[buildd-tools-devel] Bug#609932: Bug#609932: sbuild now runs apt-get update automatically while building

[Roger Leigh]

On Thu, Jan 13, 2011 at 11:29:39PM +0100, Cyril Brulebois wrote:
> Package: sbuild
> Version: 0.60.8-1
> Severity: important
> 
> sbuild now runs apt-get update while building, why?

The reason for updating prior to a build is to ensure that:

• Needed packages are actually available on the mirror, and haven't
  been deleted.
  There are a number of wierd special cases in sbuild where we update
  e.g. if source downloading fails, and then retry; it's much more
  simple and robust to just keep everything up-to-date rather than
  having complex hacks that make things much less deterministic.

• The baseline state of the chroot must be the same before and after
  build-dep/conflicts install/removal and subsequent remove/install.
  If the chroot is outdated to start with, we might not be able to
  return to the baseline state if any packages changed in the interim.
  This basically protects us from breaking the chroot and requiring
  manual intervention to clean up.

The latter should also be coupled with an upgrade to ensure that the
baseline state is up-to-date prior to any installations and removals.
This is why the default is also to do an upgrade.  We don't do a
distupgrade by default; that's probably not sufficiently safe.  With
the use of cloned chroots, this is much less of an issue since we
just delete the chroot.  But for non-cloned chroots, this means the
chroot won't randomly break when apt-get can't cope, and most sbuild
users are using non-cloned chroots.

This is still configurable if you wish to change it; it's just the
default that's changed.

Note that buildd always asks sbuild to update itself on every run
already (--apt-update).


Regards,
Roger

-- 
  .''`.  Roger Leigh
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