https://www.5ok.sk/tags/systemd/Recent content in Systemd on 5ok — sysadmin, devops, hostingHugoskSat, 21 Mar 2026 00:00:00 +0000https://www.5ok.sk/blog/systemd-timers-namiesto-cronu/Sat, 21 Mar 2026 00:00:00 +0000https://www.5ok.sk/blog/systemd-timers-namiesto-cronu/<p>Cron má jednu obrovskú výhodu: každý ho pozná. A jednu nevýhodu: keď zlyhá, dozviete sa to e-mailom na <code>root@localhost</code>, ktorý nikto nečíta.</p> <p>systemd timers riešia presne toto.</p> <h2 id="základ">Základ</h2> <p>Timer sa skladá z dvoch súborov — <code>.service</code> (čo sa má spustiť) a <code>.timer</code> (kedy).</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">Nočná záloha</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">Spusti zálohu každú noc</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><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-bash" data-lang="bash"><span class="line"><span class="cl">systemctl <span class="nb">enable</span> --now backup.timer </span></span><span class="line"><span class="cl">systemctl list-timers </span></span></code></pre></div><h2 id="čo-cron-nevie">Čo cron nevie</h2> <p><strong><code>Persistent=true</code></strong> — ak bol stroj v čase spustenia vypnutý, úloha sa spustí hneď po štarte. Cron ju jednoducho preskočí.</p>