# rsync

Related articles

- Full system backup with rsync
- Synchronization and backup programs

rsync is an open source utility that provides fast incremental file transfer.

## Installation

Install the rsync package.

Note: rsync must be installed on both the source and the destination machine.

## Usage

For more examples, search the Community Contributions and General Programming forums.

### As a cp alternative

rsync can be used as an advanced alternative for the `cp` command, especially for copying larger files:

    $ rsync -P source destination

The `-P` option is the same as `--partial --progress`, which keeps partially transferred files and shows a progress bar during transfer.

You may want to use the `-r --recursive` option to recurse into directories.

Files can be copied locally as with cp, but the motivating purpose of rsync is to copy files remotely, i.e. between two different hosts. Remote locations can be specified with a host-colon syntax:

    $ rsync source host:destination

or

    $ rsync host:source destination

Network file transfers use the SSH protocol by default.

Whether transferring files locally or remotely, rsync first creates an index of block checksums of each source file. This index is used to find any identical blocks of data which might exist in the destination. Such blocks are used in-place, rather than being copied from the source. This can greatly accelerate the synchronization of large files with small changes. For more information, see official documentation, how rsync works.

#### Trailing slash caveat

Arch by default uses GNU cp (part of GNU coreutils). However, rsync follows the convention of BSD cp, which gives special treatment to source directories with a trailing slash "/". Although

    $ rsync -r source destination

creates a directory "destination/source" with the contents of "source", the command

    $ rsync -r source/ destination

copies all of the files in "source/" directly into "destination", with no intervening subdirectory - just as if you had invoked it as

    $ rsync -r source/. destination

This behavior is different from that of GNU cp, which treats "source" and "source/" identically (but not "source/."). Also, some shells automatically append the trailing slash when tab-completing directory names. Because of these factors, there can be a tendency among new or occasional rsync users to forget about rsync's different behavior, and inadvertently create a mess or even overwrite important files by leaving the trailing slash on the command line.

Thus it can be prudent to use a wrapper script to automatically remove trailing slashes before invoking rsync:

    #!/bin/zsh
    new_args=();
    for i in "$@"; do
        case $i in /) i=/;; */) i=${i%/};; esac
        new_args+=$i;
    done
    exec rsync "${(@)new_args}"

This script can be put somewhere in the path, and aliased to rsync in the shell init file.

### As a backup utility

The rsync protocol can easily be used for backups, only transferring files that have changed since the last backup. This section describes a very simple scheduled backup script using rsync, typically used for copying to removable media. For a more thorough example and additional options required to preserve some system files, see Full system backup with rsync.

#### Automated backup

For the sake of this example, the script is created in the `/etc/cron.daily` directory, and will be run on a daily basis if a cron daemon is installed and properly configured. Configuring and using cron is outside the scope of this article.

First, create a script containing the appropriate command options:

    /etc/cron.daily/backup

    #!/bin/bash
    rsync -a --delete /folder/to/backup /location/of/backup &> /dev/null

`-a`
  indicates that files should be archived, meaning that most of their characteristics are preserved (but not ACLs, hard links or extended attributes such as capabilities)
`--delete`
  means files deleted on the source are to be deleted on the backup as well

Here, `/folder/to/backup` should be changed to what needs to be backed-up (`/home`, for example) and `/location/to/backup` is where the backup should be saved (`/media/disk`, for instance).

Finally, the script must be executable:

    # chmod +x /etc/cron.daily/backup

#### Automated backup with SSH

If backing-up to a remote host using SSH, use this script instead:

    /etc/cron.daily/backup

    #!/bin/bash
    rsync -a --delete -e ssh /folder/to/backup remoteuser@remotehost:/location/of/backup &> /dev/null

`-e ssh`
  tells rsync to use SSH
`remoteuser`
  is the user on the host `remotehost`
`-a`
  groups all these options `-rlptgoD` (recursive, links, perms, times, group, owner, devices)

#### Automated backup with NetworkManager

This script starts a backup when you plugin your wire.

First, create a script containing the appropriate command options:

    /etc/NetworkManager/dispatcher.d/backup

    #!/bin/bash

    if [ x"$2" = "xup" ] ; then
            rsync --force --ignore-errors -a --delete --bwlimit=2000 --files-from=files.rsync /folder/to/backup /location/to/backup
    fi

`-a`
  group all this options `-rlptgoD` recursive, links, perms, times, group, owner, devices
`--files-from`
  read the relative path of /folder/to/backup from this file
`--bwlimit`
  limit I/O bandwidth; KBytes per second

Also, the script must have write permission for owner (root, of course) only (see NetworkManager dispatcher for details).

#### Automated backup with systemd and inotify

Note:

- Due to the limitations of inotify and systemd (see this question and answer), recursive filesystem monitoring is not possible. Although you can watch a directory and its contents, it will not recurse into subdirectories and watch the contents of them; you must explicitly specify every directory to watch, even if that directory is a child of an already watched directory.
- This setup is based on a systemd/User instance.

