http://www.topology.org/linux/reiser.html

To create a 20-MiByte Reiser file system file (on a SuSE 9.0 system), do something like this.

root@shark# dd if=/dev/zero of=reiser1.img count=40960
40960+0 records in
40960+0 records out

root@shark# ls -l reiser1.img
-rw-r--r--    1 root     root     20971520 Nov 17 19:16 reiser1.img

root@shark# losetup /dev/loop3 reiser1.img

root@shark# losetup /dev/loop3
/dev/loop3: [0700]:109 (reiser1.img) offset 0, no encryption

root@shark# mkfs.reiserfs /dev/loop3
mkfs.reiserfs 3.6.9 (2003 www.namesys.com)

Now continuing…

root@shark# mkdir reiser1

root@shark# ls -ld reiser*
drwxr-xr-x    2 root     root           48 Nov 17 19:55 reiser1
-rw-r--r--    1 root     root     104857600 Nov 17 19:52 reiser1.img

root@shark# mount /dev/loop3 reiser1

root@shark# df reiser1
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/loop3              102392     32840     69552  33% /home2/rsoft/reiser1

Well, what could be simpler!!

Ironically, the file reiser1.img is itself in a file system which is an encrypted loop-mounted Reiser file system.

The next logical step is to work out how to undo the deed.

root@shark# umount reiser1

root@shark# df reiser1
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hdd1            156275512  24241608 132033904  16% /home2

root@shark# losetup /dev/loop3
/dev/loop3: [0700]:109 (reiser1.img) offset 0, no encryption

root@shark# losetup -d /dev/loop3

root@shark# losetup /dev/loop3
loop: can't get info on device /dev/loop3: No such device or address

So let's try this just once more to make sure it's all okay.

root@shark# losetup /dev/loop3 reiser1.img
root@shark# mount /dev/loop3 reiser1
root@shark# df reiser1
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/loop3              102392     32840     69552  33% /home2/rsoft/reiser1