systemctl is the command-line tool for managing systemd services and units
It allows you to control, monitor, and troubleshoot system services
systemd is the system and service manager used by most modern Linux distributions
Services are called "units" in systemd terminology

What systemctl can do:

Start, stop, restart, and reload services
Check service status and health
Enable/disable services to start at boot
View service logs
Check service dependencies
Troubleshoot failed services

:zap: Basic Commands

Getting Help

systemctl --help

Shows all available systemctl commands and options.

systemctl status

Shows the overall system status, including:

System state (running, degraded, etc.)
Number of loaded units
Number of failed units
System uptime
systemd version

Example output:

● fedora
    State: running
    Units: 746 loaded (incl. loaded aliases)
     Jobs: 0 queued
   Failed: 0 units
    Since: Thu 2025-11-13 03:33:58 AST; 11h ago
  systemd: 258.1-1.fc43

:mag: Checking Service Status

Viewing a Specific Service Status

systemctl status servicename

What this does:

Shows detailed information about a service
Displays current state (active/inactive, running/stopped)
Shows recent log entries
Indicates if the service is enabled to start at boot

Common service names:

sshd - SSH server
nginx - Nginx web server
httpd or apache2 - Apache web server
libvirtd - Virtualization daemon
NetworkManager - Network management
docker - Docker daemon
postgresql - PostgreSQL database

Example:

systemctl status sshd

What you'll see:

Service state (active/inactive, running/stopped)
Whether it's enabled at boot
Recent log entries
Process information
Loaded configuration file path

Quick Status Checks

Check if a service is active (running):

systemctl is-active servicename

Output:

active - Service is running
inactive - Service is not running
Exit code 0 = active, non-zero = inactive

Check if a service is enabled (starts at boot):

systemctl is-enabled servicename

Output:

enabled - Service will start at boot
disabled - Service will not start at boot
masked - Service is prevented from starting (even manually)
Exit code 0 = enabled, non-zero = disabled/masked

Check if a service has failed:

systemctl is-failed servicename

Output:

failed - Service has failed
Empty output - Service is not in failed state
Exit code 0 = not failed, non-zero = failed

:desktop: Listing Services

List All Running Services

systemctl list-units --type=service --state=running

What this does:

Shows all services that are currently running
Displays service name, load state, active state, and description

Example output:

  UNIT                       LOAD   ACTIVE SUB     DESCRIPTION
  abrt-journal-core.service  loaded active running ABRT coredumpctl message creator
  abrt-oops.service          loaded active running ABRT kernel log watcher
  abrt-xorg.service          loaded active running ABRT Xorg log watcher
  abrtd.service              loaded active running ABRT Daemon

What each column means:

UNIT: Service name
LOAD: Whether the unit file is loaded
ACTIVE: High-level activation state
SUB: Low-level activation state (running, dead, etc.)
DESCRIPTION: What the service does

List All Failed Services

systemctl list-units --type=service --state=failed

What this does:

Shows only services that have failed
Critical for troubleshooting system issues
Helps identify what's broken

When to use it:

System is behaving strangely
Something isn't working
After system updates
Troubleshooting boot issues

If no failed services:

  UNIT LOAD ACTIVE SUB DESCRIPTION

0 loaded units listed.

List All Services (All States)

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

What this does:

Shows all services regardless of state
Includes inactive, failed, and running services
Useful for finding a specific service

List Enabled Services (Start at Boot)

systemctl list-unit-files --type=service --state=enabled

What this does:

Shows all services that are enabled to start at boot
Displays the unit file state and preset state

Example output:

UNIT FILE                             STATE   PRESET
abrt-journal-core.service             enabled enabled
abrt-oops.service                     enabled enabled
abrt-vmcore.service                   enabled enabled
abrt-xorg.service                     enabled enabled

:wrench: Controlling Services

Starting a Service

sudo systemctl start servicename

What this does:

Starts a service immediately
Does not enable it to start at boot (use enable for that)
Requires root privileges (sudo)

Example:

sudo systemctl start sshd

When to use it:

Service is stopped and you need it running
Testing if a service works
Temporarily starting a disabled service

Stopping a Service

sudo systemctl stop servicename

What this does:

Stops a running service immediately
Does not disable it from starting at boot
Requires root privileges

Example:

sudo systemctl stop sshd

When to use it:

Service is misbehaving and needs to be stopped
Temporarily disabling a service
Before making configuration changes

