So I've recently started using Ubuntu on WSL2, and I'm trying to use X2Go as my X window system to run GUI apps. I start up the Ubuntu WSL, and run the SSH daemon. Then, I use the x2go client on Windows to connect to the X2Go server running on the Ubuntu WSL, and it all works fine.
But I want to normally use the Windows Terminal for running BASH, and run the GUI applications in the X2Go client. For this, the $DISPLAY environment variable needs to be set.
In this case, the value for the environment variable would be DISPLAY=:60.0 (where 60 is the display number in the screenshot above and 0 indicates monitor 0). But, every time I restart the client session, I get a different display number (previous display number + 1), and the value of the environment variable needs to be changed again.
Is there any way I can make the display number consistent and set the DISPLAY environment variable in .bashrc so that I do not need to export it every time? I'm new to this, so let me know if something doesn't make sense or if there's an entirely different approach that's better for this.
Not exactly what you are after, but you can find the display number by looking at the full command line for the x2goagent process -- the display will be at the end:
$ pgrep -a x2goagent
So if you add the following to your .bashrc
x2g() {
export DISPLAY=`pgrep -a x2goagent | rev | cut -d " " -f 1 | rev`
}
you can use the x2g function at the bash prompt to set your DISPLAY variable to wherever X2Go has decided to put the screen this time:
$ x2g
$ echo $DISPLAY
:55
It's not ideal because you need to enter this command for every shell, and do so after you have started the X2Go session. But it's a bit easier than finding the display manually every time.
Note that if you were to use a terminal executing within the WSL environment where the X2Go agent is running, DISPLAY is set automatically to the correct value (as long as you don't redefine it somewhere in your .bashrc or equivalent). I understand from your question that you are working from the Windows terminal running bash, however, you could potentially use (say) an xterm running in WSL for launching X11 apps, then continue to use the Windows terminal for everything else.
Related
I have a application that launches xterm and dumps uart logs. I am able to see it launch and dump the logs in the GUI. However, Using a remote session I want the xterm output to be running as a background process somewhere so that I can switch back and forth within a single terminal.
Using GUI
Using remote terminal (SSH)
$ xterm
xterm: Xt error: Can't open display: :0
I tried to do something like, but failed to work -
alias xterm="/bin/bash -c"
I don't want to have X forwarding and launch a window on my local machine as well.
If you just need the logs, you most likely don't need an X server or xterm.
You can simply run the target command itself. From your screenshot it looks like the command might be telnet 127.0.0.1 <port_number>. You can find it from the script that your application launches, or with ps -ef when it's running. If it's an UART, then you can also use minicom or socat to connect directly to serial port without any extra programs. This way, you don't even need telnet.
You can combine this command with either screen or tmux so that it's running in the background and you can switch to it from any terminal or console. Just run screen with no arguments, then run the command on virtual screen. Detach with CTRL-a d, and your command will continue to run in the background ready for you to reconnect to it at any time with screen -r.
Moreover, screen can also connect to serial port directly so you get two for the price of one.
The thing with xterm is that it will not write the logs anywhere except in the graphics buffer, and even there it will be only as flashing pixels which is not suitable for any processing. If you insist on going that way, you have several options:
Change the script that application runs (might not be possible depending on your situation)
Replace /usr/bin/xterm with your dummy script that just runs bash instead of xterm, and redirects the output to a file (ugly, but you could probably avoid breaking other applications by changing PATH and putting it somewhere else). In your script, you can use bash's redirection features such as >, or pipe output to tee.
Start a VNC server in the background and set the DISPLAY environment variable when you run your application to the number of virtual screen. In this case, any windows from application will open on VNC virtual screen and you can connect to it as you please.
Use xvfb as a dummy X server and combine it with xterm logging, etc.
Solution 1: Fake xterm on X11-less systems
You can also create a wrapper script that replaces xterm with another function. Test this out on a laptop with X11:
$ function xterm {
echo "hello $#"
}
$ xterm world 1
hello world 1
$ export -f xterm
$ /bin/xterm # opens a new xterm session
$ xterm world 2 # commands executed in second terminal
hello world 2
This means that you've replaced the command xterm for a function in all of the child processes.
Now, if you already know that your script will work in a terminal without xterm, you could create a function that accepts all of the parameters and executes it. No need for complicated screen stuff or replacing /usr/bin/xterm.
Solution 2: Dump UART data for the winz
If you want to save all of the uart data into a file, this is easily fixed by creating a screen session and a log file. Below the command will create a session named myscreensessionname that listens on the serial connection /dev/ttyUSB0 and writes its data to /home/$USER/myscreensessionname.log.
$ screen -dmS myscreensessionname -L -Logfile /home/$USER \
/myscreensessionname.log /dev/ttyUSB0 115200
Note that if you're going to use multiple screen sessions, you might want to use serial ids instead of /dev/ttyUSB0. You can identify the connections with udevadmin as follows.
$ udevadm info --name=/dev/ttyUSB0 | grep 'by-id'
S: serial/by-id/usb-FTDI_TTL232R-3V3_FTBDBIQ7-if00-port0
E: DEVLINKS=/dev/serial/by-id/usb-FTDI_TTL232R-3V3_FTBDBIQ7-if00-port0 /dev/serial/by-path/pci-0000:00:14.0-usb-0:4.4.4.1:1.0-port0
Here, instead of /dev/ttyUSB0, I would make use of /dev/serial/by-id/usb-FTDI_TTL232R-3V3_FTBDBIQ7-if00-port0.
EDIT:
You can attach the screen session with the following command. Once in the screen session, press crtl+a, and press d to detach.
$ screen -Dr myscreensessionname
To view all of your screen sessions:
$ screen -list
There is a screen on:
2382.myscreensessionname (04/02/2021 10:32:07 PM) (Attached)
1 Socket in /run/screen/S-user.
I have a bash script that I have to regularly run on a remote server. Part of the script includes running a backup which takes a while, and after it has run, I have to hit "Y" to confirm that the backup worked before the script will continue.
I would like to know if there is a way to get my laptop to make a beep (or some sort of sound) when that happens. I know that echo -e '\a' makes a beep, but if I run it from within a script on the remote server, the beep happens on the remote server.
I have control of the script that is being run, so I could easily change it to do something special.
You could send the command through ssh back to your computer like:
ssh user#host "echo -e '\a'"
Just make sure you have ssh key authentication from your server to your computer so the command can run smoothly
In my case the offered solutions with echo didn't work. I'm using a macbook and connect to an ubuntu system. I keep the terminal open and I'd like to be informed when a long running bash script is ready.
What I did notice is that if I shutdown the remote system then it will beep the macbook and show an alarm icon on the relevant tab. So I have now implemented a bit of dirty workaround:
sudo shutdown 1440 && shutdown -c
This will initiate the system to shutdown and will immediately cancel the request. And I do get the alarm beep + icon. You will need to setup sudo to allow the user to permit shutdown. As it was my own remote server it was no problem but could limit the usability for others.
I am trying to do some work on a remote machine and disconnect without terminating the work. I have tried both nohup and screen, unfortunately it is not working out. After I type exit to logout my work also terminates immediately.
I am trying to run 108 simulations on a remote machine. For that purpose I have written a script named batch.sh which runs one simulation after the other until all 108 are done. The program that actually runs a simulation launches 5 programs in 5 different terminals (using xterm -e). I run batch.sh using:
nohup bash batch.sh &
As long as I am connected everything works just fine. If I disconnect and then reconnect to check whether everything is working as it should...no joy :(
Are there any caveats I am overlooking? Possibly because my program launches other programs in external terminals?
