DNS setting (resolv.conf) change without reboot

[Michael Fog Kristensen]

Dear all,

I need to change the DNS nameserver parameters in the resolv.conf file on my HP-UX 11 boxes, as our DNS server IP address is changing.

I expect that any changes to resolv.conf will not be in effect immediately, but is there a way to tell HP-UX to reload/reread the resolv.conf file (something like inetd -c) without having to reboot the box?

Thanks in advance

/Michael

[Jeff_Traigle]

Changes are immediate. No need to reboot or restart or reload anything.

[Michael Fog Kristensen]

Thanks, thats good news :o)

/Michael

[Geoff Wild]

Yes, change is immediate.

Also, as a tip, you can add these settings:

retrans 2500
retry 2


That means server will only try a dns server twice - if it doesn't respond, then it will go to the next one.

man resolv.conf for more info.

Rgds...Geoff

[rick jones]

Certainly, and newly created processes will see the changes in resolv.conf. In the past at least, and perhaps this has changed, processes which had already performed name/address lookups would have cached the DNS server information and would not consule resolv.conf again.

So, it wasn't necessary to _reboot_ to have the change take effect, but it could be necessary to restart certain long-lived processes.

One way to test the hpothesis would be to write your own long-lived process. Have it make a getaddrinfo() call (because everyone should have migrated off of gethostbyname by now) and then go to sleep for a while. Then change the resolve.conf file and see if when the process wakes-up and tries another getaddrinfo() call if it rereads resolve.conf - you can do that with the tusc system call trace utility - you should see open/read of resolve.conf and then if a long-lived process is going to see changes, either another arbitrary open/read of resolv.conf, or a stat() of it.