Am Freitag, den 30.10.2009, 11:14 -0500 schrieb Eric Sandeen: > Alexey Fisher wrote: > > Am Freitag, den 30.10.2009, 10:14 -0500 schrieb Eric Sandeen: > > ... > > >> 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. > > So point it at the partition not the drive: > > [root@neon ~]# hdparm -r 1 /dev/sda1 > > /dev/sda1: > setting readonly to 1 (on) > readonly = 1 (on) > [root@neon ~]# hdparm -r /dev/sda2 > > /dev/sda2: > readonly = 0 (off) > > It doesn't change the hardware, it sets a flag on the kernel's block > device structure. ok, got it. Every day learning something new. It was not clear for me, after i read man hdparm: "Get/set read-only flag for the device. When set, Linux disallows write operations on the device." > > 2. the fact xfs and ext[3,4] use different options for true_ro make > > things complicated. > > the hazards of being an open source sysadmin I guess. :( are there any plans to unify mount options? > > 3. the definition of ro is broken. > > depends on what you mean by ro. A user can only read from the > filesystem so it is accurate in that respect. Is "ro" for the fs or the > bdev? Semantic differences but not necessarily broken. Hmm... bdev. any chance to do temporary recovery and load it as external journal if ro used? Anyway, you already pointed me to hdparm, so i can use it too. > > 4. many frustrated admins who mounted part of raid1 only with "-o ro" > > Dunno what you mean by that ... raid1 is down, so you need for some reasons to mount ro only one disk of the array. Needed to do it for short time (i used -o ro), now i know this probably was a bad idea (bad me, should read documentation). Need to check my raid now. Suddenly i'm not alone who doing this :( > -Eric > > > Regards, > > Alexey Eric, Greg, Thank you 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
