psql: FATAL: no pg_hba.conf entry for host "[local]", user "root", database "postgres", SSL off

# psql postgres
psql: FATAL:  no pg_hba.conf entry for host "[local]", user "root", database "postgres", SSL off
Solution is to move to the "postgres" user's shell before entering the PostgreSQL client:
# su - postgres
Last login: Fri Feb 23 22:24:18 EET 2018 on pts/0
-bash-4.2$ psql postgres
psql (9.2.23)
Type "help" for help.

postgres=#
Byat