[juju-2.0] trusty package doesn't install juju-2.0 commands via update-alternatives

[Felipe Reyes]

In some cases /usr/bin/juju is juju 2.0 when upgrading a trusty environment that has ppa:juju/stable PPA enabled.

[Impact]

Users may end up inadvertently using the juju command from 2.0 and without the option to manage their juju-1.x deployed environments.

[Test]

lxc launch ubuntu:14.04 juju
lxc exec juju /bin/bash
$ sudo apt-get update
$ sudo apt-get install -y juju
$ juju --version
1.25.6-trusty-amd64
$ sudo add-apt-repository -y ppa:juju/stable
$ sudo apt-get update
$ sudo apt-get upgrade

Expected result:

/usr/bin/juju points to juju 1.25

Actual result:

In some cases /usr/bin/juju may be actually juju-2.0, because the juju-2.0 package doesn't use update-alternatives

$ dpkg -L juju-2.0
/.
...
/usr/bin/juju
/usr/bin/juju-metadata
/usr/bin/jujud
/usr/bin/juju-upgrade-mongo
...

[Mario Splivalo (mariosplivalo)]

I can confirm this.

I installed trusty, added juju stable ppa, and installed latest 1.25 from the ppa. This is the situation most of the long-time juju users will be at.
After doing dist-upgrade /usr/bin/juju points to juju2, rendering existing juju1 deployment inaccessible.

To remedy this one needs to run 'dpkg-reconfigure juju-core'.

Here is the shortlog:

ubuntu@jujutest:~$ apt-cache policy juju
juju:
  Installed: 1.25.6-0ubuntu1~14.04.1~juju1
  Candidate: 1:2.0.0-0ubuntu1~14.04.2~juju1
  Version table:
     1:2.0.0-0ubuntu1~14.04.2~juju1 0
        500 http://ppa.launchpad.net/juju/stable/ubuntu/ trusty/main amd64 Packages
     1.25.6-0ubuntu1.14.04.1 0
        500 http://archive.ubuntu.com/ubuntu/ trusty-updates/universe amd64 Packages
 *** 1.25.6-0ubuntu1~14.04.1~juju1 0
        500 http://ppa.launchpad.net/juju/stable/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status
     1.18.1-0ubuntu1 0
        500 http://archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages
ubuntu@jujutest:~$ which juju
/usr/bin/juju
ubuntu@jujutest:~$ ls -al /usr/bin/juju
lrwxrwxrwx 1 root root 22 Oct 14 20:35 /usr/bin/juju -> /etc/alternatives/juju

After the 'apt-get dist-upgrade':

ubuntu@jujutest:~$ apt-cache policy juju
juju:
  Installed: 1:2.0.0-0ubuntu1~14.04.2~juju1
  Candidate: 1:2.0.0-0ubuntu1~14.04.2~juju1
  Version table:
 *** 1:2.0.0-0ubuntu1~14.04.2~juju1 0
        500 http://ppa.launchpad.net/juju/stable/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status
     1.25.6-0ubuntu1.14.04.1 0
        500 http://archive.ubuntu.com/ubuntu/ trusty-updates/universe amd64 Packages
     1.25.6-0ubuntu1~14.04.1~juju1 0
        500 http://ppa.launchpad.net/juju/stable/ubuntu/ trusty/main amd64 Packages
     1.18.1-0ubuntu1 0
        500 http://archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages
ubuntu@jujutest:~$ ls -al /usr/bin/juju
lrwxrwxrwx 1 root root 24 Oct 13 23:59 /usr/bin/juju -> ../lib/juju-2.0/bin/juju

Then the fix:

ubuntu@jujutest:~$ sudo dpkg-reconfigure juju-core
update-alternatives: using /usr/lib/juju-1.25.6/bin/juju to provide /usr/bin/juju (juju) in auto mode
ubuntu@jujutest:~$ ls -al /usr/bin/juju
lrwxrwxrwx 1 root root 22 Oct 14 20:42 /usr/bin/juju -> /etc/alternatives/juju
ubuntu@jujutest:~$ juju --version
1.25.6-trusty-amd64
ubuntu@jujutest:~$

[Nicholas Skaggs (nskaggs)]

This issue should have no effect on 1.25 deployments. Users will have to run update-alternatives after upgrading no matter what. Running it now results in restoring juju-1.25, which is the desired outcome. After a new package for 2.0 is uploaded that supports using update-alternatives (and thus this bug is fixed), it will allow you to easily toggle between them as expected. That will be the only change from the current setup.

[Nicholas Skaggs (nskaggs)]

Since juju 2 is not wanted as an upgrade path, I've removed the package completely. It may take a little while to propagate. If you have upgraded already, you will want to manually uninstall the package to remove it from your system.

Leaving this bug open at a lower priority to discuss if a replacement package is desirable and what that would look like.