[Next] Configurable Btrfs subvol names #480

fused0 · 2025-11-23T16:44:19Z

Here's the start of configurable subvolume names, to support non-ubuntu layout (at least layouts that only have different names, not nested ones).

It's functional, but I'm sure some (small?) issues are remaining.

Advice and suggestions appreciated.

See issues #368, #405, #266, etc

Best,
fused0

Save and load config for btrfs subvolume names. Added variables for home and root subvolumes to Main.

…e as system subvolume name

ygerlach · 2025-11-23T17:42:13Z

Nice! i just ran into this issue today, as i tried to run timeshift on debian in btrfs mode (I had to manually rename @rootfs to @ and fix my grub for it to work)

I think in the long term we should allow an arbitrary amount of subvolumes for backups. I believe some distros allow /boot or /etc to be their own subvolume. But i guess that would be a bigger topic.

I think there is some room to improve add_opt_btrfs_subvolume_names :

it seems the code for creating home and root text box is quite similar. maybe we could create a function like create_btrfs_subvolume_selection to de-duplicate this.
There should be some kind of guard against entering a wrong subvolume names. Maybe even use a select box instead of a text box
the boxes should be hidden or greyed-out when btrfs mode is inactive
i think the home subvolume selection could be moved to the thing where it asks to backup @home at all (see screenshot). I am thinking a selection box with the options: "Disabled", @home, @boot, ...)
selecting the same subvolume twice should also be guarded against.

Some other thing: i don't know if we need to care about changes of names in the config. What if i configure @rootfs, make some snapshots, rename it to @ maybe fuck up my system some time later, want to restore my old @rootfs snapshot, but because i changed the name in the timeshift config its now failing.

The question is: should we use the configured btrfs subvolume, or just restore all subvolumes in the snapshot folder or use the information from info.json? Im not sure how it is currently handled. (Enable and Disable backup of @home could have a similar problem)

src/Core/Main.vala

fused0 · 2025-11-23T18:01:01Z

Thanks for the quick review, I'll get to the improvement suggestions soon :)

Regarding:

I am thinking a selection box with the options: "Disabled", @home, @boot, ...)

What would "Disabled" do?

selecting the same subvolume twice should also be guarded against.

Thanks, definitely, that seems like it could fail spectacularly.

ygerlach · 2025-11-23T18:04:08Z

What would "Disabled" do?

the same as not selecting the checkbox seen in the screenshot. (I would replace the checkbox with the dropdown)

fused0 · 2025-11-23T18:18:50Z

I put the option into the backup type page, because it depends on the type of backup used. Selecting rsync is the equivalent of the option being disabled.

To me, it would be a little confusing to have it on the users page, but I'm also not super familiar with the full functionality of this page, because I saw it allows selecting home directories in cases where multiple users exist on the system.

Please let me know what you think.

Also deduplicated the subvolume ui selection code

fused0 · 2025-11-24T07:59:11Z

I've turned the subvolume name selection into a combo box, which should address almost all of the issues you had, except the one about the location of the option

Not entirely sure what the common options are (please let me know) and if there should be a "custom" option as well. The custom option would make it tricky in terms of making sure the config is valid.

into a single combobox to select a predefined layout

fused0 · 2025-11-24T09:46:23Z

Actually, I went and change the two comboboxes into a single one, to select a predefined layout. Hopefully I left some room to add a "custom" option (implementation would be similiar how the custom date format is done, presumably).

The current state would be more than sufficient for my - and probably most users - needs.

Still not sure about the debian layout/subvolume names.

Also, I'd like to change some of the messages in the UI, but I'm not sure how to proceed in regards to the translation, example:

status_details = _("Select BTRFS system disk with root subvolume" + @" ($(App.root_subvolume_name))");

on first launch of timeshift, based on distro id

fused0 · 2025-11-30T09:16:59Z

@ygerlach apologies for the ping, but any advice or suggestions how to proceed from here?

ygerlach · 2025-11-30T11:55:30Z

apologies for the ping

@fused0 no problem, the PR looks fine to me.

Not entirely sure what the common options are (please let me know) and if there should be a "custom" option as well.

i think we will get issues if people miss some layout. so we can add it then, if we miss it here.

Actually, I went and change the two comboboxes into a single one, to select a predefined layout.

i think that is reasonable

Just checked the ui again on debian. Here how it looks (for others interested in this PR):

I think it looks nice. Making it "disabled" when rsync is active is nice.

