It transfers contents of a local file ~/.backpack and itself to remote host, sources it and continues with normal ssh session.
works best as alias ssh=backpack won’t create any files on remote hosts (even temporary) tries to fallback to normal ssh when remote shell is not bash self-replication allows you to use backpack again directly from remote host, in this case backpack will keep original local file as you go deaper from host to host.”
dbus can also start a program. For example when one notification was generated and no notification daemon is running, then dbus launch one to handle the request.