication failures to syslog by default. But if we change the file as shown, we can track every command run:


...
# Defaults specification
Defaults:logfile=/var/log/sudolog
...

The user can also only be given specific commands:


...
zubin     ALL=    /bin/kill,/sbin/linuxconf, /usr/sbin/zubin/
...

The "ALL" above refers to a network-wide sudo. In general, the particular machine name can be specified.

To give zubin the power to kill users "user1" and "user2"'s processes, we could do:


...
zubin     localhost=(user1,user2)   /bin/kill, /usr/sbin/zubin/
...

But then, zubin would have to do this every time:


[zubin@localhost etc]$ sudo -u user1

To avoid, this, we simply add this to the defaults section:


Defaults:zubin    timestamp_timeout=-1, runas_default=user1

AVG and GMail POP3 Forwarding

2005-10-25T22:41:00.000+02:00

The general directions on getting them to play nice are here.

Image resizing the easy way

2005-10-23T14:43:00.000+02:00

Here's another one of my god-he's-so-new-to-Linux posts.

I wanted to resize a very large (1280x1024) image into an avatar-sized (50x50) image and I found a really simple way of doing it:


[zubin@localhost ~]$ convert ~/Desktop/big_image.jpg -resize 50x50 ~/Desktop/avatar.jpg

GIMP tutorial for the dummy

2005-10-23T12:44:00.000+02:00

Ever opened the GIMP and wondered "what the hell is going on"? No? I must admit that I do. The other day I found a really nice tutorial online that covers most of the tasks (subdivided into beginner, intermediate, expert, photo editing, etc.) in a very lucid fashion.

Find it all here.

Updating to GNOME 2.12

2005-10-22T23:02:00.000+02:00

From what I read, the new GNOME 2.12 desktop is really fast and has some new stuff. If you're interested in updating from 2.10 to 2.12, find instructions on how to do it here.

Author takes no responsibility.

VLC with FC4

2005-10-21T20:40:00.000+02:00

So, here comes my first 2-cent-worth post. I know it's nothing spectacular but being a newbie, I feel a lot of things that are mundane matters for the experienced user are pretty confusing for the newcomer. Anyway, I realized that after installing VideoLanClient on my box, it would give a nice little segmentation fault and crash if I tried playing *.avi files. After consulting with darkknight, my mentor, I found out that the latest version of VLC (obtained from Livna) for FC4 using a 32 bit system was unstable. The solution: get an older version from the "dries" repository. Of course, you have to disable Livna so that yum gets the older version.

This I did as follows:


[root@localhost ~]# yum --disablerepo=livna --enablerepo=dries install videolan-client

And viola!! It works!!! The only other problem I had was that subtitles failed to load. So, I went back to the terminal and looked at the error messages. A truetype font was missing. I downloaded the missing font and simply put it in the destination directory. This was done as follows:

First the directory was created because it didn't exist earlier:


[zubin@localhost ~]$ sudo mkdir -p /usr/share/fonts/truetype/freefont

And then, I moved the font from my desktop (where I had saved it) to that folder:


[zubin@localhost ~]$ sudo mv ~/Desktop/FreeSerifBold.ttf /usr/share/fonts/truetype/freefont/

And there we go - if it wasn't for the damn midterm coming up, I'd have seen the movie. I guess I'll have to wait till Monday for that.

New Member

2005-10-20T21:26:00.000+02:00

There's a new member in the scene .. meet Zub .. he's just installed FC4(i386) and is pretty new to Linux .. he'll be posting his experiences as well .. It's a good thing .. there'll probably some posts dealing with issues that are daunting to a newbie but that I find too trivial to bother with .. ;)

To boldly go .. where??

2005-10-10T14:24:00.000+02:00

This isn't really TeX or Linux related but it's pretty amazing .. while Stumbling along the net the other day, I came across this wonderful page:

http://www.mkaku.org/articles/

The articles are a must read for anyone even slightly interested in the future. I find the concept of using von Neumann probes for space exploration quite intriguing.

While we're still on the topic of the future, I just finished an article by Ray Kurzweil. It's called Human 2.0 (September 24th issue of NewScientist). It basically predicts that by 2020 we'll have $1000 machines with the intellectual capacity of the human brain.. and soon afterwards we'll be augmenting and transcending our biological being with nanotechnology and other engineered parts .. It all sounds like mixed blessings .. guess I'll find out soon enough. Cybernetic implants, here I come ... :)

A lot of other interesting articles can be found at:

KurzweilAI.net

The 64-bit browser and 32-bit plugins dilemma ...

