Removing System Encryption
Removing system encryption with dm-crypt and LUKS.
- An encrypted root filesystem or other filesystem that cannot be umounted while booted into the operating system.
- Enough drive space to store a backup.
- An Arch Linux (or other) live CD.
- A few hours.
cryptsetupto add or remove encryption to/from an existing file system. While they are still considered experimental, they may help considerably with such an effort. More information is available with
Boot into a Live Environment
Download and burn the latest archlive cd, reboot system and boot to cd.
Note About Different Setups
An example setup is shown here:
The grey sections only add a frame of reference and can be disregarded. The green partitions will be modified. Green text must match your system's setup. The yellow partition will be used as storage space and may be changed at will. In the example system: myvg contains lvs called cryptroot and cryptswap. they are located at /dev/mapper/myvg_cryptroot and /dev/mapper/myvg_cryptswap. Upon boot, luks is used along with a few crypttab entries to create /dev/mapper/root and /dev/mapper/swap. Swap will not be unencrypted as part of this guide, as undoing the swap encryption does not require any complex backup or restoration.
The example system is not indicative of all systems. Different filesystems require different tools to effectively backup and restore their data. LVM can be ignored if not used. XFS requires xfs_copy to ensure an effective backup and restore, DD is insufficient. DD may be used with ext2,3,and 4. (Someone please comment on jfs, reiserfs and reiser4fs)
Once Partitions Are Located
Load necessary modules:
modprobe dm-mod #device mapper/lvm modprobe dm-crypt #luks
Activate lvm volume group:
pvscan #scan for Physical Volumes vgscan #scan for volume groups lvscan #scan for logical volumes lvchange -ay myvg/cryptroot
Open the encrypted filesystem with luks so it can be read:
cryptSetup luksOpen /dev/mapper/myvg_cryptroot root
Enter password. Note: The only partition that will be operated on that should be mounted at this point is the backup partition. If a partition other than the backup partition is already mounted, it can be safely umounted it now.
Mounting backup space
Only if using NTFS to store the backup
# pacman -S ntfs-3g
The next step is important for backup storage.
# mount -t ntfs-3g -o rw /dev/sda5 /media/Shared
or use netcat to store the backup on a remote system
TODO: add netcat instructions.
xfs_copy -db /dev/mapper/root /media/Shared/backup_root.img
Note: -d flag preserves uuids and -b ensures direct IO is not attempted to any of the target files.
dd if=/dev/mapper/root of=/media/Shared/backup_root.img
Now the crucial moment, the point of no return if you will. Make sure you are ready to do this. If you plan to undo this later, you will have to almost start from scratch. You know how fun that is.
cryptsetup luksClose root lvm lvremove myvg/cryptroot
We have to create a new logical volume to house our root filesystem, then we restore our filesystem.
lvm lvcreate -l 100%FREE -n root myvg xfs_copy -db /media/Shared/backup_root.img /dev/mapper/myvg-root #notice the second drive name is changed now.
Reconfigure the Operating System
You need to boot into your operating system and edit /etc/crypttab, /etc/mkinitcpio.conf, /etc/fstab, and possibly /boot/grub/menu.lst.