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Bug 118184 - fails to unmount manually set up dmcrypt mounts and loopbacks
Summary: fails to unmount manually set up dmcrypt mounts and loopbacks
Alias: None
Product: Gentoo Linux
Classification: Unclassified
Component: [OLD] baselayout (show other bugs)
Hardware: All Linux
: High normal (vote)
Assignee: Gentoo's Team for Core System packages
Depends on:
Reported: 2006-01-07 08:03 UTC by Peter Hyman
Modified: 2006-01-08 04:16 UTC (History)
0 users

See Also:
Package list:
Runtime testing required: ---


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Description Peter Hyman 2006-01-07 08:03:58 UTC
I do not use dmcrypt in the init scripts and do not have devices set in fstab. Rather, I manually mount encrypted filesystems as follows in my home directory:

sudo losetup /dev/loop0 ~/stuff
sudo cryptsetup -c aes -s 256 -h plain create stuff /dev/loop0
sudo mount -t ext2 /dev/mapper/stuff ~/mnt/stuff

I also have a corresponding unmount script:

sudo umount ~/mnt/stuff
sudo cryptsetup remove stuff
sudo losetup -d /dev/loop0 

All of works fine. However, at shutdown time, if my dmcrypt drive is mounted, fails and drops me to a prompt for root maintenance. (Enter Root Password or press Control-D to continue):

Either it is trying to unmount /home before trying to unmount the dmcrypt drive or it is not reading /proc/mounts properly or is trying to run losetup -d before unmounting the loopback device?

On reboot, a check is done on my home partition because it was not unmounted cleanly. The encrypted fs is fine and no data appears to be lost or corrupted. 

Perhaps the logic of needs to be adjusted to account for this situation where dmcrypt is used, but NOT set up through init.

Some additional information:
mars bin # losetup -a
/dev/loop/0: [0307]:577565 (/home/peter/stuff)

peter@mars $ cat /proc/mounts
rootfs / rootfs rw 0 0
/dev/root / reiserfs rw,noatime 0 0
proc /proc proc rw,nodiratime 0 0
sysfs /sys sysfs rw 0 0
udev /dev tmpfs rw,nosuid 0 0
devpts /dev/pts devpts rw 0 0
/dev/hda7 /home ext3 rw,noatime,data=ordered 0 0
/dev/mapper/stuff /home/peter/mnt/stuff ext2 rw,nogrpid 0 0

could the problem be the order of unmount? Trying to unmount /home before ...stuff? should pick up the fact that /dev/mapper is a loop device, don't you think?


mars peter # emerge info
Portage 2.0.53 (default-linux/x86/2005.0, gcc-3.4.4, glibc-2.3.5-r2, 2.6.14-gentoo-r5 i686)
System uname: 2.6.14-gentoo-r5 i686 AMD Athlon(tm) XP 2800+
Gentoo Base System version 1.6.14
dev-lang/python:     2.4.2
sys-apps/sandbox:    1.2.12
sys-devel/autoconf:  2.13, 2.59-r6
sys-devel/automake:  1.4_p6, 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6-r1
sys-devel/binutils:  2.16.1
sys-devel/libtool:   1.5.20
virtual/os-headers:  2.6.11-r3
Comment 1 SpanKY gentoo-dev 2006-01-07 19:17:08 UTC
you're probably going to have to track this down yourself ... look in the script, there is already logic in there for unmounting dm-crypt loop devices regardless of how they were actually mounted
Comment 2 Peter Hyman 2006-01-08 03:54:35 UTC
remaining=$(awk '!/^#/ && $1 ~ /^\/dev\/loop/ && $2 != "/" {print $2}' proc/mounts | \...

When dmcrypt is used, the device in /proc/mounts is /dev/mapper, not /dev/loop. This is why no loopbacks get removed. 

Check out this fragment:

peter@mars ~ $ grep "^\/dev\/loop\|^\/dev\/mapper" /proc/mounts
/dev/mapper/stuff /home/peter/mnt/stuff ext2 rw,nogrpid 0 0

As opposed to:

peter@mars ~ $ grep "^\/dev\/loop" /proc/mounts
peter@mars ~ $ 

I believe the addition of the simple conditional for /dev/mapper in will fix the problem. Will report.

Comment 3 Peter Hyman 2006-01-08 04:16:36 UTC
Well, that was fun. Unfortunately, while the loopback test _DID_ find the /dev/mapper device and removed it, the dmcrypt addon never ran since I don't have a /etc/cryptfs file set up. So, shutdown still hangs because doesn't disconnect the dmcrypt device. That's why /home/peter never can unmount.

I want to keep these files completely in userspace, so I suppose I will have to remember to unmount it by hand, or add it to local.stop or suffer with the error. Marking cantfix unless you can think of a better way. I'll play around with fuse too.

This really is a user-level problem, not system.