Implication of clock skew on certificate validity
When a master server issues a certificate, it determines for how long the certificate will be valid for the host to use. The master server sets the validity of the certificate based on its own time, recording two timestamps: Not before and Not after. The certificate is valid only between these two timestamps.
The clock on the master server and the clock on the host that will receive the certificate should be in sync so that the certificate is valid for as long as is expected, given the timestamps.
The hosts can reside in different time zones, as long as the clock on each host is set to the correct time for that host's timezone. As a general practice, NetBackup recommends using a service such as Network Time Protocol (NTP) to automatically keep all clocks on all hosts in the NetBackup domain synchronized.
If the clocks are not in sync, the difference can result in the following consequences:
If the host clock is ahead of the master server, the validity period of the certificate will be less than expected on that particular host. If the difference is extreme and the clocks vary by more than the certificate's validity period, it is possible that if the master server issued a fresh certificate, it could be treated as expired.
If the host clock is behind the master server, a fresh certificate issued by the master server could be considered as unusable by the host because the host considers the certificate as not yet valid.
To determine whether the master server clock and the host clock are in sync
- Run the following command on the host to determine whether the host clock is in sync with the master server clock:
nbcertcmd -checkClockSkew -server master_server_name
- If the clock skew on the host is causing a problem with the certificate validity, take corrective actions as necessary.
The command returns one of the following results:
If both clocks are in sync, the following displays:
The current host clock is in sync with the master server.
If the current host is behind the master server, the command reports the difference in seconds:
The current host clock is behind the master server by 36 seconds(s).
If the current host is ahead of the master server, the command reports the difference in seconds:
The current host clock is ahead of the master server by 86363 second(s).
If the command is run on the master server, the command skips the check and displays the following:
Specified server is same as the current host. Clock skew check is skipped.