Do I need to re-mount NFS after IP address changed on NFS server ?

[Gary Yu]

Hi all,

We are going to change IP address on server, which has some exported NFS directories. On the NFS client servers, do I need to umount the file system before the change, which means I have to stop some very important application, or it will automatically accomodate the change (the local hosts file will be updated of course)

I don't have an environment to test this out, so I'm asking for help here...

thanks,
Gary

[Stefan Farrelly]

Well, it depends on if you update DNS at the same time. Any remote server with an nfs mount uses DNS to verify the IP of the nfs server, so if you change the server IP and update DNS at the same time (or on any nfs client change dns to search /etc/hosts first then you can edit the /etc/hosts file with the nfs servers new ip at the same time) you may be able to get away with it, but I doubt it.

Whenever we change an IP on a server we always reboot to ensure everything still works and starts up aok. Last time i tried changing the ip on the fly some stuff stopped working so I needed a reboot anyway - and when you reboot update your DNS server at the same time - which may take up to an hour or two to filter down to all nfs clients anyway, so I would go for a reboot, just to be safe.

[Pete Randall]

Though you may be able to do this on the fly, I typically use /sbin/set_parms ip_address which will prompt you to reboot the NFS server. That will cause everything to be remounted anyway.


Pete

[Uday_S_Ankolekar]

Well, If you change IP-address of a server it's good to reboot the box and if you do so NFS will mount back with new setup.

If you don't want to boot and you change your DNS and local hosts file then it should work depending upon how you resolve the address.

Goodluck
-USA..

[Gary Yu]

thank you all for the suggestion, the difference between reboot or not reboot is how long we plan for the down time, it seemed that we should plan longer just to be safe.

thanks,
Gary

[Steven E. Protter]

You can change the IP address. Then on the client umount and remount. This will only disrupt transfers in progress.

You can check that on the client with fuser -cu /mount_point

AS noted above you'll have to update the dns server at the same time so new connections will resolve properly.

So, this is something you can pull off without downtime. I however would do it during downtime.

SEP

[Gary Yu]

Hi, another question related to this, after I changed the DNS entry, will OTHER servers lookup the new IP immediately, or there's a kind of local cache to store dns entries (maybe in routing table ??) like the ARP cache.

thanks,
Gary

[Uday_S_Ankolekar · Accepted solution]

No need to change anything if you have changed on DNS server. The modified configiguration start working soon after the changes made and after restarting named process, unless you have secondary DNS servers in your env. To get latest file from primary server you need run sig_named restart on secondary servers.

-USA..