Running commands on Putty without fear of losing connection

Question

How do you use the "screen" command effectively?
Is it:

1. Type "screen"

2. Type in command

3. Lose connection

4. Check back on lost session

How do I carry out step 4?

Solution 1

With screen:

1. screen
2. type command
3. Ctrl-A-D to detach from the screen
4. logoff from the session
5. screen -RD to reattach to the screen (if there's more than one you'll get a list of current screen sessions and you'll have to supply the session number) from a new session

A simpler method that is useful for commands that leave logfiles or just throw some relevant output and do not need interactivity is nohup:

1. nohup command > logfile &
2. Logoff from the session
3. tail -f logfile from a new session

Solution 2

Here's what I have picked up about using screen (which I, too, have just started doing):

• screen -S <name> creates a screen named '<name>'. This is quite useful if you want to have several screen sessions going at the same time. For instance, I have one I use normally and one I use for my persistent processes.
• screen -ls lists the running screens.
• screen -r <name> resumes a detached screen. If the screen is already attached somewhere, use screen -dr <name>.

Also, when you start using screen, whenever you plan to leave, press ^a d (= ctrl-a followed by a d) to detach the screen you're currently running. It can then be resumed later.

In addition, I can recommend taking a look at ^a ? for a list of the different commands you can use while inside of a screen.

The most important of these (to me) are:

• ^a c to create a new window in your screen session.
• ^a ^a to switch between the two last used windows.
• ^a " to list the current windows in your session.
• ^a Esc to scroll in your screen buffer.
• ^a k to kill the current window.
• ^a x to lock your screen session, in case you need to leave your computer and don't want people to mess with it.

Solution 3

screen -dr to detach and resume the previous screen session.

Solution 4

you can also set up your environment to log you in and start screen right off the bat. There are many ways to do it. I chose to add this to my .bashrc file.

# screen management
if [ $SSH_TTY ] && [ ! $WINDOW ]; then
  SCREENLIST=`screen -ls | grep 'Attached'`
  if [ $? -eq "0" ]; then
    echo -e "Screen is already running and attached:\n ${SCREENLIST}"
  else
    screen -U -R
  fi
fi

Solution 5

A quick Google search found this screen guide

http://www.rackaid.com/resources/linux-tutorials/general-tutorials/using-screen/

So from step b) you can detach the screen using :

"Ctrl - A" "d"

and then later after the connection has been lost and your connected once again find the screen using :

# screen -ls

and then reattach using :

# screen -r <screen_session_name>

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Comments

[Duncan Jones]

Note: step 3 is entirely optional. If you close your PuTTY session without detaching, you can still reattach with screen -RD.