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diff --git a/doc/chronyc.adoc b/doc/chronyc.adoc new file mode 100644 index 0000000..b80cc1c --- /dev/null +++ b/doc/chronyc.adoc @@ -0,0 +1,1224 @@ +// This file is part of chrony +// +// Copyright (C) Richard P. Curnow 1997-2003 +// Copyright (C) Stephen Wadeley 2016 +// Copyright (C) Miroslav Lichvar 2009-2017 +// +// This program is free software; you can redistribute it and/or modify +// it under the terms of version 2 of the GNU General Public License as +// published by the Free Software Foundation. +// +// This program is distributed in the hope that it will be useful, but +// WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +// General Public License for more details. +// +// You should have received a copy of the GNU General Public License along +// with this program; if not, write to the Free Software Foundation, Inc., +// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + += chronyc(1) +:doctype: manpage +:man manual: User manual +:man source: chrony @CHRONY_VERSION@ + +== NAME + +chronyc - command-line interface for chrony daemon + +== SYNOPSIS + +*chronyc* [_OPTION_]... [_COMMAND_]... + +== DESCRIPTION + +*chronyc* is a command-line interface program which can be used to monitor +*chronyd*'s performance and to change various operating parameters whilst it is +running. + +If no commands are specified on the command line, *chronyc* will expect input +from the user. The prompt _chronyc>_ will be displayed when it is being run +from a terminal. If *chronyc*'s input or output are redirected from or to a file, +the prompt is not shown. + +There are two ways *chronyc* can access *chronyd*. One is the Internet +Protocol (IPv4 or IPv6) and the other is a Unix domain socket, which is +accessible locally by the root or _chrony_ user. By default, *chronyc* first +tries to connect to the Unix domain socket. The compiled-in default path is +_@CHRONYRUNDIR@/chronyd.sock_. If that fails (e.g. because *chronyc* is +running under a non-root user), it will try to connect to 127.0.0.1 and then +::1. + +Only the following monitoring commands, which do not affect the behaviour of +*chronyd*, are allowed from the network: *activity*, *manual list*, +*rtcdata*, *smoothing*, *sources*, *sourcestats*, *tracking*, *waitsync*. The +set of hosts from which *chronyd* will accept these commands can be configured +with the <<chrony.conf.adoc#cmdallow,*cmdallow*>> directive in the *chronyd*'s +configuration file or the <<cmdallow,*cmdallow*>> command in *chronyc*. By +default, the commands are accepted only from localhost (127.0.0.1 or ::1). + +All other commands are allowed only through the Unix domain socket. When sent +over the network, *chronyd* will respond with a '`Not authorised`' error, even +if it is from localhost. In chrony versions before 2.2 they were allowed +from the network if they were authenticated with a password, but that is no +longer supported. + +Having full access to *chronyd* via *chronyc* is more or less equivalent to +being able to modify the *chronyd*'s configuration file and restart it. + +== OPTIONS + +*-4*:: +With this option hostnames will be resolved only to IPv4 addresses. + +*-6*:: +With this option hostnames will be resolved only to IPv6 addresses. + +*-n*:: +This option disables resolving of IP addresses to hostnames, e.g. to avoid slow +DNS lookups. Long addresses will not be truncated to fit into the column. + +*-c*:: +This option enables printing of reports in a comma-separated values (CSV) +format. IP addresses will not be resolved to hostnames, time will be printed as +number of seconds since the epoch and values in seconds will not be converted +to other units. + +*-d*:: +This option enables printing of debugging messages if *chronyc* was compiled +with debugging support. + +*-m*:: +Normally, all arguments on the command line are interpreted as one command. +With this option multiple commands can be specified. Each argument will be +interpreted as a whole command. + +*-h* _host_:: +This option allows the user to specify which host (or comma-separated list of +addresses) running the *chronyd* program is to be contacted. This allows for +remote monitoring, without having to connect over SSH to the other host first. ++ +The default is to contact *chronyd* running on the same host where +*chronyc* is being run. + +*-p* _port_:: +This option allows the user to specify the UDP port number which the target +*chronyd* is using for its monitoring connections. This defaults to 323; there +would rarely be a need to change this. + +*-f* _file_:: +This option is ignored and is provided only for compatibility. + +*-a*:: +This option is ignored and is provided only for compatibility. + +*-v*:: +With this option *chronyc* displays its version number on the terminal and +exits. + +== COMMANDS + +This section describes each of the commands available within the *chronyc* +program. + +=== System clock + +[[tracking]]*tracking*:: +The *tracking* command displays parameters about the system's clock +performance. An example of the output is shown below. ++ +---- +Reference ID : CB00710F (foo.example.net) +Stratum : 3 +Ref time (UTC) : Fri Jan 27 09:49:17 2017 +System time : 0.000006523 seconds slow of NTP time +Last offset : -0.000006747 seconds +RMS offset : 0.000035822 seconds +Frequency : 3.225 ppm slow +Residual freq : -0.000 ppm +Skew : 0.129 ppm +Root delay : 0.013639022 seconds +Root dispersion : 0.001100737 seconds +Update interval : 64.2 seconds +Leap status : Normal +---- ++ +The fields are explained as follows: ++ +*Reference ID*::: +This is the reference ID and name (or IP address) of the server to which the +computer is currently synchronised. For IPv4 addresses, the reference ID is +equal to the address and for IPv6 addresses it is the first 32 bits of the MD5 +sum of the address. ++ +If the reference ID is _7F7F0101_ and there is no name or IP address, it means +the computer is not synchronised to any external source and that you have the +_local_ mode operating (via the <<local,*local*>> command in *chronyc*, or the +<<chrony.conf.adoc#local,*local*>> directive in the configuration file). ++ +The reference ID