Consider mounting /rw with "noatime" mount flag

[cfcs]

Qubes OS version (e.g., R3.2):

R3.2

Affected TemplateVMs (e.g., fedora-23, if applicable):

fedora-23 and debian-8, also / in dom0

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Expected behavior:

Unnecessary disk writes are kept to a minimum, ie /rw being mounted with -o noatime.

Actual behavior:

Atime for every inode in every vm is updated often because /rw is mounted relatime.

Steps to reproduce the behavior:

mount | grep '^/' | fgrep --color time

General notes:

from man mount:

       relatime
              Update  inode  access  times  relative to modify or change time.
              Access time is only updated if the previous access time was ear‐
              lier  than  the  current  modify  or  change  time.  (Similar to
              noatime, but it doesn't break mutt or  other  applications  that
              need  to know if a file has been read since the last time it was
              modified.)

              Since Linux 2.6.30, the kernel defaults to the behavior provided
              by   this   option  (unless  noatime  was  specified),  and  the
              strictatime option is required to obtain traditional  semantics.
              In  addition, since Linux 2.6.30, the file's last access time is
              always updated if it is more than 1 day old.

So this means that every day, fgrep -r or git grep will update metadata on everything they touch, resulting in a large amount of writes, which in turn means more data to backup every day. I personally believe atime is pretty useless, but if there are arguments for this, please do speak up!

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Related issues: