ntp init script started multiple times - causing 180 seconds wait on boot

[Kjell Braden]

Binary package hint: ntp

ntp in intrepid causes to boot to wait 180 seconds because it's started three times: once from /etc/network/if-up.d/ntpdate, which locks the lockfile, and twice from upstart (no idea why, however, I see two processes: one is "invoke-rc.d ntp start" and one is something like "/etc/rc2.d/S23ntp start").

The latter both cause the boot process to stop because of lockfile-create retrying 9 times to get the lockfile.

$ LC_ALL=C apt-cache policy ntp
ntp:
  Installed: 1:4.2.4p4+dfsg-6ubuntu1
  Candidate: 1:4.2.4p4+dfsg-6ubuntu1
  Version table:
 *** 1:4.2.4p4+dfsg-6ubuntu1 0
        500 http://archive.ubuntu.com intrepid/main Packages
        100 /var/lib/dpkg/status

[Daniel J Blueman (danielblueman)]

It's a race-condition, and is called from the ntpdate and ntp script in the DHCP exit-hook script dir:

# ls -l /etc/dhcp3/dhclient-exit-hooks.d/ntp*
-rw-r--r-- 1 root root 1242 2008-03-07 20:37 /etc/dhcp3/dhclient-exit-hooks.d/ntp
-rw-r--r-- 1 root root 802 2008-06-19 04:04 /etc/dhcp3/dhclient-exit-hooks.d/ntpdate

I see these processes:

root 6693 1 0 19:06 ? 00:00:00 /sbin/dhclient -d -sf /usr/lib/NetworkManager/nm-dhcp-client.action -pf /var/run/dhclient-eth0.pid -lf /var/run/dhclient-eth0.lease -cf /var/run/nm-dhclient-eth0.conf eth0
root 6752 1 0 19:06 ? 00:00:00 /bin/sh /etc/network/if-up.d/ntpdate
root 6756 6752 0 19:06 ? 00:00:00 lockfile-touch /var/lock/ntpdate
root 6788 6752 0 19:06 ? 00:00:00 /bin/sh /usr/sbin/invoke-rc.d --quiet ntp start
root 6804 6788 0 19:06 ? 00:00:00 /bin/sh /etc/init.d/ntp start
root 6811 6804 0 19:06 ? 00:00:00 lockfile-create /var/lock/ntpdate

It's a regression in 8.10, but as it's not installed per default, people aren't bumping into it.

The lockfile-create/remove/touchlock binaries are provided by lockfile-progs, which are a simple C wrapper around lockfile_touch(3). See 'man lockfile_touch'.

[Kees Cook (kees)]

It's actually not as much a race as a straight-up dead-lock. ntpdate tries to use the same lockfile as ntpd, and ntpdate calls ntpd stop/start, which blocks, waiting for the lock that ntpdate just created.

[Launchpad Janitor (janitor)]

This bug was fixed in the package ntp - 1:4.2.4p4+dfsg-6ubuntu2

---------------
ntp (1:4.2.4p4+dfsg-6ubuntu2) intrepid; urgency=low

  * debian/ntpdate.ifup: use a different lockfile to avoid dead-locks
    when restarting ntpd (LP: #246203).

 -- Kees Cook <email address hidden> Wed, 20 Aug 2008 09:48:33 -0700