[Bug 2034587] [NEW] Cannot reconnect to byobu session during upgrade

[Ben Nuttall]

Public bug reported:

I recently upgraded a server from 20.04 to 22.04. I connected to the
server over SSH from a laptop, and was running byobu on the server,
thinking that this would allow me to reconnect if the connection dropped
during the long upgrade process.

My laptop went to sleep at some point and when I tried to reconnect, the
SSH command just hung.

I managed to SSH onto the server using `ssh <hostname> -t bash`. The
system seemed to be in a partially upgraded state: `lsb_release` said I
was running 22.04, but there were signs the upgrade hadn't completed. I
didn't know whether the upgrade had errored or was simply waiting for me
to say "yes" to something.

I tried launching byobu, but that just hung (zero response, no error). I
tried running `byobu-select-session` and that said "server version is
too old for client" which makes sense as I'd upgraded since launching
that session.

Finally I discovered that the `do-release-upgrade` command runs in its
own separate screen session - which I managed to reconnect to using
`screen -x` as root. This dropped me back at the upgrade process which
was in fact waiting for me to say "yes" to changes to config files.

Luckily I found this before rebooting or trying something risky. I was
able to continue with the upgrade which was successful.

Perhaps this can be solved with documentation on the upgrade process -
provide guidance on how to safely run an upgrade over SSH. Or is it a
bug that you can't reconnect to byobu after upgrade, or that the SSH
connection attempt just hangs.

** Affects: ubuntu-release-upgrader (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2034587

Title:
  Cannot reconnect to byobu session during upgrade

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

Bug description:
  I recently upgraded a server from 20.04 to 22.04. I connected to the
  server over SSH from a laptop, and was running byobu on the server,
  thinking that this would allow me to reconnect if the connection
  dropped during the long upgrade process.

  My laptop went to sleep at some point and when I tried to reconnect,
  the SSH command just hung.

  I managed to SSH onto the server using `ssh <hostname> -t bash`. The
  system seemed to be in a partially upgraded state: `lsb_release` said
  I was running 22.04, but there were signs the upgrade hadn't
  completed. I didn't know whether the upgrade had errored or was simply
  waiting for me to say "yes" to something.

  I tried launching byobu, but that just hung (zero response, no error).
  I tried running `byobu-select-session` and that said "server version
  is too old for client" which makes sense as I'd upgraded since
  launching that session.

  Finally I discovered that the `do-release-upgrade` command runs in its
  own separate screen session - which I managed to reconnect to using
  `screen -x` as root. This dropped me back at the upgrade process which
  was in fact waiting for me to say "yes" to changes to config files.

  Luckily I found this before rebooting or trying something risky. I was
  able to continue with the upgrade which was successful.

  Perhaps this can be solved with documentation on the upgrade process -
  provide guidance on how to safely run an upgrade over SSH. Or is it a
  bug that you can't reconnect to byobu after upgrade, or that the SSH
  connection attempt just hangs.

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