timezone
- timezone setup
- tzdata installation with noninteractive
date
- epoch
- timestamps
- format
- IOS 8601
- rfc-3339
- utc
- timezone
- common formats
convert
chrony
systemd-timesyncd
- install
- config
- commands

references:

* imarslo: groovy time

https://en.wikipedia.org/wiki/Unix_time:

timezone

timezone setup

$ sudo dpkg-reconfigure tzdata

tzdata installation with noninteractive

[!NOTE|label:references:]

apt-get install tzdata noninteractive

# in bash
$ DEBIAN_FRONTEND=noninteractive sudo apt-get install -y tzdata

# or
$ export DEBIAN_FRONTEND=noninteractive
$ sudo apt install -y tzdata

# or
$ echo 'tzdata tzdata/Areas select Europe'       | debconf-set-selections
$ echo 'tzdata tzdata/Zones/Europe select Paris' | debconf-set-selections
$ DEBIAN_FRONTEND="noninteractive" sudo apt install -y tzdata

# or
$ sudo ln -fs /usr/share/zoneinfo/America/New_York /etc/localtime
$ export DEBIAN_FRONTEND=noninteractive
$ sudo apt-get install -y tzdata
$ sudo dpkg-reconfigure --frontend noninteractive tzdata

[!NOTE|label:references:]

Cingulata/Dockerfile.bfv

$ sudo ln -snf /usr/share/zoneinfo/$(curl https://ipapi.co/timezone) /etc/localtime
$ sudo apt install -y tzdata

or in dockerfile

RUN apt-get update \
    && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends tzdata

or ENV in dockerfile

[!NOTE|label:references:]

setting it via ENV should be actively discouraged

ENV DEBIAN_FRONTEND noninteractive
RUN apt-get update \
    && apt-get install -y --no-install-recommends tzdata

or ARG in dockerfile

[!NOTE|label:references:]

apt-get install tzdata noninteractive

from ubuntu:bionic
ARG DEBIAN_FRONTEND=noninteractive
RUN apt-get update && apt-get install -y tzdata
RUN unlink /etc/localtime
RUN ln -s /usr/share/zoneinfo/America/New_York /etc/localtime

date

epoch

references:

It is the number of seconds that have elapsed since the Unix epoch, minus leap seconds; the Unix epoch is 00:00:00 UTC on 1 January 1970

What is epoch time?

$ date -u -d '1970-01-01 00:00:00' '+Normal: %F %T %:z%nUnix: %s'
Normal: 1970-01-01 00:00:00 +00:00
Unix: 0

$ date -d '1970-01-01 00:00:00' '+Normal: %F %T %:z%nUnix: %s'
Normal: 1970-01-01 00:00:00 +08:00
Unix: -28800

$ date -u -d '1970-01-01 00:00:00 UTC +1 day' '+Normal: %F %T %:z%nUnix: %s'
Normal: 1970-01-02 00:00:00 +00:00
Unix: 86400

$ date -d '2023-01-01' +%s; date -d '2023-01-01 - 1 year' +%s
1672560000
1641024000

# using now
$ date -d'now' +%s; date -d 'now - 1 day' +%s
1706952065
1706865665

$ date '+%s%3N'
1602231334983

$ date '+%s'
1602231334

timestamps

format

[!TIP]

yyyy-MM-dd'T'HH:mm:ss.SSSZ

yyyy-MM-dd'T'HH:mm:ss

DATE FORMAT OPTION	MEANING	EXAMPLE OUTPUT
`date +%c`	locale’s date time	Sat May 9 11:49:47 2020
`date +%x`	locale’s date	05/09/20
`date +%X`	locale’s time	11:49:47
`date +%A`	locale’s full weekday name	Saturday
`date +%B`	locale’s full month name	May
`date +%m-%d-%Y`	MM-DD-YYYY date format	05-09-2020
`date +%D`	MM/DD/YY date format	05/09/20
`date +%F`	YYYY-MM-DD date format	2020-05-09
`date +%T`	HH:MM:SS time format	11:44:15
`date +%u`	Day of Week	6
`date +%U`	Week of Year with Sunday as first day of week	18
`date +%V`	ISO Week of Year with Monday as first day of week	19
`date +%j`	Day of Year	130
`date +%Z`	Timezone	PDT
`date +%m`	Month of year (MM)	05
`date +%d`	Day of Month (DD)	09
`date +%Y`	Year (YY)	2020
`date +%H`	Hour (HH)	11
`date +%H`	Hour (HH) in 24-hour clock format	11
`date +%I`	Hour in 12-hour clock format	11
`date +%p`	locale’s equivalent of AM or PM	AM
`date +%P`	same as %p but in lower case	am