Restarting a Service

sudo systemctl restart servicename

What this does:

Stops and then starts a service
Applies configuration changes
Useful after editing service configuration files

Example:

sudo systemctl restart nginx

When to use it:

After changing service configuration
Service is acting strange and needs a fresh start
Applying updates

Reloading a Service

sudo systemctl reload servicename

What this does:

Reloads service configuration without stopping it
Service continues running during reload
Not all services support reload (some require restart)

Example:

sudo systemctl reload nginx

When to use it:

After configuration changes
When you want to avoid service downtime
Services that support reload (check with systemctl status)

Try-Restart (Restart Only If Running)

sudo systemctl try-restart servicename

What this does:

Restarts the service only if it's currently running
If the service is stopped, it does nothing
Safer than regular restart

When to use it:

Restarting a service that may or may not be running
Scripts where you're not sure of the service state

Reload-or-Restart

sudo systemctl reload-or-restart servicename

What this does:

Tries to reload first (if supported)
Falls back to restart if reload is not supported
Best of both worlds

When to use it:

Applying configuration changes
When you're not sure if the service supports reload

:key: Enabling and Disabling Services

Enable Service to Start at Boot

sudo systemctl enable servicename

What this does:

Configures the service to start automatically at boot
Does not start the service immediately (use start for that)
Creates symlinks to enable the service

Example:

sudo systemctl enable sshd

When to use it:

You want a service to start automatically on boot
Setting up a new service
After installing a service that should run at boot

Disable Service from Starting at Boot

sudo systemctl disable servicename

What this does:

Prevents the service from starting at boot
Does not stop the service if it's currently running
Removes symlinks that enable the service

Example:

sudo systemctl disable sshd

When to use it:

Service should not start automatically
Reducing boot time
Disabling unnecessary services

Enable and Start Together

sudo systemctl enable --now servicename

What this does:

Enables the service to start at boot
Starts the service immediately
Combines enable and start in one command

Example:

sudo systemctl enable --now sshd

When to use it:

Setting up a new service that should run now and at boot
Quick way to enable and start in one step

Disable and Stop Together

sudo systemctl disable --now servicename

What this does:

Disables the service from starting at boot
Stops the service immediately
Combines disable and stop in one command

When to use it:

Completely disabling a service
Removing a service from the system

Masking a Service

sudo systemctl mask servicename

What this does:

Prevents a service from being started (even manually)
Creates a symlink to /dev/null
Stronger than disable - service cannot be started at all

When to use it:

Completely preventing a service from running
When disable isn't enough
Troubleshooting service conflicts

Unmasking:

sudo systemctl unmask servicename

:file_folder: Viewing Service Information

View Service Properties

systemctl show servicename

What this does:

Shows all properties of a service
Displays detailed configuration information
Useful for troubleshooting

Example:

systemctl show sshd

What you'll see:

Service ID and names
Dependencies (Requires, Wants, After, Before)
Documentation links
Description
Load state
Active state
And much more

View Service Dependencies

systemctl list-dependencies servicename

What this does:

Shows what services this service depends on
Displays the dependency tree
Helps understand service relationships

Example:

systemctl list-dependencies sshd

What you'll see:

Services that must be running before this service
Services that this service wants (optional)
Target units (like network.target, sysinit.target)

Reverse dependencies (what depends on this service):

systemctl list-dependencies --reverse servicename

View Service Configuration File

systemctl cat servicename

What this does:

Shows the service unit file content
Displays the actual configuration
Includes drop-in files (overrides)

When to use it:

Understanding service configuration
Checking what a service does
Before making changes

View Service Logs

systemctl status servicename

Shows recent log entries in the status output.

For more detailed logs:

journalctl -u servicename

For real-time log following:

journalctl -u servicename -f

See the Journalctl Troubleshooting Guide for more log viewing options.

