Service Management with systemd

Intermediate Linux Server
systemctljournalctlunit files/etc/systemd/system/

Objective

Manage system services using systemctl, create custom unit files, and investigate service logs with journalctl.

Tools & Technologies

  • systemctl
  • journalctl
  • unit files
  • /etc/systemd/system/

Key Commands

systemctl status nginx
systemctl enable --now nginx
journalctl -u nginx -n 50
systemctl list-units --failed

Architecture Overview

stateDiagram-v2 [*] --> Inactive: unit file exists Inactive --> Active: systemctl start Active --> Inactive: systemctl stop Active --> Reloading: systemctl reload Reloading --> Active: reload complete Active --> Failed: process crashes Failed --> Active: systemctl restart Inactive --> Enabled: systemctl enable Enabled --> Active: boot

Step-by-Step Process

01
Basic Service Control

Start, stop, restart, and check the status of services.

sudo systemctl start nginx
sudo systemctl stop nginx
sudo systemctl restart nginx
sudo systemctl reload nginx    # reload config without stopping
sudo systemctl status nginx
sudo systemctl enable nginx    # start at boot
sudo systemctl disable nginx
sudo systemctl is-active nginx
02
View Logs with journalctl

journalctl provides structured logs from all systemd services.

journalctl -u nginx              # all nginx logs
journalctl -u nginx -n 50        # last 50 lines
journalctl -u nginx -f           # follow (tail -f)
journalctl -u nginx --since '1 hour ago'
journalctl -p err -u nginx       # errors only
journalctl --disk-usage          # log storage size
03
Create a Custom Unit File

Write a systemd service unit file to manage a custom application.

# /etc/systemd/system/myapp.service
[Unit]
Description=My Custom App
After=network.target

[Service]
Type=simple
User=appuser
WorkingDirectory=/opt/myapp
ExecStart=/opt/myapp/myapp --config /etc/myapp.conf
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

# Load and start:
sudo systemctl daemon-reload
sudo systemctl enable --now myapp

Challenges & Solutions

  • Forgetting daemon-reload after editing unit files — systemd uses stale config
  • Unit file syntax errors silently prevent service from starting — check with systemctl status

Key Takeaways

  • systemctl list-units --failed shows all broken services at a glance
  • After=network.target ensures network is up before your service starts