If you use sudo, you may have noticed that, with Fedora Core 5, you just can’t exec a graphical application as root (for example) if you haven’t actually logged in as root in your X environment (you never do that! Do you?).
You have probably encountered this type of message:
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$ sudo kcalc
Xlib: connection to ":0.0" refused by server
Xlib: Invalid MIT-MAGIC-COOKIE-1 key
kcalc: cannot connect to X server :0
To be able to launch a graphical application as root, the XAUTHORITY environment variable must be copied to the shell launched by sudo.
Just run:
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$ sudo visudo
This will open the /etc/sudoers file.
After _XKB_CHARSET, just add XAUTHORITY. This should now look like:
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Defaults env_keep = "COLORS DISPLAY HOSTNAME HISTSIZE INPUTRC KDEDIR \
LS_COLORS MAIL PS1 PS2 QTDIR USERNAME \
LANG LC_ADDRESS LC_CTYPE LC_COLLATE LC_IDENTIFICATION \
LC_MEASUREMENT LC_MESSAGES LC_MONETARY LC_NAME LC_NUMERIC \
LC_PAPER LC_TELEPHONE LC_TIME LC_ALL LANGUAGE LINGUAS \
_XKB_CHARSET XAUTHORITY"
Now, you can try:
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$ sudo kcalc
It’ll work!