Infos zu Linux und die Unterlagen zu den Linux-Kursen am Wifi Wien.

Checking if you're running the currently installed Debian kernel

Note: this doesn't work across ABI changes, i.e. when 3.2.0-4-amd64 becomes 3.2.0-5-amd64

Find the package version for the most recently installed kernel:

dpkg -l linux-image-$(uname -r) | awk '/^ii/{ print $3 }'

Get the same information from the running kernel:

uname --kernel-version  | awk '{ print $NF }'

Compare.

Caveats when switching Xen domUs to pygrub

When switching some old Xen guests (domUs) to pygrub, some things to remember:

  • using the bootloader config setting, you must remove the config settings kernel, extra, ramdisk and root, otherwise the domU will not boot.
  • if you happen to use multiple disk devices, make sure the one with the kernel/initrd is listed first, otherwise you'll get the error
    Error: Boot loader didn't return any data

Finding Debian packages installed from backports.debian.org

Using backports is a nice way to get newer versions of software while continuing to use Debian stable. If you ever want to list the packages installed from the backports repository, aptitude can help:

aptitude search '~S ~i ~O"Debian Backports"'

You get the search term "Debian Backports" (the so-called origin) for the backports packages from the output of

apt-cache policy

For a list of valid origins depending on your APT sources, we can filter this by using grep and sort:

apt-cache policy | grep -o o=[^,]* | sort -u

So of course this also works to find out which packages got installed from other repositories.

Forcing gzip compression when building Debian packages

If you're building packages on a recent Debian-based distribution and are getting

dpkg-deb: file `blah.deb' contains ununderstood data member data.tar.xz     , giving up

when trying to install the package on an old system with dpkg version < 1.15.6, you can force the usage of the gzip compression algorithm by changing the dh_builddeb in debian/rules to:

dh_builddeb -- -Z gzip

If you do not have an old-style debian/rules files where all the dh_* calls are listed but only one generic stanza like

%:
        dh $@

then you can add

override_dh_builddeb:
        dh_builddeb -- -Zgzip

below that to set the option for dh_builddeb.

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