> I can think of two ways to acheive this (each of which may be absurd
> given better knowledge of fs internals than I have): Either a
> per-process switch disabling atime updates or a way to obtain a
> read-only clone of a block device which can be mounted ro,noatime.
The latter will not work, at least not for FFS and probably not for any
filesystem whose implementation was not specifically designed to
support it. The problem is that the `read-only' device is changing
behind the filesystem's back.
Unless you mean a read-only *snapshot* of a block device, in which case
you're basically back at snapshots, only at the block device level
instead of the filesystem level. (Actually, looking at the existing
snapshot support, it's not clear to me that's not exactly what it
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