In /etc/ntp.conf you find the line `server 0.pool.ntp.org iburst`. What does the `iburst` keyword do?
LPIC-1 Exam 102-500, objective 108. Essential system services medium
Draft — not checked yet. This question was written from the published exam objectives and cites the clause it comes from, but nobody has yet read it against that clause and signed for it.
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The options
Not correct It marks the server as the preferred source, overriding ntpd's own selection algorithm.
Wrong. That is what the separate `prefer` keyword does. iburst says nothing about which source wins the selection.
Not correct It allows this host to serve time to other clients on the network.
Wrong. Serving time is controlled by ntpd's restrict lines and by whether the daemon listens on the network at all, not by a per-server keyword.
Not correct It forces the clock to be stepped rather than slewed on the first correction.
Wrong. Step-versus-slew behaviour is governed by the tinker panic / -g settings in ntpd and by makestep in chrony, not by iburst.
Correct It sends a rapid burst of packets when the server is unreachable, so the initial synchronisation happens in seconds rather than minutes.
Correct. iburst sends a short burst of eight packets instead of one whenever the server is unreachable, which in practice means at start-up, cutting the time to first sync dramatically.
Why
pool.ntp.org is a large volunteer pool of public time servers reached through round-robin DNS; the numbered hostnames 0. through 3. (and the regional variants) are the conventional way to configure several distinct members. iburst is safe and near-universal on client `server` lines because it only affects behaviour while the source is unreachable. chrony's chrony.conf uses the same keyword, and its `pool` directive takes several addresses from one name at once.
Where this comes from
- Cited
- LPI exam objective 108.1
- What it says
- Awareness of the ntp.conf configuration file and the use of public NTP server pools.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 108 and space the ones you get wrong.