classical date format

$ secs=259200

$ date -u -d @${secs} +"%F"
1970-01-04
$ date -u -d @${secs} +"%T"
00:00:00

$ date -u -d @${secs} +"%F %T"
1970-01-04 00:00:00

$ date -u -d @${secs} -Is
1970-01-04T00:00:00+00:00

date format with timezone

$ date -u +"%Y-%m-%dT%H:%M:%SZ"
2020-10-09T08:14:47Z

$ date +%FT%T.%3N%:z
2020-10-09T17:27:18.491+08:00

$ date -u +"%Y-%m-%dT%H:%M:%S.%3NZ"
2020-10-09T08:14:47.167Z

$ date +%Y-%m-%d-T%H:%M:%S.%3N%z
2020-10-09-T17:27:18.491+0800

details

$ date -u -d "2019-01-19T05:00:00 - 2 hours" +%Y-%m-%d_%H:%M:%S%Z --debug
date: parsed datetime part: (Y-M-D) 2019-01-19 05:00:00 UTC-02
date: parsed relative part: +1 hour(s)
date: input timezone: parsed date/time string (-02)
date: using specified time as starting value: '05:00:00'
date: starting date/time: '(Y-M-D) 2019-01-19 05:00:00 TZ=-02'
date: '(Y-M-D) 2019-01-19 05:00:00 TZ=-02' = 1547881200 epoch-seconds
date: after time adjustment (+1 hours, +0 minutes, +0 seconds, +0 ns),
date:     new time = 1547884800 epoch-seconds
date: timezone: Universal Time
date: final: 1547884800.000000000 (epoch-seconds)
date: final: (Y-M-D) 2019-01-19 08:00:00 (UTC)
date: final: (Y-M-D) 2019-01-19 08:00:00 (UTC+00)
2019-01-19_08:00:00UTC

IOS 8601

FORMAT EXAMPLE

YYYY 2015

YYYY-MM 2015-12

YYYY-MM-DD 2015-12-11

YYYY-MM-DD'T'hh:mmTZD 2015-12-11T20:28+01:00 or 2015-12-11T19:28Z

YYYY-MM-DD'T'hh:mm:ssTZD 2015-12-11T20:28:30+01:00 or 2015-12-11T19:28:30Z

YYYY-MM-DD'T'hh:mm:ss.sTZD 2015-12-11T20:28:30.45+01:00 or 2015-12-11T19:28:30.45Z

where:

YYYY = four-digit year

MM = two-digit month (01=January, etc.)

DD = two-digit day of month (01 through 31)

hh = two digits of hour (00 through 23) (am/pm NOT allowed)

mm = two digits of minute (00 through 59)

ss = two digits of second (00 through 59)

s = one or more digits representing a decimal fraction of a second (i.e. milliseconds)

TZD = time zone designator (Z or +hh:mm or -hh:mm)

FORMAT	EXAMPLE
YYYY	2015
YYYY-MM	2015-12
YYYY-MM-DD	2015-12-11
YYYY-MM-DD'T'hh:mmTZD	2015-12-11T20:28+01:00 or 2015-12-11T19:28Z
YYYY-MM-DD'T'hh:mm:ssTZD	2015-12-11T20:28:30+01:00 or 2015-12-11T19:28:30Z
YYYY-MM-DD'T'hh:mm:ss.sTZD	2015-12-11T20:28:30.45+01:00 or 2015-12-11T19:28:30.45Z

$ date -I
2020-10-09

$ date -Is && date -Isecond
2020-10-09T16:31:47+08:00
2020-10-09T16:31:47+08:00

$ date -Ih
2020-10-09T16+08:00

$ date -Im
2020-10-09T16:31+08:00

rfc-3339

$ date --rfc-3339=date
2020-10-09

$ date --rfc-3339=ns
2020-10-09 17:32:14.158684000+08:00

$ date --rfc-3339=seconds
2020-10-09 17:32:14+08:00

utc

$ date
Fri Oct  9 17:09:34 CST 2020

$ date -u
Fri Oct  9 09:09:34 UTC 2020

timezone

[!NOTE|label:references:]
list all timezone:
$ timedatectl list-timezones | more

# or
$ tree /usr/share/zoneinfo/
tzdb timezone descriptions

$ date '+%Z'
CST

$ date '+%z'
+0800

$ date '+%:z'
+08:00

$ date '+%::z'
+08:00:00

$ date '+%:::z'
+08

$ echo $TZ
Asia/Beijing

$ timedatectl
      Local time: Tue 2023-08-22 05:58:45 CST
  Universal time: Mon 2023-08-21 21:58:45 UTC
        RTC time: Mon 2023-08-21 21:53:46
       Time zone: Asia/Beijing (CST, +0800)
     NTP enabled: yes
NTP synchronized: yes
 RTC in local TZ: no
      DST active: n/a

$ date -d "2024-03-11" +"%Z"
PDT
$ date -d "2024-03-10" +"%Z"
PST

common formats

[!NOTE|label:references:] Shell command: date Most common Bash date commands for timestamping

FORMAT/RESULT	COMMAND	OUTPUT
`YYYY-MM-DD`	`date -I`	2020-10-09
`YYYY-MM-DD_hh:mm:ss`	`date +%F_%T`	2020-10-09_16:48:45
`YYYYMMDD_hhmmss`	`date +%Y%m%d_%H%M%S`	20201009_164845
`YYYYMMDD_hhmmss (UTC version)`	`date --utc +%Y%m%d_%H%M%SZ`	20201009_084845Z
`YYYYMMDD_hhmmss (with local TZ)`	`date +%Y%m%d_%H%M%S%Z`	20201009_164845CST
`YYYYMMSShhmmss`	`date +%Y%m%d%H%M%S`	20201009164845
`YYYYMMSShhmmssnnnnnnnnn`	`date +%Y%m%d%H%M%S%N`	20201009164845495302000
`YYMMDD_hhmmss`	`date +%y%m%d_%H%M%S`	201009_164845
`Seconds since UNIX epoch:`	`date +%s`	1602233325
`Nanoseconds only:`	`date +%N`	505337000
`Nanoseconds since UNIX epoch:`	`date +%s%N`	1602233325508581000
`Nanoseconds since UNIX epoch:`	`date +%s%3N`	1602233325508
`ISO8601 UTC timestamp`	`date --utc +%FT%TZ`	2020-10-09T08:48:45Z
`ISO8601 UTC timestamp`	`date --utc +%FT%T%Z`	2020-10-09T08:48:45UTC
`ISO8601 UTC timestamp + ms`	`date --utc +%FT%T.%3NZ`	2020-10-09T08:48:45.517Z
`ISO8601 UTC timestamp + ms`	`date --utc +%FT%T.%3N%Z`	2020-10-09T08:48:45.520UTC
`ISO8601 Local TZ timestamp`	`date +%FT%T%Z`	2020-10-09T16:48:45CST
`YYYY-MM-DD (Short day)`	`date +%F$%a$`	2020-10-09(Fri)
`YYYY-MM-DD (Long day)`	`date +%F$%A$`	2020-10-09(Friday)

