systemd is a powerful system and service manager for Linux. It helps manage and control system services, daemons, and other system-wide tasks. Here’s a guide to get you started with using systemd effectively:

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1. Check the Status of a Service

To check the status of a service:

sudo systemctl status <service-name>

For example:

sudo systemctl status sshd

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2. Start, Stop, Restart, and Reload Services

• Start a service:

  sudo systemctl start <service-name>

• Stop a service:

  sudo systemctl stop <service-name>

• Restart a service:

  sudo systemctl restart <service-name>

• Reload a service configuration (if it supports reloading without restarting):

  sudo systemctl reload <service-name>

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3. Enable or Disable Services

• Enable a service (start it automatically on boot):

  sudo systemctl enable <service-name>

• Disable a service (prevent it from starting on boot):

  sudo systemctl disable <service-name>

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4. Check All Active Services

To list all active services:

systemctl list-units --type=service

To list all services (including inactive or failed):

systemctl list-units --type=service --all

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5. Create and Manage Custom Services

If you want to create your own service (e.g., to run a custom script), follow these steps:

(a) Create a Unit File

Create a custom service unit file in /etc/systemd/system/:

sudo nano /etc/systemd/system/myservice.service

Add the following content (replace placeholders with your details):

[Unit]
Description=My Custom Service
After=network.target

[Service]
ExecStart=/path/to/your-script.sh
Restart=always

[Install]
WantedBy=multi-user.target

(b) Reload systemd and Start the Service

1. Reload systemd to recognize the new service:

   sudo systemctl daemon-reload

2. Start the new service:

   sudo systemctl start myservice

3. Optionally enable it to start at boot:

   sudo systemctl enable myservice

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6. Check Logs

To view logs for a specific service:

sudo journalctl -u <service-name>

For example:

sudo journalctl -u sshd

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7. Disable the Graphical Mode (Optional)

On some systems, you can switch to a non-graphical mode by changing the default systemd target:

• Switch to multi-user (non-GUI) mode:

  sudo systemctl set-default multi-user.target

• Revert to GUI mode:

  sudo systemctl set-default graphical.target

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Tips:

• Always reload systemd after editing or adding new unit files:

  sudo systemctl daemon-reload

• Use the --now option to start/stop a service immediately while enabling/disabling it persistently:

  sudo systemctl enable --now <service-name>
  sudo systemctl disable --now <service-name>

Let me know if you'd like a deeper dive into a specific systemd feature!