\u2013 Chrony provides another implementation of NTP.
\n\u2013 Chrony is designed for systems that are often powered down or disconnected from the network.
\n\u2013 The main configuration file is \/etc\/chrony.conf.
\n\u2013 Parameters are similar to those in the \/etc\/ntp.conf file.
\n\u2013 chronyd is the daemon that runs in user space.
\n\u2013 chronyc is a command-line program that provides a command prompt and a number of commands. Examples:
\ntracking: Displays system time information
\nsources: Displays information about current sources.<\/p>\n
Installing Chrony<\/p>\n
Install the chrony package by using the following command:<\/p>\n
# yum install chrony
\nUse the following commands to start chronyd and to ensure chronyd starts at boot time:<\/p>\n
# systemctl start chronyd
\n# systemctl enable chronyd
\nConfiguring Chrony<\/p>\n
A sample configuration would look like below :<\/p>\n
# cat \/etc\/chrony.conf
\nserver a.b.c offline
\nserver d.e.f offline
\nserver g.h.i offline
\nkeyfile \/etc\/chrony.keys generatecommandkey
\ndriftfile \/var\/lib\/chrony\/drift makestep 10 3
\nThe parameters are described as follows:
\nserver: Identifies the NTP servers you want to use. The offline keyword indicates that the servers are not contacted until chronyd receives notification that the link to the Internet is present.
\nkeyfile: File containing administrator password. Password allows chronyc to log in to chronyd and notify chronyd of the presence of the link to the Internet.
\ngeneratecommandkey: Generates a random password automatically on the first chronyd start.
\ndriftfile: Location and name of file containing drift data.
\nmakestep: Step (start anew) system clock if a large correction is needed. The parameters 10 and 3 would step the system clock if the adjustment is larger than 10 seconds, but only in the first three clock updates.<\/p>\n
Although, all these parameters are not required. For this post purpose I am using only below two lines in the configuration file.<\/p>\n
# cat \/etc\/chrony.conf
\nserver 192.0.2.1
\nallow 192.0.2\/24
\nStarting chrony<\/p>\n
Use the systemctl command to start the chrony daemon, chronyd.<\/p>\n
# systemctl start chronyd
\nVerify<\/p>\n
To check if chrony is synchronized, use the tracking, sources, and sourcestats commands. Run the chronyc tracking command to check chrony tracking. Alternatively you could run chronyc to display a chronyc> prompt, and then run the tracking command from the chronyc> prompt.<\/p>\n
# chronyc tracking
\nReference ID : 192.0.2.1 (192.0.2.1)
\nStratum : 12
\nRef time (UTC) : Fri Aug 05 19:06:51 2016
\nSystem time : 0.000823375 seconds fast of NTP time
\nLast offset : 0.001989304 seconds
\nRMS offset : 0.060942811 seconds
\nFrequency : 1728.043 ppm slow
\nResidual freq : 1.100 ppm
\nSkew : 94.293 ppm
\nRoot delay\t : 0.000207 seconds
\nRoot dispersion : 0.016767 seconds
\nUpdate interval : 65.1 seconds
\nLeap status : Normal
\nSome of the important fields are :
\nReference ID: This is the reference ID and name (or IP address) if available, of the server to which the computer is currently synchronized.
\nStratum: The stratum indicates how many hops away from a computer with an attached reference clock you are.
\nRef time: This is the time (UT C) at which the last measurement from the reference source was processed.<\/p>\n
Run the chronyc sources command to display information about the current time sources that chronyd is accessing.<\/p>\n
# chronyc sources
\n210 Number of sources = 1
\nMS Name\/IP address Stratum Poll Reach LastRx Last sample
\n=============================================================================
\n^* 192.0.2.1 11 6 377 63 +1827us[+6783us]…
\nSome of the fields are described:
\nM: The mode of the source. ^ means a server, = means a peer, and # indicates
\na locally connected reference clock.
\nS: The state of the sources. \u201c*\u201d indicates the source to which chronyd is currently synchronized. \u201c+\u201d indicates acceptable sources that are combined with the selected source. \u201c-\u201d indicates acceptable sources that are excluded by the combining algorithm. \u201c?\u201d indicates sources to which connectivity has been lost or whose packets do not pass all tests. \u201cx\u201d indicates a clock that chronyd thinks is a false ticker, that is, its time is inconsistent with a majority of other sources. \u201c~\u201d indicates a source whose time appears to have too much variability. The \u201c?\u201d condition is also shown at start-up, until at least three samples have been gathered from it.
\nName\/IP address: This shows the name or the IP address of the source, or reference ID for reference clocks.<\/p>\n
Run the chronyc sourcestats command. This command displays information about the drift rate and offset estimation
\nprocess for each of the sources currently being examined by chronyd.<\/p>\n
# chronyc sourcestats
\n210 Number of sources = 1
\nName\/IP Address NP NR Span Frequency Freq Skew Offset Std Dev
\n==================================================================================
\n192.0.2.1 5 4 259 -747.564 1623.869 -2873us 30ms
\nStop chrony<\/p>\n
Use the systemctl command to stop the chrony daemon, chronyd.<\/p>\n
# systemctl stop chronyd
\nRun the chronyc tracking command and notice chronyc cannot talk to the chronyd daemon.<\/p>\n
# chronyc tracking
\n506 Cannot talk to daemon<\/p>\n","protected":false},"excerpt":{"rendered":"
\u2013 Chrony provides another implementation of NTP. \u2013 Chrony is designed for systems that are often powered down or disconnected from the network. \u2013 The main configuration file is \/etc\/chrony.conf. \u2013 Parameters are similar to those in the \/etc\/ntp.conf file. \u2013 chronyd is the daemon that runs in user space. \u2013 chronyc is a command-line […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[73],"tags":[],"_links":{"self":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts\/6728"}],"collection":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6728"}],"version-history":[{"count":1,"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts\/6728\/revisions"}],"predecessor-version":[{"id":6729,"href":"https:\/\/mohan.sg\/index.php?rest_route=\/wp\/v2\/posts\/6728\/revisions\/6729"}],"wp:attachment":[{"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6728"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6728"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mohan.sg\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6728"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}