Why doesn't apt-get autoremove remove my old kernels?

Question

My boot partition is on a SSD, so it doesn't have room for more than about 8 installed kernel versions, and eventually some kernel update will fail to install because my boot partition is full of old versions. There are many questions out there about how to remove old versions (even how to automate the process), but my question is simply this: Why doesn't apt-get autoremove detect and remove them automatically, and is there a way I can make it do so? I mean, apt-get is what installed them anyway, so it knows about them, so why does it choose to leave all old versions around?

Answer 1

As to answer why , refer to the file /etc/apt/apt.conf.d/01autoremove-kernels

As you can see, apt is told to never autoremove the kernels , as told by another (script) file, /etc/kernel/postinst.d/apt-auto-removal. And here it is:

If your script-fu is good enough you could edit it to save only couple kernels, though I can't help you there as my script fu isn't that good

Update:

In the /etc/kernel/postinst.d/apt-auto-removal there is this part:

if [ "$latest_version" != "$installed_version" ] \
   || [ "$latest_version" != "$running_version" ] \
   || [ "$installed_version" != "$running_version" ]
then
        # We have at least two kernels that we have reason to think the
        # user wants, so don't save the second-newest version.
        previous_version=
fi

So if you compare the output of 01autoremove-kernels file and uname -r you'll realize that the currently running kernel and the most recent before it, are kept to be never removed by that script. There turns out is another file /etc/apt/apt.conf.d/01autoremove, where there is lines:

    APT
    {
      NeverAutoRemove
      {
            "^firmware-linux.*";
            "^linux-firmware$";
      };
  VersionedKernelPackages
  {
        # linux kernels
        "linux-image";
        "linux-headers";
        "linux-image-extra";
        "linux-signed-image";
        # kfreebsd kernels
        "kfreebsd-image";
        "kfreebsd-headers";
        # hurd kernels
        "gnumach-image";
        # (out-of-tree) modules
        ".*-modules";
        ".*-kernel";
        "linux-backports-modules-.*";
        # tools
        "linux-tools";
  };

So you could comment these out, and it will allow you to auto-remove the kernels with apt-autoremove, though remember - do this at your own risk

Answer 2

For me it helped to install latest (X)ubuntu (15.10). In earlier releases kernel packages may be marked as manually installed, at least, if installed by using Software Updater, so that sudo apt-get autoremove --purge can't delete them. There are bug reports concerning the issue: Bug #1175637, Bug #1439769

In earlier release, you could try to mark kernel packages automatically installed by sudo apt-mark auto $(apt-mark showmanual | grep -E "^linux-([[:alpha:]]+-)+[[:digit:].]+-[^-]+(|-.+)$") and run sudo apt-get autoremove --purge thereafter to see, if it makes difference. The command should still not remove kernels packages shown in /etc/apt/apt.conf.d/01autoremove-kernels, but it is safest to run apt-get autoremove with --dry-run option first.

Answer 3

Here's a link to a kernel purge script with fail-safe that Dustin Kirkland wrote a few years ago. It should still work on 12.04.

http://bazaar.launchpad.net/~bikeshed/bikeshed/trunk/view/head:/purge-old-kernels

I was going to test it on my 14.04 machine, but it seems I'm no longer experiencing the problem there (finally fixed via the regular update channel?). So if anyone with a lot of old kernels on his/her machine wants to test it, please do and share your findings.

Answer 4

KERNELS1=$(uname -r|cut -d - -f1-2); KERNELS2=$(for i in $(ls -l /vmlinuz*|awk '{print $(NF-0)}'); do echo $i |xargs basename|cut -d - -f2-3; done); dpkg -l|egrep 'linux-headers-[0-9]\.[0-9]\.[0-9]-[0-9]|linux-image-[0-9]\.[0-9]\.[0-9]-[0-9]'|egrep -v ''"${KERNELS1}"'|'"${KERNELS2}"''|awk '{print $2}'|xargs apt-get purge -y

I use this on Ubuntu 12.04!

This will keep the current running kernel as well as the newest installed kernel (vmlinuz) and the one before (vmlinuz.old). All other kernels and headers will be removed.