2005-10-08T18:03:00.000+02:00

Although 64 bit OSs and hence browsers are (almost) commonplace these days, the same thing cannot be said of their plugin counterparts. To this date there are no 64bit Java and Flash plugins .. rendering a huge proportion of pages on the net inaccessible from a 64 bit browser ..

As of this moment, the popular solution to this problem is to have two browsers. A primary browser (e.g. 64 bit FireFox) and a seconday browser + plugins (32 bit). Opera seems to be a popular choice as the secondary browser since it's quite easy to get installed and use...

Open files from a terminal

2005-10-06T00:48:00.000+02:00

There's lot that can be learned from the conversations on the fedora-list. Today I learnt of a nifty little tool called gnome-open. Basically you just type something like:


[darkknight@darkworld ~]$ gnome-open file.cpp

and voila! It figures out the default application (under GNOME) for the files of type *.cpp and opens the file using that default editor. I haven't verified, but it seems that instead of a file an URL can also be specified. Mmm .. it definitely creates the possibility of writing portable scripts; at least on GNOME systems anyway :)

Addressing Individual Audio Channels of a Multichannel ALSA System

2005-10-04T00:17:00.000+02:00

At first I thought I could just use one of the audio editors to create a 5 channel sound file and blank all the channels that I don't want. Sweep claims to be a multichannel audio editor but at the moment it's not possible to edit the individual audio channels. So, I tried out Audacity. Although Audacity allows the editing of the individual channels, it's not possible to save the edited file in a multichannel format - it's invariably down-mixed to stereo. So, custom sound files were no longer an option ..

At this point, I started looking at the ALSA PCM plugins. The route plugin seemed like the perfect candidate. In order to use the plugin I had to create the plugin definitions in the file ~/.asoundrc:


[darkknight@darkworld ~]$ cat .asoundrc
pcm_slave.rt {
        pcm surround50
        channels 5
}

pcm.front_l {           #Front Left
        type route
        slave rt
        ttable.0.0 1
}

pcm.front_r {           #Front Right
        type route
        slave rt
        ttable.0.1 1
}

pcm.front_c {           #Front Center
        type route
        slave rt
        ttable.0.4 1
}

pcm.rear_l {            #Rear Left
        type route
        slave rt
        ttable.0.3 1
}

pcm.rear_r {            #Rear Right
        type route
        slave rt
        ttable.0.2 1
}

pcm.front_both {        #Front - Both
        type route
        slave rt
        ttable.0.0 1
        ttable.0.1 1
}

pcm.rear_both {         #Rear - Both
        type route
        slave rt
        ttable.0.2 1
        ttable.0.3 1
}

The plugins can be used with the aplay utility:


[darkknight@darkworld ~]$ aplay -D front_c /usr/share/sounds/alsa/Front_Center.wav
Playing WAVE '/usr/share/sounds/alsa/Front_Center.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Mono

Of course it makes sense to use only Mono files with the plugins since the mappings are always carried out from channel 1. It's the ttable entry that's responsible for the mapping. The first value is the source channel (0 = channel 1, 1 = channel 2, etc.). The second value is the channel to route to. The third value controls the volume; a value of 0 means 0% volume and a value of 1.0 means 100% volume.

With the new plugin definitions, it's even easier to balance the speaker levels. The following command will alternate between the front speakers and the center speaker until interrupted:


[darkknight@darkworld ~]$ while [ 1 ]; do /usr/bin/aplay -D front_both -q /usr/share/sounds/alsa/Noise.wav;
/usr/bin/aplay -D front_c /usr/share/sounds/alsa/Noise.wav; done

The Trek Life

2005-09-26T11:44:00.000+02:00

Love the new comic strips on Startrek.com:

The Trek Life

SUN Java on FC4

2005-09-26T11:36:00.000+02:00

There's a nice article at FedoraNEWS.ORG by Paul Howarth on how to get the SUN Java working under FC4 using the new alternatives system. So, here it is:

JPackage Java for FC4

Firefox and MathML on Linux

2005-09-26T10:36:00.000+02:00

While it's a little more work compared to Windows, getting MathML to work on Firefox isn't that hard. Now, it's easier than ever thanks to the *.spec files created by Michael A. Peters:

http://mpeters.us/fc_extras/mathematica_ttf.spec
http://mpeters.us/fc_extras/mathtype_ttf.spec

(Copies of the files are also available here)

Before we can start building RPMs as a regular user, we need to install the fedora-rpmdevtools package from the Fedora Extras repo:


[darkknight@darkworld ~]$ sudo yum install fedora-rpmdevtools

Once that's installed, we need to create the directory tree and RPM macros needed by rpmbuild:


[darkknight@darkworld ~]$ fedora-buildrpmtree

Now that we're ready to build RPMs, we download and save the SPEC files under the ~/rpmbuild/SPECS/ tree:


[darkknight@darkworld SPECS]$ wget http://mpeters.us/fc_extras/mathematica_ttf.spec http://mpeters.us/fc_extras/mathtype_ttf.spec

Once we have the spec files, we need to get the sources. We can get them from the URLs specified in the respective spec files:

MathType
Mathematica

(We need the Mathematica 4.1 Fonts)

We need to save the downloaded fonts under ~/rpmbuild/SOURCES/

Next, we need to install the cabextract package to satisfy build requirements:


[darkknight@darkworld ~]$ sudo yum install cabextract

Now, to build the font RPMs, switch to the ~/rpmbuild/SPECS directory and run:


[darkknight@darkworld SPECS]$ rpmbuild -bb mathtype_ttf.spec
[...]

[darkknight@darkworld SPECS]$ rpmbuild -bb mathematica_ttf.spec
[...]

In both cases, the long messeges should end in:


+ exit 0

If not, then you need to hunt down the problem and solve it. Assuming they both ended with the exit status '0', we can go ahead and install our freshly baked RPMs:


[darkknight@darkworld ~]$ sudo yum localinstall ~/rpmbuild/RPMS/noarch/math*

In addition to those packages, we also need the mathml-fonts package:


[darkknight@darkworld ~]$ sudo yum install mathml-fonts

Once we have all the required fonts, we have disble PANGO for firefox. In order to do this, we need to uncomment the following lines from /usr/bin/firefox :

MOZ_DISABLE_PANGO=1
export MOZ_DISABLE_PANGO

One that's done, we're good to go! We can test the new MathML rendering capabilities at:

http://www.mozilla.org/projects/mathml/demo/texvsmml.xhtml

Inkscape

2005-09-17T12:09:00.000+02:00

I installed Inkscape a few days ago out of pure curiosity. Today I'm glad that I did .. I needed to touch up some diagrams with a few translucent windows here and there and GIMP didn't seem to have any easy of doing it. So came the first field test of Inkscape ..

It works quite well - at least from the first impression. I can already see it giving MS Visio a run for its money ...

Bypassing Microsoft's "Genuine Advantage"

2005-09-03T09:00:00.000+02:00

Piece of cake; before clicking "Express" or "Custom" paste the following in the addressbar and hit enter:

javascript:void(window.g_sDisableWGACheck='all')

Got this tip from here.

Turn on 800DPI mode for the Logitech MX-510 Mouse

2005-08-27T14:09:00.000+02:00

5 easy steps:

1. Get and install the Logitech Applet from here or directly from here

2. Install the poper udev rules:
Create a file logitech-mice.rules under /etc/udev/rules.d/ with the following contents:


------------------------------------------
[darkknight@darkworld rules.d]$ cat logitech-mice.rules
BUS="usb", SYSFS{idVendor}="046d", SYSFS{idProduct}="c00e", PROGRAM="/usr/local/bin/logitech_applet -e -s 800"
BUS="usb", SYSFS{idVendor}="046d", SYSFS{idProduct}="c00f", PROGRAM="/usr/local/bin/logitech_applet -e -s 800"
BUS="usb", SYSFS{idVendor}="046d", SYSFS{idProduct}="c012", PROGRAM="/usr/local/bin/logitech_applet -e -s 800"
BUS="usb", SYSFS{idVendor}="046d", SYSFS{idProduct}="c024", PROGRAM="/usr/local/bin/logitech_applet -e -s 800"
BUS="usb", SYSFS{idVendor}="046d", SYSFS{idProduct}="c01b", PROGRAM="/usr/local/bin/logitech_applet -e -s 800"
BUS="usb", SYSFS{idVendor}="046d", SYSFS{idProduct}="c025", PROGRAM="/usr/local/bin/logitech_applet -e -s 800"
BUS="usb", SYSFS{idVendor}="046d", SYSFS{idProduct}="c01d", PROGRAM="/usr/local/bin/logitech_applet -e -s 800"
BUS="usb", SYSFS{idVendor}="046d", SYSFS{idProduct}="c031", PROGRAM="/usr/local/bin/logitech_applet -e -s 800"
------------------------------------------