:alarm_clock: Working with Timers

List All Timers

systemctl list-timers

What this does:

Shows all systemd timer units
Displays when timers will run next
Shows last run time

Example output:

NEXT                          LEFT LAST                              PASSED UNIT                         ACTIVATES
Thu 2025-11-13 16:04:14 AST  44min Thu 2025-11-13 12:08:03 AST 3h 11min ago dnf-makecache.timer          dnf-makecache.service
Fri 2025-11-14 00:00:00 AST     8h Thu 2025-11-13 07:34:00 AST       7h ago unbound-anchor.timer         unbound-anchor.service

What each column means:

NEXT: When the timer will run next
LEFT: Time until next run
LAST: When it last ran
PASSED: Time since last run
UNIT: Timer unit name
ACTIVATES: Service that the timer activates

When to use it:

Checking scheduled tasks
Understanding system maintenance schedules
Troubleshooting automated tasks

:warning: Troubleshooting Failed Services

Check for Failed Services

systemctl --failed

What this does:

Lists all failed services
Quick way to see what's broken
Equivalent to list-units --state=failed

Reset Failed State

sudo systemctl reset-failed servicename

What this does:

Clears the "failed" state from a service
Useful after fixing a service issue
Resets the service status

When to use it:

After fixing a service configuration
After resolving dependency issues
Cleaning up service state

Reset all failed services:

sudo systemctl reset-failed

Reload systemd Configuration

sudo systemctl daemon-reload

What this does:

Reloads systemd manager configuration
Rereads all unit files
Required after creating or modifying unit files

When to use it:

After creating a new service file
After modifying a service unit file
After installing a new service
Before starting a newly created service

Important: Always run this after editing service files in /etc/systemd/system/

:mag_right: Advanced Troubleshooting

View System State

systemctl status

Shows overall system health.

Check if system is degraded:

systemctl is-system-running

Possible outputs:

running - System is running normally
degraded - Some units failed but system is operational
maintenance - System is in maintenance mode
initializing - System is still booting
starting - System is starting up
stopping - System is shutting down

View Service Dependencies Graph

systemctl list-dependencies servicename --all

What this does:

Shows complete dependency tree
Includes all dependencies recursively
Shows both required and wanted dependencies

Check Service Logs with journalctl

journalctl -u servicename

Filter by priority:

journalctl -u servicename -p err

Follow logs in real-time:

journalctl -u servicename -f

Since a specific time:

journalctl -u servicename --since "1 hour ago"

See the Journalctl Troubleshooting Guide for comprehensive log viewing options.

:bulb: Common Troubleshooting Scenarios

Scenario 1: Service Won't Start

Problem: A service fails to start.

Solution:

Check service status:
```
systemctl status servicename
```
Check for errors in logs:
```
journalctl -u servicename -p err
```

Check service dependencies:

systemctl list-dependencies servicename

Verify service file:
```
systemctl cat servicename
```

Try starting with verbose output:

systemctl start servicename
systemctl status servicename

Scenario 2: Service Keeps Crashing

Problem: Service starts but immediately stops.

Solution:

Check service status for error messages:
```
systemctl status servicename
```
Follow logs in real-time:
```
journalctl -u servicename -f
```
Check for configuration errors:
```
systemctl cat servicename
```
Check system resources:
```
free -h
df -h
```

Scenario 3: Service Not Starting at Boot

Problem: Service works when started manually but doesn't start at boot.

Solution:

Check if service is enabled:
```
systemctl is-enabled servicename
```
If disabled, enable it:
```
sudo systemctl enable servicename
```

Check service dependencies:

systemctl list-dependencies servicename

Verify service file for After/Before directives:
```
systemctl cat servicename
```

Scenario 4: Finding What's Using a Port

Problem: Port is already in use, preventing service from starting.

Solution:

Find what's using the port (example for port 80):
```
sudo ss -tlnp | grep :80
```
Check the service status:
```
systemctl status servicename
```

Stop the conflicting service if needed:

sudo systemctl stop conflicting-service

Scenario 5: Service Takes Too Long to Start

Problem: Service is slow to start.

Solution:

Check service status and startup time:
```
systemctl status servicename
```

Check dependencies:

systemctl list-dependencies servicename

Check system load:
```
uptime
systemctl status
```

Review logs for slow operations:

journalctl -u servicename --since "boot"

Scenario 6: Understanding Service Dependencies

Problem: Need to understand why a service requires another service.

