What is the difference between 'service' and 'systemctl' in Ubuntu?

The 'service' command is the legacy SysVinit interface, while 'systemctl' is the modern systemd interface. On modern Ubuntu (16.04+), 'service' is a thin wrapper that calls systemctl internally. Use systemctl directly for full control — it supports enable/disable at boot, dependency management, and richer status output.

How do I make a service start automatically at boot in Ubuntu?

Use 'sudo systemctl enable servicename'. This creates a symlink in the systemd targets so the service starts on boot. To start it immediately AND enable at boot, use 'sudo systemctl enable --now servicename'. To prevent a service from starting at boot, use 'sudo systemctl disable servicename'.

How do I view real-time logs for a service in Ubuntu?

Use 'journalctl -u servicename -f' to follow (tail) the logs of a specific service in real time. Add '--since today' to filter to today's entries, or '--since "1 hour ago"' for recent logs. Use '-n 50' to show the last 50 lines.

How do I create a custom systemd service for my own application?

Create a .service file in /etc/systemd/system/ with [Unit], [Service], and [Install] sections. Define ExecStart with the command to run, set Restart=on-failure for auto-restart, and run 'sudo systemctl daemon-reload' followed by 'sudo systemctl enable --now myservice'.

Ubuntu Service Management: systemctl, journalctl, and Custom Unit Files

TL;DR — Quick Summary

Essential Ubuntu service management commands: systemctl start/stop/enable/disable, journalctl log viewing, listing services, and creating custom systemd unit files.

Ubuntu Service Management Commands

Managing services (daemons) is one of the most common tasks for any Ubuntu administrator. Modern Ubuntu uses systemd as the init system, with systemctl as the primary command for service management.

systemctl vs. service (Legacy)

Command	systemctl (Modern)	service (Legacy)
Start	`sudo systemctl start nginx`	`sudo service nginx start`
Stop	`sudo systemctl stop nginx`	`sudo service nginx stop`
Restart	`sudo systemctl restart nginx`	`sudo service nginx restart`
Reload config	`sudo systemctl reload nginx`	`sudo service nginx reload`
Status	`systemctl status nginx`	`service nginx status`
Enable at boot	`sudo systemctl enable nginx`	`sudo update-rc.d nginx defaults`
Disable at boot	`sudo systemctl disable nginx`	`sudo update-rc.d nginx remove`

Tip: On modern Ubuntu, service is a compatibility wrapper that calls systemctl internally. Use systemctl directly for the richest output and full feature set.

Essential systemctl Commands

Check Service Status

systemctl status nginx

This shows: active/inactive state, PID, memory usage, CPU time, and the last few log lines.

Start, Stop, Restart, Reload

sudo systemctl start nginx      # Start a stopped service
sudo systemctl stop nginx       # Stop a running service
sudo systemctl restart nginx    # Stop then start (brief downtime)
sudo systemctl reload nginx     # Reload config without downtime (not all services support this)

Enable / Disable at Boot

sudo systemctl enable nginx            # Start automatically on boot
sudo systemctl disable nginx           # Do NOT start on boot
sudo systemctl enable --now nginx      # Enable AND start immediately
sudo systemctl is-enabled nginx        # Check if enabled

List All Services

# List all loaded services and their states
systemctl list-units --type=service

# List only running services
systemctl list-units --type=service --state=running

# List all installed service files (including disabled)
systemctl list-unit-files --type=service

Masking a Service

To completely prevent a service from being started (even manually):

sudo systemctl mask dangerous-service       # Prevent start entirely
sudo systemctl unmask dangerous-service     # Allow start again

Viewing Logs with journalctl

systemd captures all service output via journald. Use journalctl to view logs:

# View all logs for a service
journalctl -u nginx

# Follow logs in real time (like tail -f)
journalctl -u nginx -f

# Today's logs only
journalctl -u nginx --since today

# Last hour
journalctl -u nginx --since "1 hour ago"

# Last 50 lines
journalctl -u nginx -n 50

# Show only errors and above
journalctl -u nginx -p err

# Disk usage of all logs
journalctl --disk-usage

Creating a Custom systemd Service

If you have a custom application (e.g., a Node.js app, a Go binary, or a Python script) that you want to run as a service:

Step 1: Create the Unit File

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

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

[Service]
Type=simple
User=www-data
WorkingDirectory=/opt/myapp
ExecStart=/opt/myapp/start.sh
Restart=on-failure
RestartSec=5
Environment=NODE_ENV=production

[Install]
WantedBy=multi-user.target

Step 2: Reload and Enable

sudo systemctl daemon-reload           # Read the new unit file
sudo systemctl enable --now myapp      # Enable at boot + start now
systemctl status myapp                 # Verify it is running

Key Unit File Fields

Field	Section	Description
`After`	[Unit]	Start after these targets/services
`Type`	[Service]	`simple` (default), `forking`, `oneshot`, `notify`
`User`	[Service]	Run as this user (not root)
`ExecStart`	[Service]	The command to run
`Restart`	[Service]	`on-failure`, `always`, `no`
`RestartSec`	[Service]	Seconds to wait before restart
`Environment`	[Service]	Set environment variables
`WantedBy`	[Install]	Target that enables this service