xpra-sudo is a wrapper script for Xpra that allows running the server as a
different user on the same system using sudo.
Just copy both scripts (xpra-sudo and xpra-sudo-ssh) to a directory in your
PATH. If you don't want xpra-sudo-ssh to mess up your path, you can also
place it somewhere else and set the variable SSH_HELPER in xpra-ssh
accordingly.
To start an Xpra session as user user, just run this command:
xpra-sudo start sudo:user:42 --start-child=urxvt
Xpra already supports connecting via SSH and xpra-sudo uses this mechanism:
it passes xpra-sudo-ssh as a custom SSH command to Xpra using the --ssh
option and changes sudo:user:42 to ssh:user@localhost+sudo:42.
xpra-sudo-ssh then recognizes the special hostname localhost+sudo and uses
sudo instead of SSH to run the command.
xpra-sudo works fine without the NOPASSWD option in sudo, but you might
nonetheless set it for your convenience and don't remember the syntax? Here's
my service for you, this allows the user julian to run commands as user:
julian ALL=(user) NOPASSWD: ALL