[Bug 1206164] [NEW] /etc/network/if-up.d/ntpdate does not detach correctly

[Scott Moser]

Public bug reported:

It seems that the intent of /etc/network/if-up.d/ntpdate is to
background itself, as it creates a subshell with &.

As reported in bug 1202758, this doesn't seem to work correctly.  That
doesn't close the file descriptors.  As a result, if something is
waiting on the output of 'ifup', it will sit and wait until ntpdate is
finished.

Example:
$ time sudo sh -c 'o=$(sh -c "ifdown eth0 ; ifup eth0" 2>&1) ; echo $o'

If we change the way it detaches itself to close stdout, stdderr, and
stdin, then we're fine.

I'm reporting this, but I'm not sure how much of a real problem it is.  As if th
e command sends stdin and stdout to /dev/null, then debugging its output would b
e more difficult.

Example diff:
$ diff -u /etc/network/if-up.d/ntpdate.dist /etc/network/if-up.d/ntpdate
--- /etc/network/if-up.d/ntpdate.dist  2013-07-29 15:47:54.242781947 +0000
+++ /etc/network/if-up.d/ntpdate 2013-07-29 15:48:06.946781947 +0000
@@ -56,4 +56,4 @@
   lockfile-remove $LOCKFILE
 fi

-) &
+) </dev/null >/dev/null 2>&1 &

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: ntpdate 1:4.2.6.p5+dfsg-2ubuntu2
ProcVersionSignature: User Name 3.10.0-5.15-generic 3.10.2
Uname: Linux 3.10.0-5-generic x86_64
ApportVersion: 2.11-0ubuntu1
Architecture: amd64
Date: Mon Jul 29 15:32:30 2013
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ntp
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.network.if.up.d.ntpdate: 2013-07-29T15:32:03.567775

** Affects: ntp (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug saucy uec-images

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Title:
  /etc/network/if-up.d/ntpdate does not detach correctly

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