[Bug 1646222] [NEW] calculation of needed free space in /boot is inaccurate and causes refusal to upgrade

[Steve Langasek]

Public bug reported:

I have a /boot partition which is sized just right to accommodate 3
kernels, plus a little bit of overhead.

$ df -h /boot/
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda5       280M  144M  118M  56% /boot
$

Previously, update-manager had no problem letting me upgrade kernels.
With the latest kernel update in 16.10, I got an error message that I
needed more free space on this filesystem.

After bypassing update-manager with 'sudo apt dist-upgrade', the
filesystem's usage looks like this:

$ df -h /boot/
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda5       280M  206M   56M  79% /boot
$

So update-manager is getting the disk usage requirement for /boot off by
a factor of 2 (at least? I didn't save the error message from the
dialog).

It's better to refuse to upgrade than to fail mid-upgrade due to disk
space, but not if that means getting stuck forever with an old kernel
unnecessarily.

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: update-manager 1:16.10.7
ProcVersionSignature: Ubuntu 4.8.0-27.29-generic 4.8.1
Uname: Linux 4.8.0-27-generic x86_64
ApportVersion: 2.20.3-0ubuntu8
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Nov 30 12:10:25 2016
GsettingsChanges:
 b'com.ubuntu.update-manager' b'show-details' b'true'
 b'com.ubuntu.update-manager' b'window-height' b'551'
 b'com.ubuntu.update-manager' b'first-run' b'false'
 b'com.ubuntu.update-manager' b'window-width' b'813'
 b'com.ubuntu.update-manager' b'launch-time' b'1480522730'
InstallationDate: Installed on 2010-09-24 (2259 days ago)
InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
PackageArchitecture: all
SourcePackage: update-manager
UpgradeStatus: Upgraded to yakkety on 2016-10-28 (32 days ago)

** Affects: update-manager (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug yakkety

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https://bugs.launchpad.net/bugs/1646222

Title:
  calculation of needed free space in /boot is inaccurate and causes
  refusal to upgrade

Status in update-manager package in Ubuntu:
  New

Bug description:
  I have a /boot partition which is sized just right to accommodate 3
  kernels, plus a little bit of overhead.

  $ df -h /boot/
  Filesystem      Size  Used Avail Use% Mounted on
  /dev/sda5       280M  144M  118M  56% /boot
  $

  Previously, update-manager had no problem letting me upgrade kernels.
  With the latest kernel update in 16.10, I got an error message that I
  needed more free space on this filesystem.

  After bypassing update-manager with 'sudo apt dist-upgrade', the
  filesystem's usage looks like this:

  $ df -h /boot/
  Filesystem      Size  Used Avail Use% Mounted on
  /dev/sda5       280M  206M   56M  79% /boot
  $

  So update-manager is getting the disk usage requirement for /boot off
  by a factor of 2 (at least? I didn't save the error message from the
  dialog).

  It's better to refuse to upgrade than to fail mid-upgrade due to disk
  space, but not if that means getting stuck forever with an old kernel
  unnecessarily.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.10
  Package: update-manager 1:16.10.7
  ProcVersionSignature: Ubuntu 4.8.0-27.29-generic 4.8.1
  Uname: Linux 4.8.0-27-generic x86_64
  ApportVersion: 2.20.3-0ubuntu8
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Wed Nov 30 12:10:25 2016
  GsettingsChanges:
   b'com.ubuntu.update-manager' b'show-details' b'true'
   b'com.ubuntu.update-manager' b'window-height' b'551'
   b'com.ubuntu.update-manager' b'first-run' b'false'
   b'com.ubuntu.update-manager' b'window-width' b'813'
   b'com.ubuntu.update-manager' b'launch-time' b'1480522730'
  InstallationDate: Installed on 2010-09-24 (2259 days ago)
  InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
  PackageArchitecture: all
  SourcePackage: update-manager
  UpgradeStatus: Upgraded to yakkety on 2016-10-28 (32 days ago)

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