Like it or not, systemd is the init system for practically every current distribution — Ubuntu, Debian, Fedora, Arch, openSUSE. Mastering half a dozen of its commands covers 90% of everyday service management. Here are the essentials, straight to the point.
Managing services
systemctl status nginx # estado, PID, últimas linhas de log
sudo systemctl start nginx
sudo systemctl stop nginx
sudo systemctl restart nginx
sudo systemctl reload nginx # recarrega config sem derrubar conexões
sudo systemctl enable nginx # inicia no boot
sudo systemctl disable nginx
sudo systemctl enable --now nginx # ativa no boot E inicia agora
Logs with journalctl
The journal is the sysadmin's best friend:
journalctl -u nginx # todos os logs do serviço
journalctl -u nginx -f # acompanhar em tempo real (tail -f)
journalctl -u nginx --since "1 hour ago"
journalctl -p err -b # só erros desde o último boot
journalctl --disk-usage # quanto o journal ocupa em disco
Boot diagnostics
systemd-analyze # tempo total de boot
systemd-analyze blame # quem demorou mais
systemctl list-units --failed # o que falhou
Timers: systemd's cron
systemctl list-timers # agendamentos ativos e próximas execuções
Creating your own service
Any script becomes a service with a file in /etc/systemd/system/meuapp.service:
[Unit]
Description=Minha aplicação
After=network.target
[Service]
User=www-data
WorkingDirectory=/opt/meuapp
ExecStart=/opt/meuapp/run.sh
Restart=on-failure
[Install]
WantedBy=multi-user.target
sudo systemctl daemon-reload
sudo systemctl enable --now meuapp
The Restart=on-failure alone makes this post worthwhile: your service restarts automatically if it crashes.
Bookmark this post — it's the kind of reference you'll open every week.