Rsync Backup

This documentation explain how to automaticaly backup a directory to a remote computer using rsync protocol. To achieve this goal, standard open-source software such as cron/rsync/ssh will be used.

Program	Description
cron	time-based job scheduler
ssh	network protocol to allow remote login securely
rsync	file synchronization and file transfer program

rsync client

Local copy

To synchronize two directories on the same device using rsync:

Synchronize two directories using rsync

rsync -a --delete /src/dir /dst/dir/

Options

Replace /src/dir and /dst/dir by your source and destination directories.
--delete: deletes files in the destination directory if they don't exist in the source directory.

Install ssh keys

The following procedure install ssh security keys from the client to the remote computer in order to login without the need of password. This step is mandatory for rsync to connect to the remote computer automatically.

For the full procedure, please refer to Install SSH Keys.

Configuring rsync

rsync is typically used to synchronize files and directories between two different systems. It uses a type of delta encoding (hashing files on both sides) to minimize the network usage. zlib may be used for additionnal compression, and ssh for additionnal security.

Note

The rsync client and server should be located in the same sub-network.

Configure rsync

# installing rsync
sudo apt-get install rsync

# execute one rsync task
rsync -avz -e ssh <dir> <user>@<host>:~/<remote_dir>

Replace Fields

Field	Description
<dir>	directory to backup on the client
<user>	user account of the server
<host>	address of the server
<remote_dir>	remote directory where the backup will be saved on the server

Tip

This rsync command-line synchronizes your directory with the remote backup directory.

Configuring cron

cron is a time-based job scheduler in unix operating system.
The origin of the name cron came from the Greek "chronos".

Create the cron task

/etc/cron.daily/backup_task

#!/bin/bash
rsync -avz --delete -e ssh <dir> <user>@<host>:~/<remote_dir>

Give execution right to this cron job:

sudo chmod +x /etc/cron.daily/backup_task

This rsync job will be executed daily by cron.

rsync server

Configure rsync

Install rsync on the server

# install rsync
sudo apt-get install rsync

# configure user/password
sudo nano /etc/rsyncd.secrets
<user>:<password>
sudo chmod 600 /etc/rsyncd.secrets

Important

Replace <user>:<password> with your own credentials.

Configure the rsync server configuration file:

Create rsync directory on sd-card/etc/rsyncd.conf

sudo mkdir /path/to/backup
sudo chown -R debian:debian /path/to/backup
sudo chmod 775 /path/to/backup

uid = debian
gid = debian
max connections = 3
socket options = SO_KEEPALIVE
pid file = /var/run/rsyncd.pid

[rsync_data]
path = /path/to/backup
comment = rsync backup directory
auth users = *
secrets file = /etc/rsyncd.secrets
hosts allow = <allowed-ip>
hosts deny = *
list = true
read only = no

Important

Replace /path/to/backup with your own backup directory (ex: /media/data/rsync).
Replace <allowed-ip> by the ipv4 address of the allowed rsync client.

Activate rsync

Enabling rsync

# activate rsync
sudo sed -i 's/RSYNC_ENABLE=false/RSYNC_ENABLE=true/g' /etc/default/rsync
sudo service rsync restart

# enable rsync script
sudo systemctl enable rsync
sudo systemctl is-active rsync

Tip

The rsync server is up and running.