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Date: Tue, 1 Aug 2006 16:39:51 +0100
From: Hedi Berriche <hedi@berriche.co.uk>
Subject: Re: xfs_check refuses to work on readonly fs
Message-ID: <20060801153951.GB17036@linuxathome.me>
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To: CN <cnliou9@fastmail.fm>
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Hi,

Based on the info you provided I infer that you're running Linux.

On Tue, Aug 01, 2006 at 14:00 CN <cnliou9@fastmail.fm> wrote:
| Hi!
|
| # init 1
| # mount -o ro,remount /
| # mount
| /dev/hda1 on / type xfs (rw)
| # xfs_check /dev/hda1
| xfs_check: /dev/hda1 contains a mounted and writable filesystem
|
| xfs_check/xfs_repair are willing to work only when I boot from a disk
| and check/repair the other unmounted disk.
|
| Why "mount" shows (rw) instead of (ro) even "mount -o ro,remount /" is
| issued?

Because mount is relying on /etc/mtab which couldn't be updated
precisely because / was remounted ro.

You'll need a recent xfsprogs version, at least 2.7.17 IIRC, one
that uses that uses /proc/mounts instead of /etc/mtab to check
filesystem status.

Or you can use a dirty and quick hack

    - prior to remounting ro, edit /etc/mtab and change the root fs entry from
    rw to ro.
    - remount ro
    - run your xfs_check/xfs_repair in dangerous mode.

FWIW the safe thing to do after a repair on a mounted root FS is to reboot.

Cheers,
Hedi.

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