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How to make a program continue to run after log out from ssh? [duplicate]
(6 answers)
Closed 3 years ago.
I need to run a Perl script for several days processing something. On a linux Centos server, from the SSH terminal I run this command:
nohup perl script.cgi 2>&1 &
This runs the script in the background and writes the output to nohup.out.
The problem when I close the SSH terminal or even my internet connection disconnects the script terminates.
I need to keep this command running in the background on the server after I close
the SSH terminal.
You can use Terminal multiplexer tools like screen, byobu or tmux.
I personally use screen. so install it on remote server via sudo apt-get install screen.
ssh into server
open screen session by screen -S sessionname
Now run your command (background/foreground both works)
now detach to your session by command ctrl+a then press d.
Now shut your pc and enjoy
now come back ssh into server then use command screen -x sessionname to reconnect the detached session.
Hurray! script is still running.
you can either use screen or run the command using supervisor in linux systems.
you can install screen using sudo apt install screen
then use following command to run it.
screen -S test_command
nohup perl script.cgi 2>&1 &
Then press ctrl+a and ctrl+d to leave that session running for whatever amount of time required until your server reboots.
If you want to stop the command use screen -x test_command, then ctrl+c and use ctrl+a and ctrl+d to close screen or ctrl+a and ctrl+d to leave the screen session as it is.
The only way I was able to run the command and exit the shell and keep the command running is using the "at" tool to schedule the job like this using the full script path:
echo "perl /home/username/www/script.cgi" | at now + 1 minute
Related
First of all, this may seem like a duplicate question but I have searched stack overflow/various other forum sites and still haven't managed to find a solution.
A few example forum posts I have reviewed to prove I've done my research before asking a question:
https://superuser.com/questions/130443/remotely-run-script-on-unix-get-output-locally
https://linuxconfig.org/executing-commands-remotely-with-ssh-and-output-redirection
https://zaiste.net/posts/few-ways-to-execute-commands-remotely-ssh/
https://unix.stackexchange.com/questions/474533/get-output-of-this-command-from-another-server-via-ssh
Run ssh and immediately execute command
https://www.cyberciti.biz/faq/unix-linux-execute-command-using-ssh/
There's hundreds more but I won't include them all.
I essentially need a shell script to open a command prompt on windows, login to a remote linux system and run a command.
I am aware this can be done with the following:
start cmd /k ssh user#host ls
But the problem with the above is that the ssh connection is closed upon completion of the task.
I am also aware I can keep the ssh connection open by adding:
bash -l
in some cases.
For my use case, I need to run a launch file for ROS (robot operating system) and for this I need to see the output from the command.
And when attempting to run roslaunch launchFile.launch (in place of ls above):
start cmd /k ssh user#host "roslaunch launchFile.launch"
the command prompt returns
bash: roslaunch: command not found
I've obviously sanitised the specific name of my launch file but
roslaunch launchFile.launch
runs perfectly if I login to the linux PC first:
ssh user#host
then run the command.
I have achieved this exact use case on MacOS but I now need reimplement the same solution on windows:
osascript -e 'tell app "Terminal"
do script "ssh quantum#172.23.199.1 \n
roslaunch launchFile.launch"
end tell'
Thanks in advance for any help or advice.
Try this :
start cmd /k ssh user#host "/full/path/to/roslaunch launchFile.launch; exec /bin/bash"
I'm using Linux (Mint 20.3) to run a simple Minecraft server and I want to be able to start the server with a keyboard or desktop shortcut. I also want to be able to interact with the server in a terminal after it starts. I'm currently using the server software supplied by Mojang. I wrote a little program to get things started:
#!/bin/bash
cd /home/trevor/Minecraft_Server
LD_LIBRARY_PATH=. ./bedrock_server
exec $SHELL
I can get the server to run but I have no clue how to get it to open a terminal window so I can interact with the server. I'm relatively new to Linux so any input would be greatly appreciated.
you can use screen to detach and attach to run commands into the minecraft terminal.
to install screen:
apt-get install -y screen
To launch, update your script with something like:
screen -S mcs ./bedrock_server
to reattach, run the following in a terminal:
screen -r mcs
Use screen in your script to reattach to bedrock process.
Install screen:
apt-get install screen
Define your script as:
#!/bin/bash
export LD_LIBRARY_PATH=.
cd /home/trevor/Minecraft_Server
screen -d -m -S bedrock ./bedrock_server
After invoke your script, screen creates a socket that can be used to reattach to your script terminal. You can show screen sockets available with:
screen -ls
Parameter -S defined 'bedrock' as the socket name. So you can open another terminal as you like and reattach to the bedrock process with:
screen -r bedrock
If you detach the screen with CTRL+C the screen will be closed and so the minecraft bedrock server. To deattach without close the process you must use CTRL+A and CTRL+D.
