[Bug 1723285] Re: do-release-upgrade failure leaves a btrfs snapshot

[Ubuntu Foundations Team Bug Bot]

** Tags added: zesty2artful

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https://bugs.launchpad.net/bugs/1723285

Title:
  do-release-upgrade failure leaves a btrfs snapshot

Status in ubuntu-release-upgrader package in Ubuntu:
  New

Bug description:
  1. do-release-upgrade should at least notify upon failure that there is a snapshot, and ideally explain the options (delete versus rollback).
  2. There should be a command line parameter to make do-release-upgrade not snapshot even if the filesystem supports it.

  
  Ironically, the failure was due to the snapshot using ~8 GiB and causing the root filesystem to run out of free space.

  There had been notification of the snapshot earlier in the upgrade
  process ... immediately after the download completed, i.e. at the
  point when one is no longer supposed to interrupt the process. When
  do-release-upgrade failed however, there was no notification that this
  snapshot still existed:

  
  Upgrading
  Inhibiting until Ctrl+C is pressed...
  Create a snapshot of '/tmp/apt-btrfs-snapshot-mp-9posd7z8/@' in '/tmp/apt-btrfs-snapshot-mp-9posd7z8/@apt-snapshot-release-upgrade-artful-2017-10-13_08:12:28'

  [many lines of apt output here]

  Installing new version of config file /etc/usb_modeswitch.conf ...
  dpkg: unrecoverable fatal error, aborting:
   unable to install updated status of 'usb-modeswitch': No space left on device

  Upgrade complete

  The upgrade has completed but there were errors during the upgrade
  process.

  To continue please press [ENTER]

  
  Because do-release-upgrade had cleaned up that mount in /tmp, manual cleanup had to involve re-mounting. To wit:

  
  # mount -t btrfs /dev/sda1 /mnt
  # btrfs subvolume delete /mnt/@apt-snapshot-release-upgrade-artful-2017-10-13_08\:12\:28
  Delete subvolume (no-commit): '/mnt/@apt-snapshot-release-upgrade-artful-2017-10-13_08:12:28'
  # dpkg -a --configure
  [plus some manual fixes]

  ProblemType: Bug
  DistroRelease: Ubuntu 17.10
  Package: ubuntu-release-upgrader-core 1:17.10.7
  ProcVersionSignature: Ubuntu 4.13.0-15.16-generic 4.13.4
  Uname: Linux 4.13.0-15-generic x86_64
  ApportVersion: 2.20.7-0ubuntu3
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: GNOME
  Date: Fri Oct 13 10:55:15 2017
  InstallationDate: Installed on 2016-12-02 (314 days ago)
  InstallationMedia: Ubuntu-GNOME 16.10 "Yakkety Yak" - Release amd64 (20161012.1)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to artful on 2017-10-12 (0 days ago)

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