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Old 12-05-2010, 05:46 PM   #1
fdelval
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everytime i launch a program, i cant use the console anymore...


hello,

My problem is, that everytime i launch a program, like a virtualbox image, the console launch it, but i cant use it anymore.
I use ssh with putty remotely, and the problem is that if i close putty console, the program closes too...

Can i do something to run the program independently of the console? or keep running after i close?

if its possible, how i can i keep track of it when i open console again?
 
Old 12-05-2010, 07:59 PM   #2
alunduil
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To be able to use a console again after starting a command you can do two possible things:
1. You can append an ampersand (&) to the command which starts it in the background
2. You can start the command and then hit ^z (ctrl+z) to pause it and then run bg to background it

As for running a program and having it continue after you close the console you can prepend your command with SIGHUP which lets the command ignore a SIGHUP when you log out.

Regards,

Alunduil
 
Old 12-05-2010, 08:06 PM   #3
GrapefruiTgirl
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alunduil,

I wonder if you meant to write "nohup" rather than "SIGHUP" ? `nohup` is the command to make applications ignore HUP signals, is it not?

Also, for the OP: If you want to launch an app and totally disown (fully detach) the app from your terminal, bash has the `disown` keyword. A full usage of all the mentioned things might be like:
Code:
$ nohup some_application & disown
Now, the application has been totally detached from the tty it was started from.
 
Old 12-05-2010, 08:16 PM   #4
alunduil
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I did thanks for catching that. Don't know what I was thinking.

Regards,

Alunduil
 
Old 12-06-2010, 07:53 AM   #5
Hangdog42
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If you need a console session to be maintained between logins, you can also use the screen program, which creates a virtual console that you can disconnect and connect to at will. Sort of like VNC for the console.
 
Old 12-06-2010, 08:29 AM   #6
fdelval
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Hello
thank you all

i have a mess betweek &, nohup, disown.

& = background, but when i close terminal, background running and foreground running app's are killed
nohup = ?
disown = detaches app's from console, i can close it


meanwhile, im installing screen.
Looks like i can create as many consoles as i want, and switch between them.
But i cant find a point; can i close the ssh shell where i launched screen?
If the answer is "yes", if a login again, i guess simply by doing "#screen" again, i would be able to regain control of the running apps, right?


thank you for the help, i will wait until clarification to start doing tests.
 
Old 12-06-2010, 09:09 AM   #7
reed9
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Default keybinding to detach a screen session is CTRL-a + d. You can close your ssh session and the detached screen session will continue running. To re-attach do screen -r. If you have multiple screen sessions going that will list available sessions and you would do screen -r <session#>.
 
Old 12-06-2010, 10:13 AM   #8
fdelval
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wow screen is great!

but i dont want to close the thread without understanding the nohup, &, disown commands.
 
Old 12-06-2010, 10:26 AM   #9
reed9
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nohup = ignore the hangup signal. When you close your terminal session, it sends the hangup signal to running processes to close them. This prevents that.

& = runs the process in the background, free up your console to do other things.

disown = disowns the process from its parent process. nohup makes the process ignore the hangup signal from the get go, disowning a process, AFAIK, prevents the signal from being sent.

http://playingwithsid.blogspot.com/2...-commands.html
 
Old 12-06-2010, 11:19 AM   #10
alunduil
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The nohup is simply a script that grabs the SIGHUP handler before starting the command you want to run. The & is a bash language construct that backgrounds the process when it is executed by forking the process before executing it. I'm not familiar with the disown command but will do a little research and report back with anything I find.

Regards,

Alunduil
 
Old 12-06-2010, 12:34 PM   #11
fdelval
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understood.

Guys, screen is a great trick, looks like there is a trick for every need in linux, and lot of times, we dont know them.

Have you got a web with more useful tricks like that?

other than that, problem solved. thanks.
 
Old 12-06-2010, 12:59 PM   #12
fdelval
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oh, and by the way,
i have another problem like this in windows CMD console.
I know this is linux world, so i will just whisper lol, but, is there any similar command for windows?
 
  


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