Today’s snippet is from Run Your Own Mail Server, discussing local databases in Postfix.
We discussed the aliases file back in Chapter 1. An alias is a system-wide message forwarding, so that email sent to one address on the host can be redirected to a real account. Whenever you update the aliases file you must run newaliases to regenerate the database. This is a classic Unix feature, but Postfix lets you follow that example and store most tables as local databases.
You’ll often hear these local databases called hash files. Originally a hash file was a specific format, but over decades that term has been catastrophically distorted until people apply it to almost any type of local database file. There’s the primordial Berkeley db file, btree files, DBM files, SDBM files, and more. Over drinks one might credibly argue that sqlite is backed by a super-hash file, but at that point someone pulls a blaster and the whole bar erupts.
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