Linux Reboot Command Explained (With Examples)

Introduction

Rebooting is a fundamental administrative task for any Linux system, yet it’s often misunderstood or misused. Whether you’re maintaining a cloud server, running Ubuntu on your laptop, or scripting an automated restart, understanding how to properly reboot your system is crucial for system stability and data integrity.

This comprehensive tutorial will:

• Explain the reboot command and its alternatives
• Demonstrate safe rebooting practices
• Show how to handle different reboot scenarios
• Provide troubleshooting tips for common issues
• Compare different reboot methods and their use cases

What Is reboot Command in Linux?

The reboot command in Linux is a system utility that initiates a clean restart of the operating system. It’s a crucial tool for system administrators when:

• Applying system updates
• Resolving performance issues
• Implementing configuration changes
• Recovering from system instability

If you’re new to Linux commands, you might want to start with our guide on Introduction to the Linux Terminal to understand the basics of command-line operations.

Syntax

reboot [OPTION]...

Basic Reboot Command Usage

Reboot Immediately

sudo reboot

This is the most common form of the command. It tells the system to reboot immediately. You’ll typically need sudo privileges to execute this. For a quick reference of other essential Linux commands, check out our Linux Commands Cheat Sheet.

How to Reboot Linux from Terminal

To reboot from the terminal, use any of the following methods:

sudo reboot

Or:

sudo shutdown -r now

Or, using systemctl:

# Method 1: Using reboot command
sudo reboot

# Method 2: Using shutdown command
sudo shutdown -r now

# Method 3: Using systemctl (modern systems)
sudo systemctl reboot

Each method has its advantages:

Linux Reboot Command Options

You can enhance the reboot command with specific flags:

Example:

sudo reboot -f

Warning: The -f flag forces an immediate reboot without running normal shutdown procedures. This can lead to:

• Unsaved data being lost
• Incomplete file system operations
• Potential system state inconsistencies Only use this option when absolutely necessary, such as when the system is completely unresponsive to normal reboot commands.

Using shutdown to Reboot

You can reboot using the shutdown command with the -r flag:

sudo shutdown -r +5

This schedules a reboot in 5 minutes.

Or to reboot immediately:

sudo shutdown -r now

Related: Linux Commands Cheat Sheet

Using systemctl to Reboot

Modern systems using systemd prefer:

sudo systemctl reboot

This method is clean and preferred on distributions like Ubuntu 20.04 and later.

Want to learn more about systemd?
Check out our comprehensive guide on How to Use systemctl to Manage Systemd Services and Units to master service management on modern Linux systems.

Force Rebooting a Linux System

Sometimes, a regular reboot doesn’t work. In such cases:

sudo reboot -f

Or:

echo 1 > /proc/sys/kernel/sysrq
echo b > /proc/sysrq-trigger

Caution: Force reboots should be your last resort. They don’t allow the OS to clean up processes or flush disk buffers.

Safe Reboot Practices

Before rebooting your Linux system, it’s crucial to follow these essential steps to ensure a smooth and safe restart:

1. Check Running Processes

   Identify any critical processes that might be affected by the reboot:

   ps aux | grep important_process
   

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   This command shows all running processes and filters for specific ones. Replace important_process with the name of any critical service or application you want to monitor. For more process management commands, refer to our Linux Commands Cheat Sheet.

2. Notify Users

   Inform all logged-in users about the upcoming reboot to prevent data loss:

   wall "System will reboot in 5 minutes for maintenance"
   

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   The wall command broadcasts a message to all users’ terminals. Consider adjusting the time based on your system’s needs.

3. Check System Status

   Verify the health of your system services and check for any errors:

   systemctl status
   journalctl -xe
   

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   • systemctl status shows the state of all systemd services
   • journalctl -xe displays recent system logs with detailed error information

   For detailed information about managing systemd services, refer to our guide on How to Use systemctl to Manage Systemd Services and Units.

4. Verify Disk Space

   Ensure you have sufficient disk space before rebooting:

   df -h
   

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   This command shows disk usage in human-readable format. Look for partitions that are near capacity (above 90%).

5. Backup Critical Data

   Create backups of important files before rebooting:

   # Example: Backup important files
   tar -czf backup.tar.gz /path/to/important/files
   

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   The tar command creates a compressed archive. Replace /path/to/important/files with the actual paths you need to backup.

Common Use Cases for Reboot

1. Reboot After Kernel or Package Updates

# After updating packages
sudo apt update && sudo apt upgrade
sudo reboot

2. Reboot a Cloud Server via SSH

# Connect to server
ssh user@server_ip

# Check system status
uptime
systemctl status

# Perform reboot
sudo reboot

3. Automated Reboot in Scripts

#!/bin/bash
# Example script for scheduled maintenance
logger "Starting scheduled maintenance reboot"
wall "System maintenance in 5 minutes"
sleep 300
sudo reboot

For more advanced service management and automation with systemd, including how to create and manage custom services, check out our comprehensive guide on How to Use systemctl to Manage Systemd Services and Units.

4. Emergency Reboot

# Only use when necessary
sudo reboot -f

When reboot Doesn’t Work

“Reboot command not found”

Install it with:

sudo apt install systemd-sysv  # For Debian/Ubuntu

Or use:

sudo systemctl reboot

“Operation not permitted”

You likely need sudo or root access.

