[Bug 1511875] Re: Can't upgrade from 15.10 Wily to 16.04 Xenial in LXC container

[Jon Brase]

As an update to my comment above, while the release upgrader hung and
did not finish the upgrade, it *did* disable all my ppa's and switch
over to the Xenial repositories, which ended up leaving my system broken
next time I tried pulling in updates (thinking the upgrade had failed
completely and the system was still using Trusty repositories). I'm not
sure what packages are at Xenial versions and what packages are at still
at Trusty versions, there seems to be a mix.

So it seems I can't expect Ubuntu to upgrade between LTS versions
without barfing all over itself. Gee, what fun.

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https://bugs.launchpad.net/bugs/1511875

Title:
  Can't upgrade from 15.10 Wily to 16.04 Xenial in LXC container

Status in lxc package in Ubuntu:
  Invalid
Status in ubuntu-release-upgrader package in Ubuntu:
  Triaged

Bug description:
  When I try to upgrade from 15.10 Wily to 16.04 Xenial (actual
  development version) within an LXC container, the upgrade script hangs
  at the message „Calculating the changes”.

  Steps to reproduce:
  1. Make an LXC container with Wily (quickest option is to use lxc-create -t download, choose ubuntu, wily, amd64/i386).
  2. Boot up the container, log in, „apt-get -y install ubuntu-release-upgrader-core”.
  3. Start the upgrade with „do-release-upgrade -d”.

  You will see that the upgrade process will hang at the message
  „Calculating the changes”.

  The process which hangs: „/usr/bin/python3 /tmp/ubuntu-release-
  upgrader-1mpotr5d/xenial --mode=server --frontend=DistUpgradeViewText
  --devel-release”

  With strace, it is revealed that the process hangs at a „futex” system call:
  futex(0x7f4190000c10, FUTEX_WAIT_PRIVATE, 0, NULL

  This system call never returns, the process must be interrupted with
  CTRL-C or kill.

  Upgrading to any previous release within an LXC container works
  without problems, therefore I consider it as a regression.

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