Preparing Hard Drive for Ubuntu / elementary OS Installation To LVM

I’ve been distro-hopping the past couple of weeks and ended up trying out Ubuntu 18.04 LTS and elementary OS 5.0 Juno (which is based on the aforementioned Ubuntu LTS release).

During installation, a lot of head-scratching took place because I couldn’t find how to configure LVM using the graphical installer. Unless I totally missed something, which is highly likely, admittedly, I could only configure LVM by wiping the hard drive housing my Windows installation. Although a lot of us are longing for “The Year of the Linux Desktop”, this aggressive marketing message didn’t resonate with me.

The custom, “set-it-up-yourself” option provided by the installer had a lot more levers to play with, but I couldn’t seem to find the option that’d allow me to configure LVM. So I ended up configuring everything using the command line. I always find learning about the libraries / APIs that power apps such as GParted interesting, so even if it turns out that this wasn’t strictly necessary, time wasn’t wasted!

Here, I’ll describe the steps I took to prepare my hard drive for Ubuntu / elementary OS installations to LVM. Note that the commands that follow assume root privileges (sudo su, sudo -s, etc).

Get Device File, Capacity and Sector Size

Using fdisk, we can find the device file, capacity in bytes and physical sector of the disk we want to work with.

fdisk -l

# Disk /dev/sdb: 232.9 GiB, 250059350016 bytes, 488397168 sectors
# Disk model: Samsung SSD 850
# Units: sectors of 1 * 512 = 512 bytes
# Sector size (logical/physical): 512 bytes / 512 bytes
# I/O size (minimum/optimal): 512 bytes / 512 bytes
# Disklabel type: gpt
# Disk identifier: 819251F4-C01F-4595-A657-222FEAEEC9B9

We make note of the following:

  • Device file: /dev/sdb
  • Capacity: 250059350016
  • Physical sector size: 512

Wipe Disk

We set the disk_size_bytes and physical_sector_size variables to the values we made note of earlier. The dd command uses these variables to wipe the disk. You need to triple-check that the command that follows is correct, otherwise you will end up wiping the wrong disk.

disk_size_bytes=250059350016
physical_sector_size=512
dd if=/dev/zero \
  of=/dev/sdb \
  bs=$physical_sector_size \
  count=$(($disk_size_bytes / $physical_sector_size)) \
  seek=0 \
  conv=notrunc \
  status=progress

To re-iterate, make sure that the output file path (of) matches the device file of the disk you want to wipe! Feel free to use /dev/urandom as your input file (if), but keep in mind that it will likely be slower than writing zeroes. Also keep in mind that there are limits to how securely disks can be wiped. The Arch Linux wiki collates a lot of useful information on the topic. Please do your own research. Once dd is done, we can proceed to the next step.

Create GUID Partition Table

We begin by creating a GUID partition table.

parted /dev/sdb mklabel gpt

Create EFI System Partition

Our first partition will be an EFI system partition which is mandatory for an UEFI boot. We must create this partition on the main partition table and not in LVM.

parted /dev/sdb mkpart primary fat32 1MiB 551MiB
parted /dev/sdb set 1 esp on # On the first partition, enable the esp flag
mkfs.fat -F 32 /dev/sdb1

Note that the fat32 part in the first command is to do with partition metadata. That is, it does not make parted format the partition. All it does is ensure that anyone trying to read information about the partition will be told that the partition is of type FAT32. mkfs.fat is what actually formats the partition.

Configure LVM

Now we can configure LVM. This involves creating an LVM partition, a physical volume, a volume group, and logical volumes.

Create LVM Partition

To create an LVM partition, we create a partition that takes up the entirety of the remaining free space and enable the lvm flag.

parted /dev/sdb mkpart primary 551MiB 100%
parted /dev/sdb set 2 lvm on # On the second partition, enable the lvm flag

Create Physical Volume

Here, we create a physical volume from the partition we just created. Note that we’re now referring to /dev/sdb2 which is the second partition of our /dev/sdb drive.

pvcreate /dev/sdb2

Create Volume Group

Now we create a volume group on the created physical volume. Here, we name the volume group vg-ubuntu. Make note of the name as we’ll be using it later.

vgcreate vg-ubuntu /dev/sdb2

Create Logical Volumes

With all that out of the way, we can start creating our logical volumes. The process is straight-forward, consisting of the actual logical volume creation using lvcreate and the appropriate format command. Note that we must format the logical volumes – not the LVM partition we created earlier. The device files corresponding to the logical volumes we create will be in /dev/<volume-group-name>/<logical-volume-name>.

Here, we will create logical volumes for swap, root (/) and home (/home).

Swap

On the vg-ubuntu volume group, create a logical volume named lv-swap with a size of 8 gibibytes, and format it to prepare it for use as a swapping space.

lvcreate --size 8GiB vg-ubuntu --name lv-swap
mkswap /dev/vg-ubuntu/lv-swap

Root

On the vg-ubuntu volume group, create a logical volume named lv-root with a size of 20 gibibytes, and format it into an ext4 filesystem.

lvcreate --size 20GiB vg-ubuntu --name lv-root
mkfs.ext4 /dev/vg-ubuntu/lv-root

Home

On the vg-ubuntu volume group, create a logical volume named lv-home that takes up the entirety of the remaining free space on the physical volume, and format it into an ext4 filesystem.

lvcreate --extents 100%FREE vg-ubuntu --name lv-home
mkfs.ext4 /dev/vg-ubuntu/lv-home

Graphical Installer

Now that our disk has been prepared, we can return to the graphical installer to complete the installation. We choose the advanced option and do the following:

  • Set the bootloader to install on the drive we’ve been working with (here, /dev/sdb)
  • Ensure that the EFI system partition we created is configured to be used as such (here, /dev/sdb1)
  • Ensure that lv-swap is configured to be used as swap memory
  • Configure lv-root with a mount point of /
  • Configure lv-home with a mount point of /home

That should do it. Proceed with the installation.

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