Linux Reboot vs Shutdown

Use shutdown for more control and user notification. Use reboot for quick actions.

Legacy: init 6 for Reboot

In SysV systems:

sudo init 6

This is outdated and not recommended on modern systems using systemd.

Best Practices and Security Tips

• Use sudo: Avoid running commands as root unless necessary. Learn more about Linux permissions and sudo usage in our terminal guide.
• Inform users: Avoid abrupt disruptions on multi-user systems.
• Avoid force flags unless necessary.
• Log your actions: Use logger "Rebooting system due to XYZ". For a comprehensive list of logging and system commands, see our Linux Commands Cheat Sheet.

Frequently Asked Questions

1. How do I reboot a Linux server from the terminal?

A: There are several methods to reboot a Linux server from the terminal:

# Method 1: Using reboot command
sudo reboot

# Method 2: Using shutdown command
sudo shutdown -r now

# Method 3: Using systemctl (modern systems)
sudo systemctl reboot

Each method has its use case:

• reboot is quick and straightforward
• shutdown -r offers more control over timing and user notifications
• systemctl reboot is preferred on modern systemd-based distributions

2. What’s the difference between reboot and shutdown -r now?

A: While both commands achieve the same end result, they have different features:

• reboot is simpler and designed for immediate restarts
• shutdown -r offers more flexibility:
  • Can schedule reboots (e.g., shutdown -r +5 for 5 minutes later)
  • Provides better user notification options
  • Allows cancellation of scheduled reboots
  • More detailed logging of the reboot process

3. How can I safely reboot a production server?

A: Follow these steps for a safe production server reboot:

1. Notify users and stakeholders

   wall "Server maintenance scheduled in 10 minutes"
   

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2. Check system status

   systemctl status
   uptime
   df -h
   

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3. Schedule the reboot with notification

   sudo shutdown -r +10 "Server maintenance"
   

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4. Monitor the reboot process

   journalctl -f
   

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5. Verify services after reboot

   systemctl status
   

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   # View logs from logger command
   journalctl -t logger
   
   # Or check system logs for reboot entries
   grep reboot /var/log/syslog
   

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4. What should I do if a normal reboot fails?

A: If a normal reboot fails, follow this troubleshooting sequence:

1. First, try alternative reboot methods:

   sudo shutdown -r now
   sudo systemctl reboot
   

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2. Check for hung processes:

   ps aux | grep -i "D"
   

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3. Check system logs:

   journalctl -xe
   # Check reboot-related logs
   journalctl -t logger
   grep reboot /var/log/syslog
   

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4. As a last resort, use force reboot:

   sudo reboot -f
   

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5. If all else fails, use the magic SysRq key:

   echo 1 > /proc/sys/kernel/sysrq
   echo b > /proc/sysrq-trigger
   

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5. How can I automate server reboots for maintenance?

A: You can automate server reboots using several methods:

1. Using cron for scheduled reboots

   # Add to crontab
   0 3 * * 0 root /sbin/shutdown -r +5 "Weekly maintenance"
   

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2. Using systemd timer

   # Create a timer unit
   [Unit]
   Description=Weekly Reboot
   
   [Timer]
   OnCalendar=Sun 03:00
   Persistent=true
   
   [Install]
   WantedBy=timers.target
   

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3. Using a shell script

   #!/bin/bash
   logger "Starting scheduled maintenance"
   wall "System maintenance in 5 minutes"
   sleep 300
   sudo reboot
   

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Remember to:

• Always notify users before automated reboots

• Choose maintenance windows during low-traffic periods

• Monitor the reboot process

• Have a rollback plan if issues occur

• Check logs after automated reboots:

  # View maintenance logs
  journalctl -t logger
  # Check system logs for reboot entries
  grep reboot /var/log/syslog
  

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6. Do I need sudo to use the reboot command?

A: Yes, you need sudo privileges to use the reboot command. This is because rebooting is a system-level operation that affects all users and processes on the machine. Standard users don’t have the necessary permissions to initiate a system reboot for security reasons. To reboot your system, you’ll need to use sudo:

7. How can I reboot my system safely?

A: Before rebooting:

• Save all work.
• Notify users.
• Unmount disks if needed.
• Use:

sudo shutdown -r +1

To give time for a clean restart.

8. What to do if reboot isn’t working?

A: Try shutdown -r now or systemctl reboot. If that fails, check for file system errors, hung processes, or permission issues. As a last resort, a forced reboot (reboot -f) can be used, though it may cause data loss.

Conclusion

The linux reboot command is simple yet powerful. It’s essential for performing system maintenance, applying updates, or resolving system-level errors. Whether you’re rebooting manually, automating restarts, or maintaining remote cloud servers, understanding the nuances of Linux rebooting commands will help you maintain stability and avoid common pitfalls.

For a deeper understanding of Linux command-line operations, check out our Introduction to the Linux Terminal guide, which covers essential concepts like environment variables, command execution, and shell navigation.

Continue Learning:
How to Use systemctl to Manage Systemd Services and Units
Linux Commands Cheat Sheet

Ready to master system administration?
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