ssh and shell through ssh : how to exit?

Question

I'm launching a distant script through SSH like this:

ssh user@ipaddress '~/my_script.sh'

Everything is going fine but once the script is finished, the connection is not closed. I Have to press CTRL-C to break the current connection.

I've tried the "exit" command in '~/my_script.sh' and it's useless. I've tried the "logout" command in '~/my_script.sh' and I get a message:

logout: not login shell: use exit

...

Any idea how I could do to close automatically and properly the SSH once the script is done?

(Modification for clarification :) Here's what's inside my script :

#!/bin/sh
path_sources_qas=/sources/QuickAddress/
path_qas_bin=/usr/bin/qas

umount_disque_qas()
{
  # Umount du disque 'qas' s'il n'avait pas été 'umount' :
  nom_disque_monte=`cat /etc/mtab | grep qas | awk '{ print $2}'`
  if [ "$nom_disque_monte" != "" ]
  then
    echo "For safety, umount : $nom_disque_monte"
    umount $nom_disque_monte
  fi

}

# Umount twice (we never know if a st***d guy mounted it twice) :
umount_disque_qas
umount_disque_qas

echo "--------------------------------"
echo "Install ISO quick address..."
nom_fichier_iso=`ls -t $path_sources_qas | awk '{if (NR==1) {print $1}}'`
echo "Mount disk $nom_fichier_iso..."
mount -o loop -t iso9660 $path_sources_qas/$nom_fichier_iso /mnt/qas
echo "Done."

# All the folders are like this :
# /usr/bin/qas/Data.old.10
# /usr/bin/qas/Data.old.11
# /usr/bin/qas/Data.old.12
# ...

echo "--------------------------------"
echo "Stopping QuickAdress server..."
cd $path_qas_bin/apps/
./wvmgmtd shutdown qaserver:2021
sleep 3
echo "Done."

# Get last number of the folder:
num_dernier_dossier_backup=`ls -Atd $path_qas_bin/Data.old* | awk '{if (NR==1) {print $1}}' | awk -F . '{print $NF}'`
# Add 1 :
let "num_dernier_dossier_backup += 1"
# Full name :
nom_dossier_backup=Data.old.$num_dernier_dossier_backup
echo "--------------------------------"
echo "Saving Data to $nom_dossier_backup..."
cd $path_qas_bin
mv Data $nom_dossier_backup
echo "Done."


echo "--------------------------------"
echo "Copying new folder Data..."
cd $path_qas_bin
cp -r /mnt/qas/Data .
echo "Done."

echo "--------------------------------"
echo "Deleting unused datas..."
cd $path_qas_bin/apps/
rm -f $path_qas_bin/Data/frxmos.dap
echo "Done."

echo "--------------------------------"
echo "Restart server..."
cd $path_qas_bin/apps/
./qaswvd &
sleep 3
echo "Done."
sleep 3

echo "--------------------------------"
echo "Check: server state: you should read 'OK':"
./wvmgmtd srvlist
echo "Done."

echo "--------------------------------"
echo "Check: active licences (only one here):"
./wvmgmtd licencelistread qaserver:2021
echo "Done."

echo "--------------------------------"
echo "Check: counters: number of addresses left:"
./wvmgmtd counterinforead qaserver:2021
echo "Done."

echo "--------------------------------"
echo "Check: Datasets avalaibles:"
./wvmgmtd datalistread current qaserver:2021
echo "Done."

echo "--------------------------------"
echo "Check: "meters" for "licence by click":"
./wvmgmtd meterslistread current qaserver:2021
echo "Done."

echo "--------------------------------"
echo "Removing virtual disk..."
umount_disque_qas
echo "Done."

echo "All done"
echo "Click 'Ctrl-C' to quit."

exit

When I launch it through SSH, it runs and at the end, I read "All done." so this means it reaches the last 2 lines.

Any idea how I could do to close automatically and pr

Solution 1

The exit in the shell script does not work because it is exiting from the script, not the shell. To exit from the shell after the script completes do

ssh user@ipaddress '~/my_script.sh && exit'

This will run the script then exit from the shell.

Solution 2

The ssh connection remains open when the process started by ssh (here, a shell) exits, if there are other processes that are still using it. I don't know the exact rules that the ssh daemon follows, but a connection is in use, at least, if the standard output of any child process is still connected to the original pipe provided by ssh. Compare:

ssh somehost 'sleep 5 &'  # exits after 5 seconds
ssh somehost 'sleep 5 >/dev/null &'  # exits immediately seconds

When you start a daemon, you should background it and close its file descriptors. At least, use this:

./qaswvd </dev/null >/dev/null 2>/dev/null &

You may want to add nohup in front; it won't make a difference here but would be useful if the script was run from a terminal. Many programs that are designed to act as daemon have a command-line options to get them to fork, close file descriptors, ignore signals and other niceties. Check in the qaswvd documentation if it has one. You could also investigate “daemonizer” utilities.

