nohup — Keep a command running after logout

Linux / Service and process management / nohup.html

Makes a command ignore hangup signals and redirects output so it survives logout.

Basic Information

What is this command?

nohup ignores SIGHUP and redirects standard output and error to nohup.out by default.

It is the simplest way to keep a long job alive when an SSH session may drop.

What problems does it solve?

• Keep a long backup running after SSH exits.
• Prevent a dropped session from killing a build.
• Capture output in a file for later review.
• Run an ad-hoc batch job in the background.

Key features

Signal handling

Runs the child with SIGHUP ignored.

• When to use: Environments where sessions drop
• What you get: Still running after logout
• Limitations: A KILL signal still ends it

Output redirection

When output is not a terminal it appends to nohup.out.

• When to use: When keeping a run log
• What you get: Records into nohup.out
• Limitations: The file keeps growing

Combining with background

A trailing & returns the shell immediately.

• When to use: When the shell is still needed
• What you get: A job running in the background
• Limitations: Completion must be checked separately

Installation and usage

Check whether it is installed

nohup --version

apt install coreutils # usually already present

Real-world examples

Background run

Start a job that survives logout.

# Keep running after logout, in the background
nohup ./long-task.sh &

Custom log file

Write to a chosen path instead of nohup.out.

# Write output to a specific file
nohup ./backup.sh > /var/log/backup.log 2>&1 &

Check the job

Check state with jobs and ps.

# Confirm the job is still alive
ps -ef | grep long-task