[buildd-tools-devel] Bug#751732: Bug#751732: Bug#751732: sbuild-createchroot: No overlay configured by default

[Johannes Schauer]

Hi,

On Wed, 18 Jun 2014 23:20:43 +0100 Roger Leigh <rleigh at codelibre.net> wrote:
> On Mon, Jun 16, 2014 at 09:02:10AM +0100, Wookey wrote:
> > +++ Martin Pitt [2014-06-16 06:40 +0200]:
> > > Package: sbuild
> > > Version: 0.64.1-1
> > > 
> > > Hello,
> > > 
> > > When calling sbuild-createchroot like shown in the manpage example:
> > > 
> > >   sudo sbuild-createchroot jessie /tmp/jessie http://ftp.de.debian.org/debian/
> > 
> > > I. e. this uses type=directory without *any* overlay,
> > > 
> > > I'd say this is a fairly unexpected and even misleading default
> > > configuration. IMHO it should set up a proper union-type, or if that's
> > > somehow not appropriate (e. g. if not all Debian kernel support aufs),
> > > rather default to type=tarball.
> > 
> > I don't think it's 'unexpected' for a chroot-creation tool to just
> > make a plain chroot by default. That certainly what I always
> > expected. However in the context of building packages, which is really
> > sbuild's main purpose, a clean chroot for repeatable builds is such a
> > good idea that I agree it should be the default. Or at the very least
> > that the manpage example shows the tarball case (which is the one I
> > always quote in docs).
> 
> Historically, we defaulted to plain directories for simplicity.
> Today, making tar the default for sbuild is the simplest way
> to get working throwaway sessions.  As before, more complex/
> performant configuration will require manual action.  For
> portability, tar is definitely preferable to overlays as the
> default.
> 
> I'd be happy for sbuild-createchroot to switch to tar by default;
> please feel free to commit and upload such a change.

unfortunately the current synopsis of sbuild-createchroot is:

sbuild-createchroot [...] SUITE TARGET-DIRECTORY DEBIAN-MIRROR-URI

If tarball creation were to become the default, then the TARGET-DIRECTORY
positional argument would become a tarball path instead. Would this not break
backwards compatibility with users/scripts assuming that this argument is a
directory? It is even assumed to be a directory when adding the
--make-sbuild-tarball option.

So how about doing this instead:

 - promote the --make-sbuild-tarball option more in the EXAMPLES section of the
   sbuild-createchroot man page as it is already done in the sbuild wiki page.

 - when creating a directory based schroot, add union-type=overlay option by
   default

What do you think?

cheers, josch
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