How can I run a second window manager?

Specifically, I'd like to run awesome-git at the same time as awesome . I've tried running the former from a shell in the latter: $ awesome-git/pkg/awesome-git/usr/bin/awesome […] E: awesome: main:653: another window manager is already running (can't select SubstructureRedirect) I get the same result if I add --replace . After changing to a different VT: $ awesome-git/pkg/awesome-git/usr/bin/awesome […] E: awesome: main:592: cannot open display (error 5) If I try to specify a display I get the following: $ DISPLAY=:1 awesome-git/pkg/awesome-git/usr/bin/awesome […] E: awesome: main:592: cannot open display (error 1) I tried to rm ~/.Xauthority , but that didn't help.