[buildd-tools-devel] Bug#797781: Bug#797781: diffoscope does not seem to work with schroot]

[Aurelien Jarno]

On 2015-09-06 19:01, Roger Leigh wrote:
> On 06/09/2015 18:28, Aurelien Jarno wrote:
> >On 2015-09-02 14:28, Santiago Vila wrote:
> >>Hello.
> >>
> >>I've just reassigned this report to schroot.
> >>
> >>Below is the reason.
> >>
> >>Thanks.
> >>
> >>----- Forwarded message from Mattia Rizzolo <mattia at mapreri.org> -----
> >>
> >>Date: Wed, 2 Sep 2015 14:08:42 +0000
> >>From: Mattia Rizzolo <mattia at mapreri.org>
> >>To: Santiago Vila <sanvila at debian.org>, 797781 at bugs.debian.org
> >>Subject: [Reproducible-builds] Bug#797781: Bug#797781: diffoscope does not seem to work with schroot
> >>User-Agent: Every email client sucks, this one just sucks less.
> >>
> >>On Wed, Sep 02, 2015 at 01:41:23PM +0000, Santiago Vila wrote:
> >>>Package: diffoscope
> >>>Version: 31
> >>>
> >>>Greetings. I'm running jessie with several chroots created with
> >>>schroot. As a normal user, I do this:
> >>>
> >>>schroot -c sid
> >>>diffoscope some.deb someother.deb
> >>>
> >>>and this is the result:
> >>>
> >>>CRITICAL /dev/shm is not available or not on a tmpfs. Unable to create semaphore.
> >>>
> >>>I believe such error is not supposed to happen.
> >>
> >>Well, quite a lot of stuff requires shm nowadays.
> >>
> >>Consider that we rb people run diffoscope inside scrhoot, and it just
> >>works.  We have
> >>
> >>     /dev/shm    /dev/shm    none    rw,bind     0   0
> >>
> >>in /etc/schroot/default/fstab.
> >>
> >>
> >>Personally I'd not consider this a diffoscope bug.
> >
> >The buildd flavour of the configuration mount a tmpfs in /dev/shm. AFAIK
> >this is not done for the default flavour as too options are possible
> >there:
> >- Bind mount like above. This means sharing the shm directory with the
> >   outside world. This might have some security implications, and
> >   unwanted consequences.
> >- Empty tmpfs like for buildds. This means the processes do not have
> >   accesses to shared memory from processes outside of the chroot.
> >
> >Depending on how the user want to use schroot, one or the other
> >configuration should be used. I don't know how we should choose the
> >default one.
> 
> I would think the main question is this:
> - does any process in the build chroot need to share memory with the host
> using POSIX SHM?
> 
> I can't think of any valid reason to do so in the context of package
> building, so it should be safe to simply mount an empty tmpfs in the chroot
> in all cases.

For what I understand, the bug has not been reported in the context of
package building. I think the user uses schroot to execute diffoscope on
a different environment (sid) than the host machine (stable) in order to
get the latest version.

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien at aurel32.net                 http://www.aurel32.net