Cooked up a script to limit the number of files in a directory to a defined value. Thought I’d mention it here under this title and preface, to make it searchable, since I didn’t find anything premade using them as search terms.
Make some noise
I adapted Geek Thoughts‘ “Making Noise with ImageMagick” in creating video noise — a video simulating what you used to get when you turned on a television with no signal, back in the analog days. To combine the noise frames created by ImageMagick I used Netpbm, which I had to install separately (that is, it wasn’t installed by default in Lenny).
Here’s the Bash multi-liner I used to generate 48 frames worth of noise:
(for i in `seq 1 48`; \ do convert -size 640x480 xc: +noise Random \ -blur 1x1 -fx intensity -normalize ppm:-; done) \ | ppmtompeg kohina.txt
And here’s kohina.txt which specifies how ppmtompeg packs the frames. Note that I just threw this together without too much thought, so it definitely needs tweaking depending on what the video is used for and so what (quality, compression, speed) matters. For example, I only used I-frames due to lack of imagination.
PATTERN IIIIIIII OUTPUT kohina.mpeg INPUT_DIR stdin BASE_FILE_FORMAT PPM INPUT_CONVERT * GOP_SIZE 8 SLICES_PER_FRAME 30 PIXEL HALF RANGE 2 PSEARCH_ALG LOGARITHMIC BSEARCH_ALG SIMPLE IQSCALE 1 PQSCALE 1 BQSCALE 1 REFERENCE_FRAME ORIGINAL
And here’s what it looks like, recompressed with Theora (using Oggconvert): kohina.ogg (2,8 MB). Generating an accompanyng soundtrack is trivial with Audacity.
SSH inside a while read loop
Got bit by the fact that SSH inherits stdin from its parent, which rendered my fancy remote-command-in-a-loop useless. Passing -n to ssh made it work the way I’d expected.
vrms
jani@gojira:~$ vrms
No non-free or contrib packages installed on gojira! rms would be proud.
Well, that’s not accurate: at least I have the non-free version of VirtualBox installed. Now I’m trying to find out if this is a bug or a limitation set by something in my setup.
aptmethod error when doing security updates with reprepro update
Got this error message when trying to do a reprepro update:
aptmethod error receiving 'http://security.debian.org/debian-security/dists/lenny/updates/main/debian-installer/binary-i386/Packages.gz': '404 Not Found'
This was caused by a missing UDebComponents: none in the security update source definition, in conf/updates. Quite obvious really, but got me scratching my head for a while.
The command to print the release codename
jani@gojira:~$ lsb_release -sc
lenny
Fetch and sequentially store webcam images at intervals, v. 0.01
#!/bin/bash if [ $# -lt 2 ] ; then echo foo exit 1 fi if [ $1 -eq $1 2> /dev/null ]; then while true do wget "$2" -O `date +%s`.jpg sleep $1 done else echo bar exit 1 fi
GRUB, subprocess post-installation script returned error exit status 1
Note to self: the next time GRUB starts exiting with 1 during postinst (when upgrading the kernel), check /boot/grub/device.map. Apparently the last time this happened, I had to change hd0 to point to sda, and this time I had to change it to point back to hda. Without this change grub-probe would fail, causing update-grub and thus the postinst to fail also.
Also, don’t be fooled by update-grub staying quiet; update-grub && echo success lets you know whether it did actually complete or not.
Creating ISO images
I just learned that mkisofs has been superseded by genisoimage.
Querying dd for statistics
To get the statistics of a running dd, you send it a USR1 with kill:
kill -USR1 $PID