I want to run "screen" on a debian linode server, starting up over a ssh terminal window. I'd like a shell script to start and detach a screen, so that a process can continue when I log off. I'd also like the logging file screenlog.0 to be produced, so that there's a record if the process crashes.
But there's a problem in getting the log file to write. Locally, on a mac terminal window,
% screen -dm -L sh -c 'echo hello'
works fine, "hello" gets written to screenlog.0. But the same command issued in a ssh window to the server executes, but nothing gets written.
However, if in that window I go into screen,
% screen -L
and then do some stuff, the activity is written to screenlog.0 (on the server).
What am I missing?
It turns out that the screen() command can have problems. The above command sends no output to screenlog.0 under 'Debian GNU/Linux 9 (stretch)' , while 'Ubuntu 14.04.1 LTS' writes the odd message, "error: could not start server! try running as root!", to screenlog.0, even when running as root. 'Linux Mint 18.1' and MacOSX run correctly.
I was advised to use the venerable unix command "nohup" to solve my problem of detaching a process and logging its output, even when you close the ssh connection. Ordinarily, when you close a terminal window, the signal SIGHUP is sent to any processes that were started there. But
% nohup myprog > logfile.txt &
works perfectly. Old way, good way.
I am using SSH to start a background process on a remote server. This is what I have at the moment:
ssh remote_user#server.com "nohup process &"
This works, in that the process does start. But the SSH session itself does not end until I hit Ctr-C.
When I hit Ctr-C, the remote process continues to run in the background.
I would like to place the ssh command in a script that I can run locally, so I would like the ssh session to exit automatically once the remote process has started.
Is there a way to make this happen?
The "-f" option to ssh tells ssh to run the remote command in the background and to return immediately. E.g.,
ssh -f user#host "echo foo; sleep 5; echo bar"
If you type the above, you will get your shell prompt back immediately, you will then see "foo" output. Five seconds later you will then see "bar" output. In the meantime, you could have been using the shell.
When using nohup, make sure you also redirect stdin, stdout and stderr:
ssh user#server 'DISPLAY=:0 nohup xeyes < /dev/null > std.out 2> std.err &'
In this way you will be completely detached from the remote process. Be carefull with using ssh -f user#host... since that will only put the ssh process in the background on the calling side. You can verify this by running a ps -aux | grep ssh on the calling machine and this will show you that the ssh call is still active, but just put in the background.
In my example above I use DISPLAY=:0 since xeyes is an X11 program and I want it started on the remote machine.
You could use screen to run your process on this screen, detach from screen Ctrl-a :detach and exit your current session without problem. Then you can reconnect to SSH and attach to this screen again to continue with your task or check if is finished.
Or you can send the command to an already running screen. Your local script should look like this:
ssh remote_user#server.com
screen -dmS new_screen sh
screen -S new_screen -p 0 -X stuff $'nohup process \n'
exit
For more info see this tutorial
Well this question is almost 10 years old, but I recently had to launch a very long script (taking several hours to complete) on a remote server and I found a way using the crontab.
If can edit your user's crontab on the remote server, connect with ssh to the server, edit the crontab and add an entry that will start your script the next minute. Let's say it's 15h03. Add this line :
4 15 * * * /path/to/your/script.sh
save your crontab, wait a minute for the script to be launched. Then edit again your crontab to remove this entry.
You can then safely exit ssh, even shut down your computer while the script is running.
I'm connecting to my ubuntu server using ssh. I start an encoding program using a command. However, it seems that when my ssh session closes (because I started it on a laptop which went to sleep). Is there a way to avoid this (of course preventing my laptop from sleeping is not a permanent solution).
Run your command with nohup or use screen
nohup is better when your program generate some loging output because it's forward to file and then you can check it, but with screen you can detach ssh session and when you log again you can restore your work-space. For encoding I'll use nohup. It is easier and you probably run it in background, so you really don't need detaching
Screen is the best for you.
screen -S some_name
than run it. Detach it with: ctrl+a d
Next time, attach it with:
screen -rd some_name
You can have more runnning screens. To show the list of them:
screen -ls
Install "screen" on your ubuntu server, that way you can start any program in your session, disconnect the output of the program from your current session and exit.
Later when you connect again to your server, you can restore the program which will continue running and see its progress.