is printed as a hexadecimal number. Note that in older +versions it used to be printed in quad-dotted notation and could be confused +with an IPv4 address. +*Stratum*::: +The stratum indicates how many hops away from a computer with an attached +reference clock we are. Such a computer is a stratum-1 computer, so the +computer in the example is two hops away (i.e. _foo.example.net_ is a +stratum-2 and is synchronised from a stratum-1). +*Ref time*::: +This is the time (UTC) at which the last measurement from the reference +source was processed. +*System time*::: +In normal operation, *chronyd* by default never steps the system clock, because +any jump in the time can have adverse consequences for certain application +programs. Instead, any error in the system clock is corrected by slightly +speeding up or slowing down the system clock until the error has been removed, +and then returning to the system clock's normal speed. A consequence of this is +that there will be a period when the system clock (as read by other programs) +will be different from *chronyd*'s estimate of the current true time (which it +reports to NTP clients when it is operating in server mode). The value reported +on this line is the difference due to this effect. +*Last offset*::: +This is the estimated local offset on the last clock update. +*RMS offset*::: +This is a long-term average of the offset value. +*Frequency*::: +The '`frequency`' is the rate by which the system's clock would be wrong if +*chronyd* was not correcting it. It is expressed in ppm (parts per million). +For example, a value of 1 ppm would mean that when the system's clock thinks it +has advanced 1 second, it has actually advanced by 1.000001 seconds relative to +true time. +*Residual freq*::: +This shows the '`residual frequency`' for the currently selected reference +source. This reflects any difference between what the measurements from the +reference source indicate the frequency should be and the frequency currently +being used. ++ +The reason this is not always zero is that a smoothing procedure is +applied to the frequency. Each time a measurement from the reference +source is obtained and a new residual frequency computed, the estimated +accuracy of this residual is compared with the estimated accuracy (see +'`skew`' next) of the existing frequency value. A weighted average is +computed for the new frequency, with weights depending on these accuracies. +If the measurements from the reference source follow a consistent trend, the +residual will be driven to zero over time. +*Skew*::: +This is the estimated error bound on the frequency. +*Root delay*::: +This is the total of the network path delays to the stratum-1 computer from +which the computer is ultimately synchronised. +*Root dispersion*::: +This is the total dispersion accumulated through all the computers back to +the stratum-1 computer from which the computer is ultimately synchronised. +Dispersion is due to system clock resolution, statistical measurement +variations, etc. ++ +An absolute bound on the computer's clock accuracy (assuming the stratum-1 +computer is correct) is given by: ++ +---- +clock_error <= |system_time_offset| + root_dispersion + (0.5 * root_delay) +---- +*Update interval*::: +This is the interval between the last two clock updates. +*Leap status*::: +This is the leap status, which can be _Normal_, _Insert second_, _Delete +second_ or _Not synchronised_. + +[[makestep]]*makestep*:: +*makestep* _threshold_ _limit_:: +Normally *chronyd* will cause the system to gradually correct any time offset, +by slowing down or speeding up the clock as required. In certain situations, +the system clock might be so far adrift that this slewing process would take a +very long time to correct the system clock. ++ +The *makestep* command can be used in this situation. There are two forms of +the command. The first form has no parameters. It tells *chronyd* to cancel any +remaining correction that was being slewed and jump the system clock by the +equivalent amount, making it correct immediately. ++ +The second form configures the automatic stepping, similarly to the +<<chrony.conf.adoc#makestep,*makestep*>> directive. It has two parameters, +stepping threshold (in seconds) and number of future clock updates for which +the threshold will be active. This can be used with the <<burst,*burst*>> +command to quickly make a new measurement and correct the clock by stepping if +needed, without waiting for *chronyd* to complete the measurement and update +the clock. ++ +---- +makestep 0.1 1 +burst 1/2 +---- ++ +BE WARNED: Certain software will be seriously affected by such jumps in the +system time. (That is the reason why *chronyd* uses slewing normally.) + +[[maxupdateskew]]*maxupdateskew* _skew-in-ppm_:: +This command has the same effect as the +<<chrony.conf.adoc#maxupdateskew,*maxupdateskew*>> directive in the +configuration file. + +[[waitsync]]*waitsync* [_max-tries_ [_max-correction_ [_max-skew_ [_interval_]]]]:: +The *waitsync* command waits for *chronyd* to synchronise. ++ +Up to four optional arguments can be specified. The first is the maximum number +of tries before giving up and returning a non-zero error code. When 0 is +specified, or there are no arguments, the number of tries will not be limited. ++ +The second and third arguments are the maximum allowed remaining correction of +the system clock and the maximum allowed skew (in ppm) as reported by the +<<tracking,*tracking*>> command in the *System time* and *Skew* fields. If not +specified or zero, the value will not be checked. ++ +The fourth argument is the interval specified in seconds in which the check is +repeated. The interval is 10 seconds by default. ++ +An example is: ++ +---- +waitsync 60 0.01 +---- ++ +which will wait up to about 10 minutes (60 times 10 seconds) for *chronyd* to +synchronise to a source and the remaining correction to be less than 10 +milliseconds. + +=== Time sources + +[[sources]]*sources* [*-v*]:: +This command displays information about the current time sources that *chronyd* +is accessing. ++ +The optional argument *-v* can be specified, meaning _verbose_. In this case, +extra caption lines are shown as a reminder of the meanings of the columns. ++ +---- +210 Number of sources = 3 +MS Name/IP address Stratum Poll Reach LastRx Last sample +=============================================================================== +#* GPS0 0 4 377 11 -479ns[ -621ns] +/- 134ns +^? foo.example.net 2 6 377 23 -923us[ -924us] +/- 43ms +^+ bar.example.net 1 6 377 21 -2629us[-2619us] +/- 86ms +---- ++ +The columns are as follows: ++ +*M*::: +This indicates the mode of the source. _^_ means a server, _=_ means a peer +and _#_ indicates a locally connected reference clock. +*S*::: +This column indicates the state of the source. +* _*_ indicates the source to which *chronyd* is currently synchronised. +* _+_ indicates acceptable sources which are combined with the selected + source. +* _-_ indicates acceptable sources which are excluded by the combining + algorithm. +* _?