We want to have a separate ext4 boot partition because Ubuntu's grub doesn't really like booting from btrfs. So we have something like
MOUNT POINT SIZE TYPE
/ 474G new btrfs
/boot 2G new ext4
/boot/efi 1G existing vfat
At the end of install, when you are prompted to view the full log or reboot, press Ctrl + Alt + F2 to open a shell.
Unmount everything with
sudo umount -a
Mount the root partition with
sudo mount /dev/<sdaX|nvme0n1pX> /mnt
Copy resolv.conf
sudo cp -vf /etc/resolv.conf /mnt/etc/resolv.conf
Remove swapfile
sudo rm /mnt/swap.img
Snapshot root, thereby creating a root level subvolume
sudo btrfs su snapshot /mnt/ /mnt/@
Remove the main installed contents
sudo rm -r /mnt/{bin,bin*,boot,cdrom,etc,home,lib,lib*,media,mnt,opt,root,run,sbin,sbin*,snap,srv,sys,tmp,usr,var}
Create the rest of the subvolumes
sudo btrfs su create /mnt/@{home,var,tmp,snapshots,swap}
Move var to its own subvolume
sudo mv /mnt/@/var/* /mnt/@var
Unmount the root partition
sudo umount /mnt
Mount the subvolumes as follows:
sudo mount -o subvol=@ /dev/<sdaX|nvme0n1pX> /mnt
sudo mount -o subvol=@home /dev/<sdaX|nvme0n1pX> /mnt/home
sudo mount -o subvol=@tmp /dev/<sdaX|nvme0n1pX> /mnt/tmp
sudo mount -o subvol=@var /dev/<sdaX|nvme0n1pX> /mnt/var
sudo mkdir /mnt/.snapshots
sudo mount -o subvol=@snapshots /dev/<sdaX|nvme0n1pX> /mnt/.snapshots
sudo mkdir /mnt/swap
sudo mount -o subvol=@swap /dev/<sdaX|nvme0n1pX> /mnt/swap
Mount boot partitions
sudo mount /dev/<sdaY|nvme0n1pY> /mnt/boot
sudo mount /dev/<sdaZ|nvme0n1pZ> /mnt/boot/efi
Mount dev, proc, sys, and run in preparation for chroot
for d in dev proc sys run; do sudo mount --rbind /$d /mnt/$d; done
Chroot into the created environment
sudo chroot /mnt /bin/bash
Because we are using subvolumes with btrfs we need to regenerate the grub configuration file and update the fstab file. First, regenerate the grub configuration file.
sudo grub-mkconfig -o /boot/efi/EFI/ubuntu/grub.cfg
sudo update-grub
Create the swapfile
btrfs filesystem mkswapfile --size 4g --uuid clear /swap/swapfile
Next, update the fstab with sudo vim /etc/fstab to look like this for each subvolume
/dev/<sdaX|nvme0n1pX> / btrfs ssd,noatime,space_cache=v2,compress=lzo,discard=async,subvol=@ 0 0
Change the last line for the swapfile to look like this:
/swap/swapfile none swap defaults 0 0
Update everything
sudo apt update && sudo apt upgrade -y
Install snapper
sudo apt install snapper
We need to make some prep-work to set snapper to save our snapshots to the subvolume @snapshots that we created previously.
cd /
sudo umount .snapshots
sudo rm -r .snapshots
Now we can create a new configuration for Snapper with:
sudo snapper -c root create-config /
Remove the auto-created subvolume, recreate the directory, and remount @snapshots
sudo btrfs subvolume delete /.snapshots
sudo mkdir /.snapshots
sudo mount -av
Add the sudo group to allow users to use snapper:
sudo snapper -c root set-config 'ALLOW_GROUPS=sudo'
sudo snapper -c root set-config 'SYNC_ACL=yes'
Create our first snapshot
sudo snapper -c root create --description "default fresh install"
List the snapshots
sudo snapper ls
To make a rollback use the command
sudo snapper --ambit classic rollback <snapshot_number>
sudo reboot