Just a thought: do we really need a selection? Can't timeshift find the correct layout itself? Because usually there should only be one valid layout possible and if the user fucks up the selection, timeshift behaves badly. So best keep the user out of this decision? And if a user has a layout that matches multiple layouts, with subvolumes like @rootfs, @, @homefs and @home, the user will be proficient enough to edit the timeshift config himself.

So if we have some detection what subvolumes are existing and choose the correct layout and maybe display the chosen selection like: "Using subvolume layout: Ubuntu (@, @home)" would be fine i guess.

Do all systems always have a seperate home subvolume? (EDIT: No, my debian test vm aparently only has @rootfs)

When i try to create a snapshot i get:

(timeshift did not exit)

Maybe you should run some tests with your branch on some different systems/vms (debian, fedora, linuxmint, ...)

P.S: im not a timeshift maintainer, just an contributor, so my opinion is not binding :)

fused0 · 2025-11-30T13:42:03Z

@fused0 no problem, the PR looks fine to me.

Thanks, but after your reply, there is more to consider.

Just a thought: do we really need a selection?

The layout actually is auto detected for the intial config values, based on the distro name. I wondered the same, when I added it. I suppose one could parse the fstab to find what subovlumes (if any) root and home map to... Seems like a simple enough solution for the entire problem. It would catch all reasonable user-defined layouts.

the user will be proficient enough to edit the timeshift config himself.

Unfortunately, due to how the timeshift handles the settings and wizard dialogs - more or less immediately overwriting the config - there can only be two options: Having no option in the UI at all, or supporting "custom" layouts with settings in the UI. Otherwise, the edited config would be overwritten when you accidentally (or not) open the settings or wizard.

I think I'll go for it and add the custom layout option.

Do all systems always have a seperate home subvolume? (EDIT: No, my debian test vm aparently only has @rootfs)

Now I know why I couldn't find anything on the name of the home subvolume in Debian. :)

I'm wondering if timeshift would work if you configure it to not backup the home subvolume and leave the home subvolume option blank or wiht a dummy value - or if supporting layouts without a separate home would imply more work. I would very much appreciate if you could give it a try.

Maybe you should run some tests with your branch on some different systems/vms (debian, fedora, linuxmint, ...)

Unfortunately I'm on a rather limited and flaky internet connection at the moment.

P.S: im not a timeshift maintainer, just an contributor, so my opinion is not binding :)

Seems I wrongfully assumed you to be a maintainer :) Thank you for your detailed reply and suggestions, much appreciated.

I suppose it would be good to get a maintainer to weigh in on the issue.

Thanks,
fused0

empty home subvolume name and force include_btrfs_home_for_backup to false

fused0 · 2025-11-30T14:48:16Z

@ygerlach Interestingly, timeshitft handles leaving the home subvolume name empty somewhat gravefully. I've made some more tweaks to make it work on debian without a separate home subvolume - it feels a bit hacky, but it works!

Now I'm wondering if this solution is adequate, or if parsing fstab and adding a custom input group is even needed.

Copilot

Pull request overview

This PR implements configurable Btrfs subvolume names to support different Linux distribution layouts beyond Ubuntu's default @ and @home convention. The implementation adds a UI for selecting preset layouts (Ubuntu, Debian, Fedora) or configuring custom subvolume names, addressing issues #368, #405, and #266.

Key Changes:

Added root_subvolume_name and home_subvolume_name properties to Main.vala with distro-specific defaults
Created UI in SnapshotBackendBox.vala for subvolume layout selection with preset and custom options
Replaced all hardcoded "@" and "@home" references throughout the codebase with configurable names

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 15 comments.

Show a summary per file

File	Description
src/Core/Main.vala	Added subvolume name properties, distro detection logic, config persistence, and updated all references to use configurable names
src/Gtk/SnapshotBackendBox.vala	Implemented UI for subvolume layout selection with combo box and custom entry fields
src/Gtk/UsersBox.vala	Added logic to disable home subvolume backup checkbox when home_subvolume_name is empty
src/Gtk/SnapshotListBox.vala	Updated size calculation displays to use configurable subvolume names
src/Gtk/RestoreWindow.vala	Updated restore logic to check for configurable home subvolume name
src/Core/Subvolume.vala	Updated subvolume removal logic to use configurable names
src/Core/SnapshotRepo.vala	Updated mount path handling to use configurable subvolume names
src/Core/Snapshot.vala	Updated snapshot reading logic to use configurable subvolume names

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Copilot · 2025-12-08T15:49:10Z

src/Core/Main.vala

+				&& sys_subvolumes.has_key(home_subvolume_name)
+				&& (sys_subvolumes[home_subvolume_name].id == subvol_id)){

-				subvol = sys_subvolumes["@home"];
+				subvol = sys_subvolumes[home_subvolume_name];


Similar to the issue on lines 4186-4189, this code is vulnerable to null pointer exceptions when home_subvolume_name is empty. If home_subvolume_name is an empty string (as it is for Debian), attempting to access sys_subvolumes[home_subvolume_name].id could fail.

