Additional Btrfs Subvolumes Proposal

[antony-linux]

A year or two ago I came to using Btrfs as my default filesystem after running out of storage space on my 1TB Acer laptop. Enjoy using compression and instantaneous snapshots and rock solid reliability (so far!!). System reliably comes back up after major outages, such as system-lock or running out of battery. Backups always roll back reliably and predictably, unlike ZFS on GhostBSD-Xfce!

Have been looking around at other distros lately - namely Arch-based EndeavourOS and Manjaro (can never get CachyOS to install on any of my laptops!). Dislike a few things about the Arch way of doing things - especially the AUR -> each user having to compile their own programs seems anachronistic and wasteful in terms of time and more importantly energy!

One thing that struck me though from both of these installs was that each system created additional Btrfs subvolumes for /var/cache and /var/log.

Thinking about this - that it's a good idea in terms of smaller, less convoluted snapshots and for continuity of system logging (no rollback to a previous state) has led me to retroactively setting up these subvolumes on my Linux Mint system too, with the help of Google Gemini!

System works well and uses resources more optimally than before. I use compress=zstd(3) in my /etc/fstab for all subvolumes, but also noticed that Manjaro sets up compress=zstd:1 by default which I found interesting - evidently it's the ideal level of compression for NVMes. I have been pleasantly surprised as to how fast Btrfs is - on a par with Ext4, if not faster for certain things.

Would like to think the development team could look at this proposal for these additional subvolumes and include it in upcoming versions. Already appreciate the fact that you take care to set up Btrfs subvolumes correctly in the first place! - unike (X)ubuntu.

[Fantu]

Unfortunately, Btrfs support in the Debian and Mint installers is not good, so I also need to do manual changes on Debian servers where I use btrfs for root fs in latest 10 years (and more) and also on 2 mint 22 installs from the previous year.
About Mint I wrote a post, like an how to, time ago: https://github.com/orgs/linuxmint/discussions/549#discussioncomment-13962662
Someone already started a PR to improve the default in the Mint installer some months ago: linuxmint/live-installer#172

[antony-linux]

Thanks for replying Fantu - excellent 'howto' on setting up Btrfs subvolumes. Appreciate the problems getting this stuff implemented. Good to know you're all over the subject already.

I came to Btrfs from Ext4 where I had just a main root partition of about 40GB and the rest dedicated to my home partition. I persisted with this setup whilst using Btrfs - until very recently when I realized that this wasn't optimal for Btrfs where just a main root partition and subvolumes coming off it was the better way to go. Not sure if it is even possible, and from what you have said probably not at the moment anyway - could subvolume level formatting ever be a thing in the installer? I used to keep my data on my separate home partition, which I could leave unformatted whilst root partition was wiped clean. That level of granularity of selective formatting of subvolumes would be nice. I could of course go back to having a separate home partition but for Btrfs that is not optimal is it?. Just a thought anyway. Thanks for your time.

[Fantu]

In theory, with btrfs with custom subvolumes you can also install multiple systems on the same fs but the installer should support both custom subvolumes and not formatting the partition and subvolumes, I have never installed lmde but from the mint installer if I remember correctly there is or was a bug for which it does not respect the flag of not formatting even in ext4 so you have to be very careful and make a backup first even if apparently it supports reusing the same partition.

Regarding keeping the home directory, or copying it later from a backup (making sure to change the owner/group if necessary), it's basically possible. While it seems to me to be much less problematic than keeping a user profile on Windows, but there are some problems also with Linux, so I usually prefer to start from a clean user profile and import the profiles or settings folders/files only for specific programs, such as Thunderbird and Firefox. I almost always reuse the firefox and thunderbird profile as is and it has good support, I even have some that have been maintained for many years, such as my mother's ones from Windows XP to some Ubuntu LTS and now on Mint 22.

While many years ago, when I tried to keep the entire home directory, I had problems with the DE. I didn't invest time in investigating, but probably have more problems with customizations and extensions that are no longer supported. Since almost all the Linux desktop installations I do are for inexperienced PC users and should avoid problems, I always do clean installs and reinstall/reconfigure what's necessary. I only import browser and email client profiles and data from a previous installation or backup. I usually leave a .txt file on any installed PC documenting all the installed items, settings, and customizations so I have a record of them for later reinstallations of a new version. I also have some of those basic "documentation" files that I use as a starting point to speed up installations and avoid forgetting anything.

As for in-place updates, I often do it on servers instead. The Linux servers I manage are almost all minimal Debian without DE (I manage with ssh) and with only the necessary software. On those, I can also make several version inplace upgrades over the years, saving time rather than reinstalling from scratch. On a server in the office, I even upgraded from Debian 5 to 12 over the years.

On desktops, however, I did it a few times with major versions, with Ubuntu 10.04, 12.04 and 14.04, then seeing that it takes less time to redo clean (and less risk of unforeseen events) I did only clean installations and imported not entire home profiles but settings of only some programs and data.
If you want to do major in-place updates or reinstallations by re-importing the entire home, you should ask someone more experienced in this area what things to consider to avoid or solve problems.

[antony-linux]

Ah, interesting stuff, hadn't even considered multiple OS's on one filesystem - just the same as LVM on other filesystems I suppose.

Whenever I did a clean install of a major version I always took care to clean out the config files & directories from my home partition first using the Mint live ISO, thus getting the best of both worlds - a clean install & continuity of user data. Useful to hear about the dependability of Firefox & Thunderbird config files though, thanks.