Solution 3

I saw this post when I googled for the solution of the same situation. Although it's kinda late to solve @Oliver's problem, since the accepted answer was clearly not working either to OP or me (don't know why it's accepted), I'd still like to post my own solution for future googler. It's simple: add a -f option in ssh command:

ssh -f user@ipaddress '~/my_script.sh'

EDIT

The effect of -f option is to put ssh in the background, so without any further option added it is possible that the connection is still alive even it seems that it's broken. One may refer to the answer given in another post on this site if interested.

Solution 4

Like Ignacio, I'm curious to know what's in your script.

Perhaps you could try and reduce your script to the smallest possible example that produces the error condition.

Or start from an empty script and add a command at a time until you see the problem, then you'll know what command causes your script to lock up.

If the empty script causes you a problem, you might want to investigate your ssh configuration, for example, is .bash_logout or some such called on exit that may cause an issue?

Solution 5

You may probably use jobs in your script. If that is the case shell just waits for your jobs to be finished and doesn't want to detach itself.

I'm not gonna repost, just will forward you http://en.wikipedia.org/wiki/Nohup#Existing_jobs

View more solutions

Comments

[Admin]

What's in the script?

[Admin]

@Olivier: Do you forward any ports (including the agent and X)? The ssh connection is closed when the command terminates and all TCP connections have been closed.

[Admin]

@Gilles : nope I just make a shell connexion to run a script, nothing is forwarded.

[Admin]

@Olivier: If you have a ~/.ssh/config, try without it, and pass the options -a -x (and no -o) to ssh to make sure there's no forwarding going on. If it still doesn't work, show the contents of the script.

[Admin]

@Olivier: does the script start any background job it may be waiting on? Unfortunately jobs does not seem to return anything when in an ssh script. Example: ssh <yourusername>@localhost '(ls; sleep 10 &); echo Done; jobs' will list files, display done and wait 10 seconds before returning.

[Admin]

I've modified my question: I've added the whole script. Maybe this may help.

[Dennis Williamson]

It should be exiting. The script is the shell.

[Wuffers]

@Dennis: It isn't working for him so this may work instead.

[Gilles 'SO- stop being evil']

@Mr. Man: Your command is equivalent to the original, except that it forces a shell to exist between sshd and the shell running myscript.sh. The exit you wrote will act when the script exits, which doesn't help. The only way your solution could work is if the script does something bizarre when its parent is sshd and doesn't do that bizarre thing when its parent is a shell.

[Wuffers]

How does it not help? Exit will close the shell and end the connection, correct? And is this not what the poster wants to do?

[Wermerb]

It doesn't work... :'(

[Gilles 'SO- stop being evil']

@MrMan: ~/my_script.sh && exit exits as soon as ~/my_script.sh exits. If the shell script didn't exit, your command would never get to the exit bit anyway. So it's just useless.

[Wermerb]

Thank you for your questions, I've now added the sample of my script in my question, and it definitely reaches the last two lines.

[Gilles 'SO- stop being evil']

@Olivier: You've added only irrelevant parts of your script. Post a script (and usage instructions if necessary) that would allow readers to reproduce your problem. Simplify the script as much as possible, but no further.

[OmnipotentEntity]

Olivier Pons, when you log in to a machine you are launching a shell as specified in your profile, when you run a script you are launching another shell which runs the commands and then exits. You've exited the first shell but not the second one.

[Wermerb]

@OmnipotentEntity Thank you. I've modified my question and added the whole script. Hope this helps. Thanks again

[Wermerb]

@Gilles Thank you. I've modified my question and added the whole script. Hope this helps. It seems that the problem may be the fact that I'm launching a background process (the line "./qaswvd &"). Could this be the origin of the problem?

[Wermerb]

I've modified my question and added the whole script. Hope this helps. It seems that the problem may be the fact that I'm launching a background process (the line "./qaswvd &"). If you're right, this could be the origin of the problem?

[asoundmove]

@Olivier: Yes, your main process will wait for the background process to stop before exiting. If you want something to keep running after you exit, you might want to try nohup. Not sure it works with ssh though, but give it a try it won't hurt.

[Gilles 'SO- stop being evil']

The backgrounded process is the problem, but nohup isn't directly the issue here as there is no terminal on the server side: I think the culprit is specifically the open file descriptor.

[christian.prins]

Yep, I think that is the problem, you can try to comment that or apply the hack from the link above

[madD7]

Caution: This (-f) will not work if the original script has prompt(s) for user input.

[Andy]

Had the same problem, and this works. The accepted answer do not work.

[Dami]

This is 10 years old. But for anyone who is trying to understand it, after your script runs and finished, then, exit will automatically happen, so && exit part could be useless. To check, run a script which takes sometime and check ssh activity on the remote instance/machine with a command like ss | grep -i ssh (through a seperate ssh login). You'll be able to see ssh connection of script stays alive only while the script gets executed then it automatically closes down.

[BuvinJ]

Aha! Here's the actual answer to make the script itself terminate the SSH session.