LUKS - Disk Encryption

Encryption on Debian 9

Install dm-crypt
```
apt-get install cryptsetup
```
If you encrypted data drives during initial system setup, your swap space will be encrypted as well. First remove the swap encryption.
```
sudo mkswap -f /dev/sda6
sudo swapon /dev/sda6
```
Add the swap space to /etc/fstab. If you have swap on multiple drives, where the remaining space is allocated to a software RAID, add the swap partitions with the same priority.
```
/dev/hda6	none	swap	sw,pri=1	0	0
```
Remove the fstab entry for mounting the encrypted volume

Add the following commands to rc.local executed as root

echo "volume password" | sudo cryptsetup luksOpen /dev/mapper/vg-lv my_encrypted_volume
mount /dev/mapper/my_encrypted_volume /mount/point

To lock the container again, it needs to be unmounted first

sudo umount /media/my_device
sudo cryptsetup luksClose my_encrypted_volume

Set Up LUKS Header

sudo cryptsetup luksFormat /dev/mapper/<vg name>-<lv name>

Create a Filesystem on the Partition. You have to map this physical device to a virtual device. What gets written to the virtual device will be encrypted before being stored on the physical device.
```
sudo cryptsetup luksOpen /dev/mapper/<vg name>-<lv name> <vg name>-<lv name>_crypt
sudo mkfs.ext4 /dev/mapper/<vg name>-<lv name>_crypt
```

Mount Encrypted Partition

sudo mount /dev/mapper/<vg name>-<lv name>_crypt /mountpoint

If you need a directory tree to be copied from a backup location back to the newly encrypted drive, do it with rsync
```
rsync -av --progress --exclude '/home/user/VirtualBox VMs' /home/user /mountpoint/
```

Or, for an entire BackupPC structure

rsync -avxHAWX --info=progress2 /backup/ /new-backup/

Verify the structure between source and destination
```
rsync -avcn /backup/ /new-backup/
```

These steps have to be taken to increase a Raid Disk Array with the following configuration: RAID → LVM → LUKS → ext4.

Close LUKS:

cryptsetup luksClose vg_backup-lv_backup_crypt

Resize the physical volume to consume all free space in LVM:
```
pvresize /dev/md3
```
Resize the logical volume to consume all free space in LVM:
```
lvresize -l+100%FREE /dev/vg_backup/lv_backup
```

Open LUKS and enter the volume password:

cryptsetup luksOpen /dev/mapper/vg_backup-lv_backup vg_backup-lv_backup_crypt

Check the filesystem:

e2fsck -f /dev/mapper/vg_backup-lv_backup_crypt

Extend the filesystem to consume all free space:
```
resize2fs /dev/mapper/vg_backup-lv_backup_crypt
```

Mount file system:

mount /dev/mapper/vg_backup-lv_backup_crypt /backup

You could do an online resize by avoiding to unmount the file system and closing LUKS, but I find this approach safer. If you decide to do an online resize, skip steps 2 and 3, and instead of step 6 (open LUKS) do a crypt resize:
```
cryptsetup resize vg_backup-lv_backup_crypt
```
.