Comment 16 for bug 14927

Message-ID: <email address hidden>
Date: Fri, 1 Apr 2005 23:13:02 +0100
From: Henning Makholm <email address hidden>
To: <email address hidden>
Cc: Thomas Hood <email address hidden>
Subject: Bug #302519: ifupdown: postinst fails

To the submitter: A better short-term workaround if you prefer not to
edit conffiles that are hopefully going to be fixed soon, is to do

# mkdir /var/run/network
# ln -sf /var/run/network/ /etc/network/run

Otherwise the underlying bug might show up next time you boot, anyway.

The culprit seems to be the following snippet (lines 92ff, reformated
for email) in the postinst of -4.12:

 if RUN_CANONICALDIR="$(readlink -f /etc/network/run)" &&
    [ "$RUN_CANONICALDIR" ] ; then
   if ! mkdir "$RUN_CANONICALDIR" ; then
      report_err "Failure creating directory ${RUN_CANONICALDIR}. Aborting."
      exit 1
   fi
 else
   report_err \
    "The canonical path of /etc/network/run could not be determined. Aborting."
   exit 1
 fi

The problem is that "readlink -f /etc/network/run" returns nothing and
exits with failure when /etc/network/run is a dangling symlink, so the
mkdir that is the point of this code never gets a chance to run.

This behavior is exhibited by the readlink in coreutils 5.2.1-2
(sid+sarge), but not for the readlink in debianutils 1.6.2woody1
(woody).

Code that depends on readlink -f being able to stop at a dangling
symlink also appears in /etc/init.d/{ifupdown,ifupdown-clean}
and will abort the boot initialization on systems where
/etc/network/run refers to a ramdisk. (Which I suppose is the default,
as I do not remember having done anything to redirect /etc/network/run
myself).

Refusing to work with dangling links is the documented behavior in GNU
readlink, so coreutils probably cannot be faulted for this. A
quick-and-dirty workaround that should work in the most common cases
would be to say

   $(readlink -f /etc/network/run || readlink /etc/network/run)

instead of just

   $(readlink -f /etc/network/run)

in all three affected files.

--
Henning Makholm "I ... I have to return some videos."