AutomaticUpdates

Revision 7 as of 2005-11-02 16:41:42

Clear message

Summary

Automatic Updates - automatic installation of (security) updates, possible even when current user has no sudo privileges

Rationale

When ubuntu is used by a user without sudo privileges, he cannot upgrade it with security updates. This can mean a machine will be vulnerable to security risks for a prolonged period of time. Also some people just don't care about updates and other technical stuff. They just don't want to be bothered and have ubuntu to keep itself updated and secure.

Use cases

Scope

Design

The problem with unattended upgrades are packages that ask questions in postinst. Fortunately there are few of them nowdays, but we still have kernel, libc, etc. Another problem is that there may be conffile questions during the upgrade. BR

We may run dpkg with --force-conf-old. A problem with this is that:

  • a security upgrade may be using a new version for a (default) conffile
  • a upgrade may need a new conffile format

The packages must be prepared for it (don't ask questions, don't prompt, no new conffile). We will limit ourself to security upgrades for the installed distro (origin: ubuntu-security), if anything is installed/upgraded that does not comes from ubuntu-security we will ignore it.

Implementation

Write it in python-apt, check what's upgradable and comes from security; verify if it does not a) break/remove anything b) installs stuff outside security; upgrade it. It will be tied into the apt cron-job we have already.

Code

   1 import apt
   2 cache = apt.Cache()
   3 pkgs = []
   4 for pkg in cache:
   5         if pkg.isUpgradable() and pkg.candidateOrigin == "breezy-security":
   6                 pkg.markUpgradable()
   7                 if we_shouldnt_continue_because_it_adds_non_security_stuff():
   8                         #cache = apt.Cache()
   9                         for pkg in cache:
  10                                 pkg.markKeep()
  11                         for pkg2 in pkgs:
  12                                 pkg2.markUpgradable()
  13                 else:
  14                         pkgs.append(pkg)

Data preservation and migration

Outstanding issues

  • update-notifier would need a way to figure if the pkg-database is locked or not. Write an informational file next to the dpkg lock when acquiring it? Stale locks may be a problem here. Frontends should catch SIGINT and cancel their locks, the boot process should remove any stale locks.
  • flock has advisory locks, which can be used on directory you cannot write in. (DoS? -- one option would be to use an advisory lock to inform user processes, but not to make that the locking protocol between APT frontends; i.e., it should be entirely advisory for frontends; only the main fcntl lock should be mandatory)

BoF agenda and discussion