From: Miroslav Lichvar Date: Tue, 27 Mar 2018 15:57:17 +0000 (+0200) Subject: doc: improve FAQ X-Git-Tag: 3.3~4 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4b7cb161a81faa7d9f44e5bf7991c5fc8ebc5a49;p=thirdparty%2Fchrony.git doc: improve FAQ --- diff --git a/doc/faq.adoc b/doc/faq.adoc index 0b76dfe9..5bad34f3 100644 --- a/doc/faq.adoc +++ b/doc/faq.adoc @@ -393,16 +393,31 @@ things Some other program running on the system may be using the device. +=== What if my computer does not have an RTC or backup battery? + +In this case you can still use the `-s` option to set the system clock to the +last modification time of the drift file, which should correspond to the system +time when `chronyd` was previously stopped. The initial system time will be +increasing across reboots and applications started after `chronyd` will not +observe backward steps. + == NTP-specific issues -=== Can `chronyd` be driven from broadcast NTP servers? +=== Can `chronyd` be driven from broadcast/multicast NTP servers? + +No, the broadcast/multicast client mode is not supported and there is currently +no plan to implement it. While the mode may be useful to simplify configuration +of clients in large networks, it is inherently less accurate and less secure +(even with authentication) than the ordinary client/server mode. + +When configuring a large number of clients in a network, it is recommended to +use the `pool` directive with a DNS name which resolves to addresses of +multiple NTP servers. The clients will automatically replace the servers when +they become unreachable, or otherwise unsuitable for synchronisation, with new +servers from the pool. -No, the broadcast client mode is not supported and there is currently no plan -to implement it. The broadcast and multicast modes are inherently less -accurate and less secure (even with authentication) than the ordinary -server/client mode and they are not as useful as they used to be. Even with -very modest hardware a single NTP server can serve time to hundreds of -thousands of clients using the ordinary mode. +Even with very modest hardware, an NTP server can serve time to hundreds of +thousands of clients using the ordinary client/server mode. === Can `chronyd` transmit broadcast NTP packets?