_ indicates sources to which connectivity has been lost or whose packets + do not pass all tests. It is also shown at start-up, until at least 3 samples + have been gathered from it. +* _x_ indicates a clock which *chronyd* thinks is a falseticker (i.e. its + time is inconsistent with a majority of other sources). +* _~_ indicates a source whose time appears to have too much variability. +*Name/IP address*::: +This shows the name or the IP address of the source, or reference ID for reference +clocks. +*Stratum*::: +This shows the stratum of the source, as reported in its most recently +received sample. Stratum 1 indicates a computer with a locally attached +reference clock. A computer that is synchronised to a stratum 1 computer is +at stratum 2. A computer that is synchronised to a stratum 2 computer is at +stratum 3, and so on. +*Poll*::: +This shows the rate at which the source is being polled, as a base-2 +logarithm of the interval in seconds. Thus, a value of 6 would indicate that +a measurement is being made every 64 seconds. *chronyd* automatically varies +the polling rate in response to prevailing conditions. +*Reach*::: +This shows the source's reachability register printed as an octal number. The +register has 8 bits and is updated on every received or missed packet from +the source. A value of 377 indicates that a valid reply was received for all +from the last eight transmissions. +*LastRx*::: +This column shows how long ago the last good sample (which is shown in the next +column) was received from the source. Measurements that failed some tests are +ignored. This is normally in seconds. The letters _m_, _h_, _d_ or _y_ indicate +minutes, hours, days, or years. +*Last sample*::: +This column shows the offset between the local clock and the source at the +last measurement. The number in the square brackets shows the actual measured +offset. This can be suffixed by _ns_ (indicating nanoseconds), _us_ +(indicating microseconds), _ms_ (indicating milliseconds), or _s_ (indicating +seconds). The number to the left of the square brackets shows the original +measurement, adjusted to allow for any slews applied to the local clock +since. The number following the _+/-_ indicator shows the margin of error in +the measurement. Positive offsets indicate that the local clock is ahead of +the source. + +[[sourcestats]]*sourcestats* [*-v*]:: +The *sourcestats* command displays information about the drift rate and offset +estimation process for each of the sources currently being examined by +*chronyd*. ++ +The optional argument *-v* can be specified, meaning _verbose_. In this case, +extra caption lines are shown as a reminder of the meanings of the columns. ++ +An example report is: ++ +---- +210 Number of sources = 1 +Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev +=============================================================================== +foo.example.net 11 5 46m -0.001 0.045 1us 25us +---- ++ +The columns are as follows: ++ +*Name/IP Address*::: +This is the name or IP address of the NTP server (or peer) or reference ID of the +reference clock to which the rest of the line relates. +*NP*::: +This is the number of sample points currently being retained for the server. +The drift rate and current offset are estimated by performing a linear +regression through these points. +*NR*::: +This is the number of runs of residuals having the same sign following the +last regression. If this number starts to become too small relative to the +number of samples, it indicates that a straight line is no longer a good fit +to the data. If the number of runs is too low, *chronyd* discards older +samples and re-runs the regression until the number of runs becomes +acceptable. +*Span*::: +This is the interval between the oldest and newest samples. If no unit is +shown the value is in seconds. In the example, the interval is 46 minutes. +*Frequency*::: +This is the estimated residual frequency for the server, in parts per +million. In this case, the computer's clock is estimated to be running 1 part +in 10^9 slow relative to the server. +*Freq Skew*::: +This is the estimated error bounds on *Freq* (again in parts per million). +*Offset*::: +This is the estimated offset of the source. +*Std Dev*::: +This is the estimated sample standard deviation. + +[[reselect]]*reselect*:: +To avoid excessive switching between sources, *chronyd* can stay synchronised +to a source even when it is not currently the best one among the available +sources. ++ +The *reselect* command can be used to force *chronyd* to reselect the best +synchronisation source. + +[[reselectdist]]*reselectdist* _distance_:: +The *reselectdist* command sets the reselection distance. It is equivalent to +the <<chrony.conf.adoc#reselectdist,*reselectdist*>> directive in the +configuration file. + +=== NTP sources + +[[activity]]*activity*:: +This command reports the number of servers and peers that are online and +offline. If the *auto_offline* option is used in specifying some of the servers +or peers, the *activity* command can be useful for detecting when all of them +have entered the offline state after the network link has been disconnected. ++ +The report shows the number of servers and peers in 5 states: ++ +*online*::: +the server or peer is currently online (i.e. assumed by *chronyd* to be reachable) +*offline*::: +the server or peer is currently offline (i.e. assumed by *chronyd* to be +unreachable, and no measurements from it will be attempted.) +*burst_online*::: +a burst command has been initiated for the server or peer and is being +performed; after the burst is complete, the server or peer will be returned to +the online state. +*burst_offline*::: +a burst command has been initiated for the server or peer and is being +performed; after the burst is complete, the server or peer will be returned to +the offline state. +*unresolved*::: +the name of the server or peer was not resolved to an address yet; this source is +not visible in the *sources* and *sourcestats* reports. + +[[ntpdata]]*ntpdata* [_address_]:: +The *ntpdata* command displays the last valid measurement and other +NTP-specific information about the specified NTP source, or all NTP sources if +no address was specified. An example of the output is shown below. ++ +---- +Remote address : 203.0.113.15 (CB00710F) +Remote port : 123 +Local address : 203.0.113.74 (CB00714A) +Leap status : Normal +Version : 4 +Mode : Server +Stratum : 1 +Poll interval : 10 (1024 seconds) +Precision : -24 (0.000000060 seconds) +Root delay : 0.000015 seconds +Root dispersion : 0.000015 seconds +Reference ID : 47505300 (GPS) +Reference time : Fri Nov 25 15:22:12 2016 +Offset : -0.000060878 seconds +Peer delay : 0.000175634 seconds +Peer dispersion : 0.000000681 seconds +Response time : 0.000053050 seconds +Jitter asymmetry: +0.00 +NTP tests : 111 111 1111 +Interleaved : No +Authenticated : No +TX timestamping : Kernel +RX timestamping : Kernel +Total TX : 24 +Total RX : 24 +Total valid RX : 24 +---- ++ +The fields are explained as follows: ++ +*Remote address*::: +The IP address of the NTP server or peer, and the corresponding reference ID. +*Remote port*::: +The UDP port number to which the request was sent. The standard NTP port is +123. +*Local address*::: +The local IP address which received the response, and the corresponding +reference ID. +*Leap status*::: +*Version*::: +*Mode*::: +*Stratum*::: +*Poll interval*::: +*Precision*::: +*Root delay*::: +*Root dispersion*::: +*Reference ID*::: +*Reference time*::: +The NTP values from the last valid response. +*Offset*::: +*Peer delay*::: +*Peer dispersion*::: +The measured values. +*Response time*::: +The time the server or peer spent in processing of the request and waiting +before sending the response. +*Jitter asymmetry*::: +The estimated asymmetry of network jitter on the path to the source. The +asymmetry can be between -0.5 and 0.5. A negative value means the delay of +packets sent to the source is more variable than the delay of packets sent +from the source back. +*NTP tests*::: +Results of RFC 5905 tests 1 through 3, 5 through 7, and tests for maximum +delay, delay ratio, delay dev ratio, and synchronisation loop. +*Interleaved*::: +This shows if the response was in the interleaved mode. +*Authenticated*::: +This shows if the response was authenticated. +*TX timestamping*::: +The source of the local transmit timestamp. Valid values are _Daemon_, +_Kernel_, and _Hardware_. +*RX timestamping*::: +The source of the local receive timestamp. +*Total TX*::: +The number of packets sent to the source. +*Total RX*::: +The number of all packets received from the source. +*Total valid RX*::: +The number of valid packets received from the source. + +[[add_peer]]*add peer* _address_ [_option_]...:: +The *add peer* command allows a new NTP peer to be added whilst +*chronyd* is running. ++ +Following the words *add peer*, the syntax of the following +parameters and options is similar to that for the +<<chrony.conf.adoc#peer,*peer*>> directive in the configuration file. +The following peer options can be set in the command: *port*, *minpoll*, +*maxpoll*, *presend*, *maxdelayratio*, *maxdelay*, *key*. ++ +An example of using this command is shown below. ++ +---- +add peer foo.example.net minpoll 6 maxpoll 10 key 25 +---- + +[[add_server]]*add server* _address_ [_option_]...:: +The *add server* command allows a new NTP server to be added whilst +*chronyd* is running. ++ +Following the words *add server*, the syntax of the following parameters and +options is similar to that for the <<chrony.conf.adoc#server,*server*>> +directive in the configuration file. +The following server options can be set in the command: *port*, *minpoll*, +*maxpoll*, *presend*, *maxdelayratio*, *maxdelay*, *key*. ++ +An example of using this command is shown below: ++ +---- +add server foo.example.net minpoll 6 maxpoll 10 key 25 +---- + +[[delete]]*delete* _address_:: +The *delete* command allows an NTP server or peer to be removed +from the current set of sources. + +[[burst]] +*burst* _good_/_max_ [_mask_/_masked-address_]:: +*burst* _good_/_max_ [_masked-address_/_masked-bits_]:: +*burst* _good_/_max_ [_address_]:: +The *burst* command tells *chronyd* to make a set of measurements to each of +its NTP sources over a short duration (rather than the usual periodic +measurements that it makes). After such a burst, *chronyd* will revert to the +previous state for each source. This might be either online, if the source was +being periodically measured in the normal way, or offline, if the source had +been indicated as being offline. (A source can be switched between the online +and offline states with the <<online,*online*>> and <<offline,*offline*>> +commands.) ++ +The _mask_ and _masked-address_ arguments are optional, in which case *chronyd* +will initiate a burst for all of its currently defined sources. ++ +The arguments have the following meaning and format: ++ +_good_::: +This defines the number of good measurements that *chronyd* will want to +obtain from each source. A measurement is good if it passes certain tests, +for example, the round trip time to the source must be acceptable. (This +allows *chronyd* to reject measurements that are likely to be bogus.) +_max_::: +This defines the maximum number of measurements that *chronyd* will attempt +to make, even if the required number of good measurements has not been +obtained. +_mask_::: +This is an IP address with which the IP