convert

$ date +"%Y-%m-%dT%H:%M:%SZ"
2020-10-09T17:16:37Z

$ date -u +"%Y-%m-%dT%H:%M:%SZ"
2020-10-09T09:16:37Z

$ date -d $(date -u +"%Y-%m-%dT%H:%M:%SZ")
Fri Oct  9 17:16:37 CST 2020

HUMAN-READABLE TIME	SECONDS
1 hour	3600 seconds
1 day	86400 seconds
1 week	604800 seconds
1 month (30.44 days)	2629743 seconds
1 year (365.24 days)	31556926 seconds

timestamps to epoch

$ echo $EPOCHSECONDS
1602235097

$ date -d $(date -u +"%Y-%m-%dT%H:%M:%SZ") +%s
1602235097
$ date --date=$(date -u +"%Y-%m-%dT%H:%M:%S.%3NZ") +%s%3N
1602235097801

$ date -d '2023-01-01' +%s; date -d '2023-01-01 - 1 day' +%s
1672560000
1672473600

$ date -d '2023-01-01' +%s; date -d '2023-01-01 - 1 year' +%s
1672560000
1641024000

# using now
$ date -d'now' +%s; date -d 'now - 1 day' +%s
1706952065
1706865665

epoch to timestamps

$ date -u +"%Y-%m-%dT%H:%M:%S.%3NZ"
2020-10-09T09:18:17.795Z

$ date -d @1602235097 +%c
Fri Oct  9 17:18:17 2020

$ date -d @1602235097
Fri Oct  9 17:18:17 CST 2020

$ date -d @1602235097 -u
Fri Oct  9 09:18:17 UTC 2020

epoch with 13 digits

# wrong
$ date -d @1718731558409 +%c
Thu 08 Jun 56434 01:53:29 AM PDT

# solution: epoch/1000
$ date -d @$((1718731558409/1000)) +%c
Tue 18 Jun 2024 10:25:58 AM PDT

convert epoch with milliseconds

Convert unix timestamp to hh:mm:ss:SSS (where SSS is milliseconds)

d=$(date +%s%3N)
s=${d%???}
ms=${d#"$s"}
date -d "@$s" +"%F %T.$ms %z"

result

2020-10-09 18:28:34.534 +0800

d: 1602239314534
s: 1602239314
ms: 534

convert in different timezone

[!NOTE|label:references:]
CST to UTC conversion
timezone can be found via:
$ cat /usr/share/zoneinfo

# or
$ timedatectl list-timezones | more

$ TZ="Asia/Shanghai" date -d @$(date -d "2023-01-01 00:00:00 GMT" +"%s")
Sun Jan  1 08:00:00 CST 2023

$ TZ="America/Los_Angeles" date -d @$(date -d "2023-01-01 00:00:00 GMT" +"%s")
Sat Dec 31 16:00:00 PST 2022

convert to another timezone

$ date --date='TZ="GTM" 15:00 tomorrow'
Tue Aug 22 08:00:00 PDT 2023

$ echo $TZ
America/Los_Angeles
$ date --date='TZ="Asia/Shanghai" 16:00 tomorrow'
Wed Aug 23 01:00:00 PDT 2023

$ echo $TZ
America/Los_Angeles
$ TZ="Asia/Shanghai" date -d 'TZ="America/Los_Angeles" 0:00 tomorrow'
Tue Aug 22 15:00:00 CST 2023

convert to different timezone with daylight saving

$ getDateTime() { echo "$1 | "$( TZ="$1" date '+%Y-%m-%d-%H-%M-%S %Z %z' ); }

$ getDateTime Asia/Hong_Kong
Asia/Hong_Kong | 2024-03-01-13-08-02 HKT +0800

$ getDateTime America/Los_Angeles
America/Los_Angeles | 2024-02-29-21-08-08 PST -0800

$ getDateTime America/New_York
America/New_York | 2024-03-01-00-08-08 EST -0500

$ getDateTime Pacific/Honolulu
Pacific/Honolulu | 2024-02-29-19-08-08 HST -1000

$ getDateTime Asia/Hong_Kong
Asia/Hong_Kong | 2024-03-01-13-08-09 HKT +0800

get daylight saving

$ date -d "2024-03-11" +%Z
PDT
$ date -d "2024-03-10" +%Z
PST

$ echo $(( ($(date -d "2024-03-10 UTC" +%s) - $(date -d "2024-03-10 PST" +%s))/(60*60) ))
-8
$ echo $(( ($(date -d "2024-03-11 UTC" +%s) - $(date -d "2024-03-11 PDT" +%s))/(60*60) ))
-7

another

$ if perl -e 'exit ((localtime)[8])' ; then
    echo winter
  else
    echo summer
  fi

how many days from timestamps

[!NOTE|label:references:]

How to find the difference in days between two dates?

