On Jun 13, 2012, at 11:53 PM, Shawn Wells wrote:
I received this note from a colleague today regarding content in the
scap-security-guide for RHEL6:
> Ext4 mounts devices with the relatime option by default. Probably not a good idea
for secure environments. Means atime is not accurate. Very bad for systems using AIDE.
RHEL 6 security guide needs to turn atime back on for Ext4 mounts.
> cat /proc/mounts
> Sent from iPhone.
When he states that "atime is not accurate" I believe he's referring to how
relatime maintains atime data, but not for each time the file was accessed. Only modified.
From a performance perspective relatime makes a lot of sense. Enablement of relatime
means that the filesystem will not write read-times to a file when read. Imagine recording
every time a file in hadoop or a highly utilized fileshare was read... that could be a lot
of overhead which relatime prevents.
With that said, we're writing a security guide and not a performance guide. What does
everyone think about this, and what should we do? One option is to set
"default_relatime=0" in grub to prevent any filesystem from doing this. Is that
Audit rules record when something you care about has been accessed.