On Tue, Apr 28, 2009 at 6:39 PM, Duncan <1i5t5.dun...@cox.net> wrote: > Nikos Chantziaras <rea...@arcor.de> posted gt7r28$cq...@ger.gmane.org, > excerpted below, on Wed, 29 Apr 2009 00:05:33 +0300: > >> I have "defaults,noatime" and yet mount reports: >> >> /dev/root on / type ext4 (rw,noatime,barrier=1,data=ordered) >> >> Where does "rw,barrier=1,data=ordered" come from if not from "defaults"? > > Those (but for rw which is the normal default) are defaults of either > the kernel or the filesystem itself, as set at mkfs time or with tune2fs. > > There's really quite a hierarchy of options and fall-thru defaults: > > Anything set on the mount commandline takes priority (well, after > physical properties such as read-only for CDROM and floppies with write- > protect set), > > followed by what's in fstab or the hal config, > > followed by options set for that particular filesystem at mkfs time or > with the filesystem tuner (tun2fs, reiserfstune, whatever), > > followed by kernel defaults specific to that type of fs (ext3 defaulted > to data=ordered but that's set to change to data=writeback in 2.6.30, > after some fixes they've done but it's still rather controversial), > > followed by mount's normal defaults.
Seems root mounts get special treatment as well. Compare my / & /opt - both ext4, both created identically & mounted with just noatime: /dev/vg/root on / type ext4 (rw,noatime,barrier=1,data=ordered) /dev/mapper/vg-opt on /opt type ext4 (rw,noatime) Or perhaps its just more verbose since like Duncan said data=ordered is the default & barriers are currently disabled on lvm. Wil
