31.5 Configuring the Secondary DNS | HP Certified: HP-UX System Administration

The secondary name server provides backup to the primary DNS so that if the primary server fails, users can still resolve host names using the secondary name server. To configure the secondary name server, you don't need to run hosts_to_named . Simply follow these steps.

Create a /etc/named.data directory using the mkdir command.
Copy the boot.sec or boot.sec.save file as /etc/named.boot from the primary name server. If you copy named.sec , DNS data base files will not be created on the local disk. This is useful if you have limited disk space on the secondary server. The drawback is that the server will not be started at boot time if the primary server is not up and running. If you use named.sec.save , local DNS data base files will be created and the server will be able to start at boot time even if the primary server is down.
Copy db.127.0.0 from the primary server to the /etc/named.data directory.
Copy db.cache from the primary server to the /etc/named.data directory.
If you want to create local disk data base files, download the remaining files from the /etc/named.data directory on the primary server to the local /etc/named.data directory.
Update the /etc/rc.config.d/namesvrs file to start named at boot time. The value of the NAMED variable in this file should be changed to 1.
Start named using the /sbin/init.d/named start command.

Updating Data Base Files on the Secondary Server

DNS data base files contain a part in the beginning like the one shown here.

 @       IN      SOA     myhp.boota.com. root.myhp.boota.com. (                                   1       ; Serial                                   10800   ; Refresh every 3 hours                                   3600    ; Retry every hour                                   604800  ; Expire after a week                                   86400 ) ; Minimum ttl of 1 day

This part contains important information for the secondary name server. Fields in this part are explained next .

`Serial`	This field shows the serial number of the data base file. When updating data base files on the primary server, this serial number should be incremented. The secondary server checks the serial number from time to time, and if it finds that the serial number is incremented on the primary server, it downloads the updated file automatically.
`Refresh`	This is the time in seconds after which the secondary server checks any updated files on the primary server. The above entry uses a refresh time of 3 hours. This is the time when the secondary server checks the serial numbers of data files on the primary server to refresh its own files.
`Retry`	If the primary server can't be contacted at the refresh time, the secondary server retries after the retry interval. This is again a time in seconds.
`Expire`	All data are expired if the primary server can't be contacted within this time.
`Minimum ttl`	This is the minimum time for a file to be retained if no time is specified.

The secondary server keeps its data base updated automatically depending on this information. However, you can update the secondary server data base at any time using the sig_named restart command.

Top