SRT - (Snapper) Snapshot Restoration Tool

[danboid]

Hi snapper devs and users

SRT is a script that uses snapper created snapshots but functions a bit like zfs rollback, reverting all files in the current users home directory to how they were as per a pre-defined snapper timeline created snapshot but it doesn't destroy the intervening snapshots so you could potentially revert to a newer snapshot after reverting to an older one, if available. A new snapshot or subvol is not created when you rollback with SRT.

srt restores snapshots via an easy to use dialog/ncurses TUI.

https://github.com/danboid/SRT

I'm happy to make a PR to add SRT as it is to the snapper repo but can it be easily improved somehow or can we adjust some snapper defaults to make it easier for people to use SRT before it gets committed?

For example, snapper could make ~/.snapshots readable by a specific user or group by default and if the info.xml files within each snapshot dir could be read by a non root user then it would be able to build the snapshot menu much faster than using snapper list as it currently does. That would save srt users having to configure that themselves for each user.

Thanks

[aschnell]

The slowness you mention could be caused by the space calculation which requires btrfs quota rescan. This can be avoided by the option --disable-used-space.

Apart from the I do not see the big difference to snapper undochange. On difference is that rsync does not use the clone feature of btrfs (e.g. like cp --reflink does).

[danboid]

Hi @aschnell

Thanks v.much for your reply. I didn't know about the --disable-used-space option for snapper list. That has made listing snapshots MUCH faster so I have updated SRT to use this option by default.

snapper undochange is closer to how I wanted snapper rollback to work but I think its confusing that it undoes the changes between two snapshots and I think this needs more explanation in the snapper man page.

So, if a user has 4 snapshots of their home directory named 1, 2, 3 and 4, for example, and they run

snapper undochange 2 3

Would this result in the user having the files present in snapshot 1 and the new files added in 4 but not any of the new files added or deleted in snapshots 2 and 3?

Because undochange requires the user specify 2 snapshots to undo (between), I really think this subcommand should have a dry run option to show what it would do when run.

I have updated the README of SRT to also mention these complexities with undochange which means SRT is still useful IMO. Also, srt is easier to use because of its dialog interface which means the user doesn't have to run snapper list... then snapper undochange... when wanting to rollback to a previous snapshot.

[danboid]

Again coming from ZFS, I was expecting/hoping that all users would have read access to their ~/.snapshots dir by default to enable a tool like this to work, as is the case for ~/.zfs where ZFS stores its snapshots.

With ZFS I use httm (HotTubTimeMachine https://github.com/kimono-koans/httm ) to make restoring of files from snapshots easier. It claims to support BTRFS too but I failed to get httm to work with Snapper BTRFS snapshots, hence SRT.

As a result of Snapper's defaults, the root user has to run:

chown root:USERS_GID /home/USER/.snapshots/
chmod g+rx /home/USER/.snapshots/

In order for SRT to be used by non-root users.

Could we either change the default permissions of ~/.snapshots or could we add a new snapper option to remove the need for the user to change the permissions of ~/.snapshots to the above?

I can probably submit a PR for these changes but I'm not going to spend any time working on a feature that might not be accepted hence I'm asking first.

[danboid]

I have opened a PR to add this to the snapper repo's scripts directory.

#1118