Can one mount the root filesystem with noatime?Generally speaking, one can mount any of the filesystems with noatime.
Whether or not this is a good thing depends on your use. As was
previously mentioned, some software (but not a lot) depends on it.
The only thing that comes to mind offhand is mail software that
uses a single-file monolithic mailbox. (Cyrus IMAPd, for example,
uses one file per message, so noatime doesn't affect its behavior).
With noatime, you also (obviously) lose the ability to look at
access times. *Once*, in my career, that was useful for doing
forensics on a cracked system.
OTOH, it can make a good performance improvement. On SSDs, it's
can also help extend the drive's life.