address of each of *chronyd*'s +sources is to be masked. +_masked-address_::: +This is an IP address. If the masked IP address of a source matches this +value then the burst command is applied to that source. +_masked-bits_::: +This can be used with _masked-address_ for CIDR notation, which is a shorter +alternative to the form with mask. +_address_::: +This is an IP address or a hostname. The burst command is applied only to +that source. +:: ++ +If no _mask_ or _masked-address_ arguments are provided, every source will be +matched. ++ +An example of the two-argument form of the command is: ++ +---- +burst 2/10 +---- ++ +This will cause *chronyd* to attempt to get two good measurements from each +source, stopping after two have been obtained, but in no event will it try more +than ten probes to the source. ++ +Examples of the four-argument form of the command are: ++ +---- +burst 2/10 255.255.0.0/1.2.0.0 +burst 2/10 2001:db8:789a::/48 +---- ++ +In the first case, the two out of ten sampling will only be applied to sources +whose IPv4 addresses are of the form _1.2.x.y_, where _x_ and _y_ are +arbitrary. In the second case, the sampling will be applied to sources whose +IPv6 addresses have first 48 bits equal to _2001:db8:789a_. ++ +Example of the three-argument form of the command is: ++ +---- +burst 2/10 foo.example.net +---- + +[[maxdelay]]*maxdelay* _address_ _delay_:: +This allows the *maxdelay* option for one of the sources to be modified, in the +same way as specifying the *maxdelay* option for the +<<chrony.conf.adoc#server,*server*>> directive in the configuration file. + +[[maxdelaydevratio]]*maxdelaydevratio* _address_ _ratio_:: +This allows the *maxdelaydevratio* option for one of the sources to be +modified, in the same way as specifying the *maxdelaydevratio* option for the +<<chrony.conf.adoc#server,*server*>> directive in the configuration file. + +[[maxdelayratio]]*maxdelayratio* _address_ _ratio_:: +This allows the *maxdelayratio* option for one of the sources to be modified, +in the same way as specifying the *maxdelayratio* option for the +<<chrony.conf.adoc#server,*server*>> directive in the configuration file. + +[[maxpoll]]*maxpoll* _address_ _maxpoll_:: +The *maxpoll* command is used to modify the maximum polling interval for one of +the current set of sources. It is equivalent to the *maxpoll* option in the +<<chrony.conf.adoc#server,*server*>> directive in the configuration file. ++ +Note that the new maximum polling interval only takes effect after the next +measurement has been made. + +[[minpoll]]*minpoll* _address_ _minpoll_:: +The *minpoll* command is used to modify the minimum polling interval for one of +the current set of sources. It is equivalent to the *minpoll* option in the +<<chrony.conf.adoc#server,*server*>> directive in the configuration file. ++ +Note that the new minimum polling interval only takes effect after the next +measurement has been made. + +[[minstratum]]*minstratum* _address_ _minstratum_:: +The *minstratum* command is used to modify the minimum stratum for one of the +current set of sources. It is equivalent to the *minstratum* option in the +<<chrony.conf.adoc#server,*server*>> directive in the configuration file. + +[[offline]] +*offline* [_address_]:: +*offline* [_masked-address_/_masked-bits_]:: +*offline* [_mask_/_masked-address_]:: +The *offline* command is used to warn *chronyd* that the network connection to +a particular host or hosts is about to be lost, e.g. on computers with +intermittent connection to their time sources. ++ +Another case where *offline* could be used is where a computer serves time to a +local group of computers, and has a permanent connection to true time servers +outside the organisation. However, the external connection is heavily loaded at +certain times of the day and the measurements obtained are less reliable at +those times. In this case, it is probably most useful to determine the +gain or loss rate during the quiet periods and let the whole network coast through +the loaded periods. The *offline* and *online* commands can be used to achieve +this. ++ +There are four forms of the *offline* command. The first form is a wildcard, +meaning all sources. The second form allows an IP address mask and a masked +address to be specified. The third form uses CIDR notation. The fourth form +uses an IP address or a hostname. These forms are illustrated below. ++ +---- +offline +offline 255.255.255.0/1.2.3.0 +offline 2001:db8:789a::/48 +offline foo.example.net +---- ++ +The second form means that the *offline* command is to be applied to any source +whose IPv4 address is in the _1.2.3_ subnet. (The host's address is logically +and-ed with the mask, and if the result matches the _masked-address_ the host +is processed.) The third form means that the command is to be applied to all +sources whose IPv6 addresses have their first 48 bits equal to _2001:db8:789a_. The +fourth form means that the command is to be applied only to that one source. ++ +The wildcard form of the address is equivalent to: ++ +---- +offline 0.0.0.0/0.0.0.0 +offline ::/0 +---- + +[[online]] +*online* [_address_]:: +*online* [_masked-address_/_masked-bits_]:: +*online* [_mask_/_masked-address_]:: +The *online* command is opposite in function to the <<offline,*offline*>> +command. It is used to advise *chronyd* that network connectivity to a +particular source or sources has been restored. ++ +The syntax is identical to that of the <<offline,*offline*>> command. + +[[onoffline]] +*onoffline*:: +The *onoffline* command tells *chronyd* to switch all sources to the online or +offline status according to the current network configuration. A source is +considered online if it is possible to send requests to it, i.e. a route to the +network is present. + +[[polltarget]]*polltarget* _address_ _polltarget_:: +The *polltarget* command is used to modify the poll target for one of the +current set of sources. It is equivalent to the *polltarget* option in the +<<chrony.conf.adoc#server,*server*>> directive in the configuration file. + +[[refresh]]*refresh*:: +The *refresh* command can be used to force *chronyd* to resolve the names of +configured