https://www.5ok.eu/tags/automation/Recent content in Automation on 5ok — sysadmin, devops, hostingHugoenSat, 21 Mar 2026 00:00:00 +0000https://www.5ok.eu/blog/systemd-timers-instead-of-cron/Sat, 21 Mar 2026 00:00:00 +0000https://www.5ok.eu/blog/systemd-timers-instead-of-cron/<p>Cron has one enormous advantage: everyone knows it. And one disadvantage: when it fails, you find out by email to <code>root@localhost</code>, which nobody reads.</p> <p>systemd timers fix exactly that.</p> <h2 id="the-basics">The basics</h2> <p>A timer is two files — <code>.service</code> (what runs) and <code>.timer</code> (when).</p> <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-ini" data-lang="ini"><span class="line"><span class="cl"><span class="c1"># /etc/systemd/system/backup.service</span> </span></span><span class="line"><span class="cl"><span class="k">[Unit]</span> </span></span><span class="line"><span class="cl"><span class="na">Description</span><span class="o">=</span><span class="s">Nightly backup</span> </span></span><span class="line"><span class="cl"><span class="na">After</span><span class="o">=</span><span class="s">network-online.target</span> </span></span><span class="line"><span class="cl"> </span></span><span class="line"><span class="cl"><span class="k">[Service]</span> </span></span><span class="line"><span class="cl"><span class="na">Type</span><span class="o">=</span><span class="s">oneshot</span> </span></span><span class="line"><span class="cl"><span class="na">ExecStart</span><span class="o">=</span><span class="s">/usr/local/bin/backup.sh</span> </span></span></code></pre></div><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-ini" data-lang="ini"><span class="line"><span class="cl"><span class="c1"># /etc/systemd/system/backup.timer</span> </span></span><span class="line"><span class="cl"><span class="k">[Unit]</span> </span></span><span class="line"><span class="cl"><span class="na">Description</span><span class="o">=</span><span class="s">Run backup nightly</span> </span></span><span class="line"><span class="cl"> </span></span><span class="line"><span class="cl"><span class="k">[Timer]</span> </span></span><span class="line"><span class="cl"><span class="na">OnCalendar</span><span class="o">=</span><span class="s">*-*-* 02:30:00</span> </span></span><span class="line"><span class="cl"><span class="na">RandomizedDelaySec</span><span class="o">=</span><span class="s">15m</span> </span></span><span class="line"><span class="cl"><span class="na">Persistent</span><span class="o">=</span><span class="s">true</span> </span></span><span class="line"><span class="cl"> </span></span><span class="line"><span class="cl"><span class="k">[Install]</span> </span></span><span class="line"><span class="cl"><span class="na">WantedBy</span><span class="o">=</span><span class="s">timers.target</span> </span></span></code></pre></div><h2 id="what-cron-cant-do">What cron can&rsquo;t do</h2> <p><strong><code>Persistent=true</code></strong> — if the machine was off at the scheduled time, the job runs at next boot. Cron just skips it.</p>