Change the file permissions:


------------------------------------------
[darkknight@darkworld rules.d]$ sudo chown root.root logitech-mice.rules
[darkknight@darkworld rules.d]$ sudo chmod 644 logitech-mice.rules && ls -l
total 24
-rw-r--r--  1 root root  146 Apr 13 20:30 10-wacom.rules
-rw-r--r--  1 root root 7406 May 21 05:45 50-udev.rules
-rw-r--r--  1 root root  888 Sep  6 23:12 logitech-mice.rules
------------------------------------------

3. Modify /etc/X11/xorg.conf as follows to support the thumb buttons:


------------------------------------------
Section "InputDevice"
    Identifier  "Mouse0"
    Driver      "mouse"
    Option      "Protocol" "ExplorerPS/2"
    Option      "Device" "/dev/input/mice"
    Option      "ZAxisMapping" "6 7"
    Option      "Buttons" "7"
    Option      "Emulate3Buttons" "no"
EndSection
------------------------------------------

4. Create a script xmouse.sh under /etc/X11/xinit/xinitrc.d with the following contents:


------------------------------------------
[darkknight@darkworld xinitrc.d]$ cat xmouse.sh
#!/bin/bash

/usr/X11R6/bin/xmodmap -e "pointer = 1 2 3 6 7 4 5"
------------------------------------------

This ensures that the scrolling funtion is correctly assigned to the wheel and not to the thumb buttons.

Make sure that the file permissions are correct:


------------------------------------------
[darkknight@darkworld xinitrc.d]$ sudo chmod 755 xmouse.sh && ls -l
total 16
-rwxr-xr-x  1 root root 1579 Apr 11 13:43 xinput.sh
-rwxr-xr-x  1 root root   81 Sep  2 17:36 xmbind.sh
-rwxr-xr-x  1 root root   66 Sep  6 23:41 xmouse.sh
------------------------------------------

5. Reboot (Or simply unplug/re-plug mouse and restart X)

Happy surfing! Got the udev rules from the Ubuntu Forum (modified the PROGRAM line to use logitech_applet instead of lmctl).

Edit [July 30, 2007]:
It has been a while since the steps above were posted. The syntax of UDEV rules have changed much since then. The updated rule is (for my MX-510):


$ cat /etc/udev/rules.d/60-logitech-mouse.rules
SUBSYSTEMS=="usb", ATTRS{idVendor}=="046d", ATTRS{idProduct}=="c01d", RUN+="/usr/local/bin/logitech_applet -e -s 800"

Device details necessary for writing UDEV rules can be discovered using (substitute /dev/input/mouse1 with path to device of interest):


# udevinfo -a -p $(udevinfo -q path -n /dev/input/mouse1)

MATLAB 7 SP2 on FC4 (x86_64)

2005-08-25T10:16:00.000+02:00

The installer will not run on a default install. To get that working, I needed to install the xorg-x11-deprecated-libs.x86_64 package. It appears to contain some libraries needed by the graphical installer. Once installed, the 64bit version spits out the following error (the 32bit install is fine):


------------------------------------------
*** glibc detected *** malloc(): memory corruption: 0x0000000000598840 ***
------------------------------------------

The fix is:


------------------------------------------
$ LD_ASSUME_KERNEL=2.4.1
$ export LD_ASSUME_KERNEL
------------------------------------------

It's best to put these lines at the top of $MATLAB/bin/.matlab7rc.sh
(where $MATLAB is the installation directory).

Got this little hint from the MATLAB Support site.

