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# Encrypt Hard Drive Disk under Linux - LUKS and cryptsetup
- URL: https://www.bagz.fr/encrypt-hard-drive-disk-under-linux-luks-and-cryptsetup/
- Published: 2014-07-25T12:00:03.000Z
- Updated: 2014-07-25T12:00:03.000Z
- Author: bgazui
- Tags: Linux, #Migrated-1790668826633, #wp, #wp-post, #Import 2026-09-29 08:00

You want to add a new hard drive disk (or a new partition) to your Linux system but this disk will contain some private data then you want it to be encrypted so you can restrict its access to whom will have the key.

Be careful, there are some parameters you have to take in consideration before performing these actions:

- The passphrases used for encryption will never been saved, you have to be really careful about this and do not lose it. If you do, it will be impossible to retrieve data on this disk.
- The encryption will impact your system performances (due to the CPU usage for encrypt/decrypt actions). Be sure that you use this disk for passive data (avoid any executables files for example), and prefer newest CPU with latest instructions set for AES so the performances can be improved (AES-NI).

I am going to present here the encryption of a new disk (pretty small, a 1GB disk for the example) identified as */dev/sdb* on the system:\~$ sudo fdisk -l /dev/sdb  

Disk /dev/sdb: 1073 MB, 1073741824 bytes  
  
255 heads, 63 sectors/track, 130 cylinders, total 2097152 sectors  
  
Units = sectors of 1 \* 512 = 512 bytes  
  
Sector size (logical/physical): 512 bytes / 512 bytes  
  
I/O size (minimum/optimal): 512 bytes / 512 bytes  
  
Disk identifier: 0x00000000

Disk /dev/sdb doesn't contain a valid partition table

First of all, we need to install tools, like **cryptsetup** that we will use to encrypt/decrypt our disk (it's a system tool allowing dm-crypt/LUKS encryption on hard drive, partition or even file):

\~$ sudo apt-get install cryptsetup

We can now indicate that we want to crypt our */dev/sdb* disk using AES and a hash alorithm SHA-256:

\~$ sudo cryptsetup luksFormat -c aes -h sha256 /dev/sdb

You will get a confirmation message to which you will have to type "YES" to validate. Then, you will be asked for the passphrase you want to use (this password won't be saved, so don't forget it!) to encrypt your data:

WARNING!  
\========  
This will overwrite data on /dev/sdb irrevocably.  
  
Are you sure? (Type uppercase yes): YES  
Enter LUKS passphrase:  
Verify passphrase:

If you want to add some other keys for this encryption, you can do it using this following command:

\~$ sudo cryptsetup luksAddKey /dev/sdb

Thanks to this command, you can add up to 8 different keys for the disk, allowing up to 8 different users to access to these data (by using each one its own passphrase):

You can also check whenever you want the state of the slots (used or not) so you can manage the keys. For that, you can just use this command:

\~$ sudo cryptsetup luksDump /dev/sdb  
LUKS header information for /dev/sdb  
  
Version: 1  
Cipher name: aes  
Cipher mode: cbc-plain  
Hash spec: sha256  
Payload offset: 4096  
MK bits: 256  
MK digest: 48 1c 08 25 ff 51 ad 53 ff f1 07 5d f9 b1 c2 10 21 70 d9 9e  
MK salt: c4 6b b3 d5 b5 18 ac ce 2d e6 84 14 0b c3 74 82  
 46 7f 8a ae 77 29 85 34 70 7a 19 21 4b e5 ac 4c  
MK iterations: 22625  
UUID: 441706d5-9c07-4b33-bff0-ccd9232a0da3  
  
Key Slot 0: ENABLED  
 Iterations: 90691  
 Salt: 38 3a 7c eb 7f 17 b3 72 eb 6d 7b 80 c9 f0 1e 77  
 a5 56 28 a5 eb 7c 4a 1e b4 e4 a7 b9 e1 7c 88 b4  
 Key material offset: 8  
 AF stripes: 4000  
Key Slot 1: DISABLED  
Key Slot 2: DISABLED  
Key Slot 3: DISABLED  
Key Slot 4: DISABLED  
Key Slot 5: DISABLED  
Key Slot 6: DISABLED  
Key Slot 7: DISABLED  

Now that the disk is encrypted, we need to create our partition and our file system so we can use it. We will decrypt our disk in a first time and create the mapping with a custom name *encrypteddata*:

\~$ sudo cryptsetup luksOpen /dev/sdb encrypteddata

Right now, we can find this new mapping under */dev/mapper*:

\~$ ls /dev/mapper/  
control encrypteddata

We can now work with this new mapping point. A mapping for an encrypted disk can be checked at any time by using the parameter *status* of *cryptsetup* command:

\~$ sudo cryptsetup -v status encrypteddata  
/dev/mapper/encrypteddata is active.  
 type: LUKS1  
 cipher: aes-cbc-plain  
 keysize: 256 bits  
 device: /dev/sdb  
 offset: 4096 sectors  
 size: 2093056 sectors  
 mode: read/write  
Command successful.

Then, we will create our partition and our file system with ext3:

\~$ sudo mkfs.ext3 /dev/mapper/encrypteddata  
mke2fs 1.42 (29-Nov-2011)  
Filesystem label=  
OS type: Linux  
Block size=4096 (log=2)  
Fragment size=4096 (log=2)  
Stride=0 blocks, Stripe width=0 blocks  
65408 inodes, 261632 blocks  
13081 blocks (5.00%) reserved for the super user  
First data block=0  
Maximum filesystem blocks=268435456  
8 block groups  
32768 blocks per group, 32768 fragments per group  
8176 inodes per group  
Superblock backups stored on blocks:  
 32768, 98304, 163840, 229376  
  
Allocating group tables: done  
Writing inode tables: done  
Creating journal (4096 blocks): done  
Writing superblocks and filesystem accounting information: done

We are now able to mount our new decrypted disk on any local point to read/write its content:

\~$ sudo mount -t ext3 /dev/mapper/encrypteddata /mnt/

Our disk is now available on */mnt*:

\~$ ls /mnt/  
lost+found

To close an encrypted disk, you will need to unmount it and then use the *luksClose* method:

\~$ sudo umount /mnt  
\~$ sudo cryptsetup luksClose /dev/mapper/encrypteddata

The disk is now closed and encrypted again until someone will open it.

You can also choose to mount thi sdisk automatically on system start-up. For that, you will use **/etc/crypttab** file to define the encrypted volume configuration and then the **/etc/fstab** to define its mount (as you used to do for a standard disk). Using this mechanism, the key to decrypt the disk will be asked on system start-up:

\~$ cat /etc/crypttab  
\#   
encrypteddata /dev/sdb none luks\~$ cat /etc/fstab  
\# /etc/fstab: static file system information.  
#  
\#   
/dev/mapper/encrypteddata /mnt ext3 defaults 0 1  

Warning: if there is already a line existing in */etc/fstab* for this disk, you will need to comment it so you don't get any error on start-up.

Right now, you know how to encrypt your own disk ;) !