Entries tagged as programming
Tuesday, April 22. 2008
CUDA on Debian lenny
CUDA is a technology by NVIDIA to accelerate scientific computations by the help of GPUs. Unfortunately, Debian isn’t supported officially yet. The toolkit for Ubuntu should come closest to it. First, the toolkit has to be installed, e.g. to $HOME/share/cuda, and then the SDK, e.g. to $HOME/share/NVIDIA_CUDA_SDK. These two paths shall be referred to as $CUDA_PATH and $SDK_PATH in the following. GCC and g++ have to be downgraded to version 4.1 (from ‘etch’), as 4.2 (from ‘lenny’) doesn’t work with CUDA yet.
Like described in $SDK_PATH/ReleaseNotes.html, $CUDA_PATH/bin has to be in the $PATH and $CUDA_PATH/lib in the $LD_LIBRARY_PATH. Unfortunately, this isn’t enough for Debian to successfully compile the examples (via cd $SDK_PATH && make): The $CUDA_INSTALL_PATH in line 38 of the Makefile $SDK_PATH/common/common.mk has to be corrected to the $CUDA_PATH.
To compile the GLUT code, the development package freeglut3-dev has to be installed. With that it’s now possible to compile the examples; the binaries go into $SDK_PATH/bin/linux/release.
Monday, February 25. 2008
Debugging the bash
It’s a really good tip to use the -x flag to debug bash scripts. I had a problem that GDM wasn’t starting anymore after the regular aptitude upgrade. I didn’t find a hint in the log files and had a look at its init-script /etc/init.d/gdm, which appeared quite complex to me: It sources various config files and calls macros that are defined in there. How the heck should I trace the problem down? The best way was to change the initial line to
what starts the debug mode when the script is invoked. Here’s what it does: It prints every single command that is executed line by line in a fully expanded form, no matter if macros were defined or several other shell scripts are invoked from within. The lines are indented by a sequence of plus symbols to represent the invocation depth of the other scripts. By this, I saw that the last calls referred to splashy, a bootsplash package that I had installed for test purposes but never had configured. The solution was to simply remove that package.
Another tip: Don’t do experiments on a system that is supposed to work! This also means to not install the complete Debian ‘testing’ version on it. If you need a selected number of some more recent software, upgrade it individually, but keep the basic packages ‘stable’. On the other hand, you wouldn’t learn much if you weren’t forced to fix things once in a while. 
Saturday, November 4. 2006
Host automatically up and down
For the usage of a local backup host, I defined the following scenario, which could also be used for a printer server or any other type of host, which shouldn’t run 24/7, but:
- The host should be able to be woken up manually by a special signal on the LAN, i.e., it should be capable of WOL. (This is only a hardware issue)
- If it is woken up, it should run at least for 30 minutes before trying to shutdown again.
- It shouldn’t shut down while certain processes are running, such as a backup, i.e., it should be capable of a shutdown-lock. If the lock is removed, it might shutdown.
- The host shouldn’t shut down as long as a certain client, e.g. a backup client, is (still) up and running (pingable)
- If the criteria above aren’t hurt, the host should finally shut down.
And here’s the shell-script which implements the above. It’s enough to have it run every five minutes. The “echoes” are only interesting for debugging purposes.
Continue reading "Host automatically up and down"
Monday, October 9. 2006
Password generator in bash
# Number of letters as argument, default 7
if [ “$1” != “” ]; then
num=$1
else
num=7
fi
generate() {
# Take 1 block from /dev/urandom, encode it base64,
# remove first two and last status line, purge capital letters and
# special characters from output, cut desired length from front
# sed with [A-Z] doesn’t work with Suse - typical!
password=$(dd if=/dev/urandom count=1 2>/dev/null | uuencode -m - \
| head -n 2 | tail -n 1 | sed -e ’s:[/+A-Z]::g’ | cut -c -$num)
}
# Repeat until letters AND digits occur
while true; do
generate
if echo $password | grep [a-z] | grep [0-9]; then break; fi
done
Wednesday, February 15. 2006
Generating passwords in Lotus Notes
_Cannabis := @HashPassword(_Weed);
_Tobacco := @LowerCase(_Cannabis);
_Hand := @ReplaceSubstring(_Tobacco; “(”:“)”:“/”:“+”:“o”:“l”; “”);
_Side := 7;
_Pass_The_Cutchie_On_The := @Left(_Hand; _Side);
Friday, December 16. 2005
Changes between development and public directory
Tuesday, July 26. 2005
View uncommitted RCS changes
If RCS is used separately from CVS (e.g. for system configuration management), I sometimes want to know whether there are any uncommitted changes pending. Here’s my bash alias to get an overview:
Maybe you want rcsdiff to be an alias for a home-made rcscolordiff, which itself simply calls
rcsdiff $@ | colordiff --no-banner.
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