What is the first Linux kernel release to set relatime as the default mount option?

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    The spelling of that option is very unfortunate: I will forever parse it as a misprint of "realtime". – dmckee --- ex-moderator kitten Aug 1 '11 at 22:47

I remember the change, but couldn't remember the date. It seems that it was back in 2007. According to the article, relatime was available in 2.6.20, and it became the default option a few versions after that (2.6.24) maybe.

Edit: man mount /relatime says 2.6.30.

From ChangeLog-2.6.30:

commit 0a1c01c9477602ee8b44548a9405b2c1d587b5a2
Author: Matthew Garrett <mjg@redhat.com>
Date:   Thu Mar 26 17:53:14 2009 +0000

Make relatime default

Change the default behaviour of the kernel to use relatime for all
filesystems. This can be overridden with the "strictatime" mount

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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  • Hmm, my CentOS 5 servers using 2.6.21 don't appear to have relatime. Strange. – Xiong Chiamiov Nov 28 '12 at 22:41

relatime mount option is default default since RHEL/CentOS/Scientific Linux version 6 (see here).

If relatime option is used, the atime is updated when:

  1. old atime is <= than mtime/ctime
  2. at least 24 hours (hardcoded in fs/inode.c) have passed since the last atime update
  3. inode is dirty (or the file contents have been changed but it’s in the buffer and have not been written to the physical disk yet)
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