diff --git a/doc/faq.adoc b/doc/faq.adoc index 65f3522..1eadd09 100644 --- a/doc/faq.adoc +++ b/doc/faq.adoc @@ -49,6 +49,44 @@ added to +chrony+ to deal with this. == Configuration issues +=== What is the minimum recommended configuration for an NTP client? + +First, the client needs to know which NTP servers it should ask for the current +time. They are specified by the +server+ or +pool+ directive. The +pool+ +directive can be used for names that resolve to multiple addresses. For good +reliability the client should have at least three servers. The +iburst+ option +speeds up the initial synchronisation. + +To stabilize the initial synchronisation on the next start, the estimated drift +of the system clock is saved by adding the +driftfile+ directive. + +If the system clock can be far from the true time after boot for any reason, ++chronyd+ should be allowed to correct it quickly by stepping instead of +slewing, which would take a very long time. The +makestep+ directive does +that. + +In order to keep the real-time clock (RTC) close to the true time on Linux, so +the system time is reasonably close to the true time when it's initialized on +the next boot from the RTC, the +rtcsync+ directive enables a kernel mode in +which the system time is copied to the RTC every 11 minutes. + +If you want to use public NTP servers from the +http://www.pool.ntp.org/[pool.ntp.org] project, the minimal 'chrony.conf' file +could be: + +---- +pool pool.ntp.org iburst +driftfile /var/lib/chrony/drift +makestep 1 3 +rtcsync +---- + +=== How do I make an NTP server from an NTP client? + +You need to add an +allow+ directive to the 'chrony.conf' file in order to open +the NTP port and allow +chronyd+ to reply to client requests. +allow+ with no +specified subnet allows all IPv4 and IPv6 addresses. + === I have several computers on a LAN. Should be all clients of an external server? The best configuration is usually to make one computer the master, with