bug#19771: Missing documentation on enviroment variables for guix-deamon

[ludo@gnu.org (Ludovic Courtès)]

Andrei Osipov <andrspv@gmail.com> skribis:

> <andreoss`> how to change the temporary directory from /tmp to /var/tmp?
>                                                                         [08:14]
> <andreoss`> i have /tmp as tmpfs and it has no enough space to build gcc
> <Sleep_Walker> hm, I can't find it either in ./configure, either as parameter
>                to guix-daemon                                           [08:29]
> <Sleep_Walker> it seems it could respect TMPDIR environment variable    [08:34]
> <Sleep_Walker> andreoss`: could you confirm?                            [08:36]
> <Sleep_Walker> export TMPDIR=/var/tmp ; guix-daemon <your_parameters>
> <andreoss`> Sleep_Walker: confirmed                                     [08:39]

I’ve added two paragraphs to that effect:

     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.

     The build directory is automatically deleted upon completion, unless
  the build failed and the client specified ‘--keep-failed’ (*note
  ‘--keep-failed’: Invoking guix build.).

Thanks for the report!

Ludo’.