ssh command, nohup and startx

j_kubik · 08-31-2010, 02:33 PM

Hello

I am having a server, which normaly doesn't use X. However i am using Xvfb when i connect to it via SSH, and seting tunneling to vnc port. Server script looks like

Code:

#!/bin/bash

xset -display :25 -q &> /dev/null

if [ $? != 0 ]; then
  echo "Starting X'es"
  nohup startx startkde -- Xvfb :25 -screen 0 1270x740x24 &> /dev/null &
else
  echo "X'es started"
fi

x11vnc -display :25

When I log in interactively via ssh, and then run the script, the Xvfb session lasts as long as i don't log out of kde - which means that i can freely create and close VNC connections without killing X sever.
However when i use ssh remote command to automate process (simply a saved putty session with set up host address, tunneling and script name) then as soon as i close VNC connection and script ends, the Xvfb also gets killed. It's happening despite using nohup. Is this behavior normal? How to make Xvfb last?

chrism01 · 08-31-2010, 11:15 PM

Not sure if this will work, but try 'source'ing the script, so it runs in the 'current' shell rather than invoking a sub-shell.

j_kubik · 09-01-2010, 03:08 AM

Quote:

Originally Posted by chrism01

Not sure if this will work, but try 'source'ing the script, so it runs in the 'current' shell rather than invoking a sub-shell.

Not sure what do you mean by 'source'ing script - i tried removing #!/bin/bash from begining of script file, but it didn't change anything. In both cases pstree looked like

Code:

     |-sshd-+-sshd---sshd---bash---konsole---bash---pstree
     |      `-sshd---sshd---runvnc-+-startx---xinit-+-Xvfb
     |                             |                `-startkde---kwrapper
     |                           `  -x11vnc

so i am guessing that there is only one shell created in both cases.

I think that difference between interactive and non-interactive mode of ssh may be in signals sent when terminating applications.

estabroo · 09-01-2010, 07:41 AM

when you do the ssh try adding -t -t to the options, could be that something is checking to see if it's in a tty or not and is behaving differently based on that

j_kubik · 09-14-2010, 03:46 PM

Sorry but it seems that i haven't stressed it enough - i am not using ssh, i am using putty from windows machine. I tried plain ssh (on linux client) and it works fine. problem shows up only with putty - i have no idea about possible differences.
I am sure that putty forces creating tty (as -t -t would also have done). Anyway it's not necessary, cause on linux client command like

Code:

ssh -f -L 55$1:localhost:5900 [user]@[host] /path/to/runvnc

is enough.

estabroo · 09-14-2010, 08:58 PM

have you tried cygwin ssh and see if it works?

chrism01 · 09-15-2010, 12:08 AM

Putty can go via telnet or ssh; your choice; just specify Port 22

j_kubik · 06-24-2011, 02:09 PM

Quote:

Putty can go via telnet or ssh; your choice; just specify Port 22

True. But server that Iam connecting to doesn't necesairly need to use telnet, right

Anyway, I guess using telnet it would be exactly the same.