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ANNOUNCE: LSD mount utilities.
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Date: 2007-01-30 (11:51)
From: ls-ocaml-developer-2006@m...
Subject: ANNOUNCE: LSD mount utilities.

The LSD mount utilities are written in OCaml, so I hope the
announcement is not OT here.

Don't hesitate either to flame me or ask questions if I'm OT or the
utilities don't work as advertised.

Since those need to be SUID programs help in reviewing them or
discussion of security aspects would be appreciated.

Regards, Markus



The LSD mount utilities allow to automate mounting of encrypted
filesystems in linux with cryptsetup and loopback devices and enable
users (not only root) to mount encrypted filesystems when appropriate
entries to /etc/fstab have been added by root.

The LSD mount utilities are licensed/distributed under the the terms
of the GPL Version 2 (no later version). We'll usually be happy though
to relicense under other OS licenses, but you have to ask and get the
licensing change from us in writing.

The LSD mount utilities can be downloaded from

What does it do? How does it work?

In Linux /sbin/mount calls /sbin/mount.$FSTYPE and /sbin/umount calls
/sbin/umount.$FSTYPE if those programs exist. This leads to the
observation, that the filesystem types either in /etc/fstab or passed
to mount with -t rather more characterize a mounting mechanism than a
file system type.

With the LSD mount utilities this mechanism is used to delegate
mounting of encrypted loopback devices to mount.lcrypt which automates
the steps necessary to set up those devices (like: modprobe, losetup,

mount.lcrypt on the other side should know the filesystem of the
decrypted device from a mount option. (This does not work yet,
presently all lcrypt devices have the decrypted filesystem type ext2).

Mounting directly

Pass '-t lcrypt' to mount:

 mount -t lcrypt /data/encrypted-image /mnt 

You'll be asked for the passphrase.

With fstab / allow user mounting

Use lcrypt as filesystem type. Use the option 'user', if non
privileged users should be able to mount the device:

 /data/encrypted-image /secret-mnt lcrypt  rw,noauto,user,exec 0 0 

Any user can now use

 mount /data/encrypted-image 

and is then asked for the passphrase.