Solution:

View dependencies:

systemctl list-dependencies servicename

View reverse dependencies:

systemctl list-dependencies --reverse servicename

View service properties:

systemctl show servicename | grep -i depend

:floppy_disk: Service File Locations

System service files:

/etc/systemd/system/ - Local system service files (highest priority)
/run/systemd/system/ - Runtime service files
/usr/lib/systemd/system/ - Package-installed service files (lowest priority)

User service files:

~/.config/systemd/user/ - User service files

Drop-in files (overrides):

/etc/systemd/system/servicename.service.d/ - Service-specific overrides
/etc/systemd/system/servicename.service.d/override.conf - Common override file

After editing service files: Always run:

sudo systemctl daemon-reload

:keyboard: Quick Reference

Status Commands

systemctl status                    # Overall system status
systemctl status servicename        # Service status
systemctl is-active servicename     # Quick active check
systemctl is-enabled servicename    # Quick enabled check
systemctl is-failed servicename     # Quick failed check
systemctl --failed                  # List failed services

Control Commands

sudo systemctl start servicename    # Start service
sudo systemctl stop servicename     # Stop service
sudo systemctl restart servicename  # Restart service
sudo systemctl reload servicename   # Reload service
sudo systemctl reload-or-restart servicename  # Reload or restart

Enable/Disable Commands

sudo systemctl enable servicename           # Enable at boot
sudo systemctl disable servicename          # Disable at boot
sudo systemctl enable --now servicename     # Enable and start
sudo systemctl disable --now servicename    # Disable and stop
sudo systemctl mask servicename             # Mask service
sudo systemctl unmask servicename           # Unmask service

Listing Commands

systemctl list-units --type=service                    # All services
systemctl list-units --type=service --state=running    # Running services
systemctl list-units --type=service --state=failed     # Failed services
systemctl list-unit-files --type=service --state=enabled  # Enabled services
systemctl list-timers                                  # All timers

Information Commands

systemctl show servicename                    # Service properties
systemctl list-dependencies servicename      # Service dependencies
systemctl cat servicename                    # Service file content
journalctl -u servicename                    # Service logs

Maintenance Commands

sudo systemctl daemon-reload                  # Reload systemd config
sudo systemctl reset-failed servicename      # Reset failed state
sudo systemctl reset-failed                   # Reset all failed

Summary

This guide covered:

Basic Commands:

Getting help with --help
Checking overall system status
Viewing service status

Status Checking:

status - Detailed service status
is-active - Quick active check
is-enabled - Quick enabled check
is-failed - Quick failed check

Listing Services:

Running services
Failed services
Enabled services
All services

Controlling Services:

Start, stop, restart, reload
Try-restart and reload-or-restart
Enable and disable at boot
Mask and unmask services

Service Information:

Viewing service properties
Checking dependencies
Viewing configuration files
Viewing service logs

Timers:

Listing scheduled tasks
Understanding timer output

Troubleshooting:

Finding failed services
Resetting failed state
Reloading systemd configuration
Common troubleshooting scenarios

Service File Locations:

Where service files are stored
Drop-in files and overrides

Next Steps:

Practice with services on your system
Combine with journalctl for comprehensive troubleshooting
Learn about creating custom service files
Explore timer units for scheduling tasks

For more advanced topics, see the Journalctl Troubleshooting Guide for detailed log analysis.

Systemctl Troubleshooting - ryzendew/Linux-Tips-and-Tricks GitHub Wiki

Systemctl Troubleshooting for Beginners

Table of Contents

:pencil: What is systemctl?

:zap: Basic Commands

Getting Help

:mag: Checking Service Status

Viewing a Specific Service Status

Quick Status Checks

:desktop: Listing Services

List All Running Services

List All Failed Services

List All Services (All States)

List Enabled Services (Start at Boot)

:wrench: Controlling Services

Starting a Service

Stopping a Service

Restarting a Service

Reloading a Service

Try-Restart (Restart Only If Running)

Reload-or-Restart

:key: Enabling and Disabling Services

Enable Service to Start at Boot

Disable Service from Starting at Boot

Enable and Start Together

Disable and Stop Together

Masking a Service

:file_folder: Viewing Service Information

View Service Properties

View Service Dependencies

View Service Configuration File

View Service Logs

:alarm_clock: Working with Timers

List All Timers

:warning: Troubleshooting Failed Services

Check for Failed Services

Reset Failed State

Reload systemd Configuration

:mag_right: Advanced Troubleshooting

View System State

View Service Dependencies Graph

Check Service Logs with journalctl

:bulb: Common Troubleshooting Scenarios

Scenario 1: Service Won't Start

Scenario 2: Service Keeps Crashing

Scenario 3: Service Not Starting at Boot

Scenario 4: Finding What's Using a Port

Scenario 5: Service Takes Too Long to Start

Scenario 6: Understanding Service Dependencies

:floppy_disk: Service File Locations

:keyboard: Quick Reference

Status Commands

Control Commands

Enable/Disable Commands

Listing Commands

Information Commands

Maintenance Commands

Summary