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

[Julian Taylor]

On Fri, Feb 7, 2014 at 2:09 PM, Antonio Terceiro <terceiro at 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=writeback, commit=3600 etc.)
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