From: Milan Broz <[email-masked]>

Add description of dm-crypt to device-mapper documentation.

Signed-off-by: Milan Broz <[email-masked]>
Signed-off-by: Alasdair G Kergon <[email-masked]>
---
 Documentation/device-mapper/dm-crypt.txt |   52 +++++++++++++++++++++++++++++++
 1 files changed, 52 insertions(+)

Index: linux-2.6.25/Documentation/device-mapper/dm-crypt.txt
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.25/Documentation/device-mapper/dm-crypt.txt	2008-04-24 19:44:25.000000000 +0100
@@ -0,0 +1,52 @@
+dm-crypt
+=========
+
+Device-Mapper's "crypt" target provides transparent encryption of block devices
+using the kernel crypto API.
+
+Parameters: <cipher> <key> <iv_offset> <device path> <offset>
+
+<cipher>
+    Encryption cipher and an optional IV generation mode.
+    (In format cipher-chainmode-ivopts:ivmode).
+    Examples:
+       des
+       aes-cbc-essiv:sha256
+       twofish-ecb
+
+    /proc/crypto contains supported crypto modes
+
+<key>
+    Key used for encryption. It is encoded as a hexadecimal number.
+    You can only use key sizes that are valid for the selected cipher.
+
+<iv_offset>
+    The IV offset is a sector count that is added to the sector number
+    before creating the IV.
+
+<device path>
+    This is the device that is going to be used as backend and contains the
+    encrypted data.  You can specify it as a path like /dev/xxx or a device
+    number <major>:<minor>.
+
+<offset>
+    Starting sector within the device where the encrypted data begins.
+
+Example scripts
+===============
+LUKS (Linux Unified Key Setup) is now the preferred way to set up disk
+encryption with dm-crypt using the 'cryptsetup' utility, see
+http://luks.endorphin.org/
+
+[[
+#!/bin/sh
+# Create a crypt device using dmsetup
+dmsetup create crypt1 --table "0 `blockdev --getsize $1` crypt aes-cbc-essiv:sha256 babebabebabebabebabebabebabebabe 0 $1 0"
+]]
+
+[[
+#!/bin/sh
+# Create a crypt device using cryptsetup and LUKS header with default cipher
+cryptsetup luksFormat $1
+cryptsetup luksOpen $1 crypt1
+]]