Cannot remount ntfs

[Agostino Russo]

Binary package hint: ntfs-3g

In Hardy (ntfs-3g version 1.1120) it is no longer possible to remount ntfs partitions. The error message is: "Remounting is not supported at present. You have to umount volume and then mount it again". But that seemed to work in Gutsy (ntfs-3g version 1.913). So it looks like a regression.

[Agostino Russo (ago)]

Confirmed in Hardy build 28-Feb-2008:

ago@ago-laptop:~$ sudo mount -t ntfs-3g -o remount,ro /dev/disk/by-uuid/0A22653721620251 /host
Remounting is not supported at present. You have to umount volume and then mount it once again.

[Agostino Russo (ago)]

With ntfs-3g 1.2216 I get the following.

root@ago-laptop:~# mount -o ro /dev/sdb1 /mnt
root@ago-laptop:~# mount -o remount,rw /mnt
root@ago-laptop:~# cat /proc/mounts|grep /mnt
/dev/sdb1 /mnt fuseblk rw,nosuid,nodev,noatime,relatime,user_id=0,group_id=0,allow_other 0 0
root@ago-laptop:~# touch /mnt/test
touch: cannot touch `/mnt/test': No such file or directory
root@ago-laptop:~# blockdev --setrw /dev/sdb1
root@ago-laptop:~# touch /mnt/test
touch: cannot touch `/mnt/test': No such file or directory

I.E. the filesystem can be remounted, and it shows as rw in /proc/mounts but I cannot actually write to it...

[Agostino Russo (ago)]

remounting ro -> rw does not work
remounting rw -> ro works

root@ago-laptop:~# mount -o rw /dev/sdb1 /mnt
root@ago-laptop:~# touch /mnt/trasg
root@ago-laptop:~# mount -o remount,ro /mnt
root@ago-laptop:~# touch /mnt/trasgs
touch: cannot touch `/mnt/trasgs': Read-only file system

[Florent Mertens (givre)]

Don't have that problem with 1.2216 :

root@flo-laptop:~# udevinfo -q all --name=/dev/sda6 | grep FS_TYPE
E: ID_FS_TYPE=ntfs
root@flo-laptop:~# mount /dev/sda6 /mnt/test
root@flo-laptop:~# touch /mnt/test/test
root@flo-laptop:~# sudo mount -o remount,ro /mnt/test
root@flo-laptop:~# touch /mnt/test/test
touch: cannot touch `/mnt/test/test': Read-only file system
root@flo-laptop:~# sudo mount -o remount,rw /mnt/test
root@flo-laptop:~# touch /mnt/test/test
root@flo-laptop:~#

Please test again and feel free to reopen it if it still fail.

[Agostino Russo (ago)]

Florent,

Please try to mount ro to begin with and then remount rw.

Mounting rw + remounting ro + remounting rw works
Mounting ro + remounting rw does not work

That is with 1.2216

Second case is relevant since it is what happens in the initrd/init.

[Florent Mertens (givre)]

Still see no issues with your 2nd use case.

root@flo-laptop:~# umount /dev/sda6
root@flo-laptop:~# mount -o ro /dev/sda6 /mnt/test/
root@flo-laptop:~# touch /mnt/test/test
touch: cannot touch `/mnt/test/test': Read-only file system
root@flo-laptop:~# mount -o remount,rw /dev/sda6 /mnt/test/
root@flo-laptop:~# touch /mnt/test/test
root@flo-laptop:~#

[Agostino Russo (ago)]

hmm strange:

root@ago-laptop/#mount -o ro /dev/sda2 /mnt
root@ago-laptop/#mount -o remount,rw /dev/sda2 /mnt
root@ago-laptop/#touch /mnt/test.trash
touch: cannot touch `/mnt/test.trash': No such file or directory

[Florent Mertens (givre)]

Ok, I see the problem now.
Touching an existant file don't fail
but creating a new file fail.

Same issue with latest ntfs-3g+fuse-lite

[Florent Mertens (givre)]

Szaka, could you take a look at it ?

Thanks.

[Szabolcs Szakacsits (szaka)]

Unfortunately neither fuse nor ntfs-3g support remount at the moment.
The "working" rw->ro case is by pure accident and could lead to data loss.

[yogg (yogg22315)]

I have tested this on ubuntu 10.04.4 LTS and Ubuntu 10.10.

Mount the device as "ro".
mount | grep DEVICE
/dev/DEVICE on /MOUNTPOINT type fuseblk (ro,nosuid,nodev,allow_other,blksize=4096)

With "-t" mount gives back a good error why this does not work.
mount -t ntfs-3g -o remount,rw /dev/disk/by-uuid/DEVICE /MOUNTPOINT
Remounting is not supported at present. You have to umount volume and then mount it once again.

Without "-t" mount just does it. The device is listed as "rw", but its not possible to write on the device.
mount -o remount,rw /dev/DEVICE

mount | grep DEVICE
/dev/DEVICE on /MOUNTPOINT type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096)

touch /MOUNTPOINT/testfile
touch: cannot touch `/MOUNTPOINT/testfile': No such file or directory

It would be nice if the remount error message ("Remounting is not supported ...") comes up always. Would have saved me lot of time for searching.
But it would be even nicer if the remount works.