“perl/Tk unusable, cannot create main windows.” when running using “sudo”

Question

Full error message for sudo /usr/local/bin/tlmgr -gui (TeX Live 2017 manager) I'm getting on my OpenSUSE Tumbleweed with Gnome 3:

No protocol specified
perl/Tk unusable, cannot create main windows.
That could be a consequence of not having X Windows installed or started!
Error message from creating MainWindow:
  couldn't connect to display ":0" at /usr/lib/perl5/vendor_perl/5.24.1/x86_64-linux-thread-multi/Tk/MainWindow.pm line 53.
Tk::MainWindow->new() at /usr/local/bin/tlmgr line 4704.

No such error message when starting it without sudo (can't use it this way though since I installed it system-wide).

Same result if

• doing sudo -H
• doing it inside sudo -i (should be the same as sudo -H AFAIK)
• using pkexec instead of sudo (apparently the new replacement for gksu/gksudo?)

Then I tried being clever and played around with the X authority file (got the idea from posts such as https://unix.stackexchange.com/a/8250):

ln -s /run/user/1000/gdm/Xauthority /root/.Xauthority

# inside sudo -i then
export XAUTHORITY=/root/.Xauthority

After that I'm getting the error message with the following first two lines (and the rest the same as previously):

Invalid MIT-MAGIC-COOKIE-1 keyperl/Tk unusable, cannot create main windows.
That could be a consequence of not having X Windows installed or started!

Output for xauth list:

linux-q1xc/unix:  MIT-MAGIC-COOKIE-1  fa445a3c038b19300e8e45d4ae0ae55a
#ffff#6c696e75782d71317863#:  MIT-MAGIC-COOKIE-1  fa445a3c038b19300e8e45d4ae0ae55a

For sudo xauth list:

linux-q1xc/unix:10  MIT-MAGIC-COOKIE-1  7e608058d97a6bf4ae346879f4f5fd46

For ssh -X localhost xauth list:

linux-q1xc/unix:10  MIT-MAGIC-COOKIE-1  faaf2ba1724d5efe85aa5ef6cb4fcc52

For ssh -X root@localhost xauth list:

linux-q1xc/unix:10  MIT-MAGIC-COOKIE-1  e8168ff05f56458663f187ec38f744fe

After sudo ln -sf ~/.Xauthority /root

Output for xauth list:

linux-q1xc/unix:  MIT-MAGIC-COOKIE-1  fa445a3c038b19300e8e45d4ae0ae55a
#ffff#6c696e75782d71317863#:  MIT-MAGIC-COOKIE-1  fa445a3c038b19300e8e45d4ae0ae55a

Output for sudo xauth list:

linux-q1xc/unix:10  MIT-MAGIC-COOKIE-1  faaf2ba1724d5efe85aa5ef6cb4fcc52

Error message is again the first one.

xauth list output inside su - or using sudo -E (both where it works):

linux-q1xc/unix:  MIT-MAGIC-COOKIE-1  fa445a3c038b19300e8e45d4ae0ae55a                                                                                                                        
#ffff#6c696e75782d71317863#:  MIT-MAGIC-COOKIE-1  fa445a3c038b19300e8e45d4ae0ae55a

(Same as the first one.)

---

Works with ssh -X localhost tlmgr -gui. Also works inside su - and using sudo -E.

What is the underlying issue and how can it be solved?

Answer 1

As discussed in the comments the problem has to do with DISPLAY not being preserved with sudo, therefore using sudo -E is a possible solution.