Am Freitag, den 30.10.2009, 10:14 -0500 schrieb Eric Sandeen: > Greg Freemyer wrote: > > On Fri, Oct 30, 2009 at 4:22 AM, <bugzilla-daemon@xxxxxxxxxxxxxxxxxxx> wrote: > >> http://bugzilla.kernel.org/show_bug.cgi?id=14354 > >> > >> --- Comment #152 from Alexey Fisher <bug-track@xxxxxxxxxxxxxxxxx> 2009-10-30 08:22:10 --- > >> Ted, > >> Thank you for explanation :) > >> Notice: i learning computer forensic, and was trained to mount all evidence > >> systems with "-o ro" to not contaminate it. It seems like ext4 break this > >> tradition, so many forensics will surprised why md5sum do not match. > > > > Ted, (Alexey there is a response to further down). > > > > I have not followed this thread ultra-closely but Alexey's comment got > > my attention. > > > > Ignoring computer forensics, with LVM snapshots, hardware raid array > > snapshots, etc. even in the presence of a dirty log, we need to be > > able to mount a drive in true read-only fashion fro many backup > > operations to function correctly. > > > > XFS added an extra mount flag for that 5 or so years ago. > > I hope ext4 either has or will add a true read-only mount option. > > Maybe Eric Sandeen remembers the actual drivers for adding that > > feature to XFS. > > > > After a little brief digging I'm not sure when the xfs mount option went > in or why... > > But for both > > xfs: mount -o ro,norecovery > > and > > ext[34]: mount -o ro,noload > > I don't think either one should touch the disk. > > Also, both should skip journal replay if you set the block device > readonly prior to mount (hdparm -r can do this). Interesting tip, thank you. But there is some problems: 1. "hdparm -r" will set complete drive to ro mode. This is bad if i use /dev/sda1 for root and /dev/sda5 need to be forced readonly. 2. the fact xfs and ext[3,4] use different options for true_ro make things complicated. 3. the definition of ro is broken. 4. many frustrated admins who mounted part of raid1 only with "-o ro" Regards, Alexey -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
