X11 trouble shooting
"cannot open display" as another user
When trying to open a program as another user (in this case, I'm trying to execute gdmsetup as root), if you get an error like::
# gdmsetup (gdmsetup:9178): Gtk-WARNING **: cannot open display:
export DISPLAY=:0 as that user, and
xhost + as the user that
own the X session.
A reference that may help is here.
Wrong font size when porting to another system/distro
DPI (dots per inch) change among Unix systems and GNU/Linux distributions. There is no default configuration. Whenever you port your application to another system, it is a good idea to check if DPI match.
To change DPI in a Unix system, with Xorg, does that:
First, in your
~/.Xresources file (or wherever it be), insert the
85.0 for the best DPI for you. Then, load the file into X
$ xrdb -load .Xresources
Now, you have to tell the driver about the new DPI you want to use::
$ xrandr --dpi 85
*Note*: Not all drivers support changing it at runtime from the
should be able to set it directly in your X server configuration file
This two resources were really valuable for me:
X Server DPI
Xorg - Display size and DPI - ArchWiki
Although using -X, cannot forward X11
There are many causes to this problem. You should be able to check what is
causing this by checking ssh debug output, so connect with
ssh -v -X. The
-v option will enable debug output we need. Check if you see the
debug1: Remote: No xauth program; cannot forward with spoofing.
If you see this, it means that your system probably lacks the xauth program. Install it.
xterm insists in printing strange character when I type Alt+key
Many applications use Meta key as a keyboard shortcut to perform some operations. In some computers that lack a Meta key, the Alt key is normally used as meta.
You might want to use Meta key in some text applications. In irssi_, for
instance, I use it in combination with other keys to change windows. The
problem comes when pressing the Meta key prints a non-ASCII instead of sending
the correct signals (ESC characters). Meta-Q, for instance, will print
~. This is because xterm is not configured to send ESC when making a
combination with the Meta key. To change that behaviour
you can add the following like to your "X resources" file::
The reference that help me:
Irssi - Startup How-To