UPDATE
If I use the suggestions of adding -oForwardX11=no to ssh and unset DISPLAY before launching my script I get these errors:
nohup: ignoring input and appending output to nohup.out
In nohup.out I have these messages:
xterm Xt error: Can't open display:
xterm: DISPLAY is not set
Apparently your script/program is trying to launch xterm on its own. These days many systems enable X11 forwarding for their SSH client by default - as a result the DISPLAY variable is set in your shell session but becomes invalid once you disconnect. Therefore, as long as you are connected to the remote system, the xterm processes can access the X server on your local machine through the SSH connection, but die once that connection is severed.
I have occasionally encountered the same issue with Java programs that use e.g. the Java AWT subsystem to generate image files, even when there is no actual graphical window. You should first see if your program will somehow adapt if there is no X server available. One option is to disable X11 forwarding with the -oForwardX11=no option to ssh:
$ ssh -oForwardX11=no user#server.host.name
You could also try unsetting the DISPLAY environment variable before starting your script and see what happens.
However, if your program is launching xterm windows indiscriminately then you'd have to make it e.g. use an output file on the server instead - by modifying it, if necessary. As an added advantage, you would get rid off the network load and timing overhead involved with forwarded X connections.
If you cannot change the way your program works and you do not actually care about the output in those xterm windows, then you could try launching a virtual framebuffer X server on the remote system and have your script use that for xterm.
I'm opening an ssh-session to a remote server and execute a larger (around 1000 lines) bash-script on the remote machine. It involves several very CPU-intensive calls which run for up to three minutes each. To track the scripts progress it echoes messages placed at several points in the script.
In general the script runs smoothly. From time to time the script runs trough (the resulting file on the remote machine is correct) but the output to the terminal stops. Ctrl-C doesn't help, no prompt, just a frozen session. top in a separate session shows normal execution of the script.
My question: How keep the session alive?
local machine:
$ sw_vers
ProductName: Mac OS X
ProductVersion: 10.9
BuildVersion: 13A603
remote machine:
$ lsb_release -d
Description: Ubuntu 12.04.3 LTS
Personally, I would recommend using screen or tmux on the remote terminal for exactly this reason.
Those apps will allow the remote process to continue even if your local SSH session times out.
http://www.bangmoney.org/presentations/screen.html
http://tmux.sourceforge.net/
Start a screen on the remote machine and run your command from it:
screen -S largeScript
And then
./yourLargeScript.sh
Whenever your ssh session gets frozen, you can kill it with ~.
If you ssh again, you can grab back your screen by:
screen -dr largeScript
Make it log to a file instead (perhaps via syslog), and tail that file from wherever is convenient for you. This also helps detach the script so you can run it headless, from a cron job, etc. Also, if the log file has read access for others, they too can monitor it.
I am trying to keep gvim as my default editor when I use VNC to my machine. But want to keep vim as my default editor when I am logged in through SSH. I am not sure how to differentiate in my .bashrc file to do this automatically. Similarly, is there a way I can know the session is through a console directly connected with my machine.
Thanks
It sounds like you don't actually care whether it's SSH, VNC or console. You care whether you have a GUI to run gvim on or not.
You can check this with $DISPLAY:
[[ $DISPLAY ]] && export EDITOR=gvim || export EDITOR=vim
This will set your editor to gvim for VNC as well as XDMCP, NX, Chromoting, local graphical logins, ssh with graphical forwarding, and anything else with an X11 display.
It will set your editor to vim for regular SSH logins as well as Telnet, rsh, serial consoles, local logins, and all other non-X11 based logins.
The environment variable $SSH_AUTH_SOCK should be set in any SSH session. So in your .bashrc, you could have
if [ -n "$SSH_AUTH_SOCK" ]
then
# code for SSH sessions here
fi
As for determining whether you're on a directly attached console, see this question; to get the tty name in the shell (rather than from within a C program), use the tty command.
Thanks for the hint from ajk
I looked into the variables set and saw that VNCDESKTOP is set only in case of vnc.
I used the way suggested above and it works now.
Though I still hope someone can suggest if this is a complete solution or not