# man ntpdate
COMMAND LINE OPTIONS
-B Force the time to always be slewed using the adjtime() system call, even if the measured
offset is greater than +-500 ms. The default is to step the time using settimeofday() if
the offset is greater than +-500 ms. Note that, if the offset is much greater than +-500
ms in this case, that it can take a long time (hours) to slew the clock to the correct
value. During this time. the host should not be used to synchronize clients.
-b Force the time to be stepped using the settimeofday() system call, rather than slewed
(default) using the adjtime() system call. This option should be used when called from a
startup file at boot time.
-u Direct ntpdate to use an unprivileged port for outgoing packets. This is most useful when
behind a firewall that blocks incoming traffic to privileged ports, and you want to syn‐
chronize with hosts beyond the firewall. Note that the -d option always uses unprivileged
ports.
# ntpdate -Buv xx.xx.xx.xx
# /etc/init.d/ntpd stop # ntpdate -b -f xx.xx.xx.xx # /etc/init.d/ntpd start
# systemctl stop chronyd # ntpdate -b -f xx.xx.xx.xx # systemctl start chronyd