Custom Keybinding (GNOME)

2005-08-25T09:42:00.000+02:00

This is useful for multimedia keyboards that aren't automatically recognized. Also useful when you want actions other that those offered in "gnome-keybinding-properties". The first step is to check if the buttons are recognized at all. This can be accomplised by running "xev"

$ xev

Once the little window pops up, press any of the buttons and see if you get an output like the following:


---------------------------------------------------------------------------------------------
KeyPress event, serial 29, synthetic NO, window 0x3c00001,
root 0xd6, subw 0x0, time 2073408, (1033,644), root:(1051,745),
state 0x0, keycode 231 (keysym 0x0, NoSymbol), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False

KeyRelease event, serial 29, synthetic NO, window 0x3c00001,
root 0xd6, subw 0x0, time 2073529, (1033,644), root:(1051,745),
state 0x0, keycode 231 (keysym 0x0, NoSymbol), same_screen YES,
XLookupString gives 0 bytes:
---------------------------------------------------------------------------------------------

If you do get the output, the important thing to note is the keycode (keycode 231 here). Once you have the keycode for a key, you need to define a Key Symbol for it. To do this, you need a xmodmap file. You can get a copy of it using:


---------------------------------------------------------------------------------------------
$ xmodmap -pke > ~/.xmodmaprc
---------------------------------------------------------------------------------------------

Once the current map is dumped, open the file for editing and locate the required keycode:


---------------------------------------------------------------------------------------------
$ vi ~/.xmodmaprc
[snip]
keycode 231 =
[snip]
---------------------------------------------------------------------------------------------

As we can see there is no symbol associated with the keycode 231 yet. To get a list of available symbols, look at /usr/X11R6/lib/X11/XKeysymDB. Since the button is marked as Refresh, we can use XF86Refresh as a suitable symbol:


---------------------------------------------------------------------------------------------
[snip]
keycode 231 = XF86Refresh
[snip]
---------------------------------------------------------------------------------------------

Once all the required keys have been set, save the file.

To make the new map take effect (in GNOME):


---------------------------------------------------------------------------------------------
$ gconftool-2 --set "/desktop/gnome/peripherals/keyboard/general/known_file_list" --type list --list-type string "[.xmodmaprc]"

$ gconftool-2 --set "/desktop/gnome/peripherals/keyboard/general/update_handlers" --type list --list-type string "[.xmodmaprc]"
---------------------------------------------------------------------------------------------

At this point you probably need to logout and log back in.

Now, for the case where xev doesn't already detect the key. Start by tailing the /var/log/messeges file:


---------------------------------------------------------------------------------------------
$ sudo tail -f /var/log/messages
---------------------------------------------------------------------------------------------

The last lines of the file will be displayed. Now, press the desired key. Now, you should see something like


---------------------------------------------------------------------------------------------
Aug 27 13:55:58 darkworld kernel: atkbd.c: Unknown key pressed (translated set 2, code 0x96 on isa0060/serio0).
Aug 27 13:55:58 darkworld kernel: atkbd.c: Use 'setkeycodes e016 <keycode>' to make it known.
Aug 27 13:55:58 darkworld kernel: atkbd.c: Unknown key released (translated set 2, code 0x96 on isa0060/serio0).
Aug 27 13:55:58 darkworld kernel: atkbd.c: Use 'setkeycodes e016 <keycode>' to make it known.
---------------------------------------------------------------------------------------------

So, as suggested, we make it known by:


---------------------------------------------------------------------------------------------
$ setkeycodes e016 187
---------------------------------------------------------------------------------------------

I chose 187 since it doesn't appear to be used by any key yet. Once all the keycodes have been set, repeat as before to assign the key symbols.

[Edit (Sept. 8, 2005)]
It seems that there is a better way to choose the kernel keycode. We can run getkeycodes to see which keycodes are currently in use. We can use any keycode between 84 and 255 that is not already used.


