On Wed, Apr 05, 2000 at 03:11:44PM -0400, Lyle Seaman wrote:
> How does a readonly filesystem become inconsistent?
> (esp: "how does ext3 on readonly media" become inconsistent?)
> The obvious answer is "well, it *wasn't* readonly when it
> became inconsistent".
> If that's the case, then why do you care? Naively, I wouldn't
> think this is a big deal. Why am I wrong?
Because (a) existing Linux installations expect to mount the
root filesystem readonly until basic consistency checking has
been done; and (b) after a cold reboot, the filesystem will
need recovery before it can be mounted.
In practice there is no problem mounting the root filesystem
read-write if you have journaling, with one important exception:
if you detect actual errors on the fs such that a constency
check is required, mounting the fs read-write is dangerous.
(Ext2/ext3 mark an error flag in the superblock if they detect
dangerous inconsistencies in the fs so that a subsequent fsck
will be forced. I don't know if xfs does this or not.)