[postgres@single ~]$ psql
psql (9.6.1)
Type "help" for help.

postgres=#
无需输入密码，可以修改pg_hba.conf文件来要求输入密码。
设置完成后需要重启之后生效。

以下为设置不需要密码的情况：

[postgres@single pgdata]$ vi pg_hba.conf
# "local" is for Unix domain socket connections only
local   all             all                                   trust
# IPv4 local connections:
host    all             all             127.0.0.1/32          trust
"pg_hba.conf" 93L,4466C written                                                                                                                                                                                         
[postgres@single pgdata]$ psql
Password:
psql: fe_sendauth: no password supplied
[postgres@single pgdata]$ pg_ctl stop
LOG:  received fast shutdown request
LOG:  aborting any active transactions
LOG:  autovacuum launcher shutting down
LOG:  shutting down
waiting for server to shut down....LOG:  database system is shut down
 done
server stopped  
[postgres@single pgdata]$ pg_ctl start
server starting
[postgres@single pgdata]$ LOG:  database system was shut down at 2016-11-17 16:54:37 CST
LOG:  MultiXact member wraparound protections are now enabled
LOG:  database system is ready to accept connections
LOG:  autovacuum launcher started

[postgres@single pgdata]$ psql
psql (9.6.1)
Type "help" for help.

postgres=#