[Bug 1791959] [NEW] [SRU] remove orphaned initrd old-dkms files in /boot

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Tiago Stürmer Daitx (tdaitx):

[Impact]
If a dkms package is installed which has REMAKE_INITRD or the same setting has been manually configured by a user then when a kernel is removed its possible for an ".old-dkms" file to be left in /boot with no associated kernel.

bug 1515513 dealt with removing old-dkms initrd files using the kernel's
prerm hook, but that is only executed for the kernel version being
removed: any other old-dkms file generated prior to that would not be
removed by the hook, taking space in the /boot directory and being
carried forward with every upgrade.

Note: Filling up the /boot partition causes updates and upgrades to
fail.

[Test Case]
As the fix for bug 1515513 is available on Xenial and Bionic it is no longer possible to reproduce this by simply installing and updating kernels - dkms 2.2.0.3-2ubuntu11.3/xenial or 2.3-3ubuntu1/bionic would be required for that. In order to replicate it an old dkms file will be created by hand.

This assumes a new Xenial/Bionic schroot.

1) create files to work as a placeholders for old dkms files (there are 4 possible namings for these files)
touch /boot/initrd-4.0.0-0-generic.img.old-dkms /boot/initramfs-4.0.0-0-generic.img.old-dkms /boot/initrd.img-4.0.0-0-generic.old-dkms /boot/initrd-4.0.0-0-generic.old-dkms

2) install 3 old kernels, r8168-dkms, and the current initramfs-tools
* xenial:
apt-get install -y linux-image-4.4.0-21-generic linux-image-4.4.0-22-generic linux-image-4.4.0-24-generic r8168-dkms initramfs-tools=0.122ubuntu8.12
* bionic:
apt-get install -y linux-image-4.15.0-32-generic linux-image-4.15.0-33-generic linux-image-4.15.0-34-generic r8168-dkms initramfs-tools=0.130ubuntu3.3

3) install the headers for the old kernels (forces dkms to run)
* xenial:
apt-get install -y linux-headers-4.4.0-21-generic linux-headers-4.4.0-22-generic linux-headers-4.4.0-24-generic
* bionic:
apt-get install -y linux-headers-4.15.0-32-generic linux-headers-4.15.0-33-generic linux-headers-4.15.0-34-generic

4) verify that there are 7 old-dkms, the 4 manually created ones and one for each installed kernel
ls -1 /boot/*.old-dkms

5) install the initramfs-tools from proposed that contains this fix
apt-get install -y initramfs-tools

6) verify that the manually created old-dkms files were removed and that there are only 3 files now, one for each installed kernel
ls /boot/*.old-dkms

7) mark kernel images and headers as automatically installed
apt-mark auto linux-image-4*-generic linux-headers-4*-generic

8) autoremove the older kernel
apt-get autoremove -y

9) verify that there are now only 2 old-dkms, one for each installed kernel
ls -1 /boot/*.old-dkms


These steps guarantees that:
- orphaned old-dkms are correctly removed from /boot
- non-orphaned old-dkms are kept
- when kernel is removed the related old-dkms are also deleted

[Regression Potential]
Somebody out there might expect the .old-dkms file to be kept, but that seems like an odd expectation.

One notices *.old-dkms files being left behind still sitting on the disk
after purging the related kernel. This can cause /boot to become full,
and when it gets really bad, even sudo apt-get autoremove won't fix the
problem - only deleting the old-dkms files manually solves the problem.

** Affects: dkms (Ubuntu)
     Importance: Medium
         Status: Invalid

** Affects: initramfs-tools (Ubuntu)
     Importance: Medium
         Status: Confirmed

** Affects: dkms (Ubuntu Xenial)
     Importance: Undecided
         Status: Invalid

** Affects: initramfs-tools (Ubuntu Xenial)
     Importance: Undecided
         Status: New

** Affects: dkms (Ubuntu Bionic)
     Importance: Undecided
         Status: Invalid

** Affects: initramfs-tools (Ubuntu Bionic)
     Importance: Undecided
         Status: New


** Tags: patch xenial
-- 
[SRU] remove orphaned initrd old-dkms files in /boot
https://bugs.launchpad.net/bugs/1791959
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