NTP Server : Configure NTP Server (Chrony)2026/04/24

	Install Chrony and Configure NTP server for time adjustment. NTP uses 123/UDP.
[1]	Install and Configure Chrony.

root@dlp:~#

apt -y install chrony

root@dlp:~#

vi /etc/chrony/sources.d/ubuntu-ntp-pools.sources

# line 4 : comment out default settings and add NTP server pool you like to use
# * OK to keep default if you do not have specific requirements
#pool 1.ntp.ubuntu.com iburst maxsources 1 nts prefer
#pool 2.ntp.ubuntu.com iburst maxsources 1 nts prefer
#pool 3.ntp.ubuntu.com iburst maxsources 1 nts prefer
#pool 4.ntp.ubuntu.com iburst maxsources 1 nts prefer
pool ntp.nict.jp iburst

root@dlp:~#

vi /etc/chrony/chrony.conf

# add to last line
# add network range you allow to receive time syncing requests from clients
allow 10.0.0.0/24

root@dlp:~#

systemctl restart chrony

[2]	If UFW is enabled, allow NTP service. NTP uses [123/UDP].

root@dlp:~#

ufw allow ntp

Rule added
Rule added (v6)

[3]	Verify it works normally.

root@dlp:~#

chronyc sources

MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^- ntp-b2.nict.go.jp             1   6    17    37  -1628us[-1628us] +/-   10ms
^* ntp-a2.nict.go.jp             1   6    17    38    +11us[ +260us] +/- 8633us
^- ntp-a3.nict.go.jp             1   6    17    37  -1336us[-1336us] +/- 9438us
^- ntp-k1.nict.jp                1   6    17    37   -235us[ -235us] +/- 8343us

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