June 02, 2007

Jess joins Pat

Yesterday evening, I adjusted CompSoc’s DNS and mail servers… we should manage to avoid having all the domains fail dismally next Wednesday. (It will be four weeks since the authoritative DNS server became unavailable because of The Cupboard Incident, and there was a nasty timeout lurking.) Now that we’re able to configure DNS again, I finally set up our new backup mail relay – both ‘pat.warwickcompsoc.co.uk’ and ‘jess.warwickcompsoc.co.uk’ now work.

Managing mail servers is one of the more enjoyable things I do – it causes pain when ‘pat’ disappears, though; it has been not just our only off-campus mail relay, it is the vehicle through which our outgoing off-campus mail is delivered. Fortunately, from Postfix 2.3, we can use the smtp_fallback_relay option to reroute the outgoing mail via either ‘jess’ or the Warwick mail relays. (I tested it by stopping pat’s mail server temporarily, and mailing an off-campus account.) So we now have automatic backup routes for both incoming and outgoing mail. In the past, an admin (that’s me) would have to manually change the default smtp relay.

There are still possible failure cases where I won’t be able to read my email – for instance, if molotov becomes inaccessible. It would be nice to create some redundancy here, but that would probably involve another off-campus server, and some complicated mirroring.

It takes quite a bit for email to actually stop being received – both molotov and pat would have to become inaccessible, at which point we lose DNS. It would be nice if we could add more nameservers to the domain records – for instance, we could put one on jess. I don’t know if that’s possible with our current domain provider, though.

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From 20th August 2007, this blog is no longer being updated. For something more recent, please visit Tim Retout’s website.

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