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; running them in the background frees the terminal.

& Method

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

|     |<br/>| --- |<br/># ping www.baidu.com output goes to ping.log<br/>root@master-01:~# ping www.baidu.com &>> ping.log &<br/>[1] 1254658<br/># View running process<br/>root@master-01:~# jobs<br/>[1]+  Running   ping www.baidu.com &>> ping.log &<br/># Kill the job<br/>root@master-01:~# kill %1

nohup Method (recommended)

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

Syntax

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

Example:

# Run ping in background, output goes to nohup.out
root@master-01:~# nohup ping www.baidu.com &
[1] 1266070
nohup: ignoring input and appending output to 'nohup.out'
# View jobs
root@master-01:~# jobs
[1]+  Running   nohup ping www.baidu.com &
# View nohup.out
root@master-01:~# ll nohup.out
-rw------- 1 root root 1745 Apr 21 19:23 nohup.out
# Kill the job
root@master-01:~# kill %1
root@master-01:~# jobs
[1]+  Terminated   nohup ping www.baidu.com

Redirect output to a specific file

Syntax:

nohup command >> myout.file 2>&1 &

Explanation: command>>out.file appends standard output to out.file; 2>&1 redirects standard error to the same file; the final & runs the command in background.

Example:

# Ping and redirect both stdout and stderr to ping.log
root@master-01:~# nohup ping www.baidu.com >> ping.log 2>&1 &
[1] 1270295
# View ping.log
root@master-01:~# tail -f ping.log
64 bytes from 182.61.200.110: icmp_seq=1 ttl=48 time=6.03 ms
...

Switching and Controlling Foreground/Background Jobs

CTRL+Z

pauses a foreground job and moves it to the background. bg resumes a stopped job in background; bg %jobnumber resumes a specific job. fg brings a background job to foreground; fg %jobnumber selects a specific job.

screen Method

screen

is a full‑screen window manager that multiplexes several 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 (keep it running)
Ctrl+a d   # or screen -d
exit        # close window
# List windows
screen -ls
# Reattach to a window
screen -r <id>

Key shortcuts: Ctrl+a c (create), Ctrl+a w (list), Ctrl+a n/p (next/previous), Ctrl+a 0‑9 (switch), Ctrl+a K (kill), Ctrl+a d (detach).