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

Concept

When working in a terminal you may not want a job to occupy the screen, especially for disk‑intensive processes that should run during off‑peak hours; therefore you need ways to run them in the background.

& Method

Using [shell] & runs a process in the background, but the job ends when the terminal session is closed.

Example:

# ping www.baidu.com >> ping.log &
[1]+  Running    ping www.baidu.com &>> ping.log &
ps -aux | grep ping
kill %1

nohup Method (Recommended)

Appending & submits a job to the background, but it stops when the terminal closes. The nohup command ignores hang‑up signals, allowing the process to continue after logout.

Syntax:

|   |   |
|---|---|
|   | nohup Command [ Arg … ] [&] |

Example:

# nohup ping www.baidu.com &
[1] 1266070
nohup: ignoring input and appending output to 'nohup.out'
jobs
[1]+  Running    nohup ping www.baidu.com &

Redirecting nohup Output to a File

Syntax: nohup command >> myout.file 2>&1 & command>>out.file redirects standard output to the file.

2>&1 redirects standard error to the same file; the final & runs the command in background.

Example:

# nohup ping www.baidu.com >> ping.log 2>&1 &
[1] 1270295
nohup: ignoring input and appending output to 'nohup.out'
... (output of ping.log) ...
kill %1

Switching Between Foreground and Background Processes

Keyboard shortcut CTRL+Z pauses a foreground job and moves it to the background.

Use bg to resume a stopped job in the background, optionally specifying bg %jobnumber. Use fg to bring a background job to the foreground, optionally with fg %jobnumber.

screen Method

Screen is a full‑screen window manager that multiplexes multiple shells over a single terminal.

Installation

# CentOS
yum install -y screen

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

Usage

# Create a new window
screen -S test

# Run a command inside the window
python test.py

# Detach the window
Ctrl+a d   # or screen -d
exit       # close the window

# List windows
screen -ls

# Reattach a window
screen -r <id|name>

Related shortcuts:

Ctrl+a c   # create window
Ctrl+a w   # list windows
Ctrl+a n   # next window
Ctrl+a p   # previous window
Ctrl+a 0‑9 # switch between windows 0‑9
Ctrl+a K   # close current window
exit       # close current window
Ctrl+a d   # detach and return to original shell