Installing Debian 10 Buster with Encrypted LVM and btrfs Subvolumes
With the arrival of Debian Buster, many people will be re-installing their systems to try out some of the new features and to just "start fresh". With this comes the opportunity to try out new configurations that require starting fresh. Namely, btrfs on root. Debian currently supports formatting partitions with btrfs, but doesn't support creating subvolumes from within the installer. This tutorial will demonstrate how to set up a Debian 10 Buster system with btrfs using subvolumes on your root filesystem during the installation process. It will also cover how to do this with LVM encrypted volumes for those who want their installations to be encrypted.
Once you're familiar with this procedure, you will find that it is actually a lot easier than it seemed at first!
This procedure has been adapted from this video found on YouTube: Debian 9 | Installation mit Btrfs Subvolumes (Debian Wochen) by YouTube user "unicks.eu". This video is in German but you don't need to understand the language to follow the steps on screen. This tutorial aims to expand on the content of the video by approaching it from the perspective of wanting encrypted partitions and it also provides an English-language reference to the content of the video. Procedure
The first step is to get a copy of the Debian operating system. Get any of the images that aren't a "live" image since these live images don't let you enter into Expert install mode. I prefer the netinstall image since it is a small initial download and I can pull in whichever packages I need using the internet (my connection is reliable and fast enough to support this).
After downloading the image and putting it on a CD/DVD/USB, boot this image and choose
Advanced options > Expert install (or
Graphical expert install if you want).
Run through the installation as normal until you reach the section on partitioning:
On this screen, if you want an encrypted root file system (recommended) then choose the option
Guided - use entire disk and set up encrypted LVM. Otherwise choose the first option. If you are working with a disk that already has an operating system on it which you wish to keep or if you have more complicated partitioning needs, you will have to choose
Manual and create the partitions necessary for your configuration.
Once you have run through the setup of the partitions you should now see a screen similar to the one below:
Select your root file system (the one with the
/ as the mount point), change the
Use as: field to
btrfs journaling file system and select
Done setting up the partition. After this, select
Finish partitioning and write changes to disk, following the prompts until you arrive back in the installation menu. This will apply the chosen partitioning scheme.
After this and before continuing with the installation, type Ctrl + Alt + F2 to be put into a shell. Press Enter to activate this shell and follow the following procedure to set up subvolumes:
Setting up Subvolumes
df command to view what the current mounted partitions are. In my case there is
/dev/mapper/debianbtrfs--vg-root mounted to
/dev/vda1 mounted to
/target is the place where the Debian system files will be installed. We need to change and set some things up so that it becomes a btrfs subvolume.
The first step is to unmount both
/target/boot and then
/target using the
Then, mount the btrfs root volume (i.e. the volume that used to be mounted to
/target hereby referred to as
/mnt and then cd
Create your desired subvolumes with
btrfs subvolume create SUBVOLUME_NAME. I have created
cd back out of
/mnt and unmount it. Then mount the root subvolume to
/target like so:
mount -o noatime,compress=lzo,space_cache,subvol=@ BTRFS_VOLUME /target. Then remount this
cd into it again.
Now we want to
mkdir -p /target/etc and copy
/mnt/etc/crypttab if you are using encrypted LVM volumes) into
/target/etc. Once this is done we can
rm -r /mnt/boot /mnt/etc /mnt/media otherwise these directories will remain in your final installation (which isn't a big deal but this is done just for the sake of cleanliness). When this is done, unmount
The next step is to make the necessary subdirectories in
/target for your subvolumes. I did:
mkdir -p /target/home /target/.snapshots. Now, mount the rest of the subvolumes the same way as before like we did for the root subvolume. Also, mount the boot partition (which in my case resides on
/target/boot/efi (or just
/target/boot for a legacy BIOS system). The following screenshots show the exact commands that I ran:
Mounting Subvolumes at Boot
/target/etc/fstab (you must use
nano as unfortunately there is no version of
vi in this busybox configuration) and add the relevant entries to mount your subvolumes on boot. These should look the same as the entry that already exists but you will have to change the options from default to the ones that we used above when mounting our subvolumes and you will have to change the mount points. For example, the line for mounting the root filesystem will go from:
/dev/mapper/debianbtrfs--vg-root / btrfs defaults 0 0
/dev/mapper/debianbtrfs--vg-root / btrfs noatime,compress=lzo,space_cache,subvol=@ 0 0
Where the other lines will look similar:
Once this is all done and you have saved your changes, you may exit out of this terminal (Ctrl + D) and return to the installation (Ctrl + Alt + F1). Proceed with the installation as normal and, when you boot, you should have a btrfs filesystem working with subvolumes!
If you get stuck somewhere try asking in the many helpful areas of the internet such as the Debian User Forums, the
#debian IRC channel on the Freenode network, or the
debian-user mailing list. See this resource for more information on getting help with Debian.