borg + vorta. borg is the undelying tech, vorta is the UI. the UI is a little bit rough around the edges but it's immensely powerful for a wide array of use cases.

https://github.com/linuxmint/timeshift

For btrfs snapshots, storage on other disks is not supported.

Timeshift is designed to protect system files and settings. It is NOT a backup tool and is not meant to protect user data.

The command you're looking for is btrfs send. See man btrfs-send.

I know of at least one tool, btrbk, which automates both automatic periodic snapshots and incremental sync, but here's an example manual process so you can know the basic idea. Run all this in a root shell or sudo.

As initial setup:

• Create a btrfs filesystem on the sender drive and another on the receiver drive. No need to link them or sync anything yet, although the receiver's filesystem does need to be large enough to actually accept your syncs.
• Use btrfs subvolume create /mnt/mybtrfs/stuff on the sender, substituting the actual mount point of your btrfs filesystem and the name you want to use for a subvolume under it.
• Put all the data you care about inside that subvolume. You can mount the filesystem with a mount option like -o subvol=stuff if you want to treat the subvolume as its own separate mount from its parent.
• Make a snapshot of that subvolume. Name it whatever you want, but something simple and consistent is probably best. Something like mkdir /mnt/mybtrfs/snapshots; btrfs subvolume snapshot /mnt/mybtrfs/stuff /mnt/mybtrfs/snapshots/stuff-20250511.
• If the receiver is a separate computer, make sure it's booted up and running an SSH server. If you're sending to another drive on the same system, make sure it's connected and mounted.
• Send/copy the entire contents of the snapshot with a command like btrfs send /mnt/mybtrfs/snapshots/stuff-20250511 | btrfs receive /mnt/backup. You can run btrfs receive through SSH if the receiver is a separate system.

For incremental syncs after that:

• Make another separate snapshot and make sure not to delete or erase the previous one: btrfs subvolume snapshot /mnt/mybtrfs/stuff /mnt/mybtrfs/snapshots/stuff-20250518.
• Use another send command, this time using the -p option to specify a subvolume of the last successful sync to make it incremental. btrfs send -p /mnt/mybtrfs/snapshots/stuff-20250511 /mnt/mybtrfs/snapshots/stuff-20250518 | btrfs receive /mnt/backup.

If you want to script a process like this, make sure the receiver stores the name of the latest synced snapshot somewhere only after the receive completes successfully, so that you aren't trying to do incremental syncs based on a parent that didn't finish syncing.

Use pika backup instead of timeshift. Pika is an actual backup tool that puts your files on any drive you tell it to use (including remote). Timeshift is a snapshots tool, it reverts things to a previous state, it doesn't backup actual files and folders.

I'm pretty sure it's possible to use timeshift to create backups on another drive using rsync (instead of btrfs). They are incremental, and deduplicated, as well.

But the other commenters are correct, timeshift is not a backup tool, it's more for snapshots to undo system changes you may not want. In addition to that, it doesn't do user files by default — because again, it's not a backup tool.

btrfs send/receive technically does what you want, using btrfs to do backups to another drive, but I don't think any GUI app supports it. Plus, you would have to create snapshots for btrfs from the command line.

Your best bet are apps explicitly designed for this usecase, like someone mentioned pika, or borg or restic are good choices. They don't do BTRFS, but they do incremental, deduplicated updates in a user friendly way.

Build the snapshot with the below file

btrfs subvolume snapshot -r /path-to-sv/subvol /path-to-sv/subvol.ro

# send the subvolume to file, compress with parallel ZSTD & monitor progress
btrfs send /path-to-sv/subvol.snap.ro | \
    pv -c | pzstd -16 |  pv -c | \
    dd of=/path-to-external-backup/subvol.zstd.back

# delete read-only snapshot
btrfs subvolume delete /path-to-sv/subvol.ro

To restore subvolume from backup we run the process in reverse:

# read backup file and decompress the stream, redirect to temporary read-only snapshot
dd if=/path-to-external-backup/subvol.zstd.back | \
    pv -c | pzstd -d | pv -c | \
    btrfs receive /path-to-sv/


# make a RW subvolume 
btrfs subvolume snapshot subvol.ro subvol

# delete temporary snapshot
btrfs subvolume delete /path-to-sv/subvol.ro    

From here

https://superuser.com/questions/1396241/btrfs-imaging-a-volume-to-an-external-file

You might want to make this into a systemd timer to run at boot or before shutting down

https://linuxconfig.org/how-to-schedule-tasks-with-systemd-timers-in-linux

@Cornflake I prefer good old fashioned dump/restore, but whatever works for you. Most people seem to opt for no backups at all, obviously not a good choice.

Timeshift is not a backup tool, so it's meant to run on the filesystem you've configured it for. If you ran it across many volumes or targets like RAID, it wouldn't work as you'd expect because it's not designed to work that way.