GNU screen

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screen -r       Re-attach 
screen -x       Reconnect your session even if it is still attached somewhere. 
screen -r -d    Very useful for re-attaching screens attached elsewhere. 
                It detaches the session from wherever it may still be attached 
                and re-attaches your screen at the same time.

Starting Screen
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screen     start Screen
screen -r  Reattach to Screen
 
C-a ?      Help on using Screen
 
Commands on Windows
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C-a c      Create Window
C-a A      Name the current Window
C-a d      Detach from a Window
 
Navigating Windows
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C-a "      List windows (navigate with vim keys)
C-a C-a    Switch to last used Window
C-a n      Switch to Next Window
C-a p      Switch to Previous Window
C-a N      Switch to Window N, where N = 0..9 
 
C-a [      Copy Mode
C-a ]      Paste Mode
 
C-a _      Start / Stop monitoring current window for 30 of silence
C-a M      Start / Stop monitoring current window for activity
 
C-a S      Split Window into Regions
C-a TAB    Move input focus to next Region
C-a Q      Deletes all Regions but this one
 
C-a :      Enter Command mode
 
C-a :caption always Turns caption on