Linux Screen: A light weight approach to have persistent shell sessions

Introduction

Laymen explanation

If you use putty for connecting remote session, think of the situation when the session was disconnected when you are in middle of operation (for example, executing a code). It will be nice if the operation still continues. Linux screen helps to achieve this.

Moreover, it allows technical people to collaborate for various purpose including debugging an issue.

Technical explanation

Linux Screen allows you to:

• Use multiple shell windows from a single SSH session.

• Keep a shell active even through network disruptions.

• Disconnect and re-connect to a shell sessions from multiple locations.

• Run a long running process without maintaining an active shell session

• Allow to connect from multiple machines. This enables multiple people to collaborate (e.g. debugging)

Screen versus tmux

Refer https://hackernoon.com/a-gentle-introduction-to-tmux-8d784c404340

https://superuser.com/questions/236158/tmux-vs-screen

.Screenrc configuration

show window number

caption always # activates window caption

caption string '%{= wk}[ %{k}%H %{k}][%= %{= wk}%?%-Lw%?%{r}(%{r}%n*%f%t%?(%u)%?%{r})%{k}%?%+Lw%?%?%= %{k}][%{b} %Y-%m-%d %{k}%c %{k}]'

Screen commands

Screen commands

screen -r -> attach screen

screen -S <myscreen> -t <terminal name>

screen -x <myscreen>

Key shortcuts

Key Action Notes

Ctrl+a c new window

Ctrl+a n next window

Ctrl+a p previous window

Ctrl+a " select window from list I have window list in the status line

Ctrl+a Ctrl+a previous window viewed

“Ctrl-a” “d” Detach current screen

“Ctrl-a” “[” To scroll up the screen

Command to change screen session name

To rename the window title within a screen session use: press and release Ctrl + a and then press Shift + a.

Useful link: https://unix.stackexchange.com/questions/27780/how-to-rename-a-gnu-screen-session

Screen within Screen (Subscreen)

Occasionally, we may need to use sub-screen. For example, while debugging session, you want to login to a box and then use existing screen in that machine.

How to operate on sub-screen

ctrl+a a will pass the escape sequence to the sub-screen.. Then after you can use commands to do various operation. For example ctrl+a, a, c will create a window in the sub-screen.

How to detach an screen which is opened from within another screen

ctrl+a a will pass the escape sequence (ctrl+a) to the sub-screen.. So, ctrl+a a d will do ctrl+a d in the sub-screen (detaching it).

Command to kill frozen hanged tab

• 1. select stalled window ( C-a :select <stalled window number> )

  2. send kill command ( C-a :kill )

Ref: https://superuser.com/questions/458122/gnu-screen-kill-a-frozen-tab

Reference

http://www.pixelbeat.org/lkdb/screen.html

https://www.rackaid.com/blog/linux-screen-tutorial-and-how-to/

https://www.mattcutts.com/blog/a-quick-tutorial-on-screen/

http://unix.stackexchange.com/questions/29140/how-do-you-detach-the-2nd-screen-from-within-another-screen