How to Keep Linux Jobs Running After SSH Disconnects

Problem Introduction

Programmers often lose long‑running jobs when the SSH session ends, the screen is locked, or Ctrl+C is pressed. The default shell sends an interrupt signal to the process group attached to the terminal, causing the processes to exit.

Relevant Signals

SIGINT : generated by Ctrl+C, forces the program to terminate.

SIGHUP : sent when the terminal is closed, the network disconnects, or the screen is locked.

Methods to Run Jobs in Background

1. Using '&' Operator

Appending '&' to a command starts it in the background and makes it ignore SIGINT, but it still terminates on SIGHUP.

sh test.sh &

2. Using nohup

nohup

(no hang‑up) catches SIGHUP and redirects output to nohup.out by default, allowing the command to continue after the SSH session ends. Ctrl+C still stops the process, so it is common to combine nohup with '&'. nohup Command [Arg ...] [&] Example – run ./test.sh with stdout to out.log and stderr to err.log:

nohup ./test.sh > out.log 2> err.log &

Redirecting both streams to the same file:

nohup ./test.sh > out.log 2>&1 &

3. Job Control Commands (Ctrl+Z, jobs , bg , fg )

When a process is started in the foreground without '&', you can suspend it with Ctrl+Z, list suspended or running jobs with jobs, resume it in the background with bg, or bring it back to the foreground with fg.

[1]+ Stopped ./test.sh

jobs
[1]+ Stopped ./test.sh
[2]+ Running ./test2.sh &

bg 1
[1]+ ./test.sh &

fg 2
./test2.sh

Using GNU Screen

Installation

yum install screen

Basic Workflow

Create a new session: screen -S yourname List existing sessions: screen -ls Reattach to a session: screen -r yourname Detach a session: screen -d yourname or screen -d -r yourname Terminate a session: screen -S pid-X quit Screen creates a virtual terminal that remains alive even if the SSH connection drops, effectively preventing SIGHUP from terminating the processes running inside the screen session.