[postgres@rhel73 data]$ [postgres@rhel73 data]$ psql -l -p 5432                                  List of databases   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   access PRivileges   -----------+----------+----------+-------------+-------------+----------------------- postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |  template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +           |          |          |             |             | postgres=CTc/postgres template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +           |          |          |             |             | postgres=CTc/postgres test      | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | (4 rows)[postgres@rhel73 data]$ psql -l -p 5433psql: could not connect to server: No such file or directory ------>>>從此處可以看出,PG是用端口號來區分不同的cluster.	Is the server running locally and accepting	connections on Unix domain socket "/tmp/.s.PGSQL.5433"?[postgres@rhel73 data]$ exit[root@rhel73 ~]# netstat -lpntu| grep --color -i -E 'listen|listening' | grep 5432tcp        0      0 127.0.0.1:5432          0.0.0.0:*         LISTEN      2632/postgres---->>2632是ospid,見下面的命令tcp6       0      0 ::1:5432                :::*              LISTEN      2632/postgres       [root@rhel73 ~]# ps -ef | grep 2632postgres  2632     1  0 03:51 pts/0    00:00:00 /usr/local/pgsql/bin/postgres -D /usr/local/pgsql/datapostgres  2634  2632  0 03:51 ?        00:00:00 postgres: checkpointer process   postgres  2635  2632  0 03:51 ?        00:00:00 postgres: writer process   postgres  2636  2632  0 03:51 ?        00:00:00 postgres: wal writer process   postgres  2637  2632  0 03:51 ?        00:00:00 postgres: autovacuum launcher process   postgres  2638  2632  0 03:51 ?        00:00:00 postgres: stats collector process   root      8190  2501  0 13:41 pts/0    00:00:00 grep --color=auto 2632[root@rhel73 ~]# 額外說一句:SAP Sybase ASE也是用端口號來區分不同的數據庫服務.