screen and dtach allow to detach the current terminal from the shell. Thus you can turn off your shell (putty/teraterm) and still have your sessions running.
You can start a session with putty connect to a server, start screen(or start dtach), start a long disk clone, close the putty(this will auto detach your screen or dtach session) and you will be okay the clone will still be going on, you can turn on putty on another computer just connect to the same server and go back to your session (reattach to your screen or dtach session). The clone will be going the whole time while your driving to that other computer.
DTACH STARTING DETACHING AND REATTACHING
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dtach is a common linux utility
apt-get install dtach
Start a dtach session/socket like so:
dtach -A /tmp/session1 /bin/bash
NOTE: Now your free to do any commands, they are all within the invisible universe of the /tmp/session1 socket file (which is holding your bash shell, within it you can run commands, and even close your putty terminal and as long as /tmp/session1 still exists, then your commands still exist, its like running the commands in the background with nohup, but you get more control)
To detach: Control-\ (or just close the putty/terminal window your using)
Processes will still be running in /tmp/session1 session/socket file
To reattach to the session type this: dtach -A /tmp/session1 (so for example you closed your putty/terminal window and you reconnected, this is how you will get back to where you were, note the progress of everything will be moved forward, because dtaching doesnt stop processes, they still run in the background, thats the beauty of dtach – so if you had a copy with rsync, chances are when you reconnect/reattach that copy could be done by then)
SCREEN STARTING DETACHING AND REATTACHING
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apt-get install screen
Start Screen: screen
Better start screen: screen /bin/bash
Detach Screen: Control-a d
When detached all processes still are running
To reattach: screen -x
To reattach (substitute in the PID): screen -x PID
Before reattaching list all screen sessions: screen -ls
Scrolling on the pages
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With normal system (Without screen or byobu):
SHIFT-PAGE UP
SHIFT-PAGE DOWN
Note: byobu is an enhanced version of screen, it gives you a task bar and tabs (along with screens split tab ability and also everything runs in the background so you can be on the go)
With byobu / screen
Control-a then [
Then PAGEUP and PAGEDOWN
Also UP and DOWN arrow keys work with BYOBU
SCREEN – How to copy/save output with screen
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This is similar to copy, because you will drag a box aroudn the output you want to save.
Control-a [
To start copy process
Use arrow keys to scroll cursor up down left right to start point Hit space (top left corner will be set
Scroll down with arrow keys to end point (bottom right corner will be set)
Control-a >
This will save the stuff you just copied to a file called /tmp/screen-exchange
SCREEN – Log screen
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Control-a h
takes a “screenshot” of the current text (only whats showing – nothing behind the “walls” – nothing you have to scroll up or down to)
Control-a H
log file dump to current working directory file wil lbe called screenlog.0
Control-a t
Shows system info, hostname, time, and load average
SCREEN – Splitting and more
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Control-a S
Split screen horizontally
Control-a |
Split Screen Vertically
Just control \ (no need for holding shift to get the pipe | symbol). but with a | its easier to remember that it splits vertically.
Control-a Tab
Move to other split window
Control-a c
Creates a new session might be usefull in split screen or in general
Control-a “
To see all sessions
Use UP and DOWN arrow keys and enter to select
Control-a :remove ENTER
Unsplit
Can bind in to a simpler key:
vi ~/.screenrc
Add this in:
bind X remove
exit and save
Then control-a X will work
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Summary from my older screen article:
LINUX – screen – best commands and detaching and reattaching to session
SCREEN COMMANDS
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These are the ones that I use the most.. These are awesome, write em down, remember em.
CONTROL-A then c – create new shell
CONTROL-A then S – split window with horizontal line —
CONTROL-A then | – split window with vertical line | (control \ in reality, just | is easier to remember – so no need to hold shift for this)
CONTROL-A then TAB – move over to next window
CONTROL-A then “ – see all windows
CONTROL-A then [ – copy mode (up down left right, page up page down move around in window)
CONTROL-A then X – close window
CONTROL-A then D – detach (processes still are running)
CONTROL-A then A – set name to window
CONTROL-A then ? – help
* Note all of these work with BYOBU if you allow BYOBU to use SCREEN commands, which I would
How to recover a ‘lost’ screen session?
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Somehow I managed to close a screen window without screen ‘noticing’ it, so the session is still flagged as attached. This prevents me from re-attaching to this session. What can I do?
$ screen -r
also
$ screen -ls
There are several suitable screens on:
25028.pts-19.XXX-serv8 (01/05/2012 07:15:34 PM) (Attached)
24658.pts-19.XXX-serv8 (01/05/2012 07:11:38 PM) (Detached)
24509.pts-19.XXX-serv8 (01/05/2012 07:10:00 PM) (Detached)
18676.pts-5.XXX-serv8 (01/02/2012 06:55:33 PM) (Attached)
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Type “screen [-d] -r [pid.]tty.host” to resume one of them.
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Try detaching it first with screen -d. If that doesn’t work, you can try, in increasing order of emphasis,
-d|-D [pid.tty.host]
does not start screen, but detaches the elsewhere running screen session. It has the
same effect as typing “C-a d” from screen’s controlling terminal. -D is the equivalent
to the power detach key. If no session can be detached, this option is ignored. In
combination with the -r/-R option more powerful effects can be achieved:
-d -r Reattach a session and if necessary detach it first.
-d -R Reattach a session and if necessary detach or even create it first.
-d -RR Reattach a session and if necessary detach or create it. Use the first session if
more than one session is available.
-D -r Reattach a session. If necessary detach and logout remotely first.
-D -R Attach here and now. In detail this means: If a session is running, then reattach.
If necessary detach and logout remotely first. If it was not running create it and
notify the user. This is the author’s favorite.
-D -RR Attach here and now. Whatever that means, just do it.
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