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authorMilan Broz <mbroz@redhat.com>2008-04-24 22:11:03 +0100
committerAlasdair G Kergon <agk@redhat.com>2008-04-25 13:27:03 +0100
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tree8e257d211df10bdc750ddb2e749f7f735dfcc740 /Documentation/device-mapper
parentcf13ab8e02d452e2236d0b5fda9972b3b7f503cb (diff)
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dm crypt: add documentation
Add description of dm-crypt to device-mapper documentation. Signed-off-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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diff --git a/Documentation/device-mapper/dm-crypt.txt b/Documentation/device-mapper/dm-crypt.txt
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+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
+]]