Add an empty string check:

else if ((sys_subvolumes.size > 0) && (home_subvolume_name != "") && sys_subvolumes.has_key(home_subvolume_name) && (sys_subvolumes[home_subvolume_name].id == subvol_id)){

I'm not sure this follows, as it checks if sys_subvolumes has the key home_subvolume_name - sys_subvolumes itself is generated from fstab and crypttab, so doesn't depend on home_subvolume_name or root_subvolume_name.

src/Gtk/SnapshotBackendBox.vala

src/Gtk/UsersBox.vala

src/Core/Main.vala

Copilot · 2025-12-08T15:49:12Z

src/Gtk/SnapshotListBox.vala


-			if (bak.subvolumes.has_key("@home")){
-				size += bak.subvolumes["@home"].total_bytes;
+			if (bak.subvolumes.has_key(App.home_subvolume_name)){


Potential null pointer exception when App.home_subvolume_name is empty. If home_subvolume_name is an empty string (as configured for Debian), bak.subvolumes.has_key("") could match unintended entries or bak.subvolumes[""] could cause issues.

Consider adding an empty string check:

if ((App.home_subvolume_name != "") && bak.subvolumes.has_key(App.home_subvolume_name)){ size += bak.subvolumes[App.home_subvolume_name].total_bytes; }

Suggested change

if (bak.subvolumes.has_key(App.home_subvolume_name)){

if ((App.home_subvolume_name != "") && bak.subvolumes.has_key(App.home_subvolume_name)){

Copilot · 2025-12-08T15:49:14Z

src/Gtk/SnapshotBackendBox.vala

+		Gtk.TreeIter strore_iter;
+		int active = -1;
+		for (int idx = 0; idx < possible_layouts.length[0]; idx++) {
+			list_store.append(out strore_iter);
+			list_store.set(strore_iter,


Typo in variable name: 'strore_iter' should be 'store_iter'.

Suggested change

Gtk.TreeIter strore_iter;

int active = -1;

for (int idx = 0; idx < possible_layouts.length[0]; idx++) {

list_store.append(out strore_iter);

list_store.set(strore_iter,

Gtk.TreeIter store_iter;

int active = -1;

for (int idx = 0; idx < possible_layouts.length[0]; idx++) {

list_store.append(out store_iter);

list_store.set(store_iter,

Copilot · 2025-12-08T15:49:14Z

src/Gtk/SnapshotBackendBox.vala

+		custom_home_subvol_entry.focus_out_event.connect((entry1, event1) => {
+			App.home_subvolume_name = custom_home_subvol_entry.text;
+
+			// If home subolume name is empty, do not backup home.


Typo in comment: 'subolume' should be 'subvolume'.

Suggested change

// If home subolume name is empty, do not backup home.

// If home subvolume name is empty, do not backup home.

Copilot · 2025-12-08T15:49:15Z

src/Gtk/SnapshotListBox.vala

 			}
-			if (bak.subvolumes.has_key("@home")){
-				size += bak.subvolumes["@home"].unshared_bytes;
+			if (bak.subvolumes.has_key(App.home_subvolume_name)){


Same issue as lines 438-440. When App.home_subvolume_name is empty (e.g., for Debian), accessing bak.subvolumes[""] could cause issues.

Add an empty string check:

if ((App.home_subvolume_name != "") && bak.subvolumes.has_key(App.home_subvolume_name)){ size += bak.subvolumes[App.home_subvolume_name].unshared_bytes; }

Suggested change

if (bak.subvolumes.has_key(App.home_subvolume_name)){

if ((App.home_subvolume_name != "") && bak.subvolumes.has_key(App.home_subvolume_name)){

Copilot · 2025-12-08T15:49:15Z

src/Core/Subvolume.vala

 			}
-			else if (name == "@home"){
-				path = path_combine(App.mount_point_app + "/backup-home", "@home");
+			else if (name == App.home_subvolume_name){


Potential issue when App.home_subvolume_name is empty. For distributions like Debian that set home_subvolume_name = "", this condition name == "" will match any empty name, which could cause unintended behavior.

