Master Linux Background Jobs: &, nohup, and screen Explained

Background

When a long‑running or disk‑intensive job should continue after you log out or during off‑peak hours, it is useful to run the job in the background so the terminal remains free.

Running a command in background with &

Appending & to a command starts it as a background job. The job is terminated when the terminal session ends.

# ping www.baidu.com >> ping.log &
[1] 1254658
# jobs
[1]+  Running   ping www.baidu.com >> ping.log &
# kill %1

nohup (recommended)

nohup

ignores the SIGHUP signal, allowing the command to keep running after logout.

# nohup ping www.baidu.com &
nohup: ignoring input and appending output to 'nohup.out'
# jobs
[1]+  Running   nohup ping www.baidu.com &
# kill %1

Typical syntax: nohup Command [Arg …] [&] Example with output redirection:

# nohup ping www.baidu.com >> ping.log 2>&1 &
[1] 1266070
# tail -f ping.log
64 bytes from 182.61.200.110: icmp_seq=1 ttl=48 time=6.03 ms

Job control commands

CTRL+Z

– Suspend the foreground job and move it to the background. bg – Resume a suspended job in the background. bg %jobnumber – Resume a specific job in the background. fg – Bring the most recent background job to the foreground. fg %jobnumber – Bring a specific job to the foreground.

screen utility

screen

is a full‑screen terminal multiplexer that lets you create detachable sessions.

Installation

# CentOS
yum install -y screen
# Ubuntu
sudo apt update -y
sudo apt install -y screen

Basic usage

# Create a new session named test
screen -S test
# Run a command inside the session
python test.py
# Detach (keep it running)
Ctrl+a d   # or: screen -d
# List existing sessions
screen -ls
# Reattach to a session
screen -r test

Useful shortcuts

Ctrl+a c   – Create a new window
Ctrl+a w   – List windows
Ctrl+a n   – Switch to next window
Ctrl+a p   – Switch to previous window
Ctrl+a 0‑9 – Switch directly to window 0‑9
Ctrl+a K   – Close current window and move to next
Ctrl+a d   – Detach from the session