Command stops whenever I log out of my server

Question

I have a java program (text-based no GUI) that I have written and compiled and uploaded to a server.

I run it with java -cp myjar.jar mypackage.MyClass which starts it running processing a datafile with 20,000,000+ entries in it and printing output to System.out . I have calculated that it will take a very long time to process the data and I didn't want to have my laptop open for the 10 days of number crunching...

When I log out of my shell however, the process stops.

How can I execute the command and log out without it stopping? What is that even called?

I am using an Amazon Ubuntu EC2 server. I log in using a certificate from Mac OSX with terminal. The server seems to be using a bash shell.

Hope someone can help me out! Jason.

Answer 1

You can use nohup

nohup java -cp myjar.jar mypackage.MyClass > yourLogFile.log &

-----> http://ss64.com/bash/nohup.html

Answer 2

Consider using screen instead of nohup . It allows you to create a virtual terminal that persists even after you logout/disconnect. When you reconnect to the server, you can immediately jump into the screen session you last had open.

Typical workflow on the server:

1. type screen (you may need to press space to leave intro page)
2. type in your command that you want to leave long-running (your java program, or an OS upgrade)
3. press ctrl a+d to leave screen (make sure to hold ctrl down)

To re-enter screen just use screen -r , and you will see the previous terminal and any running programs as you left it.