---------------------------------------------------------------------------------------------
$ getkeycodes
Plain scancodes xx (hex) versus keycodes (dec)
for 1-83 (0x01-0x53) scancode equals keycode

0x50:   80  81  82  83  99   0  86  87
0x58:   88 117   0   0  95 183 184 185
0x60:    0   0   0   0   0   0   0   0
0x68:    0   0   0   0   0   0   0   0
0x70:   93   0   0  89   0   0  85  91
0x78:   90  92   0  94   0 124 121   0

Escaped scancodes e0 xx (hex)

e0 00:    0 195 196 197 198   0   0   0
e0 08:    0   0   0   0   0   0   0   0
e0 10:  165   0   0   0   0   0   0   0
e0 18:    0 163   0   0  96  97   0   0
e0 20:  113 140 164   0 166   0   0   0
e0 28:    0   0 255   0   0   0 114   0
e0 30:  115   0 150   0   0  98 255  99
e0 38:  100   0   0   0   0   0   0   0
e0 40:    0   0   0   0   0 119 119 102
e0 48:  103 104   0 105 112 106 118 107
e0 50:  108 109 110 111   0   0   0   0
e0 58:    0   0   0 125 126 127 116 142
e0 60:    0   0   0 143   0 217 156 173
e0 68:  128 159 158 157 155 226   0 112
e0 70:    0   0   0   0   0   0   0   0
e0 78:    0   0   0   0   0   0   0   0

---------------------------------------------------------------------------------------------

It also seems we need to restore the kernel keycode mapping after every reboot. This is easily accomplished by having the required commands in /etc/rc.local:


---------------------------------------------------------------------------------------------
[darkknight@darkworld ~]$ cat /etc/rc.local
#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.

touch /var/lock/subsys/local

setkeycodes e016 187 e015 188 e014 189 e013 190 e005 191
            e01e 192 e009 193 e00b 202 e008 194 e018 199
            e00a 200 e017 201 e03b 203 e03c 204 e03d 205
            e03e 206 e03f 207 e040 208 e041 211 e042 210
            e043 212 e023 213 e057 214 e058 215 e064 216
[darkknight@darkworld ~]$
---------------------------------------------------------------------------------------------

The kernel keycodes are different from the keycodes used by X. So, we need to run xev again to get the keycodes (as seen by X) of the newly found keys.

Got the hints from here.
[End Edit]

Now that we have KeySymbols, what do we do with them? Open up gconf-editor and browse to the key /apps/metacity/global_keybindings. There, choose any of the run_command_* keys marked as disabled and change the value to the desired KeySymbol (e.g. XF86AudioPrev). Then navigate to the key /apps/metacity/keybinding_commands and find the command_* key with the same number as the run_command_*. Change the value of the key to whatever command you wish to be performed when the Previous key is pressed. If you happen to run out of run_command_* and command_* key pairs, simply create new pairs from the right click menu.

HTML Redirect

2005-08-24T12:06:00.000+02:00

Ever since I started this blog, I've been looking at some HTML code fragments. Here's one to redirect pages:

<meta HTTP-EQUIV="REFRESH" content="0; url=http://www.yourdomain.com/index.html">

Right now I'm using this to redirect visitors from my pandora home page to here. Got this fragment from this page.

Importing Firefox passwords from another profile

2005-08-24T10:28:00.000+02:00

It's a lot simpler than I thought it would be - simply copy key3.db and signons.txt to the new profile and make sure they are writable.

NTFS/FAT32 Volume Labels on GNOME computer://

2005-08-23T15:03:00.000+02:00

By default, GNOME labels the drives by their sizes. The following *fdi scipt for HAL makes is possible to automount the volumes discovered at boot-time. The volumes are mounted and labeled according to their Volume Label under /media. So, here it is:


---------------------------------------------------------------------------------------------
[darkknight@darkworld ~]$ cat storage-fixed.fdi
<?xml version="1.0" encoding="ISO-8859-1"?> <!-- -*- SGML -*- -->

<deviceinfo version="0.2">
 <device>
     <match key="volume.partition.msdos_part_table_type" int="0x07">
         <merge key="volume.policy.should_mount" type="bool">true</merge>
         <merge key="volume.policy.mount_option.pamconsole" type="bool">true</merge>
         <merge key="volume.policy.mount_option.noauto" type="bool">false</merge>
         <merge key="volume.policy.mount_option.exec" type="bool">false</merge>
         <merge key="volume.policy.mount_option.umask=022" type="bool">true</merge>
         <merge key="volume.policy.mount_option.ro" type="bool">true</merge>
     </match>
 </device>

