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Lets say I've got a bit of server software. I start it up and it provides an interface on stdin/stdout that I can use to enter commands during runtime. I want to be able to start it up over SSH, exit the session, come back and hook right back into that stdin/stdout interface again.

I was thinking there must be an easy command like nohup or & that would allow me to do this. Is there?

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up vote 6 down vote accepted

Yes, use can use tmux or, the older screen. The following are excerpts of their respective man pages:

  1. tmux:

     tmux is a terminal multiplexer: it enables a number of terminals to be
     created, accessed, and controlled from a single screen.  tmux may be
     detached from a screen and continue running in the background, then later
     When tmux is started it creates a new session with a single window and
     displays it on screen.  A status line at the bottom of the screen shows
     information on the current session and is used to enter interactive
     A session is a single collection of pseudo terminals under the management
     of tmux.  Each session has one or more windows linked to it.  A window
     occupies the entire screen and may be split into rectangular panes, each
     of which is a separate pseudo terminal (the pty(4) manual page documents
     the technical details of pseudo terminals).  Any number of tmux instances
     may connect to the same session, and any number of windows may be present
     in the same session.  Once all sessions are killed, tmux exits.
     Each session is persistent and will survive accidental disconnection
     (such as ssh(1) connection timeout) or intentional detaching (with the
     'C-b d' key strokes).  tmux may be reattached using:
           $ tmux attach
  2. screen

       Screen  is  a  full-screen  window  manager that multiplexes a physical
       terminal between  several  processes  (typically  interactive  shells).
       Each  virtual  terminal  provides the functions of a DEC VT100 terminal
       and, in addition, several control functions from the ISO 6429 (ECMA 48,
       ANSI X3.64) and ISO 2022 standards (e.g. insert/delete line and support
       for multiple character sets).  There is a scrollback history buffer for
       each virtual terminal and a copy-and-paste mechanism that allows moving
       text regions between windows.
       When screen is called, it creates a single window with a  shell  in  it
       (or  the  specified  command) and then gets out of your way so that you
       can use the program as you normally would.  Then, at any time, you  can
       create new (full-screen) windows with other programs in them (including
       more shells), kill existing windows,  view  a  list  of  windows,  turn
       output  logging  on  and off, copy-and-paste text between windows, view
       the scrollback history, switch between windows in whatever  manner  you
       wish,  etc.  All  windows  run their programs completely independent of
       each other. Programs continue to run when their window is currently not
       visible  and  even  when  the whole screen session is detached from the
       user's terminal.  When a program terminates, screen (per default) kills
       the  window  that  contained it.  If this window was in the foreground,
       the display switches to the previous window; if none are  left,  screen

Both of these programs will enable you to log on to a server, launch a process, then log off and leave it running. When you want to check on it, you log back on to the server and reconnect to the running tmux or screen session and it is as though you never left. You can install both of them from the Ubuntu repositories:

sudo apt-get install screen


sudo apt-get install tmux

You can find a nice Q&A comparing the two programs on our sister site, Unix & Linux.

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