A problem that often arises when you’re dealing with lots of data is that it takes forever to process.
So you SSH into your Amazon EC2 machine, start your script, and go do other things while it’s running.
You check back a few hours later to see that your SSH session seems to be frozen or you’ve gotten a “broken pipe” error.
You log back in to your EC2 machine, only to discover your script has terminated.
What to do…
Screen for Linux
Screen is like having “tabs” for your command line. You can have multiple screens running at any time. They stay active, so even if you exit from a screen, or exit your entire SSH session, whatever you were doing inside that screen will continue.
This is great if you have a script that takes longer than EC2’s allowed session duration.
Start Screen
To start screen, just enter:
screen
Hit enter to exit out of this info screen.
How Screen Works
Once you’ve started screen, there are a few things you can do:
1. Create a screen
2. Detach from a screen (i.e. go back to your “regular” terminal)
3. Re-attach to a screen (that you’ve previously detached from).
4. List the screens you have open
This is all you need for the use case described above.
Enter commands in Screen
Once inside Screen, you can tell screen you’re about to enter a command by pressing:
Ctrl + A
Now Screen knows you’re about to enter a command.
Create a Screen
After hitting “Ctrl+A”, hit “C”.
Detach from a Screen
After hitting “Ctrl+A”, hit “D”.
Re-attach to a Screen
screen -r
List the Screens you have open
The above only works if you have only one screen open. Otherwise, you’ll see this:
If you want to re-attach to a particular screen, enter:
screen -r 14366.pts-0.affinity-proto
(Obviously you would choose the screen you want to go back to).