 <device>
     <match key="volume.partition.msdos_part_table_type" int="0x0b">
         <merge key="volume.policy.should_mount" type="bool">true</merge>
         <merge key="volume.policy.mount_option.pamconsole" type="bool">true</merge>
         <merge key="volume.policy.mount_option.noauto" type="bool">false</merge>
         <merge key="volume.policy.mount_option.exec" type="bool">true</merge>
         <merge key="volume.policy.mount_option.umask=000" type="bool">true</merge>
         <merge key="volume.policy.mount_option.rw" type="bool">true</merge>
     </match>
 </device>

 <device>
     <match key="storage.hotpluggable" bool="false">
         <match key="storage.removable" bool="false">
             <merge key="storage.policy.should_mount" type="bool">true</merge>
         </match>
     </match>
 </device>
</deviceinfo>
[darkknight@darkworld ~]$
---------------------------------------------------------------------------------------------

The file should be placed under /usr/share/hal/fdi/policy/10osvendor/

I know for sure that the NTFS part works, and someone with FAT32 volumes told me that FAT32 automount works as well.

It is also available from here.

Audigy 2 ZS on FC4

2005-08-23T14:07:00.000+02:00

I've finally got a setup that sounds just as good as it does on Windows. I've tested the surround system with a DVD and so far it sounds pretty good. I think the trouble was that there wasn't any signal generator to let me balance the speakers properly. But today I discovered that there is an alsa subdirectory under /usr/share/sounds that contains a noise file. Playing that in a loop:

$ while [ 1 ]; do aplay /usr/share/sounds/alsa/Noise.wav; done

I finally managed to get that elusive speaker balance through alsamixer. Now, all that's missing is CMSS3D :)

This site might be useful.

Prosper (TeX) Tutorials

2005-08-21T19:25:00.000+02:00

Found a couple of prosper tutorials that were particularly helpful:

VPN from Linux (x86_64)

2005-08-21T14:50:00.000+02:00

The Cisco VPN client doesn't seem to compile on the 64bit architecture. Well, open source to the rescue .. behold VPNC. Since the Cisco profile files are no good, I needed to decrypt the group password - which was a piece of cake thanks to the password decryptor on the site. They say it's done through the command:

# ltrace -i ./vpnclient connect ... 2>&1 | fgrep 805ac57

I'll try it for myself sometime.

Changing/Suppressing the "References" title from Bibliographies

2005-08-20T17:29:00.000+02:00

The command needed is:

\renewcommand\refname{New title}

This is particularly useful for slides. Found this little trick here.

WebCollage

2005-08-19T23:59:00.000+02:00

It seems FC4 has dropped the WebCollage screensaver. So I had to install it myself. It's quite easy actually: just save the file to /usr/libexec/xscreensaver/ and you're done (almost). I think it must also be owned by root and be executable by all. It's a pretty cool screensaver - you never know what you'll find ;)

Actually, the main reason I went hunting for it was to track down Driftnet. It's a cool tool that essentially sniffs out images from the local network for you to see :D. Fortunately, it was available from the Dries rpm repo.

GPLFlash 2

2005-08-19T22:49:00.000+02:00

Ok .. built and installed GPLFlash .. at least Firefox thinks it's installed. Time to give it a try: well .. seems like StarTrek.com still won't work .. guess it won't settle for anything less than Flash 6 :(

GPLFlash

2005-08-19T22:09:00.000+02:00

Ever since I installed FC4 64-bit, plugins have been a constant pain is the a**. I remembered seeing a reference to GPLFlash some time back .. so I went and grabbed the source tarball .. unfortunately it requires too many *-devel packages and I can't afford the disk space. So, rpm.pbone.net to the rescue. I managed to find a x86_64 rpm for SuSE 9.3 - so I'm gonna give that a go. Seems like it needs libresmgr which is not in any of the FC repos I use. So, I also needed to borrow that from SuSE.

It's now that I fully appreciate the new localinstall option of yum. Point to to a local rpm and it sorts out dependencies from the actives repos .. just too cool..

Ok .. this isn't going anywhere .. the dependencies are too SuSE centric .. guess I'll just have to get the *-devel packages and make do with the source tarball..

First blog

2005-08-19T21:54:00.000+02:00

Well .. I've been giving this some thought .. the main motivation behind starting this thing is the fact that I seem to forget a lot of the stuff that I found out digging through the web, linux man pages etc.. let this be my (somewhat) permanent record of the things I do .. to save myself the trouble of backtracking through memory lane...

I guess this will be mostly computer related .. Linux, TeX, etc..