How to Clone or Duplicate a Linux Server with Rsync

Cloning is the meticulous process of creating an exact replica of a live Linux server by employing the powerful rsync command-line tool, which is an efficient file synchronization and transfer tool.

Cloning entails the utilization of two server instances: the source server, which serves as the server to be cloned, and the destination server, where the actual cloning process takes place.

Through the employment of the rsync command, an intricate synchronization of all files and directories from the source server to the destination server is accomplished.

In this guide, you will learn how to hot clone a Linux server with the Rsync file synchronization tool.

Lab Setup

Here’s the lab setup that we are using for this guide, you can clone any Linux distribution using the rsync command.

• Source Server – RHEL 9 – 192.168.2.103
• Destination Server – RHEL 9 – 192.168.2.110

The source server is the one we are going to clone onto the destination server.

Setup and Requirements

Before proceeding, ensure that you have met the prerequisites below:

• Both servers need to be running the same release of the operating system i.e. RHEL 9.x or RHEL 8.x, etc.
• Additionally, the servers should have identical file systems and the same hard disk configuration i.e. whether single-disks or in RAID configuration.

Install Rsync in Linux

For cloning to be successful the rsync command-line tool needs to be present on both servers, which will be used for mirroring the source server to the destination server and syncing all the differences between the two systems.

Thankfully, modern Linux systems come with rsync already pre-installed and you can check the version of rsync installed by running:

$ rsync --version

If you want to view additional information about rsync, execute the following rpm command or dpkg-query command:

$ rpm -qi rsync [On RHEL/CentOS/Fedora and Rocky/AlmaLinux]
$ dpkg-query --status rsync [On Debian, Ubuntu and Mint]

If rsync is missing, use the default package manager to install it on your system.

$ sudo apt install rsync [On Debian, Ubuntu and Mint]
$ sudo yum install rsync [On RHEL/CentOS/Fedora and Rocky/AlmaLinux]
$ sudo emerge -a sys-apps/rsync [On Gentoo Linux]
$ sudo apk add rsync [On Alpine Linux]
$ sudo pacman -S rsync [On Arch Linux]
$ sudo zypper install rsync [On OpenSUSE] 

Configure Source Linux Server

There are directories and files that you may want to exclude from cloning because they are either already available in the destination server or are autogenerated. These include the /boot, /tmp and /dev directories.

Therefore, create an exclusion file /root/exclude-files.txt and add the following entries:

/boot
/dev
/tmp
/sys
/proc
/backup
/etc/fstab
/etc/mtab
/etc/mdadm.conf
/etc/sysconfig/network*

Save and exit the configuration file.

Cloning a Linux Server

With everything set, proceed and rsync your server to the remote or destination server using the command:

$ sudo rsync -vPa -e 'ssh -o StrictHostKeyChecking=no' --exclude-from=/root/exclude-files.txt / REMOTE-IP:/

The command will rsync everything from the source server to the destination server while excluding the files and directories you defined earlier on. Be sure to replace the REMOTE-IP: option with your destination server’s IP address.

Let’s break down the command and its components:

• sudo – It is a command that allows the execution of a command with administrative privileges.
• rsync – The rsync command itself, is used for file synchronization and transfer.
• -v: This option enables verbose output, providing detailed information about the progress of the synchronization.
• -P – This option is equivalent to --progress and enables partial file transfers and displays the progress of each file during the synchronization.
• -a – This option stands for “archive mode” and is a shorthand for preserving important file attributes such as permissions, ownership, timestamps, etc.
• -e – This option specifies the remote shell to use for the synchronization.
• -o StrictHostKeyChecking=no – Disables strict host key checking, which means that the SSH connection will not prompt for confirmation if the remote server’s host key is unknown.
• --exclude-from=/root/exclude-files.txt – This option allows you to specify a file that contains a list of patterns or paths to be excluded from the synchronization.
• / – The forward slash represents the source directory or root directory that will be cloned.
• REMOTE-IP:/ – Specifies the destination server’s IP address or hostname followed by a colon and forward slash. It indicates the remote directory where the cloned files will be copied.

After the synching is done, reboot the destination system to reload the changes and thereafter, boot into the server using the source server’s credentials. Feel free to decommission the old server since you now have a mirror copy of it.