diff options
author | Peter A. Bigot <pab@pabigot.com> | 2018-04-09 13:39:16 -0500 |
---|---|---|
committer | Sven Eden <yamakuzure@gmx.net> | 2018-08-24 16:47:08 +0200 |
commit | b6f89490bb8cebc087140af940c876124bd78263 (patch) | |
tree | 90b93174c8a373fce5e0b3995fbd0a7e80571e06 /man/elogind-time-wait-sync.service.xml | |
parent | 66f37389209ce6f969d800ddecbf6a7972ef00da (diff) |
time-wait-sync: use watchfile to coordinate with timesyncd
Systems that have an accurate real-time clock may have an initial
unsynchronized time that is close enough to the synchronized time that
the final adjustment doesn't trigger a waking "clock set" event. Have
timesyncd touch a file in its runtime directory as a secondary signal
for synchronization. Continue to support the timerfd-based trigger as a
sufficient condition when the watchfile is not present.
Closes issue #8683
Diffstat (limited to 'man/elogind-time-wait-sync.service.xml')
-rw-r--r-- | man/elogind-time-wait-sync.service.xml | 30 |
1 files changed, 18 insertions, 12 deletions
diff --git a/man/elogind-time-wait-sync.service.xml b/man/elogind-time-wait-sync.service.xml index 559379b2e..b3e158ce6 100644 --- a/man/elogind-time-wait-sync.service.xml +++ b/man/elogind-time-wait-sync.service.xml @@ -46,24 +46,30 @@ <title>Description</title> <para><filename>elogind-time-wait-sync</filename> is a system service that delays the start of units that depend on - <filename>time-sync.target</filename> until <filename>elogind-timesyncd.service</filename> or something else has - set the system time and marked it as synchronized. Reaching this state generally requires synchronization with an - external source, such as an NTP server.</para> + <filename>time-sync.target</filename> until the system time has been synchronized with an accurate time source by + <filename>elogind-timesyncd.service</filename>.</para> - <para>When this unit is not enabled the <filename>time-sync.target</filename> synchronization point may be reached - as soon as the system time is advanced by <filename>elogind-timesyncd.service</filename> to the time stored at the - last shutdown. That time may not meet the expectations of dependent services that require an accurate - clock.</para> + <para><filename>elogind-timesyncd.service</filename> notifies on successful synchronization. + <filename>elogind-time-wait-sync</filename> also tries to detect when the kernel marks the time as synchronized, + but this detection is not reliable and is intended only as a fallback for other servies that can be used to + synchronize time (e.g., ntpd, chronyd).</para> </refsect1> <refsect1> - <title>Notes</title> + <title>Files</title> + + <variablelist> + <varlistentry> + <term><filename>/run/systemd/timesync/synchronized</filename></term> + + <listitem> + <para>The presence of this file indicates to this service that the system clock has been synchronized.</para> + </listitem> + + </varlistentry> + </variablelist> - <para>This service works correctly with a time synchronization service like - <filename>elogind-timesyncd.service</filename> that uses the same protocol as NTP to set the time from a - synchronized source. When used with time synchronization services that follow a different protocol the event of - setting synchronized time may not be detected in which case this service will not complete.</para> </refsect1> <refsect1> |