nohup command is a Linux command that allows users to run a command or a script, and ignore the hangup (HUP) signal sent by the system when the user logs out or closes the terminal. This command is particularly useful when running long-term processes that need to continue running even after the user logs out or the terminal is closed.
The syntax for the
nohup command is as follows:
nohup COMMAND [ARG]...
COMMAND is the command or script that you want to run, and
ARG are the arguments that you want to pass to the command. When you run a command with
nohup, any output that would normally be sent to the terminal is redirected to a file called
nohup.out in the current directory.
Here is an example of how to use
nohup to run a script called
nohup ./myscript.sh &
In this example, the
& symbol is used to run the command in the background. This means that you can continue to use the terminal for other tasks while the script is running.
Specific Use Cases
Here are some specific use cases for the
Running a Script in the Background
Suppose you have a long-running script that you want to run in the background, and you don’t want it to be terminated when you log out of the system. You can use
nohup to accomplish this. For example:
nohup ./long_running_script.sh &
This will start the script in the background and redirect all output to
Running a Command on a Remote Server
If you are working on a remote server and need to run a command that will take a long time to complete, you can use
nohup to ensure that the command continues to run even if your connection to the server is lost. For example:
nohup ./long_running_command &
Running a Command on Boot
If you want to run a command or script when your system boots up, you can add it to the system’s startup scripts and use
nohup to ensure that it continues to run even after you log out. For example:
sudo nano /etc/rc.local
Add the following line to the end of the file:
nohup /path/to/command &
Save and exit the file. This will ensure that the command is run at startup and continues to run even after you log out.
The following table lists the available options for the
||Do not overwrite the
||Specify the process ID (PID) of a running process that you want to attach to
Here are some troubleshooting tips for the
nohup.out File for Errors
If you are experiencing issues with a command or script that you are running with
nohup, you can check the
nohup.out file for any error messages or other output. This file should be located in the same directory where you ran the
Check the Process Status
If you are unsure if a process is still running, you can use the
ps command to check its status. For example:
ps -ef | grep [PROCESS_NAME]
This will show you all processes that match the specified name.
Kill a Running Process
If you need to stop a process that is running with
nohup, you can use the
kill command to send a signal to the process. For example:
PID is the process ID of the process that you want to stop.
nohupcommand is not a replacement for a proper process management system like
supervisord. It is intended for use in specific cases where a long-running process needs to continue running even after the user logs out or the terminal is closed.
- When using
nohup, it is important to redirect all input and output to files or to
/dev/nullto ensure that the process does not hang waiting for input or output.