Add backup-with-cron blog article
Nathan Steel
3 years ago
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="utf-8">
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<meta name="description" content="Backups are fantastic, and can save hours upon hours of work if they're done. So we want to make sure they're done, and PCs are good with that, with automation.">
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<meta name="keywords" content="Blog, articles, template">
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<meta name="author" content="Nathan (Aney) Steel">
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<link rel="stylesheet" type="text/css" href="/main.css">
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<link rel="icon" type="image/png" href="/images/favicon.svg">
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<title>Automating Backups with Cronjobs</title>
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</head>
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<body>
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<header>
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<h1>Automating Backups with Cronjobs</h1>
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<hr/>
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<nav>
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<a href="/">home</a>
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<a href="/equipment.html">equipment</a>
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<a href="/projects.html">projects</a>
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<a href="/blog/">blog</a>
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<a href="/sitemap.html">misc</a>
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<a href="/support.html">support</a>
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</nav>
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<hr/>
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</header>
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<main>
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<section>
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<p class="intro">Backups are wonderful things that save hours upon hours of work, and stress, so long as they're actually made in the first place!</p>
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<p>Automatically taking backups allows for peace of mind that your work won't be lost forever whilst you go about your normal workflow..</p>
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<h2>Create a backup script</h2>
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<p>You can just call rsync, etc. in cron, but I recommend making a backup script (or a few) for each specific type of backup you want to make.</p>
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<p>Create the file where-ever you want to keep them, for the sake of this, it'll be a scripts directory in your home directory</p>
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<pre><code>vim ~/scripts/backup_script.sh</code></pre>
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<p>And add whatever your backup scripts wants to do. If you've no idea, check out my <a href="/blog/backup-with-rsync.html" target="_blank">rsync</a>, and <a href="/blog/backup-with-rdiff.html" target="_blank">rdiff</a> articles first.</p>
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<pre><code>rdiff-backup $DIRECTORY_TO_BACKUP $DIRECTORY_TO_BACKUP_TO
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rdiff-backup --force --remove-older-than 2W $DIRECTORY_TO_BACKUP_TO</code></pre>
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<p>The above example will backup a directory, and remove any changes from 2 weeks ago.</p>
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<p>Now make the script executable</p>
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<pre><code>chmod +x ~/scripts/backup_script.sh</code></pre>
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<h2>Add a cronjob</h2>
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<p>Now for the automation part. Using cron we can set this script to run at many time variations. I recommend <a href="https://crontab.guru/" target="_blank" rel="noopener">crontab guru</a> to learn more about the expressions used for cron.</p>
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<p>Edit the cron table (crontab)</p>
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<pre><code>crontab -e</code></pre>
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<p>And add the following</p>
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<pre><code>* */2 * * * /home/$USERNAME/scripts/backup_script.sh</code></pre>
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<p>This will run the backup script every 2 hours, every day</p>
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<h2>An advanced backup script</h2>
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<p>An advantage of using a script for backups, is that it allows for more intricate functionality, you may not need to use this functionality, but it's greatly useful.</p>
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<p>The script below is something I wrote to backup my home directories for each of my servers. It's used to make hourly backups, and send these backups to a remote server daily at midnight.</p>
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<pre><code>#!/bin/bash
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# Set locations to backup/backup to from the flags
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while getopts s:d:b:r:R:n: flag
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do
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case "${flag}" in
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d) DATA=${OPTARG};;
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b) BACKUPDIR=${OPTARG};;
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r) REMOTE=${OPTARG};;
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R) REMOTEBACKUP=${OPTARG};;
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n) NOW=${OPTARG};;
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esac
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done
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# If the backup directory doesn't exist, make it
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mkdir -p $BACKUPDIR
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# Incremental backup of the directory locally
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rdiff-backup $DATA $BACKUPDIR
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# Don't keep changes from over 1W ago
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rdiff-backup --force --remove-older-than 1W $BACKUPDIR
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# Backup to remote
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# Get the hour/minute time
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TIME=$(date +%H%M)
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# If it's a midnight backup, or a manual backup with -n 1 flag set
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if [ "$TIME" = 0000 ] || [ "$NOW" = 1 ]
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then
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# Create the remote directory for backup if it doesn't exist
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ssh $REMOTE mkdir -p $REMOTEBACKUP
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# Copy the backup to the remote location
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# -e ssh makes it secure
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rsync -azh -e ssh \
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--delete \
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$BACKUPDIR \
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$REMOTE:$REMOTEBACKUP
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fi
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</code></pre>
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<p>Which is called in the crontab like so</p>
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<pre><code># Hourly rdiff-backup of $DIRECTORY_TO_BACKUP
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0 */1 * * * $SCRIPT_LOCATION -d $DIRECTORY_TO_BACKUP -b $LOCATION_TO_SAVE_BACKUP -r $EXTERNAL_SERVER_SSH -R $EXTERNAL_SERVER_BACKUP_LOCATION</code></pre>
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<p>This script can easily be used for many different directories, on each server without needing to change the script itself. All that's needed is to change the cronjob, and/or add another cronjob changing the values it takes.</p>
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</section>
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</main>
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<footer>
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<hr/>
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<p>Written by <a href="http://aney.co.uk" target="_blank" rel="noopener">@aney</a> with <a href="https://danluu.com/web-bloat/" target="_blank" rel="noopener">web bloat</a> in mind | <a href="https://github.com/Aney/website" target="_blank" rel="noopener">Source Code</a></p>
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