OK to mount multiple FS in one dir?

From: Michael D. Crawford (crawford@goingware.com)
Date: Sun Feb 04 2001 - 22:08:50 EST

I was groping around my FAT/NTFS directories from Linux, mounting and
unmounting them into
/mnt, and was suprised at some point that I got the message "/dev/sda5
already mounted or
/mnt busy". (I'm using a SCSI disk, use hda* for IDE).

Upon further examination, I found that I'd accidentally mounted
/dev/sda1 (VFAT) on /mnt
while /dev/sda5 (NTFS) was still mounted there. The NTFS files remained
invisible until
I'd unmounted /dev/sda1 and then I could see them again.

This is with the 2.4.1 kernel on a Pentium III machine with an Adaptec
29160 SCSI

I found I could mount three partitions on /mnt, and they'd all show up
as mounted at
/mnt in the "mount" command, but if I unmounted one of them (only tried
with the currently
visible one), then it appeared that there were no filesystems mounted
there, but I could
continue umounting until the other two were gone.

I'm suprised this works. Note that the kernel rejected an attempt to
mount a filesystem
that was already mounted, but not to mount a filesystem at a point that
was already in use.
It looks like there is a stack of mounts on the mount point.

Looking at Documentation/Changes, I see that I need util-linux 2.10o. I
had 2.10l. But I
had the 2.10r util-linux sources on my machine and installed mount and
umount from it, and
I find that it gets it right mostly when I mount and unmount multiple
things, with the
exception that if /dev/sda5 was mounted before /dev/sda1, then if I give
the command
"umount /dev/sda5", sda1 is the one that gets unmounted rather than
sda5, so it takes the
most recently mounted filesystem rather than the one you specify.

Michael D. Crawford
GoingWare Inc. - Expert Software Development and Consulting

   Tilting at Windmills for a Better Tomorrow.

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This archive was generated by hypermail 2b29 : Wed Feb 07 2001 - 21:00:20 EST