Re: autopkgtest + chroot howto ? - Was: Re: Is it possible to run autopkgtest without a virtual machine ?

[Julian Taylor <jtaylor.debian@googlemail.com>]

On Fri, Feb 7, 2014 at 2:09 PM, Antonio Terceiro <terceiro@debian.org> wrote:

On Sun, Jan 26, 2014 at 06:09:51PM +0100, Martin Pitt wrote:
> I advise to use the schroot runner instead. schroots are easy to set
> up these days with mk-sbuild, and with some additional love (like
> installing and configuring apt-cacher-ng and symlinking
> /var/lib/schroot/union/overlay/ and /var/lib/schroot/unpack/ to /tmp/,
> and having /tmp on a tmpfs),  set up, tear down, and package
> installation are extremely fast.

This schroot tip is precious! I have just reduced the build time (which
was mostly spent installing dependencies -- I was already using
apt-cacher-ng) of a package from ~4min to ~30s!

But instead of symlinking /var/lib/schroot/union/overlay/¹ , I configured
my sbuild chroots adding

  union-overlay-directory=/dev/shm

you can archive similar speeds without a tmpfs using eatmydata, just stick
LD_PRELOAD=/usr/lib/libeatmydata/libeatmydata.so

in your rc equivalent.
This is also significantly faster than using dpkg --force-unsafe-io.

Using mount options that reduce failure safety on the partition/subvolume holding the chroot build folder also helps a bit (nobarrier, data="" commit=3600 etc.)