docker run --name ntp -d -p 123:123/udp lfkeitel/ntpd

The image exposes NTP port 123/udp.

The configuration is located at /etc/ntp.conf and by default following will be generated:

interface listen all
driftfile /var/lib/ntp/ntp.drift

statsdir /var/log/ntpstats/

statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable

restrict default kod notrap nomodify nopeer
restrict -6 default kod notrap nomodify nopeer

restrict 127.0.0.1
restrict ::1

server 127.127.1.0 # local clock
fudge 127.127.1.0 stratum 10

logfile /dev/stdout

server 0.pool.ntp.org iburst
server 1.pool.ntp.org iburst
server 2.pool.ntp.org iburst
server 3.pool.ntp.org iburst

To set servers, use the environment variables SERVERS and SERVERS_IBURST. SERVERS_IBURST will simply add the iburst option for the servers in the list. If no servers are specified, servers from the global NTP pool are used. Servers are space separated so make sure to enclose them in quotes.

docker run \
    --name ntp \
    -e SERVERS_IBURST='0.pool.ntp.org 1.pool.ntp.org'
    lfkeitel/ntpd:latest

Any other configuration can be done by either making a new image from this one with a custom config, or using a volume mount to /etc/ntp.conf.

Statistics for loopstats, peerstats, and clockstats are enabled by default and are stored in /var/log/ntpstats which is exposed as a volume. You can control this with the environment variables STATS_ENABLED and CRON_ENABLED. Unless specified otherwise, CRON_ENABLED will be the same as STATS_ENABLED. Cron is used to rotate NTP statistics logs. If you don't want to rotate logs, set CRON_ENABLED=false. To disable statistics altogether, set STATS_ENABLED=false. If statistics are disabled, cron will also be disabled.

By default, no servers are allowed to peer with ntpd. The environment variable ALLOWED_PEERS can be used to list servers that are allowed to peer. This list will generate restict lines with the format restrict $SERVER kod notrap nomodify.