Reboot Linux System Command with Examples

Rebooting a Linux system is a fundamental administrative task necessary for applying updates, troubleshooting, or system maintenance. Various commands are available to reboot a Linux system, each with specific options and use cases. This guide explores essential reboot commands such as `reboot`, `shutdown`, and `init`, illustrating their usage with practical examples to ensure a smooth and controlled reboot process.

What is Reboot in Linux System?

The reboot command is used to restart or reboot the system. In a Linux system administration, there comes a need to restart the server after the completion of some network and other major updates. It can be software or hardware that is being carried on the server. Rebooting is needed so that the changes that the user has made can affect the server. 

For example, if the user is re-compiling the server’s kernel that is going through some more advanced server administration, then he needs to restart the machine in order to complete the compilation and to have a new updated kernel version on the server. When updating the server’s memory, IP allocation, and NIC configuration are the key tasks that need to be done on the server restarted once leading to their successful implementation.

Most Linux system administrators access their servers via shell or SSH to perform a bunch of administrative activities, server management, and monitoring. So, they need to know the basic commands to restart the server from the shell. 

Syntax of reboot command

The following is the syntax of rebooting in linux:

reboot [OPTIONS...]

Options of Reboot Command

The following are the options for the reboot command with explanation of its functionality:

What are the shutdown Commands on Linux?

When a GUI isn't available, or you're remotely connected to a server, relying on command-line shutdown commands becomes essential. Here are the primary commands for shutting down or rebooting your Linux system:

1. shutdown: Initiates system shutdown or reboot based on specified parameters. It is used for shutdown the system directly or with time or message generation.

2. reboot: Reboots the system immediately without any additional options. It is used for rebooting the system.

3. halt: Halts the system immediately, effectively shutting it down. It is used for halting the system.

4. poweroff: Powers off the system immediately, shutting down all processes. It is used for poweroff the operating system.

How to Restart Linux System?

Restarting a Linux system is a fundamental administrative task that can be accomplished using several commands, each tailored for specific scenarios. Here’s a brief overview of the primary methods to restart a Linux system. The following are the different types of methods for restarting the Linux System:

1. Using reboot command to restart our Linux system

Syntax:

sudo reboot

We use `sudo` as a prefix when we use the `reboot` command because we want to execute the command with root privileges, and to ensure that we have the necessary permissions to perform a system reboot while maintaining system security and integrity.

Force Immediate reboot in Linux system:

sudo reboot -f

Here we have used `-f` option for an immediate reboot without any delay. It is used to reboot our system forcefully.

2. Using shutdown command restart our Linux System

a) Restarting Immediately

• The following command helps in restarting the linux system immediately:

sudo shutdown –r now

• Here we have used `-r` option to indicate that a restart is intended. And used `now` is an argument that will specify time of execution here it now means that to restart immediately.

Note that the usage of the reboot, halt, and poweroff is almost similar in syntax and effect. Run each of these commands with –help to see the details. 

b) Scheduled a Restart

Simple reboot command has limited usage. The shutdown command is being used instead of the reboot command to fulfill much more advanced reboot and shutdown requirements. One of those situations is a scheduled restart. Following is the syntax which is being used to reboot your system after time defines by the TIME.

$sudo shutdown –r [TIME] [MESSAGE]

Here TIME has various formats. The simplest one is “now”, already been listed in the previous section, and tells the system to restart immediately. Other valid formats we have are +m, where m is the number of minutes we need to wait until restart and HH:MM which specifies the TIME in a 24hr clock.

Below are the examples and their respective outputs. Optional MESSAGE argument can be used to intimate the users prior to reboot to prevent the possible loss of data. 

Command to reboot your system after 5 minutes

• The following command helps in rebooting your system after 5 minutes:

sudo shutdown –r +5 

Reboot your system after 02:00 A.M

• The following command helps in rebooting your system at 2:00AM:

sudo shutdown –r 02:00

c) Cancelling Restart

If you want your system to discard the previously scheduled restart or shutdown you can simply call another shutdown command with the –c option and broadcast with it a message for the users about the cancellation of the restart.

