I ran into this and had a bit of trouble tracking a diagnosis down, so here it is for the archives in case anyone else runs into this.
A new installation of dovecot was failing to start, with these messages:
$ ./sbin/dovecot Error: service(imap-urlauth): net_listen_unix(.../var/run/dovecot/token-login/imap-urlauth) failed: Invalid argument Error: service(auth): net_listen_unix(.../var/run/dovecot/token-login/tokenlogin) failed: Invalid argument Fatal: Failed to start listeners
Some of the other processes seemed to be starting up fine, and they created sockets in the expected dir, but the above two wouldn't. stracing the processes didn't show a lot, but eventually I checked the length of the installation path, and found the above two socket paths were exceeding the maximum path length limit for Unix sockets -- 108 chars on my Linux boxen. I haven't checked SuS or Posix to see what the standards say the actual minimum required size for the maximum path length is -- it might be shorter yet on other systems.
Moving the installation to a less deeply nested hierarchy fixed the problem. I hope this saves someone else a headache someday.
C. C.
C. Mills