Translations:Steam/108/en
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Logout, and then login. This allows the display manager or xinit to process /etc/X11/xinit/xinitrc.d/00-xhost and automatically grant all local connections to the X server from the local UID. This will not work if the Steam UID is different to that of the local UID. Either set the same UID when creating the Steam user, as was mentioned earlier, or if the Steam user already exists change the Steam UID with usermod -u <UID> steam to match the local UID.