Monday, January 21, 2013

My Debian tweaks

When doing a new Debian Linux installation, there are a set of basic configuration changes that I nearly always make. While the issues do not apply to everyone, I think they are common enough that many others may find them useful. As always, your mileage may vary, use at your own risk, etc.
My system is Debian Testing installed on a laptop that is typically shut down at night and that often runs disconnected from the Internet. So here are the problems I often see and my solutions:

  1. PC locked by fsck. The fsck partition check program typically runs every 30 reboots or so on EXT2/EXT3 filesystems (and maybe others). This automatically happens during the boot process and, per Murphy's law, it usually happens while setting up a critical demo or presentation. The problem is that it can't be interrupted, so the group gets to spend several minutes watching the progress bar slowly move. The fix is to add the lines:
    allow_cancellation = true
    to the file /etc/e2fsck.conf. One site that discusses this fix and potential issues is
  2. Boot pauses due to exim. When booting while not connected to the Internet, the exim mail handling program may hang for 60 seconds. I found that adding
    to /etc/exim4/exim4.conf.localmacros gets rid of the hang, where should be changed to whatever is appropriate for that PC. Depending on other configuration options, this line might belong somewhere in  /etc/exim4/conf.d instead.
  3. Annoying computer beep.For some reason, many programs seem to think a loud "beep" on errors is a helpful feature. I'm one of the legions that disagree, so I disable the pcspkr device by adding
    blacklist pcspkr
    blacklist snd_pcsp
    to a file in the /etc/modprobe.d/blacklist directory. See!%29 for example.
  4. Hardware Clock. Normal PC's have a hardware clock that keeps track of the date and time of day even when the PC is powered off, and Linux also has a system clock that keeps time when running. This system clock is initialized from the hardware clock while booting. In normal Debian setups the /etc/init.d/ script also copies the system clock back to the hardware clock during system shutdown. That's a problem in my system because it's using the less accurate clock to reset the more accurate clock. One fix is to install the ntpdate package; then the system time gets set whenever an Internet connection comes up. Another option I use sometimes is to edit to disable the hardware clock update, and just set it manually. I'm planning a more detailed post on this issue.