hostname problem with snmpd

[Dave Mason]

One other thing I forgot to include.  When the hostname is changed as I 
mentioned, the graceful kill with SIGTERM doesnt work, so we have to use 
"kill -9" in step 5 below.  Not sure if that's a symptom of this 
problem, or something that has another cause but that in turn causes 
this problem.  For some time I thought the kill -9 could be corrupting 
the data files, but I can copy them to another system, load them into an 
agent, and the agent will run OK.  It seems that only on the original 
system where the hostname was changed is there a problem.

As you can guess I'm a bit lost on this one - thanks for any help you 
might have or suggestions for where to start.
Dave

Dave Mason wrote:

> Hi,
> I'm having a strange problem where a user is changing the hostname to 
> something that doesnt resolve, and the agent does not respond even 
> after the hostname is restored to its proper value.  The problem can 
> only be fixed by deleting the persistence data files and restarting.  
> Here's the full sequence:
>
> 1. set hostname to something that DNS can't resolve, ie
>   hostname xxx
> 2. start snmpd as usual.  The same problem also happens if the agent 
> is already running before the hostname is changed.
> 3. try some SNMP GETs.  They fail as expected.
> 4. restore hostname to it's proper value, which DNS can resolve
> 5. restart snmpd with persistence data files from before.
> 6. try SNMP GETs.  agent still does not respond.
> 7. to fix. stop the agent, delete persistence data files, and restart.
>
> The obvious answer is to avoid screwing up the host name, but 
> customers being customers, they want a solution.  They believe the 
> agent should work fine once the hostname is restored, and they don't 
> want to lose their persistence data.  Is it possible that the hostname 
> is written into the persistence files somewhere, causing problems once 
> it's changed?
>
> We have had some other issues with persistence files, so I'm also 
> curious as to what is going on.  We're running on Red Hat 7.3, agent++ 
> version 3.5.3a, snmp++ version 3.1.6c.
>
> Regards,
> Dave
>