$ echo $(( ($(date --date="230301" +%s) - $(date --date="240301" +%s) )/(60*60*24) )) days
-366 days

# with timezone
#                PST/PDT according to daylight saving
#                                  v
$ echo $(( ($(date -d "2024-03-01 PST" +%s) - $(date -d "2023-03-01 UTC" +%s)) / (60*60*24) ))
366

calculate time different

$ date -d 'now + 3 weeks'
Fri Oct 30 20:32:04 CST 2020

$ date -d 'now + 3 weeks' +%s
1604061130

$ date -d 'Jan 1 + 11 weeks'
Wed Mar 18 00:00:00 CST 2020

$ date -d 'Jan 1 2021 + 11 weeks'
Fri Mar 19 00:00:00 CST 2021

time described by STRING

$ date -u +"%Y-%m-%dT%H:%M:%S.%3NZ" -d '90 day ago'
2020-07-11T08:14:03.145Z

$ date -u +"%Y-%m-%dT%H:%M:%S.%3NZ" -d '3 months ago'
2020-07-09T08:14:47.164Z

$ date -u -d "2019-01-19T05:00:00Z - 2 hours" +%Y-%m-%d_%H:%M:%S
2019-01-19_03:00:00

$ date -d "$(date -Iseconds -d "2018-12-10 00:00:00") - 5 hours - 20 minutes - 5 seconds"
Sun Dec  9 18:39:55 CST 2018

$ date -d "2018-12-10 00:00:00 5 hours ago 20 minutes ago 5 seconds ago"
Sun Dec  9 18:39:55 CST 2018

$ date -d '2023-01-01 - 1 year' +"%Y-%m-%d %H:%M:%S"
2022-01-01 00:00:00

two times different

$ seconds=$(date +%s)
$ printf "%d days %(%H hours %M minutes %S seconds)T\n" $((seconds/86400)) $seconds
18544 days 18 hours 35 minutes 48 seconds

simple one-liner

$ secs=259200
$ printf '%dh:%dm:%ds\n' $(($secs/3600)) $(($secs%3600/60)) $(($secs%60))
72h:0m:0s

with leading zero

$ printf '%02dh:%02dm:%02ds\n' $(($secs/3600)) $(($secs%3600/60)) $(($secs%60))
72h:00m:00s

with days

$ printf '%dd:%dh:%dm:%ds\n' $(($secs/86400)) $(($secs%86400/3600)) $(($secs%3600/60))   $(($secs%60))
3d:0h:0m:0s

with nanoseconds

$ printf '%02dh:%02dm:%02fs\n' $(echo -e "$secs/3600\n$secs%3600/60\n$secs%60"| bc | xargs echo)
72h:00m:0.000000s

`datediff` (`ddiff`)

$ datediff -f "%d days, %H hours, %M mins, %S secs" "$(date +'%Y-%m-%d %H:%M:%S')" "$(date +'%Y-%m-%d %H:%M:%S' -d '3 days ago')"
-3 days, 0 hours, 0 mins, 0 secs

or with specific format

$ ddiff -i '%Y%m%d%H%M%S' 20190817040001 20200312000101
17956860s

$ ddiff -f "%d days, %H hours, %M mins, %S secs" -i '%Y%m%d%H%M%S' 20190817040001 20200312000101
207 days, 20 hours, 1 mins, 0 secs

calculate with epoch

$ awk -v t=$(( $(date -d $(date +"%Y-%m-%dT%H:%M:%SZ") +%s) - $(date -d $(date +"%Y-%m-%dT%H:%M:%SZ" -d '3 days ago') +%s) )) 'BEGIN{
  printf "%d:%02d:%06.3f\n", t/3600, (t/60)%60, t%60}'
72:00:00.000

transfer date format

[!TIP]

$ date +'%Y%m%d%H%M%S'
20201009184852

$ d1=$(date +'%Y%m%d%H%M%S')
$ date --date "$(echo $d1 | sed -nr 's/(....)(..)(..)(..)(..)(..)/\1-\2-\3 \4:\5:\6/p')"
Fri Oct  9 18:48:52 CST 2020

chrony

install

from package management

# centos/rhel
$ sudo yum install -y chrony

from source

[!NOTE]
asciidoctor 2.0.22
asciidoctor is required to build docs
$ gem install asciidoctor

$ mkdir -p /opt/chrony
$ git clone https://gitlab.com/chrony/chrony.git /opt/chrony && cd $_
$ ./configure --prefix=/usr/local --mandir=/usr/share/man
$ make && make docs
$ sudo make install && sudo make install docs

conf

[!NOTE|label:references:]

chrony配置

时钟同步

CentOS使用Chrony部署内网NTP时间服务器

Chrony详解：代替ntp的时间同步服务

Systemd and ntpd problems

ntp pool project | 授时中心

North America — north-america.pool.ntp.org

210.72.145.44 国家授时中心

ntp.aliyun.com 阿里云

s1a.time.edu.cn 北京邮电大学

s1b.time.edu.cn 清华大学

s1c.time.edu.cn 北京大学

s1d.time.edu.cn 东南大学

s1e.time.edu.cn 清华大学

s2a.time.edu.cn 清华大学

s2b.time.edu.cn 清华大学

s2c.time.edu.cn 北京邮电大学

s2d.time.edu.cn 西南地区网络中心

s2e.time.edu.cn 西北地区网络中心

s2f.time.edu.cn 东北地区网络中心

s2g.time.edu.cn 华东南地区网络中心

s2h.time.edu.cn 四川大学网络管理中心

s2j.time.edu.cn 大连理工大学网络中心

s2k.time.edu.cn CERNET桂林主节点

s2m.time.edu.cn 北京大学

ntp.sjtu.edu.cn | 202.120.2.101 上海交通大学

How to configure chrony as an NTP client or server in Linux

RedHat 7: Chapter 18. Configuring NTP Using the chrony Suite

RedHad 8: Chapter 15. Configuring time synchronization

RedHat 9: Chapter 13. Configuring time synchronization

How to Sync Time in CentOS 8 using Chrony

/etc/chrony.conf

# default
$ cat /etc/chrony.conf | sed -r '/^(#.*)$/d' | sed -r '/^\s*$/d'
pool 2.centos.pool.ntp.org iburst
driftfile /var/lib/chrony/drift
makestep 1.0 3
rtcsync
keyfile /etc/chrony.keys
leapsectz right/UTC
logdir /var/log/chrony

