How to install Kubuntu 21.10 with BTRFS on root?

[oshunluvr]

OK, well, not Arch so...

As far as /var or whatever else in a separate subvolume, there are some legitimate reasons to do that IMO. For example, on my media server, the catalog (100,000s of entries, many hand-tuned) is held in /var/www. I created a subvolume for www (@www - original, right?) and mount it at /var/www. This allows specific individual backups of the catalog. While it would only take a few minutes to re-install the server OS, it could take WEEKS or longer to recreate the catalog and all of its details.

Having said that, IMO there's no reason to separate directories anymore as a general practice. It was primarily done in the olden days to allow distribution of the OS across several drives to increase drive space or performance. Especially when you consider that when using BTRFS, you are not restricted to a single device (drive or partition). If more space is needed, simply add the device to your BTRFS file system, done.

You can still make an argument for a separate /tmp, but with modern RAM sizes, tmpfs in RAM is better anyway.

SWAP is a singular case as CoW (Copy-on-Write) file systems like BTRFS do not do dynamically allocated files like SWAP files, so a SWAP partition was needed. However, since kernel 5 one can create a no-Cow non-compressed individual subvolume/file for SWAP: https://wiki.archlinux.org/title/Btrfs#Swap_file

[jfabernathy]

As to what grub-btrfs is, it's used in Archlinux to make sure when changes are made for system updates or install that grub had those snapshots made before and after the update/install as bootable images just like old versions of the kernel. In Archlinux timeshift when installed provided this same think so you can just point and click to use snapshots for restore from them.

[Snowhog]

And, at least with *buntu's, /var et al is "old school" and isn't necessary anymore. At most you need two partitions: root ( / ) and home ( /home). Maybe swap.

[oshunluvr]

Thanks, got it working. What about other subvolumes? I'm used to using one for /var, and if I was using snapper, I'd need one for @snapshots. I currently installed Timeshift and I know it only need @ and @home. Also do I need grub-btrfs installed??

What's "grub-btrfs" ? No package showing up in apt-cache search here by that name.

Once you have the install running, it's simple enough to set up additional subvolumes. Simply create, mount, and populate them.

For "live" os stuff like /var you could:

1. boot to a live USB session
2. mount the root filesystem somewhere
3. create a @var subvolume
4. move everything from @/var into @var
5. edit fstab to mount @var at /var on your next reboot
6. done

It is my practice to mount the root filesystem in /mnt/subvol so I can access @ and @home easily for snapshots. I make a folder in the root fs to hold my snapshots, like "/mnt/subvol/snapshots" and send my snaps there to keep the root fs cleaner looking.

I assume snapper will make whatever it needs (I've never used it). I use a custom cron script to take a daily snapshot and make a weekly backup instead of someone else's tool.

As far as the "Advanced" button in the installer, it's there, just labeled "Manual" or "Manual Partitioning". I wish you could specify custom subvolume names as well as other configurations like your desire to subvolume out /var.

[jfabernathy]

Thanks, got it working. What about other subvolumes? I'm used to using one for /var, and if I was using snapper, I'd need one for @snapshots. I currently installed Timeshift and I know it only need @ and @home. Also do I need grub-btrfs installed??

[GreyGeek]

The installation "how to" is in the first part of the top post in the BTRFS subforum.
https://www.kubuntuforums.net/forum/...guide-to-btrfs

Choose the manual partition method when the installation gets to the point of selecting the storage medium.
In the manual mode create the necessary partitions, depending on if you use mbr or gpt.
Create at least one partition, call it sda1 and for the OS select btrfs. For the mount point select "/". Proceed with the installation.
The results will be two subvolumes: @ and @home, which will be mounted to "/" and "/home" respectively, as shown in the /etc/fstab file.

[jfabernathy]

I'm looking for some pointers to a how-to. They must exist. I know how to install Archinux on BTRFS so the subvolumes are right for Timeshift and that was pretty easy. Plenty of videos on that. I saw one video on installing Ubuntu with BTRFS, but that required extensive editing of scripts before running ubunbu install.

I was hoping BTRFS install on root for Kubuntu would be as easy as Ubuntu on ZFS, but there doesn't seem to be an 'Advanced' button in Kubuntu installer.