Clean install, how to preserve personal subvolumes in /var/home/

[zilexa]

The following are subvolumes that I created:
/var/home/username/Documents
/var/home/username/Shared
/var/home/username/Pictures

And their snapshots, created by btrbk:
/var/home/username/.snapshots/Documents20260507
/var/home/username/.snapshots/Shared20260507
/var/home/username/.snapshots/Pictures20260507

Some are big. Pictures is 368GB.

I want to do a clean install. But I would like to keep these subvolumes. Since they are 'nested' in home. I never manually mounted them or used fstab (and don't want to rely on manually configuring them in something like fstab) I am not sure what the proper way, the smartest way would be to keep these subvolumes, what to select during manual partitioning in the installer?

For example (not sure if this is possible), use the installer to rename my current home and preserve it. Then after installation mv all the above to the new home? But that might be tricky. Especially with the snapshots, to preserve the child/parent uuid..

[repires]

ai generated: ask.projectbluefin.io

This is a good question from the user. The short answer is that the Bluefin installer (Anaconda) doesn't have a built-in "preserve these nested subvolumes" option, so the user needs to work around it manually. Here's the safest approach I'd suggest for a reply:

Recommended strategy: Move subvolumes to top-level before reinstalling

1. Boot from a live USB (the Bluefin ISO live environment works fine)

2. Mount the btrfs filesystem at its top level:

   sudo mount -o subvol=/ /dev/nvme0n1pX /mnt

3. Move (or snapshot) the subvolumes to the top level so they're siblings of home rather than nested inside it:

   # These are already subvolumes, so you can't `mv` them — 
   # but you can create read-write snapshots at top level:
   sudo btrfs subvolume snapshot /mnt/home/username/Documents /mnt/@Documents
   sudo btrfs subvolume snapshot /mnt/home/username/Pictures /mnt/@Pictures
   sudo btrfs subvolume snapshot /mnt/home/username/Shared /mnt/@Shared
   # Same for the btrbk snapshots

4. Run the installer using custom partitioning — tell it to use the existing btrfs partition without formatting it, and point / and /home at new subvolumes on it. The top-level @Documents, @Pictures, @Shared subvolumes will be untouched since the installer only touches the subvolumes it creates.

5. After installation, mount the top-level again and move/snapshot them back into the new home, or just bind-mount them via /etc/fstab entries like:

   UUID=<btrfs-uuid>  /var/home/username/Documents  btrfs  subvol=@Documents,compress=zstd:1  0  0
   

The key insight is that nested subvolumes are deleted when their parent subvolume is deleted. So if the installer wipes/recreates the home subvolume, anything nested inside is gone. Moving them to top-level first decouples them from that risk.

Regarding the btrbk snapshots and parent/child UUID relationships — btrfs subvolume snapshot preserves the parent UUID link, so the snapshots created at top-level will still reference the original. However, if the user later recreates the subvolumes in their new home (rather than bind-mounting the top-level ones), the btrbk snapshot chain will reference the old parent UUID. For ongoing btrbk use, the cleanest path is to keep the subvolumes at top-level permanently and bind-mount them into /var/home/username/.

Note that Bluefin Stable uses BTRFS with zstd:1 compression by default , and /var (including /var/home) persists across atomic OS updates , so once the user sets this up correctly after reinstall it will be durable.

One caveat: the installer's "custom partitioning" spoke in Anaconda does allow reusing an existing btrfs partition without formatting, but it can be finicky about existing subvolumes. The user should double-check their top-level subvolumes are intact after install before deleting any backups.

[zilexa]

The problem is that this ignores the snapshots that were already created (and some of the info is not correct about preserving UUIDs) and that have been send/received to usb drives. I cannot perform incremental send/receive anymore, if I do the above, because the parent subvolumes and its original snapshots that were send will no longer exist.

There are more errors in this response btw.. like the suggestion to manually change fstab. Thats a no go on Bluefin.

I asked Claude and Gemini and their responses were even worse (even suggesting to remove the ro flag of snapshots, telling me to ignore the warning that the uuid would be removed, all to je able to use mv).

[repires]

@dosu:
Thanks for flagging this — the user raises valid criticisms. Let me address the corrections:

Corrections to my previous response:

1. Nested subvolumes are NOT automatically deleted with their parent. Btrfs actually protects nested subvolumes — you cannot delete a parent subvolume unless you explicitly pass -R (recursive) [1]. My statement that "nested subvolumes are deleted when their parent subvolume is deleted" was wrong.

2. The snapshot approach breaks incremental send/receive. The user is correct — creating new snapshots at the top level produces subvolumes with new UUIDs. The received_uuid (set during send/receive operations) is what links the local subvolume to its counterpart on the USB backup drive [2]. Creating a fresh snapshot severs that link, making future incremental sends impossible against the existing backup chain.

