Public bug reported:
ntpdate and ntp conflict on the NTP well-known-socket. If ntp and
ntpdate 1:4.2.8p4+dfsg-3ubuntu5.5 are installed on Xenial, and there are
2 static interfaces configured, most often we find that ntpd is not
running after a reboot.
When the ntp service is started by systemd, ntp fails to bind the NTP
socket because ntpdate is running in the background. It's intended that
ntp and ntpdate try to avoid this conflict with a lock file, but the
locking mechanism was changed in ntpdate.if-up (from lockfile to flock),
but it was not changed in ntp.init. Previously the file locking
prevented ntp from trying to start when ntpdate was running. Not any
more.
Having multiple interfaces causes a much longer period of the socket
being unavailable, because the 2 ntpdate processes will get serialized
by the lock, while the ntp service is looking for a different lock, so
it just plows right in. Attempts by netdate.if-up to stop and start ntp
seem to overlap and when the final start is invoked, systemd seems to
thing ntp is already running, though it has failed.
In 1:4.2.8p4+dfsg-3ubuntu1 the following change was made:
debian/ntpdate.if-up: Drop lockfile mechanism as upstream is using flock now.
Looks like corresponds to rev 371 of debian/ntpdate.if-up from upstream.
This change diverged locking between ntpdate.if-up and ntp.init. This
was rectified in rev 451 of ntp.init, to use compatible locking, but
that doesn't appear in the Ubuntu version.
System Information:
lsb_release -rd:
Description: Ubuntu 16.04.2 LTS
Release: 16.04
apt-cache policy ntpdate:
ntpdate:
Installed: 1:4.2.8p4+dfsg-3ubuntu5.5
Candidate: 1:4.2.8p4+dfsg-3ubuntu5.5
Version table:
*** 1:4.2.8p4+dfsg-3ubuntu5.5 100
100 /var/lib/dpkg/status
apt-cache policy ntp:
ntp:
Installed: 1:4.2.8p4+dfsg-3ubuntu5.5
Candidate: 1:4.2.8p4+dfsg-3ubuntu5.5
Version table:
*** 1:4.2.8p4+dfsg-3ubuntu5.5 100
100 /var/lib/dpkg/status
** Affects: ntp (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1706818
Title:
mismatched file locking since 1:4.2.8p4+dfsg-3ubuntu1 causes race
leaving ntp dead on reboot
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