Consider adding an explicit check:

else if ((App.home_subvolume_name != "") && (name == App.home_subvolume_name)){

Suggested change

else if (name == App.home_subvolume_name){

else if ((App.home_subvolume_name != "") && (name == App.home_subvolume_name)){

src/Gtk/SnapshotBackendBox.vala

Co-authored-by: Copilot <[email protected]>

When root subvolume name is misconfigured to empty string, don't early out, but treat it the same as empty home subvolume name

Co-authored-by: Copilot <[email protected]>

fused0 added 4 commits November 23, 2025 15:53

Added ui for btrfs subvolume names

4d528da

Save and load config for btrfs subvolume names. Added variables for home and root subvolumes to Main.

Merge branch 'linuxmint:master' into btrfs_subvol_names

85efc0b

Improve subvolume name option layout

6cf8745

early out of subvolume listing if configured subvolume is not the sam…

bd54ed4

…e as system subvolume name

ygerlach reviewed Nov 23, 2025

View reviewed changes

src/Core/Main.vala Outdated Show resolved Hide resolved

fix add missing return value in Main.query_subvolume_id

f3e3bc8

Subvolume selection is now a combobox

52b7cf4

Also deduplicated the subvolume ui selection code

fused0 added 2 commits November 24, 2025 10:23

improved subvolume selection by adding a distribution hint

9cc883b

combine subvol comboboxes

0ebe92a

into a single combobox to select a predefined layout

fused0 added 5 commits November 24, 2025 13:18

detect subvolume layout

4e13156

on first launch of timeshift, based on distro id

Merge branch 'linuxmint:master' into btrfs_subvol_names

69b8468

cleanup create_btrfs_subvolume_selection

04bfffd

call init_backend on layout change

dd769f5

also call type_changed on subvol layout change

d7b5070

mtwebster changed the title ~~Configurable Btrfs subvol names~~ [WIP] Configurable Btrfs subvol names Nov 27, 2025

fused0 added 2 commits November 30, 2025 15:41

Disable "include home subvol" option when home subvolume name is empty

0e71046

fix for debian style layout

7f55d83

empty home subvolume name and force include_btrfs_home_for_backup to false

fused0 added 2 commits November 30, 2025 20:14

added ui for custom subvolume layout

aaccff3

Merge branch 'linuxmint:master' into btrfs_subvol_names

a1f3892

fused0 marked this pull request as ready for review December 8, 2025 06:48

fused0 changed the title ~~[WIP] Configurable Btrfs subvol names~~ Configurable Btrfs subvol names Dec 8, 2025

mtwebster requested a review from Copilot December 8, 2025 15:36

mtwebster changed the title ~~Configurable Btrfs subvol names~~ [Next] Configurable Btrfs subvol names Dec 8, 2025

Copilot started reviewing on behalf of mtwebster December 8, 2025 15:37 View session

Copilot AI reviewed Dec 8, 2025

View reviewed changes

fused0 and others added 6 commits December 8, 2025 17:31

Change variable name in SnapshotBackendBox

44edb09

Co-authored-by: Copilot <[email protected]>

Simplify toggling checkbox sensitivity in UsersBox

7528ba9

Co-authored-by: Copilot <[email protected]>

Change early out of query_subvolume_id to has_key

deb0ecb

Co-authored-by: Copilot <[email protected]>

Properly fix query_subvolume_id

6a0240f

When root subvolume name is misconfigured to empty string, don't early out, but treat it the same as empty home subvolume name

Simplify vbox_subvolume_custom.visible assignment

216393b

Co-authored-by: Copilot <[email protected]>

Fix typo in comment

59339bb

Co-authored-by: Copilot <[email protected]>

	if (bak.subvolumes.has_key(App.home_subvolume_name)){
	if ((App.home_subvolume_name != "") && bak.subvolumes.has_key(App.home_subvolume_name)){

	// If home subolume name is empty, do not backup home.
	// If home subvolume name is empty, do not backup home.

	else if (name == App.home_subvolume_name){
	else if ((App.home_subvolume_name != "") && (name == App.home_subvolume_name)){

[Next] Configurable Btrfs subvol names #480

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[Next] Configurable Btrfs subvol names #480

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ygerlach commented Nov 23, 2025 •

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