sources to IP addresses again, e.g. after suspending and resuming +the machine in a different network. ++ +Sources that stop responding will be replaced with newly resolved addresses +automatically after 8 polling intervals, but this command can still be useful +to replace them immediately and not wait until they are marked as unreachable. + +=== Manual time input + +[[manual]] +*manual* *on*:: +*manual* *off*:: +*manual* *delete* _index_:: +*manual* *list*:: +*manual* *reset*:: +The manual command enables and disables use of the <<settime,*settime*>> +command, and is used to modify the behaviour of the manual clock driver. ++ +The *on* form of the command enables use of the *settime* command. ++ +The *off* form of the command disables use of the *settime* command. ++ +The *list* form of the command lists all the samples currently stored in +*chronyd*. The output is illustrated below. ++ +---- +210 n_samples = 1 +# Date Time(UTC) Slewed Original Residual +==================================================== + 0 27Jan99 22:09:20 0.00 0.97 0.00 +---- ++ +The columns are as as follows: ++ +. The sample index (used for the *manual delete* command). +. The date and time of the sample. +. The system clock error when the timestamp was entered, adjusted to allow + for changes made to the system clock since. +. The system clock error when the timestamp was entered, as it originally was + (without allowing for changes to the system clock since). +. The regression residual at this point, in seconds. This allows '`outliers`' + to be easily spotted, so that they can be deleted using the *manual delete* + command. +:: ++ +The *delete* form of the command deletes a single sample. The parameter is the +index of the sample, as shown in the first column of the output from *manual +list*. Following deletion of the data point, the current error and drift rate +are re-estimated from the remaining data points and the system clock trimmed if +necessary. This option is intended to allow '`outliers`' to be discarded, i.e. +samples where the administrator realises they have entered a very poor +timestamp. ++ +The *reset* form of the command deletes all samples at once. The system clock +is left running as it was before the command was entered. + +[[settime]]*settime* _time_:: +The *settime* command allows the current time to be entered manually, if this +option has been configured into *chronyd*. (It can be configured either with +the <<chrony.conf.adoc#manual,*manual*>> directive in the configuration file, +or with the <<manual,*manual*>> command of *chronyc*.) ++ +It should be noted that the computer's sense of time will only be as accurate +as the reference you use for providing this input (e.g. your watch), as well as +how well you can time the press of the return key. ++ +Providing your computer's time zone is set up properly, you will be able to +enter a local time (rather than UTC). ++ +The response to a successful *settime* command indicates the amount that the +computer's clock was wrong. It should be apparent from this if you have entered +the time wrongly, e.g. with the wrong time zone. ++ +The rate of drift of the system clock is estimated by a regression process +using the entered measurement and all previous measurements entered during the +present run of *chronyd*. However, the entered measurement is used for +adjusting the current clock offset (rather than the estimated intercept from +the regression, which is ignored). Contrast what happens with the +<<manual,*manual delete*>> command, where the intercept is used to set the +current offset (since there is no measurement that has just been entered in +that case). ++ +The time is parsed by the public domain _getdate_ algorithm. Consequently, you +can only specify time to the nearest second. ++ +Examples of inputs that are valid are shown below: ++ +---- +settime 16:30 +settime 16:30:05 +settime Nov 21, 2015 16:30:05 +---- ++ +For a full description of getdate, see the getdate documentation +(bundled, for example, with the source for GNU tar). + +=== NTP access + +[[accheck]]*accheck* _address_:: +This command allows you to check whether client NTP access is allowed from a +particular host. ++ +Examples of use, showing a named host and a numeric IP address, are as follows: ++ +---- +accheck foo.example.net +accheck 1.2.3.4 +accheck 2001:db8::1 +---- ++ +This command can be used to examine the effect of a series of *allow*, *allow +all*, *deny*, and *deny all* commands specified either via *chronyc*, or in +*chronyd*'s configuration file. + +[[clients]]*clients*:: +This command shows a list of clients that have accessed the server, through +either the NTP or command ports. It does not include accesses over +the Unix domain command socket. There are no arguments. ++ +An example of the output is: ++ +---- +Hostname NTP Drop Int IntL Last Cmd Drop Int Last +=============================================================================== +localhost 2 0 2 - 133 15 0 -1 7 +foo.example.net 12 0 6 - 23 0 0 - - +---- ++ +Each row shows the data for a single host. Only hosts that have passed the host +access checks (set with the <<allow,*allow*>>, <<deny,*deny*>>, +<<cmdallow,*cmdallow*>> and <<cmddeny,*cmddeny*>> commands or configuration +file directives) are logged. The intervals are displayed as a power of 2 in +seconds. ++ +The columns are as follows: ++ +. The hostname of the client. +. The number of NTP packets received from the client. +. The number of NTP packets dropped to limit the response rate. +. The average interval between NTP packets. +. The average interval between NTP packets after limiting the response rate. +. Time since the last NTP packet was received +. The number of command packets received from the client. +. The number of command packets dropped to limit the response rate. +. The average interval between command packets. +. Time since the last command packet was received. + +[[serverstats]]*serverstats*:: +The *serverstats* command displays how many valid NTP and command requests +*chronyd* as a server received from clients, how many of them were dropped to +limit the response rate as configured by the +<<chrony.conf.adoc#ratelimit,*ratelimit*>> and +<<chrony.conf.adoc#cmdratelimit,*cmdratelimit*>> directives, and how many +client log records were dropped due to the memory limit configured by the +<<chrony.conf.adoc#clientloglimit,*clientloglimit*>> directive. An example of +the output is shown below. ++ +---- +NTP packets received : 1598 +NTP packets dropped : 8 +Command packets received : 19 +Command packets dropped : 0 +Client log records dropped : 0 +---- + +[[allow]]*allow* [*all*] [_subnet_]:: +The effect of the allow command is identical to the +<<chrony.conf.adoc#allow,*allow*>> directive in the configuration file. ++ +The syntax is illustrated in the following examples: ++ +---- +allow foo.example.net +allow all 1.2 +allow 3.4.5 +allow 6.7.8/22 +allow 6.7.8.9/22 +allow 2001:db8:789a::/48 +allow 0/0 +allow ::/0 +allow +allow all +---- + +[[deny]]*deny* [*all*] [_subnet_]:: +The effect of the allow command is identical to the +<<chrony.conf.adoc#deny,*deny*>> directive in the configuration file. ++ +The syntax is illustrated in the following examples: ++ +---- +deny foo.example.net +deny all 1.2 +deny 3.4.5 +deny 6.7.8/22 +deny 6.7.8.9/22 +deny 2001:db8:789a::/48 +deny 0/0 +deny ::/0 +deny +deny all +---- + +[[local]] +*local* [_option_]...:: +*local* *off*:: +The *local* command allows *chronyd* to be told that it is to appear as a +reference source, even if it is not itself properly synchronised to an external +source. (This can be used on isolated networks, to allow one computer to be a +master time server with the other computers slaving to it.) ++ +The first form enables the local reference mode on the host. The syntax is +identical to the <<chrony.conf.adoc#local,*local*>> directive in the +configuration file. ++ +The second form disables the local reference mode. + +[[smoothing]]*smoothing*:: +The *smoothing* command displays the current state of the NTP server time +smoothing, which can be enabled with the +<<chrony.conf.adoc#smoothtime,*smoothtime*>> directive. An example of the +output is shown below. ++ +---- +Active : Yes +Offset : +1.000268817 seconds +Frequency : -0.142859 ppm +Wander : -0.010000 ppm per second +Last update : 17.8 seconds ago +Remaining time : 19988.4 seconds +---- ++ +The fields are explained as follows: ++ +*Active*::: +This shows if the server time smoothing is currently active. Possible values +are _Yes_ and _No_. If the *leaponly* option is included in the *smoothtime* +directive, _(leap second only)_ will be shown on the line. +*Offset*::: +This is the current offset applied to the time sent to NTP clients. Positive +value means the clients are getting time that's ahead of true time. +*Frequency*::: +The current frequency offset of the served time. Negative value means the +time observed by clients is running slower than true time. +*Wander*::: +The current frequency wander of the served time. Negative value means the +time observed by clients is slowing down. +*Last update*::: +This field shows how long ago the time smoothing process was updated, e.g. +*chronyd* accumulated a new measurement. +*Remaining time*::: +The time it would take for the smoothing process to get to zero offset and +frequency if there were no more updates. + +[[smoothtime]] +*smoothtime* *activate*:: +*smoothtime* *reset*:: +The *smoothtime* command can be used to activate or reset the server time +smoothing process if it is configured with the +<<chrony.conf.adoc#smoothtime,*smoothtime*>> directive. + +=== Monitoring access + +[[cmdaccheck]]*cmdaccheck* _address_:: +This command is similar to the <<accheck,*accheck*>> command, except that it is +used to check whether monitoring access is permitted from a named host. ++ +Examples of use are as follows: ++ +---- +cmdaccheck foo.example.net +cmdaccheck 1.2.3.4 +cmdaccheck 2001:db8::1 +---- + +[[cmdallow]]*cmdallow* [*all*] [_subnet_]:: +This is similar to the <<allow,*allow*>> command, except that it is used to +allow particular hosts or subnets to use *chronyc* to monitor with *chronyd* on +the current host. + +[[cmddeny]]*cmddeny* [*all*] [_subnet_]:: +This is similar to the <<deny,*deny*>> command, except that it is used to allow +particular hosts or subnets to use *chronyc* to monitor *chronyd* on the +current host. + +=== Real-time clock (RTC) + +[[rtcdata]]*rtcdata*:: +The *rtcdata* command displays the current RTC parameters. ++ +An example output is shown below. ++ +---- +RTC ref time (GMT) : Sat May 30 07:25:56 2015 +Number of samples : 10 +Number of runs : 5 +Sample span period : 549 +RTC is fast by : -1.632736 seconds +RTC gains time at : -107.623 ppm +---- ++ +The fields have the following meaning: ++ +*RTC ref time (GMT)*::: +This is the RTC reading the last time its error was measured. +*Number of samples*::: +This is the number of previous measurements being used to determine the RTC +gain or loss rate. +*Number of runs*::: +This is the number of runs of residuals of the same sign following the +regression fit for (RTC error) versus (RTC time). A value which is small +indicates that the measurements are not well approximated by a linear model, +and that the algorithm will tend to delete the older measurements to improve +the fit. +*Sample span period*::: +This is the period that the measurements span (from the oldest to the +newest). Without a unit the value is in seconds; suffixes _m_ for minutes, +_h_ for hours, _d_ for days or _y_ for years can be used. +*RTC is fast by*::: +This is the estimate of how many seconds fast the RTC when it thought +the time was at the reference time (above). If this value is large, you +might (or might not) want to use the <<trimrtc,*trimrtc*>> command to bring the +RTC into line with the system clock. (Note, a large error will not affect +*chronyd*'s operation, unless it becomes so big as to start causing rounding +errors.) +*RTC gains time at*::: +This is the amount of time gained (positive) or lost (negative) by the real +time clock for each second that it ticks. It is measured in parts per +million. So if the value shown was +1, suppose the RTC was exactly right when +it crosses a particular second boundary. Then it would be 1 microsecond fast +when it crosses its next second