systemctl

Overview

The systemctl command controls the systemd system and service manager. It’s used to manage system services, check system status, and change system state.

Syntax

systemctl [options] command [name]

Common Commands

Command	Description
start	Start service
stop	Stop service
restart	Restart service
reload	Reload configuration
status	Check status
enable	Enable at boot
disable	Disable at boot
is-active	Check if active
is-enabled	Check if enabled
list-units	List units
list-unit-files	List unit files
daemon-reload	Reload systemd

Common Options

Option	Description
-H HOST	Remote host
-M CONTAINER	Container name
-t TYPE	List specific type
-a, --all	Show all units
-l, --full	Don’t ellipsize
--failed	Show failed units
--user	User service manager
--system	System service manager

Key Use Cases

1. Service management
2. System state control
3. Boot configuration
4. Service monitoring
5. System troubleshooting

Examples with Explanations

Example 1: Service Status

systemctl status nginx

Check nginx service status

Example 2: Start Service

systemctl start mysql

Start MySQL service

Example 3: Enable Service

systemctl enable ssh

Enable SSH at boot

Common Usage Patterns

1. Service control:

   systemctl restart service

2. Boot management:

   systemctl enable --now service

3. Status check:

   systemctl is-active service

Service States

• active (running)
• active (exited)
• active (waiting)
• inactive (dead)
• failed
• activating
• deactivating

Related Commands

• service - Init service control
• chkconfig - Update runlevels
• init - Process control
• shutdown - System shutdown
• journalctl - View logs

Additional Resources

• Systemctl Manual
• Systemd Guide
• Service Management

Best Practices

1. Regular status checks
2. Enable required services
3. Monitor failed units
4. Document changes
5. Security considerations

Troubleshooting

1. Failed services
2. Boot problems
3. Dependencies
4. Configuration errors
5. Resource issues

Unit Types

1. service
2. socket
3. device
4. mount
5. target