networking and sendmail

[Matthew Gillen]

On 05/04/2011 12:39 PM, Jerry Feldman wrote:
> At work I have a number of VMs. When these VMs were configured with
> dynamic IP addresses, they booted very quickly, but now they tend to
> wait on sendmail and sm_client to time out. Everything else is fine. I
> can even ssh into the VM while it is waiting for sendmail. Sendmail is
> not configured.
> 
> Why would sendmail (and sm_client) timeout on a static IP but not with a
> dynamic IP.

Because sendmail is obnoxious in it's use of dns/name-resolution on
startup.  I've had this problem with sendmail going back as long as I've
been using it where if it can't look up the local hostname (or if the
hostname is misconfigured), then it just hangs on startup.

So I'm guessing you were using network manager when you used the DHCP
addresses, and NM rewrites the /etc/hosts file when it gets an address.

If you're still using NM with your static addresses, be aware that NM
has (until very recently) had some obnoxious behavior w.r.t. /etc/hosts
and static ip configurations (e.g. re-writing /etc/hosts such that the
hostname always pointed to 127.0.0.1 instead of the public IP).

In short, I think it's a DNS/name resolution issue.  Setting /etc/hosts
correctly should fix it, but watch out for NM rewriting it (and
re-breaking it in many cases).

HTH,
Matt