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chrony
net-misc/chrony is a versatile implementation of the Network Time Protocol (NTP). It can synchronize the system clock with NTP servers, reference clocks (e.g. GPS receiver), and manual input using wristwatch and keyboard. It can also operate as an NTPv4 (RFC 5905) server and peer to provide a time service to other computers in the network.
Installation
USE flags
USE flags for net-misc/chrony NTP client and server programs
+caps
|
Use Linux capabilities library to control privilege |
+cmdmon
|
Support for command and monitoring |
+nettle
|
Use dev-libs/nettle for hash functions or nts |
+ntp
|
Support for the Network Time Protocol (NTP) |
+nts
|
Support for Network Time Security (NTS). Uses net-libs/gnutls |
+phc
|
Support for the PTP (Precision Time Protocol) Hardware Clock (PHC) interface |
+readline
|
Enable support for libreadline, a GNU line-editing library that almost everyone wants |
+refclock
|
Support for reference clocks |
+rtc
|
Support for the Linux Real Time Clock interface |
+seccomp
|
Enable seccomp (secure computing mode) to perform system call filtering at runtime to increase security of programs |
+sechash
|
Enable support for hashes other than MD5 |
debug
|
Get DEBUG_LOG output from chronyd when passing -dd parameter |
html
|
Install HTML documentation |
libtomcrypt
|
Support different hashes via dev-libs/libtomcrypt |
nss
|
Use dev-libs/nss for hash functions |
pps
|
Support for the Linux Pulse Per Second (PPS) interface |
samba
|
Add support for SAMBA (Windows File and Printer sharing) |
selinux
|
!!internal use only!! Security Enhanced Linux support, this must be set by the selinux profile or breakage will occur |
verify-sig
|
Verify upstream signatures on distfiles |
Emerge
Install the chrony package:
root #emerge --ask net-misc/chronyConfiguration
/etc/chrony/chrony.conf is the configuration file for chronyd. The default configuration is populated with:
/etc/chrony/chrony.conf# Use public NTP servers from the pool.ntp.org project. pool pool.ntp.org iburst # Record the rate at which the system clock gains/losses time. driftfile /var/lib/chrony/drift # In first three updates step the system clock instead of slew # if the adjustment is larger than 1 second. makestep 1.0 3 # Enable kernel synchronization of the real-time clock (RTC). rtcsync hwclockfile /etc/adjtime
Time zones and location of the server do not matter for the NTP protocol; it synchronizes via UTC.
On systems where a network connection is not always available at boot (laptops, etc.), it might help to change the pool line in the server configuration:
/etc/chrony/chrony.confpool pool.ntp.org iburst auto_offline
This tells chronyd that the machine will be assumed to have gone offline when 2 requests have been sent to it without receiving a response. You will need to use the chronyc online command to re-enable polling (See below)
Acting as a local NTP server
By default, chronyd only synchronizes the local machine time. By adding allow and deny rules, it will act as a local NTP source:
/etc/chrony/chrony.conf# Note order does not matter for this example, order does matter with 'allow all' or 'deny all' # Allow a specific IP allow 1.2.3.4 # Deny a certain subnet deny 1.2.3 # Allow all of the 1.2.x.x subnet allow 1.2
Usage
chronyc Client Interface Tool
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. A full list of commands can be found in the manual, man 1 chronyc
Examples:
root #chronyc offline # Set all sources offline
root #chronyc online # Set all sources online
chronyd service
Add chronyd to the default runlevel to have the time synchronized automatically.
root #rc-service chronyd start
root #rc-update add chronyd defaultTo monitor status of the server:
root #rc-service chronyd status