[Bug 1769297] Re: resume from hibernation broken when resume image is autodetected

[amk]

Reached to this bug because of a similar issue we were able to resolve
using information here.

In 18.10, at least in our case, the RESUME variable is set with
partition device name, not UUID. Yet the identification failed, because
the device is not a link and readlink ${resume} returns nothing (or
invalid argument when invoked with -v).

Got things working by assigning $resume into $DEV directly. This could
be more universal approach:

DEV=$(readlink ${resume})
DEV="${DEV:-$resume}"
DEV=/sys/class/block/${DEV##*/}/dev

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https://bugs.launchpad.net/bugs/1769297

Title:
  resume from hibernation broken when resume image is autodetected

Status in initramfs-tools package in Ubuntu:
  Confirmed

Bug description:
  I found a reason of non-functioning resume from hibernation when
  resume partition/file is autodetected by intiramfs hook /usr/share
  /initramfs-tools/hooks/resume.

  Here is the scenario:
  1) hook /usr/share/initramfs-tools/hooks/resume creates config conf/conf.d/zz-resume-auto saved in initrd image, containing one variable: RESUME=UUID=106238b0-707d-4422-866d-a7534da50702 in my case

  2) during boot init script sets 'resume' variable to 'RESUME' value
  from conf/conf.d/zz-resume-auto, then it executes local-premount
  scripts including local-premount/resume

  3) resuming script local-premount/resume (/usr/share/initramfs-tools/scripts/local-premount/resume) tries to get resume device major-minor numbers by these lines:
  DEV=$(readlink ${resume})
  DEV=/sys/class/block/${DEV##*/}/dev
  if [ -r "$DEV" ]; then
          read MAJMIN < "$DEV"
  fi

  4) next check fails and resume process silently aborts:
  if [ -z "$MAJMIN" ]; then
          exit 1
  fi

  Resuming script fails to get device major-minor because
  resume=UUID=106238b0-707d-4422-866d-a7534da50702 -- it's not resolved
  into device path in init script.

  Commonly mentioned workaround is to explicitly specify kernel
  parameter resume=UUID=106238b0-707d-4422-866d-a7534da50702 -- only in
  this case init script resolves it to device path.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: initramfs-tools 0.130ubuntu3
  Uname: Linux 4.16.6-041606-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7
  Architecture: amd64
  CurrentDesktop: ubuntu:GNOME
  Date: Sat May  5 11:32:31 2018
  InstallationDate: Installed on 2018-03-27 (38 days ago)
  InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180327)
  PackageArchitecture: all
  SourcePackage: initramfs-tools
  UpgradeStatus: No upgrade log present (probably fresh install)

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