Install Linux Mint 20.3 with custom partition layout

Last edited on 2022-06-08 • Tagged under #mint #linux #encrypt

If I'm installing Linux Mint on a computer with >256GB of storage, I like to create a separate (encrypted) partition to hold the contents of my home directory from the partition (also encrypted) that contains the operating system. It makes it easier if I decide in the future to re-install Linux without overwriting user files.

I use a four partition layout (for UEFI-boot systems):

1 - EFI System Partition
2 - boot partition
3 - encrypted root partition
4 - encrypted partition + Logical Volume Manager (LVM) with home Logical Volume (LV)

This is how I do it ...

1. Create partitions 1, 2, 3 during install

Run the Mint Installer.

For Installation type, select Something else to create a custom layout.

Using the graphical partition tool, I create:

Partition 1 - 300MiB - EFI System Partition
Partition 2 - 1000MiB - unencrypted - mounted as /boot
Partition 3 - 30000MiB - Linux Unified Key Setup (LUKS) encrypted - with:
- /dev/mapper/DEVICE_crypt - mounted as /

Commit the changes, and continue with the install.

When Installer is finished, select Continue testing.

2. Create partition 4 after install

Open a terminal. Switch to root with sudo -i.

Identify disks with lsblk -f.

Set disk to be partitioned (example: sdX) ...

export disk="/dev/sdX"

Create a new LUKS encrypted partition that uses all of the remaining storage ...

sgdisk -n 0:0:0 -t 0:8309 -c 0:luks $disk

Print and re-read the new partition table ...

sgdisk -p $disk
partprobe $disk

3. Encrypt partition

Encrypt the new partition ...

cryptsetup --type luks2 -y -v luksFormat ${disk}4

Note: If the same password used to encrypt the earlier root partition is used again for partition #4, it will be automatically unlocked after root is manually unlocked during bootup. Courtesy of systemd-ask-password, which comes with a cache functionality. It will cache the password, and try it on the next LUKS partition. See Why is my LUKS partition mounted without asking for more details.

4. LUKS + LVM

I use this encrypted storage along with LVM to create a “virtual partition” (Logical Volumes or LV) for the home filesystem. Installing LVM on top of LUKS allows the creation of multiple LVs protected by a single passphrase, and dynamic resizing of LVs as needed.

Open partition #4 mapped to cryptdev ...

cryptsetup open ${disk}4 cryptdev

Create the LVM physical volume...

pvcreate /dev/mapper/cryptdev

Create the LVM vg volume group ...

vgcreate vg /dev/mapper/cryptdev

5. Prepare home

Create an LV container for home and assign storage (example: +90% of free space) ...

lvcreate -l +90%FREE vg -n home

View modifications with lvdisplay.

Format the LV ...

mkfs.ext4 /dev/vg/home

Move the contents of /home on the root partition to the new home LV ...

mount /dev/vg/home /mnt
mv /target/home/* /mnt

6. Fstab

Create an entry for /home in /target/etc/fstab ...

/dev/mapper/vg-home /home           ext4    defaults        0       2

7. Crypttab

Obtain the UUID of the LUKS + LVM partition and append to /target/etc/crypttab ...

cryptsetup luksUUID ${disk}4 >> /target/etc/crypttab

Open the file in an editor - nano /target/etc/crypttab - and edit that appended line to create an entry for cryptdev ...

cryptdev UUID=<uuid-of-luks+lvm-partition> none luks,discard

8. Finish up

Unmount home ...

umount /mnt

Deactivate volume group ...

lvchange -an vg

Remove the encrypted device map ...

cryptsetup close /dev/mapper/cryptdev

Reboot.

A prompt appears to enter the password for the first LUKS partition (root). If the same password was used for the second LUKS + LVM partition, it will be auto-mounted and the system will continue booting to the login screen.

Good stuff!

See also: Customize LVM on LUKS after installing Linux Mint for an alternate method.

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