btrfs-sync/README.md

# btrfs-sync

> **Note**: This fork simply adds in-transfer `zstd` compression support and snapshot locking capability (see [Features](#features))

Smart and easy sync of BTRFS snapshots, locally or through SSH.

See example [gif](resources/btrfs-sync.gif).

Can be used in conjunction with [btrfs-snp](https://ownyourbits.com/2017/12/27/schedule-btrfs-snapshots-with-btrfs-snp/)

```
# btrfs-sync --verbose --delete /home/user/.snapshots user@server:/media/USBdrive/home-snapshots
* Skip existing '/home/user/.snapshots/monthly_2018-01-09_200102'
* Skip existing '/home/user/.snapshots/monthly_2018-02-08_200102'
* Skip existing '/home/user/.snapshots/weekly_2018-02-09_140102'
* Skip existing '/home/user/.snapshots/weekly_2018-02-16_150102'
* Skip existing '/home/user/.snapshots/weekly_2018-02-23_150102'
* Skip existing '/home/user/.snapshots/weekly_2018-03-02_180102'
* Skip existing '/home/user/.snapshots/daily_2018-03-03_000101'
* Skip existing '/home/user/.snapshots/daily_2018-03-04_080101'
* Skip existing '/home/user/.snapshots/daily_2018-03-05_100102'
* Skip existing '/home/user/.snapshots/daily_2018-03-06_100102'
* Skip existing '/home/user/.snapshots/daily_2018-03-07_110102'
* Synchronizing '/home/user/.snapshots/hourly_2018-03-08_090101' using seed '.snapshots/hourly_2018-03-07_090101'...
time elapsed [0:00:24] | rate [11.1MiB/s] | total size [ 132MiB]
* Synchronizing '/home/user/.snapshots/hourly_2018-03-08_100101' using seed '.snapshots/hourly_2018-03-09_090101'...
time elapsed [0:01:05] | rate [11.1MiB/s] | total size [ 275MiB]
* Deleting non existent snapshots...
Delete subvolume (no-commit): '/media/USBdrive/home-snapshots/hourly_2018-03-08_090101'
Delete subvolume (no-commit): '/media/USBdrive/home-snapshots/hourly_2018-03-08_100101'
```

## Features

- Simple syntax
- Optional progress indication (using `pv`)
- Support for `zstd`, `xz` or `pbzip2` compression in order to save bandwidth.
- Snapshot locking while sync (`btrfs-send`) is in progress to prevent snapshot deletion, namely by `btrfs subvolume delete ...` invoked e.g as part of `btrfs-snp`
- Retention policy
- Automatic incremental synchronization
- Cron friendly

## Usage

The syntax is similar to that of _scp_

```
Usage:
  btrfs-sync [options] <src> [<src>...] [[user@]host:]<dir>

  -k|--keep NUM     keep only last <NUM> sync'ed snapshots
  -d|--delete       delete snapshots in <dst> that don't exist in <src>
  -z|--xz           use xz     compression. Saves bandwidth, but uses one CPU
  -Z|--pbzip2       use pbzip2 compression. Saves bandwidth, but uses all CPUs
  -s|--zstd         use zstd compression.
  -q|--quiet        don't display progress
  -v|--verbose      display more information
  -h|--help         show usage

<src> can either be a single snapshot, or a folder containing snapshots
<user> requires privileged permissions at <host> for the 'btrfs' command
```

## Examples

### Manual

Synchronize snapshots of _home_ to a USB drive

```
# btrfs-sync /home/user/.snapshots /media/USBdrive/home-snapshots
```

Synchronize snapshots of _home_ to a USB drive in another machine

```
# btrfs-sync /home/user/.snapshots user@server:/media/USBdrive/home-snapshots
```

Synchronize one snapshot of _home_ to a USB drive in another machine

```
# btrfs-sync /home/user/.snapshots/monthly_2018-02-08_200102 user@server:/media/USBdrive/home-snapshots
```

Synchronize only monthly snapshots of _home_ to a USB drive in another machine

```
# btrfs-sync /home/user/.snapshots/monthly_* user@server:/media/USBdrive/home-snapshots
```

### Cron

Daily synchronization over the internet, keep only last 50

```
cat > /etc/cron.daily/btrfs-sync <<EOF
#!/bin/bash
/usr/local/sbin/btrfs-sync --quiet --keep 50 --xz /home user@host:/path/to/snaps
EOF
chmod +x /etc/cron.daily/btrfs-sync
```

Daily synchronization in LAN, mirror snapshot directory

```
cat > /etc/cron.daily/btrfs-sync <<EOF
#!/bin/bash
/usr/local/sbin/btrfs-sync --quiet --delete /home user@host:/path/to/snaps
EOF
chmod +x /etc/cron.daily/btrfs-sync
```

### Credits

Original work by *nachoparker* of [ownyourbits.com](https://ownyourbits.com/2018/03/09/easy-sync-of-btrfs-snapshots-with-btrfs-sync/)

zstd compression support and snapshot locking capability added by wanderer of [dotya.ml](https://git.dotya.ml/wanderer)