How to Use `rsync` for File Synchronization on Arch Linux

In the realm of file synchronization, data backups, and mirroring, one tool stands out for its flexibility, performance, and reliability: rsync. This powerful command-line utility has become a cornerstone in Linux-based systems for efficient data transfer. Whether you’re syncing directories across systems, backing up important files, or keeping folders in sync in real-time, rsync has got your back.

In this article, we’ll explore how to use rsync for file synchronization on Arch Linux, discuss common use cases, and walk through practical examples to help you get started.

What is rsync?

rsync is a fast and versatile command-line utility for copying and synchronizing files and directories between two locations. It can sync files locally (on the same machine) or remotely (over SSH or rsync daemons). What makes rsync so efficient is its ability to perform differential transfers—meaning it only copies the differences between source and destination files.

Key features of rsync include:

• Delta transfer algorithm (transfers only changed parts of files)
• Compression support during data transfer
• Preserving file permissions, ownership, timestamps, and symbolic links
• Ability to exclude files with patterns
• Sync over SSH or using the rsync daemon
• Verbose and dry-run modes for safer operations

Installing rsync on Arch Linux

Arch Linux typically provides rsync out of the box, but if it’s not installed, you can install it easily using pacman:

sudo pacman -S rsync

Once installed, verify the version and that it’s available:

rsync --version

Basic rsync Syntax

The general syntax of the rsync command is:

rsync [options] source destination

Here are some basic options you’ll frequently use:

• -a – Archive mode (recursive copy and preserve permissions, symbolic links, etc.)
• -v – Verbose output
• -z – Compress file data during the transfer
• -P – Show progress and allow resumption of interrupted transfers
• -e ssh – Specify SSH as the remote shell

Local File Synchronization

Let’s say you want to sync a local directory /home/user/documents/ to /mnt/backup/documents/.

rsync -avh /home/user/documents/ /mnt/backup/documents/

Explanation:

• -a enables archive mode.
• -v enables verbose output.
• -h makes the output human-readable.

Note: The trailing slash / in the source path is important. If included, rsync copies contents of the source directory. Without it, it copies the directory itself.

Without Trailing Slash

rsync -avh /home/user/documents /mnt/backup/

This will result in /mnt/backup/documents/.

With Trailing Slash

rsync -avh /home/user/documents/ /mnt/backup/documents/

This results in only the contents of documents/ being synced.

Remote File Synchronization over SSH

To sync files from your local system to a remote Arch Linux server, you can use rsync over SSH. Assume your remote username is archadmin, and the server’s IP is 192.168.1.100.

rsync -avz -e ssh /home/user/documents/ archadmin@192.168.1.100:/home/archadmin/documents/

You can also sync in the other direction (remote to local):

rsync -avz -e ssh archadmin@192.168.1.100:/home/archadmin/documents/ /home/user/documents/

Adding the -z option enables compression, which is useful for speeding up transfers over slow connections.

Excluding Files and Directories

rsync allows you to exclude specific files or directories using the --exclude option.

rsync -av --exclude 'node_modules' --exclude '*.log' /home/user/project/ /mnt/backup/project/

You can also use an exclude file:

rsync -av --exclude-from='exclude-list.txt' /home/user/project/ /mnt/backup/project/

Contents of exclude-list.txt:

*.log
node_modules/
*.tmp

Performing a Dry Run

A dry run simulates what rsync will do, without making any changes. This is very useful for testing.

rsync -av --dry-run /home/user/docs/ /mnt/backup/docs/

Using rsync for Incremental Backups

Since rsync only transfers changes, it’s a great choice for incremental backups. You can set up a daily cron job or systemd timer to sync changes regularly.

A typical script might look like this:

#!/bin/bash
rsync -a --delete /home/user/documents/ /mnt/backup/documents/

The --delete flag ensures that deleted files in the source are also removed from the destination, keeping them perfectly in sync.

Scheduling Regular Syncs with systemd

Instead of cron, Arch Linux users may prefer systemd timers for scheduling. Here’s how:

Step 1: Create a systemd service file

Create a file at /etc/systemd/system/rsync-backup.service:

[Unit]
Description=Rsync Documents Backup

[Service]
Type=oneshot
ExecStart=/usr/bin/rsync -a --delete /home/user/documents/ /mnt/backup/documents/

Step 2: Create a systemd timer file

Create /etc/systemd/system/rsync-backup.timer:

[Unit]
Description=Run rsync backup daily

[Timer]
OnCalendar=daily
Persistent=true

[Install]
WantedBy=timers.target

Enable and start the timer:

sudo systemctl enable --now rsync-backup.timer

You can check its status with:

systemctl list-timers

Syncing Over Rsync Daemon

For more advanced network sync setups, rsync can run as a daemon, listening for connections. While less common in personal setups, it’s useful for servers.

Here’s a very basic /etc/rsyncd.conf:

uid = nobody
gid = nobody
use chroot = no
max connections = 4
log file = /var/log/rsyncd.log
timeout = 300

[backup]
    path = /srv/rsync/backup
    comment = Backup directory
    read only = no
    auth users = rsyncuser
    secrets file = /etc/rsyncd.secrets

And in /etc/rsyncd.secrets:

rsyncuser:yourpassword

Set correct permissions:

chmod 600 /etc/rsyncd.secrets

Start the daemon:

sudo rsync --daemon

Then sync from a client like this:

rsync rsync://rsyncuser@server_ip/backup

Tips for Secure Usage

• Always prefer SSH (-e ssh) for encrypted transfers.
• Use SSH keys for automation and enhanced security.
• Avoid using --delete without a dry run to prevent accidental data loss.
• Use --checksum if you want rsync to check file contents, not just mod time and size.

Graphical Frontends

For users who prefer GUI tools, there are a few frontends available for rsync:

• Grsync: A simple GTK-based interface.

  Install it via:

  sudo pacman -S grsync
  

It’s helpful for learning the command syntax and testing before automating with scripts.

Conclusion

rsync is an essential tool in any Arch Linux user’s toolkit. Whether you’re managing a home server, performing daily backups, or syncing files across machines, rsync provides an efficient, reliable, and secure solution. With options ranging from basic local file copy to advanced remote synchronization, rsync continues to be a go-to utility for file management.

By mastering its options and leveraging its features, you can ensure your data stays safe, consistent, and well-organized—with minimal effort and maximum control.