GNU bug report logs - #33171
TMPDIR and build containers

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: "pelzflorian (Florian Pelz)" <pelzflorian <at> pelzflorian.de>
To: bug-guix <at> gnu.org
Subject: TMPDIR and build containers
Date: Sat, 27 Oct 2018 03:23:36 +0200

Hello,

The manual says that TMPDIR does not leak into the build environment:

>    You can influence the directory where the daemon stores build trees
> via the ‘TMPDIR’ environment variable.  However, the build tree within
> the chroot is always called ‘/tmp/guix-build-NAME.drv-0’, where NAME is
> the derivation name—e.g., ‘coreutils-8.24’.  This way, the value of
> ‘TMPDIR’ does not leak inside build environments, which avoids
> discrepancies in cases where build processes capture the name of their
> build tree.


However, later it says:

>    When the daemon performs a build on behalf of the user, it creates a
> build directory under ‘/tmp’ or under the directory specified by its
> ‘TMPDIR’ environment variable; this directory is shared with the
> container for the duration of the build.  Be aware that using a
> directory other than ‘/tmp’ can affect build results—for example, with a
> longer directory name, a build process that uses Unix-domain sockets
> might hit the name length limitation for ‘sun_path’, which it would
> otherwise not hit.


This seems like a contradiction, or do I misunderstand?

Regards,
Florian

Message #10 received at 33171-done <at> debbugs.gnu.org (full text, mbox):

From: ludo <at> gnu.org (Ludovic Courtès)
To: "pelzflorian \(Florian Pelz\)" <pelzflorian <at> pelzflorian.de>
Cc: 33171-done <at> debbugs.gnu.org
Subject: Re: bug#33171: TMPDIR and build containers
Date: Thu, 01 Nov 2018 16:09:02 +0100

Hello Florian,

"pelzflorian (Florian Pelz)" <pelzflorian <at> pelzflorian.de> skribis:

> The manual says that TMPDIR does not leak into the build environment:
>
>>    You can influence the directory where the daemon stores build trees
>> via the ‘TMPDIR’ environment variable.  However, the build tree within
>> the chroot is always called ‘/tmp/guix-build-NAME.drv-0’, where NAME is
>> the derivation name—e.g., ‘coreutils-8.24’.  This way, the value of
>> ‘TMPDIR’ does not leak inside build environments, which avoids
>> discrepancies in cases where build processes capture the name of their
>> build tree.
>
>
> However, later it says:
>
>>    When the daemon performs a build on behalf of the user, it creates a
>> build directory under ‘/tmp’ or under the directory specified by its
>> ‘TMPDIR’ environment variable; this directory is shared with the
>> container for the duration of the build.  Be aware that using a
>> directory other than ‘/tmp’ can affect build results—for example, with a
>> longer directory name, a build process that uses Unix-domain sockets
>> might hit the name length limitation for ‘sun_path’, which it would
>> otherwise not hit.
>
>
> This seems like a contradiction, or do I misunderstand?

Indeed.  The sentences that starts with “Be aware” is inaccurate; I’ll
remove it.

Thank you!

Ludo’.

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