rdate
UDP 37¹øÆ÷Æ® »ç¿ë
ntpdate
123¹øÆ÷Æ® »ç¿ë
-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 synchronize with hosts beyond the firewall. Note that the -d option always uses unprivileged ports.
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