RHEL7: Create and configure LUKS-encrypted partitions and logical volumes to prompt for password and mount a decrypted file system at boot.

Install the LUKS package (if it’s not already installed):

# yum install -y cryptsetup

Activate LUKS module:

# modprobe dm_crypt

Check the module is running:

# lsmod | grep dm_crypt
dm_crypt 12894 0
dm_mod 82839 9 dm_crypt,dm_mirror,dm_log

Create a logical volume (here called lv_vol with a size of 100MB in the vg volume group):

# lvcreate --size 100M --name lv_vol vg

Convert the new logical volume to the LUKS format:

# cryptsetup luksFormat /dev/vg/lv_vol
WARNING!
========
This will overwrite data on /dev/vg/lv_vol irrevocably.
Are you sure? (Type uppercase yes): YES
Enter LUKS passphrase: MyPassphrase
Verify passphrase: MyPassphrase

Open and give a name to the LUKS logical volume (here vol):

# cryptsetup luksOpen /dev/vg/lv_vol vol
Enter passphrase for /dev/vg/lv_vol: MyPassphrase

Create an EXT4 file system on the LUKS logical volume:

# mkfs.ext4 /dev/mapper/vol
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
25168 inodes, 100352 blocks
5017 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=33685504
13 block groups
8192 blocks per group, 8192 fragments per group
1936 inodes per group
Superblock backups stored on blocks:
        8193, 24577, 40961, 57345, 73729

Allocating group tables: done
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

Create the /etc/crypttab file and add the following line:

vol /dev/vg/lv_vol /root/luks.key

Note: if you put ‘none‘ instead of ‘/root/luks.key‘, you will be asked for the passphrase at each boot at the console. Since RHEL 7.5, there is now another solution called Network-Bound Disk Encryption (see here and here for details).

Create the /root/luks.key file for example to store the passphrase:

MyPassphrase

Add the passphrase to the LUKS logical volume:

# cryptsetup luksAddKey /dev/vg/lv_vol /root/luks.key
Enter any passphrase: MyPassphrase

Edit the /etc/fstab file and add the following line (be careful when editing the /etc/fstab file or configure a virtual console):

/dev/mapper/vol /vol ext4 defaults 1 2

Note: A best practice is to execute the mount -a command, each time you change something in the /etc/fstab file to detect any boot problem before it occurs.

Create the mount point:

# mkdir /vol

Mount the LUKS logical volume:

# mount /vol

Note: To remove a LUKS file system, go to the page dealing with LUKS usage.