Re: noatime on ufs2

> Why not make noatime the default across the whole system? Outside of mbox why is recording access time actually useful?

Exactly.

I've never found any compelling reason in most uses to enable "atime", except perhaps local mail but as addressed in other answers it is a relic of the past mostly irrelevant today.  And its drawbacks are well known and can be serious.

The auditing use is not what I consider "normal" in the sense I suspect it concerns a small minority of users (maybe even tiny).  Plus, serious auditing requires keeping a log (generally immutable) of accesses, i.e., more than a single time and, as pointed out in another answer, at least the ID of the user performing the access.  Updating the access time field on files/directories doesn't address both.

What "relatime" only gives you is a guarantee that you know that some file has been accessed at some point after its last modification (or creation), and that the access time is correct if precision is only a day.  It also generally lowers I/O obviously, but not in some scenarios (file creation and subsequent read).

So, to me, at this point, it still sounds more than a gimmick than something really useful.  If someone has a precise use case for it and motivation, than of course please go ahead.

In the short term, I'd vote for turning "atime" off by default.

Thanks and regards.

-- 
Olivier Certner