If you need to do mysqldumps while a system is using the DB, take care regarding your parameters. Especially on Debian-based Distros there
are a few default flags you maybe do not want to be active.

An appropriate line could look like this:

mysqldump –single-transaction –skip-opt –add-drop-table –add-locks –create-options –disable-keys –extended-insert –quick –set-charset

Especially –quick seems kind of important. No buffering in memory.
You don’t want locking either, or your db “freezes” until the dump is ready.
Have fun.

Recently I struggled with the new FF9 on Debian stable (squeeze). There are certain things to keep in mind. Assume you put the content of ff9.tar.gz to /usr/local/bin/ff9

- Make sure you have ia32-libs and ia32-libs-gtk installed.
- Put a new entry to your /etc/ld.so.conf -> /usr/local/bin/ff9
- Hit “ldconfig”
- Create a small starter shell-script for your browser that includes
export GTK_PATH=/usr/lib32/gtk-2.0/
(Otherwise it tries to use the 64Bit versions, which don’t work…)

Finalize with some flash plugin:
- Visit http://get.adobe.com/de/flashplayer/ and take the .tgz for 32Bit(!) with you.
- Use your favorite way of putting/linking it to /usr/lib/mozilla/plugins/

Voila.

If you’re interested in learning more about GSM networks and playing around with them yourself, you should probably take a look at the OpenBTS project.

A much cheaper approach is followed by the OsmocomBB project. Here you start with a 15 EUR phone and an 5 EUR interface!

Just as a reminder for situations in which you need to connect to a host which is e.g. firewalled. Here is how. On the machine that can only do OUTBOUND connections, type:

ssh -f -N -R 10000:localhost:22 user@your_outside_machine

So now, you can ssh to port 10000 on your outside machine and you will actually be connecting to port 22 on the firewalled server:
ssh user@outside_machine -p 10000

Voila.

Playing around with KVM virtualization on e.g. Debian Squeeze and ever wondered if there’s a way to optimize memory usage? It’s possible!
KSM (Kernel Samepage Merging) is the magic phrase. To make it short: On a recent installation (> 2.6.32) you possibly only need to:

# echo 1 > /sys/kernel/mm/ksm/run

If KSM is running, and there are pages to be merged (i.e. more than one similar VM is running), then /sys/kernel/mm/ksm/pages_shared should be non-zero. From the kernel documentation in Documentation/vm/ksm.txt:

The effectiveness of KSM and MADV_MERGEABLE is shown in /sys/kernel/mm/ksm/:

pages_shared     - how many shared unswappable kernel pages KSM is using
pages_sharing    - how many more sites are sharing them i.e. how much saved
pages_unshared   - how many pages unique but repeatedly checked for merging
pages_volatile   - how many pages changing too fast to be placed in a tree
full_scans       - how many times all mergeable areas have been scanned

A high ratio of pages_sharing to pages_shared indicates good sharing, but
a high ratio of pages_unshared to pages_sharing indicates wasted effort.
pages_volatile embraces several different kinds of activity, but a high
proportion there would also indicate poor use of madvise MADV_MERGEABLE.