Debian Tips

Changing the Hostname

Basically /etc/hostname must contain only the host name, not the fully qualified domain name.

How the domain name is determined varies according to your setup (getting it either from a DNS service or from /etc/hosts). See man hostname for details, but often it'll be read from /etc/hosts which has an entry that includes the fully qualified domain name, either for 127.0.0.1 or for the static IP address if you have one. It seems to need to be the first entry for the particular IP address, e.g.

$ head -n 2 /etc/hosts
82.71.196.65 www.smartpixie.com www
127.0.0.1 localhost localhost.localdomain

or if only local interface, (but not very sure about this) or what to do if using DHCP:

$ head -n 1 /etc/hosts
127.0.0.1 www.smartpixie.com www localhost localhost.localdomain

Debian determines the fully qualified host name during boot by running /etc/init.d/hostname.sh so after making the changes:

# /etc/init.d/hostname.sh start

Note: stop does nothing in the hostname.sh script

To check that all is correct:

$ hostname
www

$ hostname --fqd
www.smartpixie.com

See also http://www.debian.org/doc/manuals/reference/ch-gateway.en.html

Package Mangement

Specifying the interface and priority

Run the following to change either the interface you wish to use during package installs or the level of configuration questions you are prompted for.

  • dpkg-reconfigure debconf

The defaults are usually 'Dialog' and 'medium'

Reinstalling

Extract from http://lists.debian.org/debian-user/2004/10/msg01103.html

<quote>
The following command will reinstall all packages on your system:

COLUMNS=200 dpkg -l | awk '/^ii/ {print $2}' | xargs apt-get --reinstall install
</quote>

Package Versions

  • apt-show-versions | grep /testing

Package Priority

The following shows which package the apt mechanism is choosing

  • apt-cache policy mypackage

To show the priority of each source

  • apt-cache policy

For example:

cat /etc/apt/sources.list

deb http://security.debian.org/ stable/updates main contrib non-free
deb http://ftp.uk.debian.org/debian/ sarge main contrib non-free
deb http://ftp.uk.debian.org/debian-non-US sarge/non-US main contrib non-free
deb http://ftp.uk.debian.org/debian/ etch main
deb http://volatile.debian.net/debian-volatile sarge/volatile main contrib non-free

cat /etc/apt/apt.conf

APT
{
    Default-Release "stable";
    Clean-Installed "false";
    Get
    {
        List-Cleanup "true";
    };
};

Note: the 'Default-Release' statement gives that source a priority of '990'

cat /etc/apt/preferences

Package: *
Pin: release o=volatile.debian.net,a=sarge,l=debian-volatile
Pin-Priority: 999

Package: *
Pin: release a=testing,o=Debian
Pin-Priority: -10

Downgrading

To downgrade from testing to stable

Set up your /etc/apt/preferences as follows:

    Package: *
    Pin: release a=stable
    Pin-Priority: 1001

    Package: *
    Pin: release a=testing
    Pin-Priority: 60

    Package: *
    Pin: release a=unstable
    Pin-Priority: 50

You also might need to temporarily remove APT::Default-Release "stable" from /etc/apt/apt.conf as it seems to prevent downgrading

Then run

# apt-get --dry-run dist-upgrade

Remove the --dry-run option once it all looks OK.

Use

$ apt-show-versions | grep /testing

To find any remaining packages. Some packages are risky to downgrade, e.g. libc6, so don't worry if not absolutely everything downgrades. For further hints on removing packages that fail to downgrade:

See also Downgrading report from testing to stable

-- Frank Dean - 16 Mar 2007

Removing packages with broken scripts

The install/remove scripts are all under /var/lib/dpkg/info/ named by their package.

If you can't fix the script, you can have it ignore errors by removing the '-e' flag to #!/bin/sh or comment out the 'set -e' line in the script.

See http://www.debian-administration.org/articles/251

-- Frank Dean - 20 Mar 2007

Repository

http://www.debian.org/doc/manuals/repository-howto/repository-howto

Chkrootkit

False reports of LKM Trojan

http://lists.debian.org/debian-user/2004/03/msg00282.html

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=222179

Producing and using website statistics

http://www.debian-administration.org/articles/85

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=341308

Automount with Gnome

Make sure Gnome is set to automount devices. Desktop | Preferences | Removable Drives and Media

Add your user name to the plugdev group

  • grep plugdev /etc/group
  • sudo adduser me plugdev

Logout and log back in and automounting should be working!

System V init scripts

Have a look at the 'update-rc.d' command for an easy way to amend the symbolic links for the startup scripts.

Boot command line

To see how the system was booted:

    $ cat /proc/cmdline

Default Editor

Administrators who wish to change the default editor for all users will have to update the alternatives system using:

Adminstrator can update the default editor with:

     # update-alternatives --config editor

Users should define the EDITOR environment variable by including the following lines in their profile:

     EDITOR=vi
     export EDITOR
     alias editor=$EDITOR

Installing and building from source packages

http://www.uk.debian.org/doc/manuals/debian-faq/ch-pkg_basics.en.html#s-sourcepkgs

$ apt-get source foo
$ : Check for build dependencies
$ sudo apt-get build-dep foo

Use '--download-only' for the apt-get source command if you do not want the download to be unpacked.

To build, download the .dsc, .tar.gz and .diff.gz source files.

If they need extracting into a package subdirectory:

$ dpkg-source -x foo_version-revision.dsc

To compile the binary:

$ cd foo_version-revision
$ dpkg-buildpackage -rfakeroot -b

Add '-tc' to the dpkg-buildpackage command to clear the directory tree after the build completes, i.e.

$ cd foo_version-revision
$ dpkg-buildpackage -rfakeroot -b -tc

The deb package will be created in the directory above the build directory.

If can then be installed with:

# dpkg -i ../foo_version-revision_arch.deb

Fixing mpg123

Running mpg123 under Debian 5 (Lenny) results in the following error:

[module.c:110] error: Failed to open module alsa: file not found

See Bug #561857

Fix by running with a specified library path:

$ LD_LIBRARY_PATH=/usr/lib/mpg123 mpg123 myfile.mp3

or use mp3blaster instead ;-)

-- Frank Dean - 3 Apr 2010

Related Topics: AptitudeTips, GnomeTips, JigdoTips, CreatingRescuePartition, SystemVStartupScripts

-- Frank Dean - 15 Dec 2004