[Bug 2058629] Re: snap preseed failing to umount /tmp/snapd-preseed

Wed Apr 3 13:41:19 UTC 2024

I was previously able to reproduce reliably this behavior but I am not
anymore, which is at the same time a good and a bad news. Meanwhile, I
now it a similar issue, but at the update_bootloader stage.

[18] update_bootloader
Adding 'local diversion of /etc/grub.d/30_os-prober to /etc/grub.d/30_os-prober.dpkg-divert'
Sourcing file `/etc/default/grub'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-6.5.0-9-generic
Found initrd image: /boot/initrd.img-6.5.0-9-generic
Adding boot menu entry for UEFI Firmware Settings ...
done
Removing 'local diversion of /etc/grub.d/30_os-prober to /etc/grub.d/30_os-prober.dpkg-divert'
umount: /home/paul/scratch/debootstrap-2/scratch/loopback/proc: target is busy.
umount: /home/paul/scratch/debootstrap-2/scratch/loopback: target is busy.
duration: 1.053857891s
Error: teardown failed: teardown command  "/usr/bin/umount --recursive /home/paul/scratch/debootstrap-2/scratch/loopback/proc" failed. Output: 
umount: /home/paul/scratch/debootstrap-2/scratch/loopback/proc: target is busy.

teardown command  "/usr/bin/umount /home/paul/scratch/debootstrap-2/scratch/loopback" failed. Output: 
umount: /home/paul/scratch/debootstrap-2/scratch/loopback: target is busy.

This is also not always happening and mounted dirs can be umounted manually after the build failed. So I suspect a race condition again.

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Title:
  snap preseed failing to umount /tmp/snapd-preseed

Status in Ubuntu Image:
  In Progress

Bug description:
  When building a classic image, the preseed_image steps is failing with
  the following error:

  [8] preseed_image
  ubuntu classic preseeding
  starting to preseed root: /home/paul/scratch/debootstrap-2/chroot
  using snapd binary: /tmp/snapd-preseed/usr/lib/snapd/snapd (2.61.2)
  2024/03/21 09:55:31.100621 main.go:53: running for preseeding
  2024/03/21 09:55:31.160617 overlord.go:271: Acquiring state lock file
  2024/03/21 09:55:31.160652 overlord.go:276: Acquired state lock file
  2024/03/21 09:55:31.215560 daemon.go:247: started snapd/2.61.2 (series 16; classic) ubuntu/24.04 (amd64) linux/6.5.0-27-generic.
  2024/03/21 09:55:31.234105 daemon.go:340: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
  2024/03/21 09:55:31.258774 backends.go:58: AppArmor status: apparmor is enabled and all features are available (using snapd provided apparmor_parser)
  2024/03/21 09:55:31.458153 helpers.go:146: error trying to compare the snap system key: system-key missing on disk
  2024/03/21 09:55:32.573216 daemon.go:425: stopping snapd as requested
  2024/03/21 09:55:32.618884 daemon.go:519: gracefully waiting for running hooks
  2024/03/21 09:55:32.618921 daemon.go:521: done waiting for running hooks
  2024/03/21 09:55:35.574257 overlord.go:515: Released state lock file
  unmounting: /tmp/snapd-preseed
  exit status 32remove /tmp/snapd-preseed: device or resource busy
  umount: /home/paul/scratch/debootstrap-2/chroot/sys/fs/cgroup: target is busy.
  umount: /home/paul/scratch/debootstrap-2/chroot/sys/kernel/security: target is busy.
  umount: /home/paul/scratch/debootstrap-2/chroot/proc: target is busy.
  umount: /home/paul/scratch/debootstrap-2/chroot/dev/pts: target is busy.
  umount: /home/paul/scratch/debootstrap-2/chroot/dev/pts: target is busy.
  duration: 5.286563398s
  Error: teardown failed: teardown command  "/usr/bin/umount --recursive debootstrap-2/chroot/sys/fs/cgroup" failed. Output:
  umount: /home/paul/scratch/debootstrap-2/chroot/sys/fs/cgroup: target is busy.

  teardown command  "/usr/bin/umount --recursive debootstrap-2/chroot/sys/kernel/security" failed. Output:
  umount: /home/paul/scratch/debootstrap-2/chroot/sys/kernel/security: target is busy.

  teardown command  "/usr/bin/umount --recursive debootstrap-2/chroot/proc" failed. Output:
  umount: /home/paul/scratch/debootstrap-2/chroot/proc: target is busy.

  teardown command  "/usr/bin/umount --recursive debootstrap-2/chroot/dev/pts" failed. Output:
  umount: /home/paul/scratch/debootstrap-2/chroot/dev/pts: target is busy.

  teardown command  "/usr/bin/umount --recursive debootstrap-2/chroot/dev" failed. Output:
  umount: /home/paul/scratch/debootstrap-2/chroot/dev/pts: target is busy.

  The call to snap-preseed is failing because the umounting of
  /tmp/snapd-preseed is failing.

  sudo mount -l | grep "debootstrap-2"

  devtmpfs-build on /home/paul/scratch/debootstrap-2/chroot/dev type devtmpfs (rw,relatime,size=15723176k,nr_inodes=3930794,mode=755,inode64)
  devpts-build on /home/paul/scratch/debootstrap-2/chroot/dev/pts type devpts (rw,nosuid,nodev,relatime,mode=600,ptmxmode=000)
  proc-build on /home/paul/scratch/debootstrap-2/chroot/proc type proc (rw,relatime)
  none on /home/paul/scratch/debootstrap-2/chroot/sys/kernel/security type securityfs (rw,relatime)
  none on /home/paul/scratch/debootstrap-2/chroot/sys/fs/cgroup type cgroup2 (rw,relatime)
  /home/paul/scratch/debootstrap-2/chroot/var/lib/snapd/seed/snaps/snapd_21184.snap on /home/paul/scratch/debootstrap-2/chroot/tmp/snapd-preseed type squashfs (ro,relatime,errors=continue,threads=single)

  I suspect a race condition because once the build has failed, I can
  unmount these mountpoints.

  The preseed_image state is executed after prepare_image, which is also
  calling /usr/lib/snapd/snap-preseed (but with the --reset flag).

  To reproduce: ubuntu-image --verbose --debug classic --workdir debootstrap-2 image_definition.yaml

  Image definition used:

  name: ubuntu-server-amd64
  display-name: Ubuntu Server amd64
  revision: 1
  architecture: amd64
  series: noble
  class: preinstalled
  kernel: linux-image-generic
  gadget:
    url: "https://git.launchpad.net/~canonical-foundations/snap-pc/+git/github-mirror-amd64"
    branch: classic
    type: "git"
  rootfs:
    components:
      - main
      - restricted
    seed:
      urls:
        - "git://git.launchpad.net/~ubuntu-core-dev/ubuntu-seeds/+git/"
      branch: noble
      names:
        - server
        - minimal
        - standard
        - cloud-image
  customization:
    cloud-init:
      user-data: |
        #cloud-config
        chpasswd:
          expire: true
          users:
            - name: ubuntu
              password: ubuntu
              type: text
      meta-data: |
        dsmode: local
        instance_id: ubuntu-server
    extra-snaps:
      - name: snapd
  artifacts:
    img:
      -
        name: ubuntu-24.04-preinstalled-server-amd64.img
    manifest:
      name: "filesystem-manifest.txt"
    filelist:
      name: "filesystem-filelist.txt"

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