DISPLAY environment variable not set

Question

I am using a Amazon Linux 2 (a Fedora/Cent OS like distro) EC2 machine with the Deep Learning AMI (Amazon Linux 2) Version 30.1 AMI.

I want to use xclip and gedit in the remote instance. But if I type in xclip I get

Error: Can't open display: (null)

If I do gedit filename I get

(gedit:6012): Gtk-WARNING **: 00:18:40.117: cannot open display:

I have already gone through the following links:

1. https://github.com/microsoft/WSL/issues/4933
2. xsel: Can't open display: (null)
3. https://askubuntu.com/questions/1035903/how-can-i-get-around-using-xclip-in-the-linux-subsystem-on-win-10
4. https://www.cyberciti.biz/faq/error-couldnt-open-display-null-and-solution/
5. https://superuser.com/questions/310197/how-do-i-fix-a-cannot-open-display-error-when-opening-an-x-program-after-sshi
6. https://www.linuxquestions.org/questions/linux-software-2/xdotool-error-can%27t-open-display-null-4175527094/
7. https://serverfault.com/questions/765606/xming-cant-open-display-error
8. https://serverfault.com/questions/425346/cant-open-display-x11-forwarding-cent-os
9. https://askubuntu.com/questions/305654/xclip-on-headless-server/305681#305681

And thus have,

1. installed xauth
2. manually set the environment variable DISPLAY to export DISPLAY="IP_of_remote_machine:0" export DISPLAY="127.0.0.1:0" export DISPLAY=:0.0 export DISPLAY=localhost:0 When I do this I get

   (gedit:6053): Gtk-WARNING **: 00:23:36.052: cannot open display: 127.0.0.1:0
   

3. I have tried the -Y flag (-X is not an option cause of security, also -X doesn't work)
4. I have added ForwardX11 yes in the client side's ~/.ssh/config and X11Forwarding yes in the server side's /etc/ssh/sshd_config

Nothing works. Any directions?

EDIT:

I also watched this video which says that DISPLAY should not be hardcoded. But my DISPLAY is not set automatically. When I do a echo $DISPLAY I get nothing.

So I did a xauth list which gave me

ip-x-y-x.ec2.internal/unix:10  MIT-MAGIC-COOKIE-1  c84bcd904dd50f7776f667eca7a480f5

so I did

export DISPLAY=localhost:10.0

Still I get the same error.

Solution 1

I solved this problem by simply hardcoding $DISPLAY as :1,

export DISPLAY=:1

in my .bashrc file.

I however, still don't understand why this works. Here is the output of xauth list

ip-172-31-74-230.ec2.internal:1  MIT-MAGIC-COOKIE-1  8a44b41e42cae52c6acd4747763bb985
ip-172-31-74-230.ec2.internal/unix:1  MIT-MAGIC-COOKIE-1  8a44b41e42cae52c6acd4747763bb985
ip-172-31-74-230.ec2.internal:2  MIT-MAGIC-COOKIE-1  e24f36d585762b0c0fe24010b99e448d
ip-172-31-74-230.ec2.internal/unix:2  MIT-MAGIC-COOKIE-1  e24f36d585762b0c0fe24010b99e448d
ip-172-31-74-230.ec2.internal/unix:10  MIT-MAGIC-COOKIE-1  c84bcd904dd50f7776f667eca7a480f5

Solution 2

The DISPLAY environment variable is exported to any x-Client program that needs the specification for the x-server on your original machine (the PC you typed in the ssh command on).

The way I do this these days, is to be lazy and ask the environment:

 $ env | grep SSH
SSH_CLIENT=192.168.182.159 45462 22
SSH_TTY=/dev/pts/28
SSH_CONNECTION=192.168.182.159 45462 192.168.188.120 22

SSH_CLIENT and SSH_CONNECTION show you the IP address of your origin terminal. In which case I export the following:

 $ export DISPLAY="192.168.182.159:0.0"
 $ xeyes

Start-up xeyes to satisfy yourself that everything is working for you. Your display is ready to use.

Comments

[icarus]

When you use ssh -Y user@remote are you in some kind of terminal? What happens if you say echo $DISPLAY in that terminal before you use ssh? You shouldn't need to set DISPLAY manually, that is what the -Y should be doing automatically.

[Kenster]

Try running ssh with the "-vv" option to print debugging info. Then edit your question to include the exact ssh command that you ran, the debugging output, and any relevant entries from your .ssh/config file.