# modified
$ cat /etc/chrony.conf | sed -r '/^(#.*)$/d' | sed -r '/^\s*$/d'
pool 2.rhel.pool.ntp.org iburst
driftfile /var/lib/chrony/drift
makestep 1.0 3
stratumweight 0
rtcsync
hwtimestamp *
allow 0.0.0.0/0
bindcmdaddress 127.0.0.1
bindcmdaddress ::1
local stratum 10
keyfile /etc/chrony.keys
leapsectz right/UTC
logdir /var/log/chrony
generatecommandkey
maxdistance 600.0

/usr/lib/systemd/system/chronyd.service

$ cat /usr/lib/systemd/system/chronyd.service
[Unit]
Description=NTP client/server
Documentation=man:chronyd(8) man:chrony.conf(5)
After=ntpdate.service sntp.service ntpd.service
Conflicts=ntpd.service systemd-timesyncd.service
ConditionCapability=CAP_SYS_TIME

[Service]
Type=forking
PIDFile=/run/chrony/chronyd.pid
EnvironmentFile=-/etc/sysconfig/chronyd
ExecStart=/usr/sbin/chronyd $OPTIONS
ExecStartPost=/usr/libexec/chrony-helper update-daemon
PrivateTmp=yes
ProtectHome=yes
ProtectSystem=full

[Install]
WantedBy=multi-user.target

commands

services

$ sudo systemctl enable chronyd.service
Created symlink /etc/systemd/system/multi-user.target.wants/chronyd.service → /usr/lib/systemd/system/chronyd.service.

$ sudo systemctl is-active chronyd.service
active

$ sudo systemctl is-enabled chronyd.service
enabled

server

$ sudo chronyd -q 'server 0.north-america.pool.ntp.org iburst'
2024-04-02T23:51:52Z chronyd version 3.5 starting (+CMDMON +NTP +REFCLOCK +RTC +PRIVDROP +SCFILTER +SIGND +ASYNCDNS +SECHASH +IPV6 +DEBUG)
2024-04-02T23:51:52Z Initial frequency -19.492 ppm
2024-04-02T23:51:57Z System clock wrong by 0.003261 seconds (step)
2024-04-02T23:51:57Z chronyd exiting

chronyc

$ chronyc sources -v
210 Number of sources = 4

  .-- Source mode  '^' = server, '=' = peer, '#' = local clock.
 / .- Source state '*' = current synced, '+' = combined , '-' = not combined,
| /   '?' = unreachable, 'x' = time may be in error, '~' = time too variable.
||                                                 .- xxxx [ yyyy ] +/- zzzz
||      Reachability register (octal) -.           |  xxxx = adjusted offset,
||      Log2(Polling interval) --.      |          |  yyyy = measured offset,
||                                \     |          |  zzzz = estimated error.
||                                 |    |           \
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^- 212.227.240.160               3   8   377   103  -5334us[-5080us] +/-  101ms
^? ntp1.glypnod.com              2   6     3    37   -869us[ -609us] +/-   14ms
^* LAX.CALTICK.NET               2   7   377    36   -408us[ -147us] +/-   12ms
^- 131.153.171.22                2   8   377   101  -5931us[-5677us] +/-   60ms

$ chronyc sourcestats -v
210 Number of sources = 4
                             .- Number of sample points in measurement set.
                            /    .- Number of residual runs with same sign.
                           |    /    .- Length of measurement set (time).
                           |   |    /      .- Est. clock freq error (ppm).
                           |   |   |      /           .- Est. error in freq.
                           |   |   |     |           /         .- Est. offset.
                           |   |   |     |          |          |   On the -.
                           |   |   |     |          |          |   samples. \
                           |   |   |     |          |          |             |
Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
==============================================================================
212.227.240.160            25  17   31m     +0.029      0.853   -560us   586us
ntp1.glypnod.com            2   0    64     -0.104   2000.000   -869us  4000ms
LAX.CALTICK.NET            12   4  1099     +0.014      2.198   +654ns   614us
131.153.171.22             25  14   31m     -0.834      2.524  -4084us  1801us

$ chronyc tracking
Reference ID    : 2D3F360D (LAX.CALTICK.NET)
Stratum         : 3
Ref time (UTC)  : Tue Apr 02 22:53:49 2024
System time     : 0.000157978 seconds fast of NTP time
Last offset     : +0.000261040 seconds
RMS offset      : 0.001216694 seconds
Frequency       : 19.554 ppm slow
Residual freq   : +0.014 ppm
Skew            : 2.387 ppm
Root delay      : 0.024124343 seconds
Root dispersion : 0.000968660 seconds
Update interval : 128.2 seconds
Leap status     : Normal

$ sudo chronyc clients
Hostname                      NTP   Drop Int IntL Last     Cmd   Drop Int  Last
===============================================================================
localhost                       0      0   -   -     -      13      0   4     1

