System crashed: fatal error restarting postgres

   A java application threw a major error when closing and it crashed my
system (including wiping out most of /tmp). After rebooting I su'd to user
postgres and tried to start postgresql-9.5.4, but this error displays:

postgres@salmo:~$ FATAL:  could not open shared memory segment
"/PostgreSQL.1804289383": Permission denied

   Please advise me on how I proceed to clear this and restart the
application.

TIA,

Rich