Convert and install to LUKS Encrypted Drive Ubuntu 18.04 19.10 Linux Mint and Debian Based Linux

The reason for doing this is that the installer doesn't seem to work properly for LUKS and the server installer doesn't even support LUKS anymore. When you use the GUI install on Desktop for LUKS it won't boot and will just hang after you enter your password. So the only reliable way is to do it ourselves.

1.) Make a default minimal install of Ubuntu

2.) Have a secondary disk on the server or VM.

3.) Create the following on the secondary disk (we assume it is /dev/sdb)
/dev/sdb1 = /boot 1G
/dev/sdb2 = / (rest of free space)

Use fdisk or gdisk

4.) Create LUKS for root on /dev/sdb2

cryptsetup --verbose --verify-passphrase luksFormat /dev/sdb2

WARNING!
========
This will overwrite data on /dev/sdb2 irrevocably.

Are you sure? (Type uppercase yes): YES
Enter passphrase for /dev/sdb2:
Verify passphrase:
Command successful.

5.) Open your LUKS partition now

#note when we say LUKSroot below that becomes the LUKS device we can mount and use in /dev/mapper/LUKSroot (LUKSroot is the name that it will be given)

cryptsetup luksOpen /dev/sdb2 LUKSroot
Enter passphrase for /dev/sdb2:

6.) Create Partitions on your LUKS partition
mkfs.ext4 /dev/mapper/LUKSroot

#let's setup our boot as well while we're at it

mkfs.ext4 /dev/sdb1

7.) Let's prepare our target for migration (target is our new LUKS enabled drive)

mkdir /target mount /dev/mapper/LUKSroot /target mkdir /target/boot mount /dev/sdb1 /target/boot

8.) rsync our current OS to the new LUKS partition (target)

rsync -Pha --exclude=/mnt/* --exclude=/media/* --exclude=/proc/* --exclude=/sys/* / /target

9.) Prepare to chroot into our new LUKS environment

for mount in dev proc sys; do mount -o bind /$mount /target/$mount done

#enter our new LUKS environment
chroot /target

10.) Setup our LUKS environment to boot properly (update fstab, crypttab, initramfs and grub)

We need to update /etc/fstab with the new blkid's

# blkid /dev/sdb1
/dev/sdb1: UUID="e0e4d4b6-c45d-4749-81b9-a46bdc66f7c5" TYPE="ext4"

#blkid /dev/mapper/LUKSroot
/dev/mapper/LUKSroot: UUID="ba6af9a2-6ea1-49d9-95f1-df521cbd384b" TYPE="ext4"

#fstab should now look like this:

UUID=e0e4d4b6-c45d-4749-81b9-a46bdc66f7c5 /boot ext4 defaults 0 0 /dev/mapper/LUKSroot / ext4 defaults 0 0 /swap.img none swap sw 0 0

#We need to also set /etc/crypttab
#it should be the UUID of /dev/sdb2

# blkid /dev/sdb2
/dev/sdb2: UUID="00321fcc-6ebc-4440-b62c-06b79f0aed96" TYPE="crypto_LUKS"

#crypttab should now look like this
LUKSroot UUID=00321fcc-6ebc-4440-b62c-06b79f0aed96 none luks,discard

#update our grub, initramfs and install grub to our secondary grub

update-grub update-initramfs -k all -c update-initramfs: Generating /boot/initrd.img-4.15.0-88-generic

grub-install /dev/sdb
#if your primary boot drive is /dev/sda you should install it into /dev/sda too
grub-install /dev/sda

#now reboot