`/usr/libexec/chrony-helper`

/usr/libexec/chrony-helper

$ cat /usr/libexec/chrony-helper
#!/bin/bash
# This script configures running chronyd to use NTP servers obtained from
# DHCP and _ntp._udp DNS SRV records. Files with servers from DHCP are managed
# externally (e.g. by a dhclient script). Files with servers from DNS SRV
# records are updated here using the dig utility. The script can also list
# and set static sources in the chronyd configuration file.

chronyc=/usr/bin/chronyc
chrony_conf=/etc/chrony.conf
chrony_service=chronyd.service
helper_dir=/var/run/chrony-helper
added_servers_file=$helper_dir/added_servers

network_sysconfig_file=/etc/sysconfig/network
dhclient_servers_files="/var/lib/dhclient/chrony.servers.*"
dnssrv_servers_files="$helper_dir/dnssrv@*"
dnssrv_timer_prefix=chrony-dnssrv@

. $network_sysconfig_file &> /dev/null

chrony_command() {
    $chronyc -a -n -m "$1"
}

is_running() {
    chrony_command "tracking" &> /dev/null
}

get_servers_files() {
    [ "$PEERNTP" != "no" ] && echo "$dhclient_servers_files"
    echo "$dnssrv_servers_files"
}

is_update_needed() {
    for file in $(get_servers_files) $added_servers_file; do
        [ -e "$file" ] && return 0
    done
    return 1
}

update_daemon() {
    local all_servers_with_args all_servers added_servers

    if ! is_running; then
        rm -f $added_servers_file
        return 0
    fi

    all_servers_with_args=$(cat $(get_servers_files) 2> /dev/null)

    all_servers=$(
        echo "$all_servers_with_args" |
            while read -r server serverargs; do
                echo "$server"
            done | sort -u)
    added_servers=$( (
        cat $added_servers_file 2> /dev/null
        echo "$all_servers_with_args" |
            while read -r server serverargs; do
                [ -z "$server" ] && continue
                chrony_command "add server $server $serverargs" &> /dev/null &&
                    echo "$server"
            done) | sort -u)

    comm -23 <(echo -n "$added_servers") <(echo -n "$all_servers") |
        while read -r server; do
            chrony_command "delete $server" &> /dev/null
        done

    added_servers=$(comm -12 <(echo -n "$added_servers") <(echo -n "$all_servers"))

    if [ -n "$added_servers" ]; then
        echo "$added_servers" > $added_servers_file
    else
        rm -f $added_servers_file
    fi
}

get_dnssrv_servers() {
    local name=$1 output

    if ! command -v dig &> /dev/null; then
        echo "Missing dig (DNS lookup utility)" >&2
        return 1
    fi

    output=$(dig "$name" srv +short +ndots=2 +search 2> /dev/null) || return 0

    echo "$output" | while read -r _ _ port target; do
        server=${target%.}
        [ -z "$server" ] && continue
        echo "$server port $port ${NTPSERVERARGS:-iburst}"
    done
}

check_dnssrv_name() {
    local name=$1

    if [ -z "$name" ]; then
        echo "No DNS SRV name specified" >&2
        return 1
    fi

    if [ "${name:0:9}" != _ntp._udp ]; then
        echo "DNS SRV name $name doesn't start with _ntp._udp" >&2
        return 1
    fi
}

update_dnssrv_servers() {
    local name=$1
    local srv_file=$helper_dir/dnssrv@$name servers

    check_dnssrv_name "$name" || return 1

    servers=$(get_dnssrv_servers "$name")
    if [ -n "$servers" ]; then
        echo "$servers" > "$srv_file"
    else
        rm -f "$srv_file"
    fi
}

set_dnssrv_timer() {
    local state=$1 name=$2
    local srv_file=$helper_dir/dnssrv@$name servers
    local timer

    timer=$dnssrv_timer_prefix$(systemd-escape "$name").timer || return 1

    check_dnssrv_name "$name" || return 1

    if [ "$state" = enable ]; then
        systemctl enable "$timer"
        systemctl start "$timer"
    elif [ "$state" = disable ]; then
        systemctl stop "$timer"
        systemctl disable "$timer"
        rm -f "$srv_file"
    fi
}

list_dnssrv_timers() {
    systemctl --all --full -t timer list-units | grep "^$dnssrv_timer_prefix" | \
            sed "s|^$dnssrv_timer_prefix\(.*\)\.timer.*|\1|" |
        while read -r name; do
            systemd-escape --unescape "$name"
        done
}

prepare_helper_dir() {
    mkdir -p $helper_dir
    exec 100> $helper_dir/lock
    if ! flock -w 20 100; then
        echo "Failed to lock $helper_dir" >&2
        return 1
    fi
}

is_source_line() {
    local pattern="^[ \t]*(server|pool|peer|refclock)[ \t]+[^ \t]+"
    [[ "$1" =~ $pattern ]]
}

list_static_sources() {
    while read -r line; do
        if is_source_line "$line"; then
            echo "$line"
        fi
    done < $chrony_conf
}

set_static_sources() {
    local new_config tmp_conf

    new_config=$(
        sources=$(
            while read -r line; do
                is_source_line "$line" && echo "$line"
            done)

        while read -r line; do
            if ! is_source_line "$line"; then
                echo "$line"
                continue
            fi

            tmp_sources=$(
                local removed=0

                echo "$sources" | while read -r line2; do
                    if [ "$removed" -ne 0 ] || [ "$line" != "$line2" ]; then
                        echo "$line2"
                    else
                        removed=1
                    fi
                done)

