How to Run Linux Commands in Background and Detach in Terminal

Introduction

If you are a Linux user, you may have come across a situation where you need to run a command in the background and detach it from the terminal. This can be useful if you want to run a command that takes a long time to complete, or if you want to run a command without having to keep the terminal window open. In this tutorial, we will discuss how to run Linux commands in the background and detach them from the terminal. We will also discuss how to check the status of a background process and how to bring it back to the foreground.

How to Run Linux Commands in Background and Detach in Terminal

1. To run a Linux command in the background, you can use the “&” symbol at the end of the command. For example, to run the command “sleep 10” in the background, you would type “sleep 10 &”.

2. To detach a process from the terminal, you can use the “disown” command. For example, to detach the process “sleep 10” from the terminal, you would type “disown sleep 10”.

In this guide, we shall bring to light a simple yet important concept in process handling in a Linux system, which is how to completely detach a process from its controlling terminal.

When a Linux process is associated with a terminal, two problems might occur:

  1. Your controlling terminal is filled with so much output data and error/diagnostic messages.
  2. In the event that the terminal is closed, the process together with its child processes will be terminated.

To deal with these two issues, you need to totally detach a process from a controlling terminal. Before we actually move to solve the problem, let us briefly cover how to run processes in the background in Linux.

Run Linux Command or Process in Background

If a process is already in execution, such as the tar command example below, simply press Ctrl+Z to stop it then enter the command bg to continue with its execution in the background as a job.

You can view all your background jobs by typing jobs. However, its stdin, stdout, and stderr are still joined to the terminal.

$ tar -czf home.tar.gz .
$ bg
$ jobs
Run Linux Command in Background
Run Linux Command in Background

You can as well run a Linux process in the background using the ampersand, & sign.

$ tar -czf home.tar.gz . &
$ jobs
Start Linux Process in Background
Start Linux Process in Background

Take a look at the example below, although the tar command was started as a background job, an error message was still sent to the terminal meaning the process is still connected to the controlling terminal.

$ tar -czf home.tar.gz . &
$ jobs

tar: ./.config/etcher: Cannot open: Permission denied
Linux Process Running in Background Message
Linux Process Running in Background Message

Keep Linux Process Running After Logout

We will use the disown command, which is used after the process has been executed and put in the background, its work is to remove a shell job from the shell’s active list jobs, therefore you will not use fg, bg commands on that particular job anymore.

In addition, when you close the controlling terminal or log out, the job will not hang or send a SIGHUP to any child jobs.

Let’s take a look at the below example of using the diswon bash built-in function.

$ sudo rsync Templates/* /var/www/html/files/ &
$ jobs
$ disown  -h  %1
$ jobs
Keep Linux Process Running After Closing Terminal
Keep Linux Process Running After Closing Terminal

You can also use the nohup command, which also enables a process to continue running in the background when a user exits a shell.

$ nohup tar -czf iso.tar.gz Templates/* &
$ jobs
Put Linux Process in Background After Closing Shell
Put Linux Process in Background After Closing Shell

Detach a Linux Process From Terminal

Therefore, to completely detach a process from a controlling terminal, use the command format below, this is more effective for graphical user interface (GUI) applications such as Firefox:

$ firefox </dev/null &>/dev/null &

In Linux, /dev/null is a special device file that writes off (gets rid of) all data written to it, in the command above, input is read from, and output is sent to /dev/null.

As a concluding remark, provided a process is connected to a controlling terminal, as a user, you will see several output lines of the process data as well as error messages on your terminal. Again, when you close the controlling terminal, your process and child processes will be terminated.

Importantly, for any questions or remarks on the subject, reach us by using the comment form below.

How to Run Linux Commands in Background and Detach in Terminal

Linux is a powerful operating system that allows users to run commands in the background and detach from the terminal. This is useful for running long-running commands that don’t require user input, such as a web server or a database. In this tutorial, we’ll show you how to run Linux commands in the background and detach from the terminal.

Using the & Symbol

The simplest way to run a command in the background is to append an ampersand (&) to the end of the command. For example, if you wanted to run a web server in the background, you could use the following command:

$ python -m http.server &

This will start the web server in the background and return you to the terminal prompt. You can check the status of the command by running the jobs command, which will list all the background jobs.

Using the nohup Command

The nohup command is a more robust way to run commands in the background. It allows you to run a command even after you log out of the terminal. To use it, simply prefix the command with nohup. For example:

$ nohup python -m http.server

This will start the web server in the background and return you to the terminal prompt. You can check the status of the command by running the jobs command, which will list all the background jobs.

Using the screen Command

The screen command is a powerful tool for running commands in the background. It allows you to create multiple “screens” or “windows” in the terminal, each of which can run a different command. To use it, simply type screen at the terminal prompt. This will open a new window in the terminal. You can then run the command you want to run in the background in this window. To detach from the window, press Ctrl+A followed by d. This will return you to the terminal prompt.

You can check the status of the command by running the screen -list command, which will list all the screens that are currently running.

Conclusion

In this tutorial, we’ve shown you how to run Linux commands in the background and detach from the terminal. We’ve covered the & symbol, the nohup command, and the screen command. With these tools, you can easily run long-running commands in the background and detach from the terminal.

Jaspreet Singh Ghuman

Jaspreet Singh Ghuman

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