3. fstab is actually writable and persistent on Bluefin — the user is mistaken on this point. /etc/fstab persists across atomic updates via ostree's 3-way merge [3]. That said, systemd mount units in /etc/systemd/system/ are the preferred approach over fstab entries on Bluefin.

What the user should actually do:

The real question is whether the Anaconda installer will destroy the existing home subvolume during a clean install. Given the constraints (must preserve exact subvolumes with their UUIDs for incremental send/receive), the safest approach is:

• During custom partitioning in the installer, reuse the existing btrfs partition without formatting and tell the installer to only create/format the root subvolume — leaving the home subvolume (and everything nested inside it) untouched.
• If that's not possible with Anaconda's UI, the alternative is to do a bootc install to-filesystem against a manually prepared layout where the home subvolume is simply left alone.

This is genuinely a tricky edge case that AI (including my previous answer) struggles with because it requires understanding the specific UUID semantics of btrfs send/receive chains. The user might be better served by asking in a btrfs-specific forum or the btrbk GitHub for the exact installer workflow that preserves their backup chain.

[zilexa]

I'm thinking now:

1. Start with Live USB.
2. Before starting the installer: delete all files and folders (including hidden) inside the home folder except the listed subvolumes and the .snapshots folder.
3. Start the installer and use custom partitioning without formatting. Point / to a new subvolume (delete the old) and point /home to the existing subvolume.

If this would work it's probably the easiest and fastest..

[repires]

@dosu : I see the user's proposed plan:

1. Boot live USB
2. Delete all files/folders in home except the subvolumes and .snapshots
3. Run installer with custom partitioning — don't format, point / to a new subvolume (delete old), point /home to existing subvolume

This is a reasonable idea, but there are some concerns based on what I can find about how the installer works:

The main uncertainty is whether Anaconda's custom partitioning will actually let you point /home at an existing btrfs subvolume without reformatting it. The Bluefin Stable profile configures /home as a separate partition (not a subvolume within root) by default [1]. So the behavior when manually assigning an existing subvolume as /home in the custom partitioning UI isn't well-documented or tested in this context.

Additionally, even if the subvolume survives installation, bootc-based systems don't automatically remount pre-existing subvolumes — the user may need to configure mount points post-install [2]. On Bluefin Stable, /home is typically a bind-mount from /var/home, so there's a question of whether the installer respects a custom /home subvolume assignment or overrides it with the standard ostree layout.

My honest assessment: This is an edge case that isn't covered by Bluefin's documentation or tested installer workflows. The user's plan might work, but it's risky without a backup. The safest path is probably:

1. Ensure a full btrfs send backup of all subvolumes + snapshots to USB exists first
2. Try the proposed approach
3. Verify the subvolumes and their UUID chains are intact before deleting anything

I'd suggest this is one where the user should test carefully — and given how AI tools (including me) have already given incorrect btrfs advice here, directing them to btrfs-specific communities (like the btrbk GitHub or btrfs mailing list) for the UUID chain preservation aspect might be more helpful than us guessing further.

Want me to post a response in the discussion thread acknowledging the limitations?

[zilexa]

.

[zilexa]

I used dosu as well and got the exact same 2 responses btw :)
Seems like there isn't a clear solution and the only way is to try it out, with the risk of 1) having to restore my data and 2) having to also format my usb drives and do full send/receives again. That would make me quite sad.

I'll give it a try. I wish there was better documentation on the Installer..

[zilexa]

I'm thinking now:

1. Start with Live USB.

2. Before starting the installer: delete all files and folders (including hidden) inside the home folder except the listed subvolumes and the .snapshots folder.

3. Start the installer and use custom partitioning without formatting. Point / to a new subvolume (delete the old) and point /home to the existing subvolume.

If this would work it's probably the easiest and fastest..

I can confirm this is the fastest and works!!
From now on I will always install like this 🎉
The reply from Dosu seems more related to the old installer that shipped with Fedora/Bluefin in earlier versions.

Here are the screenshots of what I selected and the summary before installation starts:

What was a little confusing:

1. the mapped subvolumes were not prefilled. I had to "guess".
2. The /home subvolume was not listed as a recommended subvolume! It should be, because the installer will create it! I had to add that line manually.

But this did work exactly the way I expected it to: apart from the Documents and Pictures subvolume and the .snapshots folder (with its snapshots) I deleted all contents of /home (also all hidden files and folders) before starting the installer.

And indeed: a fully clean install! While my personal folders were preserved!

I would suggest to make the personal files folders all subvolumes by default 🤓