            [ "$sources" == "$tmp_sources" ] && continue
            sources=$tmp_sources
            echo "$line"
        done < $chrony_conf

        echo "$sources"
    )

    tmp_conf=${chrony_conf}.tmp

    cp -a $chrony_conf $tmp_conf &&
        echo "$new_config" > $tmp_conf &&
        mv $tmp_conf $chrony_conf || return 1

    systemctl try-restart $chrony_service
}

print_help() {
    echo "Usage: $0 COMMAND"
    echo
    echo "Commands:"
    echo "  update-daemon"
    echo "  update-dnssrv-servers NAME"
    echo "  enable-dnssrv NAME"
    echo "  disable-dnssrv NAME"
    echo "  list-dnssrv"
    echo "  list-static-sources"
    echo "  set-static-sources < sources.list"
    echo "  is-running"
    echo "  command CHRONYC-COMMAND"
}

case "$1" in
    update-daemon|add-dhclient-servers|remove-dhclient-servers)
        is_update_needed || exit 0
        prepare_helper_dir && update_daemon
        ;;
    update-dnssrv-servers)
        prepare_helper_dir && update_dnssrv_servers "$2" && update_daemon
        ;;
    enable-dnssrv)
        set_dnssrv_timer enable "$2"
        ;;
    disable-dnssrv)
        set_dnssrv_timer disable "$2" && prepare_helper_dir && update_daemon
        ;;
    list-dnssrv)
        list_dnssrv_timers
        ;;
    list-static-sources)
        list_static_sources
        ;;
    set-static-sources)
        set_static_sources
        ;;
    is-running)
        is_running
        ;;
    command|forced-command)
        chrony_command "$2"
        ;;
    *)
        print_help
        exit 2
esac

exit $?

set local time with chrony

[!NOTE|label:references:]

chrony 详解

$ sudo timedatectl set-time "2020-02-23 12:23:01"                # <<========设置系统时间，因为开启了时间同步所以报错
Failed to set time: Automatic time synchronization is enabled
$ sudo systemctl stop chronyd
$ sudo timedatectl set-time "2020-02-23 12:23:01"                # <<==========stop chronyd 后修改系统时间，报错依旧
Failed to set time: Automatic time synchronization is enabled
$ sudo systemctl status chronyd
● chronyd.service - NTP client/server
   Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since 四 2021-04-15 15:45:37 CST; 21s ago
     Docs: man:chronyd(8)
           man:chrony.conf(5)
  Process: 13722 ExecStartPost=/usr/libexec/chrony-helper update-daemon (code=exited, status=0/SUCCESS)
  Process: 13716 ExecStart=/usr/sbin/chronyd $OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 13720 (code=exited, status=0/SUCCESS)
 ...

$ date
2021年 04月 15日 星期四 15:46:13 CST

$ sudo timedatectl set-ntp false
$ sudo timedatectl set-time "2020-02-23 12:23:01"
$ sudo systemctl status chronyd
● chronyd.service - NTP client/server
   Loaded: loaded (/usr/lib/systemd/system/chronyd.service; disabled; vendor preset: enabled)
   Active: inactive (dead)
     Docs: man:chronyd(8)
           man:chrony.conf(5)
           ...

$ sudo timedatectl status      　　　　                      # <<============ 显示当前系统和RTC设置
      Local time: 日 2020-02-23 12:23:39 CST
  Universal time: 日 2020-02-23 04:23:39 UTC
        RTC time: 日 2020-02-23 04:23:39
       Time zone: Asia/Shanghai (CST, +0800)
     NTP enabled: no
NTP synchronized: no
 RTC in local TZ: no
      DST active: n/a
$ sudo timedatectl set-ntp true
$ sudo timedatectl status
      Local time: 日 2020-02-23 12:24:14 CST
  Universal time: 日 2020-02-23 04:24:14 UTC
        RTC time: 日 2020-02-23 04:24:14
       Time zone: Asia/Shanghai (CST, +0800)
     NTP enabled: yes
NTP synchronized: no
 RTC in local TZ: no
      DST active: n/a
$ sudo systemctl start chronyd

$ sudo timedatectl status
      Local time: 四 2021-04-15 15:48:52 CST
  Universal time: 四 2021-04-15 07:48:52 UTC
        RTC time: 日 2020-02-23 04:24:44
       Time zone: Asia/Shanghai (CST, +0800)
     NTP enabled: yes
NTP synchronized: yes
 RTC in local TZ: no
      DST active: n/a
$ sudo timedatectl set-time "2020-02-23 12:23:01"
Failed to set time: Automatic time synchronization is enabled

$ sudo timedatectl set-ntp false      　　　　               # <<============= 禁用基于NTP的网络时间同步
$ sudo systemctl status chronyd
● chronyd.service - NTP client/server
   Loaded: loaded (/usr/lib/systemd/system/chronyd.service; disabled; vendor preset: enabled)
   Active: inactive (dead)
     Docs: man:chronyd(8)
           man:chrony.conf(5)
           ...

$ sudo timedatectl set-time "2020-02-23 12:23:01"　　　　　　# <<=========== 再次设置时间成功
$ sudo timedatectl set-ntp true  　　　　                    # <<============ 启用基于NTP的网络时间同步

$ sudo systemctl status chronyd
● chronyd.service - NTP client/server
   Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled)
   Active: active (running) since 日 2020-02-23 12:23:25 CST; 4s ago
     Docs: man:chronyd(8)
           man:chrony.conf(5)
  Process: 16110 ExecStartPost=/usr/libexec/chrony-helper update-daemon (code=exited, status=0/SUCCESS)
  Process: 16103 ExecStart=/usr/sbin/chronyd $OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 16105 (chronyd)
    Tasks: 1
   CGroup: /system.slice/chronyd.service
           └─16105 /usr/sbin/chronyd
           ...

