Setting up an NTP server

First, make sure your system has the right time itself.

You should therefore have the ntp or ntpd package installed. Now simply add a restrict line without nopeer nor noquery against the subnetwork you wanna allow e.g.,

vi /etc/ntp.conf
restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
enable mode7

Don’t forget to setup the local clock as a fail-over, if internet connection goes down, so you still provide the service,

server  127.127.1.0 # local clock
fudge   127.127.1.0 stratum 10

#server 127.127.1.1     # LCL, local clock
#fudge  127.127.1.1 stratum 12  # increase stratum

restart ntpd and call the local daemon (mode7),

ntpdc -l
ntpdc -c sysinfo

refs.