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SubjectRe: [patch] replacing "/dev/root" in /proc/mounts
Hi Tigran.

>> I tried making that symlink soon after I first heard about it,
>> and had so many problems that I promptly removed it and went
>> back to a static /etc/mtab instead.

> making symbolic link /etc/mtab -> /proc/mounts stops people from
> triggering a bug in mounting loopback device (i.e. from
> supplying -o loop option to mount instead of doing it properly,
> i.e. use losetup(8) command).

I have to admit that I wasn't aware of any such bug, and I regularly
use that very option to mount cd images for testing prior to burning
them out, and have never had any indication of a bug being present.
As a result, I would be VERY interested in details of this bug as it
exists in current 2.2 kernels.

> If there are other problems than this, I will switch to static
> /etc/mtab.

> (I assume one also made a symlink /dev/root -> /dev/sdXY)

If one uses the symlink, one would have to do so, but as I don't, I've
never bothered to do so.

> What are the other problems with /etc/mtab -> /proc/mounts?

The command `mount -o remount,r[ow]` doesn't work with the symlink if
there were any additional options supplied (either in /etc/fstab or
otherwise) when the partition was originally mounted, beyond the basic
"defaults" option.

As examples of this, I quote the following entries from my home
system, which is RedHat 6.0 using kernel 2.2.12:

Q> /dev/hdb3 /cdimage ext2 defaults,ro,user 1 1

This entry can NOT be remounted rw, other than by the superuser, if
the symlink exists, even though the user option is supplied.

Q> sun:/public /nfs/sun nfs noauto,ro,user,rsize=8192,wsize=8192

If the symlink exists, then `mount -o remount,rw /nfs/sun` results in
the rsize and wsize being reset to the default values, and performance
falls through the floor as a result.

Best wishes from Riley.

+----------------------------------------------------------------------+
| There is something frustrating about the quality and speed of Linux |
| development, ie., the quality is too high and the speed is too high, |
| in other words, I can implement this XXXX feature, but I bet someone |
| else has already done so and is just about to release their patch. |
+----------------------------------------------------------------------+

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