Use snapper snapshots to backup to external drive
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README.md

snap-sync

About

This bash script sends incremental snapshots to another drive for backing up data. Plug in and mount any btrfs-formatted device you want your system to be backed up to (like a USB drive). When you run the script you will be prompted to select a mounted btrfs device, or you can optionally select the disk using its UUID on the command line.

The script iterates through all snapper configurations by default (this can be changed using the -c flag). For each configuration it creates a new local snapshot. If you have never synced to the specified device you will be prompted to enter a directory on the device where the backup snapshots will go. Additionally you are shown the location of the backed up snapshot. If you have performed a backup to this device before, only the changes since the last backup have to be sent.

Requirements

snapper is required.

Installation

# make install

If your system uses a non-default location for the snapper configuration file, specify it on the command line with SNAPPER_CONFIG. For example, for Arch Linux use:

# make SNAPPER_CONFIG=/etc/conf.d/snapper install

The package is also available in the AUR.

Options

Usage: snap-sync [options]

Options:
 -d, --description <desc> Change the snapper description. Default: "latest incremental backup"
 -c, --config <config>    Specify the snapper configuration to use. Otherwise will perform for each snapper
                          configuration. Can list multiple configurations within quotes, space-separated
                          (e.g. -c "root home").
 -n, --noconfirm          Do not ask for confirmation for each configuration. Will still prompt for backup
                          directory name on first backup
 -u, --UUID <UUID>        Specify the UUID of the mounted BTRFS subvolume to back up to. Otherwise will prompt.
                          If multiple mount points are found with the same UUID, will prompt user.
 -s, --subvolid <subvlid> Specify the subvolume id of the mounted BTRFS subvolume to back up to. Defaults to 5.
 -r, --remote <address>   Send the snapshot backup to a remote machine. The snapshot will be sent via ssh. You 
                          should specify the remote machine's hostname or ip address. The 'root' user must be 
                          permitted to login on the remote machine.
 -p, --port <port>        The remote port.

First run

When you run snap-sync you will be prompted to choose a disk to back up to. The first time you run snap-sync for a particular disk (new UUID) you will be prompted to choose a backup location on that disk. If the directory you specify does not exist, it will be created.

Example command line usage

No arguments

# snap-sync

Select a mounted BTRFS device on your local machine to backup to.
   1) /mnt (uuid=7360922b-c916-4d9f-a670-67fe0b91143c, subvolid=5)
   0) Exit
Enter a number: 1

You selected the disk with UUID 7360922b-c916-4d9f-a670-67fe0b91143c, subovolid=5.
The disk is mounted at /mnt.

Initial configuration...

Creating new snapshot for home...
Will backup /home/.snapshots/4196/snapshot to /mnt/acer-c720/home/4196//snapshot
Continue with backup [Y/n]?

Creating new snapshot for root...
Will backup //.snapshots/8455/snapshot to /mnt/acer-c720/root/8455//snapshot
Continue with backup [Y/n]?

Performing backups...

Sending incremental snapshot for home...
At subvol /home/.snapshots/4196/snapshot
At snapshot snapshot
Modifying data for old snapshot for home...
Tagging new snapshot as latest backup for home...

Sending incremental snapshot for root...
At subvol //.snapshots/8455/snapshot
At snapshot snapshot
Modifying data for old snapshot for root...
Tagging new snapshot as latest backup for root...

Done!

The related snapshots from this on the local machine are for home:

single | 4196 |       | Sat 11 Nov 2017 01:37:44 PM EST | root |          | latest incremental backup | backupdir=acer-c720, subvolid=5, uuid=7360922b-c916-4d9f-a670-67fe0b91143c

and for root:

single | 8455 |       | Sat 11 Nov 2017 01:37:46 PM EST | root |          | latest incremental backup | backupdir=acer-c720, subvolid=5, uuid=7360922b-c916-4d9f-a670-67fe0b91143c

As you can see the userdata column for snapper is used to keep track of these snapshots for the next time the script is run so that only the changes will need to be sent.

With UUID and subvolid specified and no confirmations

# snap-sync --UUID 7360922b-c916-4d9f-a670-67fe0b91143c --subvolid 5 --noconfirm

You selected the disk with UUID 7360922b-c916-4d9f-a670-67fe0b91143c, subovolid=5.
The disk is mounted at /mnt.

Initial configuration...

Creating new snapshot for home...
Will backup /home/.snapshots/4197/snapshot to /mnt/acer-c720/home/4197//snapshot

Creating new snapshot for root...
Will backup //.snapshots/8456/snapshot to /mnt/acer-c720/root/8456//snapshot

Performing backups...

Sending incremental snapshot for home...
At subvol /home/.snapshots/4197/snapshot
At snapshot snapshot
Modifying data for old snapshot for home...
Tagging new snapshot as latest backup for home...

Sending incremental snapshot for root...
At subvol //.snapshots/8456/snapshot
At snapshot snapshot
Modifying data for old snapshot for root...
Tagging new snapshot as latest backup for root...

Done!

systemd example

service

[Unit]
Description=Run snap-sync backup 

[Install]
WantedBy=multi-user.target

[Service]
Type=simple
ExecStart=/usr/bin/snap-sync --UUID 7360922b-c916-4d9f-a670-67fe0b91143c --subvolid 5 --noconfirm

timer

[Unit]
Description=Run snap-sync weekly

[Timer]
OnCalendar=weekly
AccuracySec=12h
Persistent=true

[Install]
WantedBy=timers.target

Contributing

Help wanted! Feel free to fork and issue a pull request to add features or tackle an open issue.

License

snap-sync
Copyright (C) 2016-2018, Wes Barnett

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

See LICENSE for more information.

Related projects

See @rzerres's fork which has several enhancments.