I'm trying to execute the command:
ssh nvidia#ubuntu-ip-address "/opt/ads2/arm-linux64/bin/ads2 svcd&"
This works so far except that it hangs in the remote terminal when "/opt/ads2/arm-linux64/bin/ads2 svcd&" is executed, unless i enter ctrl+c. So I'm looking for a command that, after executing the command, exits from the remote terminal and continue executing the local bash script.
thanks in advance
When you run a command in background on a terminal, regardless of weather it be local or remotely, if you attempt to logout most systems will warn you have running jobs. One further attempt to logout and your jobs get killed as you exit.
In order to avoid this you need to detach your running jobs from terminal.
if job is already running you can
disown -h <jobspec ar reported by jobs>
If you want to run something in background and then exit leaving it running you can use nohup
nohup command &
This is certainly ok on init systems ... not sure if it works exactly like this on systems that use systemd.
Related
I am building a rest API with java, when the endpoint gets called. I will spawn a virtual shell with RunTime.getRuntime().exec(My_script.sh)
My script then proceeds to ssh into a server, create some files, and most importantly... I needs to run a script that sits on that server to process the files.
I run the command with
nohup myscript.sh > /dev/null/ 2>&1 &
I also added sleep 5 because i read that nohup may take a second to get things started
The script runs until the shell disconnects and dies.
So as of now
java application launches a shell
the bash script initiates a ssh connection and creates a subshell that runs a secondary script
while in the subshell, with our second script, we create some files and then we call nohup script to start the script
subshell exits and terminates
main shell exits and terminates
script we called disconnects and never finishes running
Some things I have tried
I have tried calling the script from the ssh connection,
psudo example
ssh user#host "nohup script.sh > /dev/null/ 2>&1 &"
also tried with different quotes
ssh user#host "nohup script.sh > /dev/null/" 2>&1 &
Another thing I can potentially do is keep the initial shell open. So that the script wont die when it disconnects... because it never will
I have looked into to other options like screen but I don't think it will be useful if the machine that initiated the script gets completely terminated after it starts
Things to note
I don't have control over the Linux box I ssh into, so I cannot install packages on that machine. I can however install packages on my shell
I have a script that executes a sudo command that runs a script that executes a binary (java). That binary seems to receive SIGHUP when the the login session ends (I run my script in an SSH session from my laptop, so network disconnects when I commute). The SIGHUP causes the binary process to abort.
I tried calling the sudo command with 'nohup' and trapping SIGHUP, with no success. I can't change the sudo command (e.g. 'sudo nohup' instead of 'nohup sudo'), or the script I execute with it (due to security constraints).
What other options exist? I know I can do a double fork, but I want the binary to run in the foreground while the session is live (it is running a query, so when the session is alive, I want to be able to wait for it to finish interactively and see results, but if I hangup, to have it continue to run)
I want to run a command silently via ssh and exit the shell, but the program should continue running.
I tried screen and nohup, but apparently with those it executes 3 processes instead of 1:
user:/bin/bash ./[script]
root: sudo [commandInTheScript]
root: [commandInTheScript]
What am I doing wrong?
P.S.: The thing is that I want to run this command with the Workflow app (iOS), but the app waits until the command is finished, so it freezes 'forever'
To run your process back ground, at end of the command you have to use &.
In your case, you have to run without session since you are planning to exit from ssh after execute the command, so you need nohup
nohup <command> &
nohup < command > &
This makes your command runs on background and shows its PID
How did you use nohup?
Eg.
nohup ruby server.rb &
Ampersand (&) is necessary to let command run in the background.
I'm running some script on remote server using ssh. The task is downloading images to remote server. I'm wondering will the script keep running after I log out the ssh session? Why? Could anyone explain in detail?
If you want the script keep running after logout you need to detach it from the terminal and run it in the background:
nohup ./script.sh &
If you close the terminal where you launched a process in, the process will receive SIGHUP and unless it handles it this means the process will get terminated. HUP means hang up, like in a phone call.
The nohup command can be used to start a process and prevent it from SIGHUP signals getting send to it. An alternative would be to use the bash builtin disown, which does basically the same:
./script.sh &
disown %1
Note that the 1 represents the job id. If you running multiple processes in the background you need to specify the correct job id.
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.