Instead of running time interval backups with time based schedules, such as those implemented in cron, it is possible to run a backup every time one of the files you are backing up changes. `systemd.path` units use `inotify` to monitor the filesystem, and can be used in conjunction with `systemd.service` files to start any process (in this case your rsync backup) based on a filesystem event.

First, create the `systemd.path` file that will monitor the files you are backing up:

    ~/.config/systemd/user/backup.path

    [Unit]
    Description=Checks if paths that are currently being backed up have changed

    [Path]
    PathChanged=%h/documents
    PathChanged=%h/music

    [Install]
    WantedBy=default.target

Then create a `systemd.service` file that will be activated when it detects a change. By default a service file of the same name as the path unit (in this case `backup.path`) will be activated, except with the `.service` extension instead of `.path` (in this case `backup.service`).

Note: If you need to run multiple rsync commands, use `Type=oneshot`. This allows you to specify multiple `ExecStart=` parameters, one for each rsync command, that will be executed. Alternatively, you can simply write a script to perform all of your backups, just like cron scripts.

    ~/.config/systemd/user/backup.service

    [Unit]
    Description=Backs up files

    [Service]
    ExecStart=/usr/bin/rsync %h/./documents %h/./music -CERrltm --delete ubuntu:

Now all you have to do is start/enable `backup.path` like a normal systemd service and it will start monitoring file changes and automatically starting `backup.service`.

#### Differential backup on a week

This is a useful option of rsync, creating a full backup and a differential backup for each day of a week.

First, create a script containing the appropriate command options:

    /etc/cron.daily/backup

    #!/bin/bash

    DAY=$(date +%A)

    if [ -e /location/to/backup/incr/$DAY ] ; then
      rm -fr /location/to/backup/incr/$DAY
    fi

    rsync -a --delete --inplace --backup --backup-dir=/location/to/backup/incr/$DAY /folder/to/backup/ /location/to/backup/full/ &> /dev/null

`--inplace`
  implies `--partial` update destination files in-place

#### Snapshot backup

The same idea can be used to maintain a tree of snapshots of your files. In other words, a directory with date-ordered copies of the files. The copies are made using hardlinks, which means that only files that did change will occupy space. Generally speaking, this is the idea behind Apple's TimeMachine.

This basic script is easy to implement and creates quick incremental snapshots using the `--link-dest` option to hardlink unchanged files:

    /usr/local/bin/snapbackup.sh

    #!/bin/bash

    # Basic snapshot-style rsync backup script

    # Config
    OPT="-aPh"
    LINK="--link-dest=/snapshots/username/last/"
    SRC="/home/username/files/"
    SNAP="/snapshots/username/"
    LAST="/snapshots/username/last"
    date=`date "+%Y-%b-%d:_%T"`

    # Run rsync to create snapshot
    rsync $OPT $LINK $SRC ${SNAP}$date

    # Remove symlink to previous snapshot
    rm -f $LAST

    # Create new symlink to latest snapshot for the next backup to hardlink
    ln -s ${SNAP}$date $LAST

There must be a symlink to a full backup already in existence as a target for `--link-dest`. If the most recent snapshot is deleted, the symlink will need to be recreated to point to the most recent snapshot. If `--link-dest` does not find a working symlink, rsync will proceed to copy all source files instead of only the changes.

A more sophisticated version checks to see if a certain number of changes have been made before making the backup and utilizes `cp -al` to hardlink unchanged files:

    /usr/local/bin/rsnapshot.sh

    #!/bin/bash

    ## my own rsync-based snapshot-style backup procedure
    ## (cc) marcio rps AT gmail.com

    # config vars

    SRC="/home/username/files/" #dont forget trailing slash!
    SNAP="/snapshots/username"
    OPTS="-rltgoi --delay-updates --delete --chmod=a-w"
    MINCHANGES=20

    # run this process with real low priority

    ionice -c 3 -p $$
    renice +12  -p $$

    # sync

    rsync $OPTS $SRC $SNAP/latest >> $SNAP/rsync.log

    # check if enough has changed and if so
    # make a hardlinked copy named as the date

    COUNT=$( wc -l $SNAP/rsync.log|cut -d" " -f1 )
    if [ $COUNT -gt $MINCHANGES ] ; then
            DATETAG=$(date +%Y-%m-%d)
            if [ ! -e $SNAP/$DATETAG ] ; then
                    cp -al $SNAP/latest $SNAP/$DATETAG
                    chmod u+w $SNAP/$DATETAG
                    mv $SNAP/rsync.log $SNAP/$DATETAG
                   chmod u-w $SNAP/$DATETAG
             fi
    fi

To make things really, really simple this script can be run from a systemd/Timers unit.

### rsync daemon

rsync can be run as daemon on a server listening on port `873`.

Edit the template `/etc/rsyncd.conf`, configure a share and start the `rsyncd.service`.

Usage from client, e.g. list server content:

    $ rsync rsync://server/share

transfer file from client to server:

    $ rsync local-file rsync://server/share/

Consider iptables to open port `873` and user authentication.

## Graphical frontends

Install the grsync package.

Categories:

- Data compression and archiving
- System recovery