boundary. + +[[trimrtc]]*trimrtc*:: +The *trimrtc* command is used to correct the system's real-time clock (RTC) to +the main system clock. It has no effect if the error between the two clocks is +currently estimated at less than a second. ++ +The command takes no arguments. It performs the following steps (if the RTC is +more than 1 second away from the system clock): ++ +. Remember the currently estimated gain or loss rate of the RTC and flush the + previous measurements. +. Step the real-time clock to bring it within a second of the system clock. +. Make several measurements to accurately determine the new offset between + the RTC and the system clock (i.e. the remaining fraction of a second + error). +. Save the RTC parameters to the RTC file (specified with the + <<chrony.conf.adoc#rtcfile,*rtcfile*>> directive in the configuration file). +:: ++ +The last step is done as a precaution against the computer suffering a power +failure before either the daemon exits or the <<writertc,*writertc*>> command +is issued. ++ +*chronyd* will still work perfectly well both whilst operating and across +machine reboots even if the *trimrtc* command is never used (and the RTC is +allowed to drift away from true time). The *trimrtc* command is provided as a +method by which it can be corrected, in a manner compatible with *chronyd* +using it to maintain accurate time across machine reboots. ++ +The *trimrtc* command can be executed automatically by *chronyd* with the +<<chrony.conf.adoc#rtcautotrim,*rtcautotrim*>> directive in the configuration +file. + +[[writertc]]*writertc*:: +The *writertc* command writes the currently estimated error and gain or loss rate +parameters for the RTC to the RTC file (specified with the +<<chrony.conf.adoc#rtcfile,*rtcfile*>> directive). This information is also +written automatically when *chronyd* is killed (by the SIGHUP, SIGINT, SIGQUIT +or SIGTERM signals) or when the <<trimrtc,*trimrtc*>> command is issued. + +=== Other daemon commands + +[[cyclelogs]]*cyclelogs*:: +The *cyclelogs* command causes all of *chronyd*'s open log files to be closed +and re-opened. This allows them to be renamed so that they can be periodically +purged. An example of how to do this is shown below. ++ +---- +# mv /var/log/chrony/measurements.log /var/log/chrony/measurements1.log +# chronyc cyclelogs +# ls -l /var/log/chrony +-rw-r--r-- 1 root root 0 Jun 8 18:17 measurements.log +-rw-r--r-- 1 root root 12345 Jun 8 18:17 measurements1.log +# rm -f measurements1.log +---- + +[[dump]]*dump*:: +The *dump* command causes *chronyd* to write its current history of +measurements for each of its sources to dump files in the directory specified +in the configuration file by the <<chrony.conf.adoc#dumpdir,*dumpdir*>> +directive. Note that *chronyd* does this automatically when it exits. This +command is mainly useful for inspection of the history whilst *chronyd* is +running. + +[[rekey]]*rekey*:: +The *rekey* command causes *chronyd* to re-read the key file specified in the +configuration file by the <<chrony.conf.adoc#keyfile,*keyfile*>> directive. + +[[rekey]]*shutdown*:: +The *shutdown* command causes *chronyd* to exit. This is equivalent to sending +the process the SIGTERM signal. + +=== Client commands + +[[dns]]*dns* _option_:: +The *dns* command configures how hostnames and IP addresses are resolved in +*chronyc*. IP addresses can be resolved to hostnames when printing results of +<<sources,*sources*>>, <<sourcestats,*sourcestats*>>, <<tracking,*tracking*>> +and <<clients,*clients*>> commands. Hostnames are resolved in commands that +take an address as argument. ++ +There are five options: ++ +*dns -n*::: +Disables resolving IP addresses to hostnames. Raw IP addresses will be +displayed. +*dns +n*::: +Enables resolving IP addresses to hostnames. This is the default unless +*chronyc* was started with *-n* option. +*dns -4*::: +Resolves hostnames only to IPv4 addresses. +*dns -6*::: +Resolves hostnames only to IPv6 addresses. +*dns -46*::: +Resolves hostnames to both address families. This is the default behaviour +unless *chronyc* was started with the *-4* or *-6* option. + +[[timeout]]*timeout* _timeout_:: +The *timeout* command sets the initial timeout for *chronyc* requests in +milliseconds. If no response is received from *chronyd*, the timeout is doubled +and the request is resent. The maximum number of retries is configured with the +<<retries,*retries*>> command. ++ +By default, the timeout is 1000 milliseconds. + +[[retries]]*retries* _retries_:: +The *retries* command sets the maximum number of retries for *chronyc* requests +before giving up. The response timeout is controlled by the +<<timeout,*timeout*>> command. ++ +The default is 2. + +[[keygen]]*keygen* [_id_ [_type_ [_bits_]]]:: +The *keygen* command generates a key that can be added to the +key file (specified with the <<chrony.conf.adoc#keyfile,*keyfile*>> directive) +to allow NTP authentication between server and client, or peers. The key is +generated from the _/dev/urandom_ device and it is printed to standard output. ++ +The command has three optional arguments. The first argument is the key number +(by default 1), which will be specified with the *key* option of the *server* +or *peer* directives in the configuration file. The second argument is the hash +function (by default SHA1 or MD5 if SHA1 is not available) and the third +argument is the number of bits the key should have, between 80 and 4096 bits +(by default 160 bits). ++ +An example is: ++ +---- +keygen 73 SHA1 256 +---- ++ +which generates a 256-bit SHA1 key with number 73. The printed line should +then be securely transferred and added to the key files on both server and +client, or peers. + +[[exit]]*exit*:: +[[quit]]*quit*:: +The *exit* and *quit* commands exit from *chronyc* and return the user to the shell. + +[[help]]*help*:: +The *help* command displays a summary of the commands and their arguments. + +== SEE ALSO + +<<chrony.conf.adoc#,*chrony.conf(5)*>>, <<chronyd.adoc#,*chronyd(8)*>> + +== BUGS + +For instructions on how to report bugs, please visit +https://chrony.tuxfamily.org/. + +== AUTHORS + +chrony was written by Richard Curnow, Miroslav Lichvar, and others. |