$ date
2021年 04月 15日 星期四 15:52:14 CST

systemd-timesyncd

[!NOTE]

issue in chrony with timedatactl

$ timedatectl
               Local time: Tue 2024-04-02 16:11:02 PDT
           Universal time: Tue 2024-04-02 23:11:02 UTC
                 RTC time: Tue 2024-04-02 23:11:02
                Time zone: America/Los_Angeles (PDT, -0700)
System clock synchronized: yes
              NTP service: n/a
          RTC in local TZ: no

$ sudo timedatectl set-ntp on
Failed to set ntp: NTP not supported

systemd-timesyncd

install

[!NOTE|label:references:]

* iMarslo: epel install

# centos 8
$ sudo dnf reinstall https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
$ sudo yum install -y systemd-timesyncd

enable and start services

$ sudo systemctl enable systemd-timesyncd.service
Created symlink /etc/systemd/system/dbus-org.freedesktop.timesync1.service → /usr/lib/systemd/system/systemd-timesyncd.service.
Created symlink /etc/systemd/system/sysinit.target.wants/systemd-timesyncd.service → /usr/lib/systemd/system/systemd-timesyncd.service.

$ sudo systemctl start systemd-timesyncd.service

$ sudo systemctl is-active systemd-timesyncd.service
active
$ sudo systemctl is-enabled systemd-timesyncd.service
enabled

config

[!NOTE]

NTP Pool Project

timesyncd.conf

systemd-timesyncd.service

$ cat /etc/systemd/timesyncd.conf | sed -r '/^(#.*)$/d' | sed -r '/^\s*$/d'
[Time]
NTP=0.north-america.pool.ntp.org 1.north-america.pool.ntp.org 2.north-america.pool.ntp.org 3.north-america.pool.ntp.org
FallbackNTP=0.pool.ntp.org 1.pool.ntp.org 0.fr.pool.ntp.org

# or
$ sudo systemd-analyze cat-config systemd/timesyncd.conf | sed -r '/^(#.*)$/d' | sed -r '/^\s*$/d'
[Time]
NTP=0.north-america.pool.ntp.org 1.north-america.pool.ntp.org 2.north-america.pool.ntp.org 3.north-america.pool.ntp.org
FallbackNTP=0.pool.ntp.org 1.pool.ntp.org 0.fr.pool.ntp.org

commands

show-timesync

$ timedatectl show-timesync --all
LinkNTPServers=
SystemNTPServers=0.north-america.pool.ntp.org 1.north-america.pool.ntp.org 2.north-america.pool.ntp.org 3.north-america.pool.ntp.org
RuntimeNTPServers=
FallbackNTPServers=0.pool.ntp.org 1.pool.ntp.org 0.fr.pool.ntp.org
ServerName=0.north-america.pool.ntp.org
ServerAddress=104.131.155.175
RootDistanceMaxUSec=5s
PollIntervalMinUSec=32s
PollIntervalMaxUSec=34min 8s
PollIntervalUSec=1min 4s
NTPMessage={ Leap=0, Version=4, Mode=4, Stratum=2, Precision=-30, RootDelay=3.097ms, RootDispersion=6.774ms, Reference=408E7A25, OriginateTimestamp=Tue 2024-04-02 16:59:33 PDT, ReceiveTimestamp=Tue 2024-04-02 16:59:33 PDT, TransmitTimestamp=Tue 2024-04-02 16:59:33 PDT, DestinationTimestamp=Tue 2024-04-02 16:59:33 PDT, Ignored=no PacketCount=1, Jitter=0 }
Frequency=1375360

timesync-status

$ timedatectl timesync-status
       Server: 104.131.155.175 (0.north-america.pool.ntp.org)
Poll interval: 1min 4s (min: 32s; max 34min 8s)
         Leap: normal
      Version: 4
      Stratum: 2
    Reference: 408E7A25
    Precision: 0 (-30)
Root distance: 8.322ms (max: 5s)
       Offset: +4.077ms
        Delay: 24.042ms
       Jitter: 0
 Packet count: 1
    Frequency: +20.986ppm

check log

$ journalctl -u systemd-timesyncd --no-hostname --since "1 day ago"

time & date

timezone

timezone setup

tzdata installation with noninteractive

date

epoch

timestamps

format

IOS 8601

rfc-3339

utc

timezone

common formats

convert

timestamps to epoch

epoch to timestamps

convert in different timezone

get daylight saving

how many days from timestamps

calculate time different

time described by STRING

two times different

simple one-liner

`datediff` (`ddiff`)

calculate with epoch

transfer date format

chrony

install

conf

commands

`/usr/libexec/chrony-helper`

set local time with chrony

systemd-timesyncd

install

config

commands

results matching ""

No results matching ""

timezone

timezone setup

tzdata installation with noninteractive

date

epoch

timestamps

format

IOS 8601

rfc-3339

utc

timezone

common formats

convert

timestamps to epoch

epoch to timestamps

convert in different timezone

get daylight saving

how many days from timestamps

calculate time different

time described by STRING

two times different

simple one-liner

datediff (ddiff)

calculate with epoch

transfer date format

chrony

install

conf

commands

/usr/libexec/chrony-helper

set local time with chrony

systemd-timesyncd

install

config

commands

results matching ""

No results matching ""

`datediff` (`ddiff`)

`/usr/libexec/chrony-helper`