Adopting LVM

I use Arch Linux on every machine in my possession.

Within a year of its use, I realized what Arch Linux F**kups really mean and why people cry about it.

But I figured out a escape to a problem I always faced during a f**kup, It's the disk partitions and re-installation.

The Trouble ↩

Traditionally you would have a setup like this.

n00b:

- /dev/sda1
	- / (OS installation)
		- /home/user (home folder)

Your everyhing is in the root partition. Now if by some reason your root is screwed, you have to spend time backing up your home partition. And if you are a data hoader, you be spending time in backing it up to wipe clean the partition for fresh install.

I have been with this setup before using Arch Linux but Ubuntu didn't screw itself up that often.

intermediate:

- /dev/sda1
	- / (OS installation)
- /dev/sda2
	- /home/use (home folder)

Now here are utilizing disk partitioning for home and root partitions.

Why? because organization. But most importantly, there is separation b/w them. There is no need to worry about first case anymore. Just wipe root and install again, you'll be up with fresh install with all your files not even touched.

This was me for a whole again. It worked flawlessly, took be 1-2 days to get back on track with packages and necessary software.

Getting better at the game ↩

The f**kups got better since then, some of them were

• A update got interrupted due to network failure, didn't verify the packages and it failed to install a critical library i18n, which was a dependency to many software including pacman. I figured out since it was installtion problem, might well re-install it. But pacman depended on this. I somehow fixed it by manually installing this libary, had to do some symlinks.
• Some startup service didn't start and the system refused to give me a shell. which required me a re-install.

The quest to tweak my Arch Linux to perfection was always on. This led me to lvm, it all sounded fancy because of it capabilities like Logical Paritions and its dynamic abilities.

Adopting LVM ↩

I found out about LVM while browsing list of applications in ArchWiki. It was the moment it struck that this is the setup I have been in grave need. A solution to a minor inconvinience.

One particular feature which I love about LVM is

That's right, running out of space because you use too many docker images? Expand your root on the fly without worrying about making up space adjacent to it. This also means I can have multiple distros saved in rather small partitons because it can resized whenever required.

Learn more about it

• An Introduction to LVM
• LVM - ArchWiki

My Setup ↩

My setup to LVM is really simple. The only reason to choose this setup to have flexibility on managing partition without a headache, which means it takes some effort to set them up.

Physical Volume Setup ↩

I have single 256GB SSD in my thinkpad x1c which I have split into 2 physical partitions /dev/sda2 and /dev/sda3, /dev/sda1 is the boot partition.

These partitions are configured to be our physical partitions. One explicitly for distros and other for datadir which will be home partitions.

$ sudo pvs
  PV         VG      Fmt  Attr PSize    PFree
  /dev/sda2  distros lvm2 a--  <118.71g <68.71g
  /dev/sda3  datadir lvm2 a--   119.26g  49.26g

If you own a system with hybrid disk setup, one being SSD usually 128GB and HDD of 1TB, the physical volumes can be set to use root to be loaded from SSD and home from HDD. Or want to be a master of optimization crafts, use parts of root and home in your SSD to speed up boot time and load the rest like Music from HDD.

Such an ambition would be a mess to implement, but LVM makes it painless.

Volume Groups Setup ↩

Volume groups are collection of physical volumes, you can collate multiple physical volumes into a single group. I choose to mirror my physical volumes as volume groups

$ sudo vgs
  VG      #PV #LV #SN Attr   VSize    VFree
  datadir   1   1   0 wz--n-  119.26g  49.26g
  distros   1   1   0 wz--n- <118.71g <68.71g

Volume groups gives you an abstract over your physical volumes, the logical volumes created are categorized into these volumes.

Logical Volumes ↩

This is the abstraction I seek to implement. On my X1C, this is the setup

$ sudo lvs
  LV                   VG      Attr       LSize
  booterror-home-crypt datadir -wi-ao---- 70.00g
  arch-main            distros -wi-ao---- 50.00g

arch-main is my current Arch Linux installation and booterror-home-crypt is the root partition for user booterror which is a LUKS encrypted partition. And Yes keep your personal data encrypted, will save you from intrusion by physical access like a theft :laughing:

Note that the size of the partitions, I can use rest of free space in volume groups to make new partitions for different distros and respective users.

Final structure ↩

Here is my final disk structure with all the necessary complexities added just so I can resize on the fly

$ lsblk
NAME                               MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                                  8:0    0 238.5G  0 disk
├─sda1                               8:1    0   511M  0 part  /boot
├─sda2                               8:2    0 118.7G  0 part
│ └─distros-arch--main             254:0    0    50G  0 lvm   /
└─sda3                               8:3    0 119.3G  0 part
  └─datadir-booterror--home--crypt 254:1    0    70G  0 lvm
	└─booterror-home               254:2    0    70G  0 crypt

There's more ↩

I figured out LVM can do snapshotting, essentially a time machine for your partitions. One useful setup would be to have a snapshot of your bare minimum arch linux installation as a snapshot, whenever there is a f**kup and its beyond fix, just revert to this snapshot. You can keep a list of all packages you need to install in a txt file and run pacman right away after reverting to this bare minimum state.

A snapshot setup would be more rewarding than a abstract just so I can resize on the fly.

I need to experiment this setup, until then...