• The following command will cancel the scheduled restart operation:

$sudo shutdown –c [MESSAGE]

Cancel your scheduled Reboot

The previously scheduled reboot can be canceled by the system administrator by simply issuing another shutdown command with the –c option and an optional message argument.

$sudo shutdown -c "our custom example of canceling a scheduled shutdown"

3. Restarting our server remotely in Linux

Simply login your server with any of the ssh client using server authentication information and simply issue any of the following commands:

Syntax:

ssh [email protected] /sbin/reboot

Example

ssh [email protected] /sbin/shutdown –r now\

4. Using init command to restart our Linux System

The Init command is actually taken from the word initialize that is widely been used to initialize/start different processes in a Linux machine, so this command used as a joint with the runlevel 6; a number which is been set for rebooting a Linux server leads to getting the server rebooted. The syntax for this is mentioned below:

Syntax

init 6

( or )

/sbin/init 6

5. Using systemctl to restart our Linux System

In Linux Distributions like Debain-based, CentOS, Fedora, Arch and RHEL, etc. These Linux distributions use sa system The `systemctl` command is a powerful utility in Linux System which allows us to manage the system and services manager.

Syntax

• To restart using systemctl command execute the following command:

sudo systemctl reboot

•  To shutdown the operating system with the systemctl method execture the following command:

sudo systemctl poweroff

6. Using telinit command to restart our Linux System

The telinit command can be used to restart our linux system, to do so we can use the syntax mentioned below.

Syntax

• To restart using telinit method execute the following command

sudo telinit 6

• To shutdown the operating system with the telinit method execture the following command:

sudo telinit 0

7. Checking your reboot logs

 /var/log/wtmp is the file records in which all logins and logouts records are kept. One can parse this file with the last command in order to access log for the reboot. Below you can find the last command usage and its output on my system.

last reboot

Rebooting a Linux System Responsibly

The following are the practices you ensure for rebooting linux systems safely and efficiently:

1. User Notifications: Always alert the users before rebooting to prevent the data loss:

Example: sudo shutdown -r +5 "System rebooting in 5 minutes"

2. chedule Reboots Wisely: Plan the reboots during the times of low activity to reduce the impact.

Example: sudo shutdown -r 02:00 "Scheduled reboot at 2 AM"

3. Graceful Shutdown of Services: Close all the running processes and services cleanly to avoid the corruption

Example: sudo systemctl stop apache2

4. Check Logs Post-Reboot: Review the system logs after rebooting for ensuring everything being safe and effective at time of reboots to minimize disruption and maintaining of data integrity.

Example: last reboot

Best practices for Rebooting Linux System Commands

Rebooting a Linux system is a critical task that should be approached with care to ensure system stability and data integrity. Here are four best practices to follow when rebooting a Linux system:

1. Notify Users: It always informs the users about implemending reboot to prevent the data loss. It useful in broadcasting the messages like shutdown to alert the users in advance.
2. Backup Critical Data: Before initiating a reboot, ensure critical data is backed up to prevent loss in case of unexpected issues.
3. Monitor System Health: Utilize monitoring tools to track system performance and detect any anomalies post-reboot.
4. Ensure All Processes are Closed: Check and close all the running processes and services gracefully before rebooting to aoid data corruption.

Conclusion

The article provides comprehensive the guidance on rebooting Linux systems through various methods, including the reboot command, shutdown command, init command, systemctl command, telinit command, and remote rebooting via SSH. It covers syntax, options, and examples for each method, offering practical solutions for both immediate and scheduled reboots.

Additionally, the article also provide the common FAQs, such as scheduling recurring reboots, the impact of reboots on running processes, remote server rebooting, forcing immediate reboots, and the differences between reboot and shutdown -r now commands after this conclusion. With this information, users can efficiently manage and execute system reboots in Linux environments, ensuring system reliability and stability.