Linux: When massive load on the disk makes the system freeze

The bad news are that Linux has been behaving pretty badly when the disk is under heavy load. The good news are that all you need is a kernel upgrade. First, let’s run a simple experiment: $ dd if=/dev/zero of=junkfile bs=1k count=20M Don’t expect anything dramatic to happen right away. It takes half a minute [...]

Video encoding. Some useful command lines

This is just a few command lines I use every now and then. Just so I have them when I need them. Convert a lot of Flash Video files to DIVX, audio rate 128 kb/sec mp3: for i in *.flv ; do ffmpeg -i “$i” -ab 128k -b 1500k -vcodec mpeg4 -vtag DIVX “${i%.*}.avi” ; [...]

Making an encrypted DVD (lazy man’s version)

This is how to make an encrypted DVD, which is automatically mounted by Fedora 12 (and others, I suppose) when the DVD is inserted (prompting for the passphrase, of course). The truth is that I don’t use this automatic feature, because only seeing the suggestion to save my passphrase as an option makes me prefer [...]

Fedora 12: Creating an initramfs image for self-compiled kernel

So I compiled the kernel I downloaded from kernel.org like I’ve always done, but the system wouldn’t boot, and it had good reasons not to: My root filesystem is both encrypted and RAID-5′ed, which requires, at least, a password to be entered. That job has to be done by some script which runs before my [...]

Setting up an encrypted ext4 disk image with dm_crypt

This script turns the file given as argument to an image of an encrypted and ext4-formatted disk image file. After this, you can do something like: losetup /dev/loop0 /storage/diskimages/thefile cryptsetup luksOpen /dev/loop0 myfakedisk mount /dev/mapper/myfakedisk /path/to/mountpoint And then close with umount /path/to/mountpoint cryptsetup luksClose myfakedisk losetup -d /dev/loop0 The operation above and the script below [...]

Cinelerra: When YUV4MPEG fails with mencoder

Somewhere in the region of version r31061-4.4.3, a bug in mplayer and mencoder made the program not cache properly. This causes issues when trying to play streams, or when rendering an edited video in Cinelerra in YUV4MPEG-to-pipe mode. The common behavior during rendering is that mencoder quits immediately or very soon, because it thinks end-of-file [...]

Gnome workaround: Downloading a MOV file from Canon 500D

One of the things I love about fancy GUI interfaces, is that they work as long as things are easy, and always fail at the critical moments. Downloading a 4 GB video clip from my Canon 500D to a Fedora 12, using the File Manager (nautilus?) was no different. As usual, when I plugged in [...]

DigiPro drawing tablet on Fedora 12

I just bought a DigiPro 5″/4″ drawing tablet to run with my Fedora 12. When plugging it in, the system recognized it, but every time I touched the tablet with the stylus pen, the cursor went to the upper left corner. Clicks worked OK, but it looked like the system needed to know the tablet’s [...]

ImageMagick convert: Making viewable copies of underexposed images

The problem is relatively simple:  Sometimes I take images that are deliberately underexposed, or such that have important parts in the dark areas. This is then fixed with GIMP. But in order to choose which image to play with, I need to those details visible in some test image, so I can browse them with [...]

Adding remarks to an existing pdf file with pdftk

This is how to solve a special case, when a PDF file is given, but I want to add my remarks in some free space. The trick is to write the remarks into another single-page pdf file, so that the new text occupies the blank area in the original. In my case, I needed the [...]