part 7: backups

I like to keep things simple and stupid wherever possible. So when I thought about making automated backups of my data, I turned to cron and rsync.

Background

cron is a daemon to execute scheduled commands¹ and rsync is a fast, versatile, remote (and local) file-copying tool². Together, they can be used to schedule backups from the command line.

Warning

If you care about your data, follow the 3-2-1 Backup Rule, which, in short, states:

• 3 copies of the data should exist
• 2 different types of media should be used to store the data
• 1 copy of the data should be kept offsite, in a remote location

Setup

Step 1: Create a backup script

Following a couple of guides (such as this and this), I put together the following, quite simple backup.sh script:

#!/bin/bash
 
src="/mnt/drive1"
dst="/mnt/drive2"
log="/var/log/backup.log"
 
echo "Backup started at $(date)" >> "$log"
 
rsync -av --delete "$src" "$dst" >> "$log" 2>&1
 
echo "Backup completed at $(date)" >> "$log"

Here, I’m backing up the contents of the drive mounted at /mnt/drive1 (my internal SSD) to the drive mounted at /mnt/drive2 (an external USB HDD). I maintain a log file /var/log/backup.log which contains some metadata and the outputs of rsync; the -v (verbose) flag is used to log the operations performed by rsync. The other flags, -a (archive) and --delete, preserve permissions and metadata, and delete files from the destination that are no longer present at the source, respectively.

Before moving on to the next step (scheduling), I ran the script manually to get a baseline.

Step 2: Schedule with crontab

With the help of https://cron.help/, I devised the following crontab:

0 3 * * 1 /home/lab/backup.sh

This schedules the execution of backup.sh every Monday at 3AM (while I am (hopefully) asleep). After it has run, the contents of /var/log/backup.log should indicate if the backup was successful:

[~] $ cat /var/log/backup.log | tail
<Files backed up go here>
sent <l> bytes  received <m> bytes  <n> bytes/sec
total size is <o>  speedup is <p>
Backup completed at Mon 22 Dec 2025 03:00:02 AM PST

Summary

Backups don’t have to be hard! This simple rsync + cron combination automatically schedules backups, providing peace of mind with minimal effort.

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Footnotes

1. https://linux.die.net/man/8/cron ↩

2. https://linux.die.net/man/1/rsync ↩