Exadata: ILOM DNS change / fix

I recently faced this error during a cell patching session:

cel01: [ERROR] Details:
cel01: ILOM DNS server 0.0.0.0 defined in system configiuration            : FAILED
cel01: [Info]: Consistency check FAILED

You can also find it in list alerthistory:

FAILED [Warning]: ILOM DNS server(s) could not be retrieved [Info]: Consistency check FAILED

This happens because the ILOM had no DNS defined as we can see below:

[root@db01 ~]# ssh cel01-ilom
Password:
-> show /sp/clients/dns
/SP/clients/dns
    Targets:
    Properties:
        auto_dns = enabled
        nameserver = (none)       <==== no DNS server
        retries = 1
        searchpath = (none)       <==== no search path
        timeout = 5
    Commands:
        cd
        set
        show
->

We can see on the log above that nor the DNS nor the search domain are defined here. We can then define them as below (this is a 100% online operation):

-> set /sp/clients/dns nameserver=10.11.12.13
Set 'nameserver' to '10.11.12.13'
-> set /sp/clients/dns searchpath=domain.com
Set 'searchpath' to 'domain.com'
-> 

And a quick check to verify that the config is now correct:

-> show /sp/clients/dns
/SP/clients/dns
    Targets:
    Properties:
        auto_dns = enabled
        nameserver = 10.11.12.13  <==== good
        retries = 1
        searchpath = domain.com   <==== good
        timeout = 5
    Commands:
        cd
        set
        show
-> 

An easy and 100% online fix !