错误

在使用 PostgreSQL 过程中，我目前遇到了 2 种错误的类型，下面是具体解决办法和具体的错误信息。

连接拒绝Connection refused

在使用 Django 应用中，使用 PostgreSQL 关系数据库，在安装的时候遇到一些问题，具体如下：

Is the server running on host "host_name" (XX.XX.XX.XX) 
and accepting TCP/IP connections on port 5432?

上面这个问题是没有启动数据库导致的。

启动失败

下面这个问题启动失败的问题，启动命令是

[root@VM_152_4_centos bootcamp]# service postgresql-11 start
Redirecting to /bin/systemctl start postgresql-11.service
Job for postgresql-11.service failed because the control process exited with error code. See "systemctl status postgresql-11.service" and "journalctl -xe" for details.

提示了运行status 和 journalctl -xe 可以查看到具体细节。

[root@VM_152_4_centos bootcamp]# systemctl status postgresql-11.service
● postgresql-11.service - PostgreSQL 11 database server
   Loaded: loaded (/usr/lib/systemd/system/postgresql-11.service; disabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Sun 2019-02-17 22:15:42 CST; 19min ago
     Docs: https://www.postgresql.org/docs/11/static/
  Process: 6220 ExecStartPre=/usr/pgsql-11/bin/postgresql-11-check-db-dir ${PGDATA} (code=exited, status=1/FAILURE)
Feb 17 22:15:42 VM_152_4_centos systemd[1]: Starting PostgreSQL 11 database server...
Feb 17 22:15:42 VM_152_4_centos systemd[1]: postgresql-11.service: control process exited, code=exited status=1
Feb 17 22:15:42 VM_152_4_centos systemd[1]: Failed to start PostgreSQL 11 database server.
Feb 17 22:15:42 VM_152_4_centos systemd[1]: Unit postgresql-11.service entered failed state.
Feb 17 22:15:42 VM_152_4_centos systemd[1]: postgresql-11.service failed.

然后再执行journalctl -xe命令。

[root@VM_152_4_centos bootcamp]# journalctl -xe
-- Unit postgresql-11.service has begun starting up.
Feb 17 22:35:03 VM_152_4_centos postgresql-11-check-db-dir[7789]: "/var/lib/pgsql/11/data/" is missing or empty.

解决办法

可以看到根本原因就是没有db，所以需要先初始化db。

[root@VM_152_4_centos ~]# /usr/pgsql-11/bin/postgresql-11-setup initdb
Initializing database ... OK

最后启动，然后查看状态

[root@VM_152_4_centos bootcamp]# systemctl start postgresql-11.service
[root@VM_152_4_centos bootcamp]# systemctl status postgresql-11.service
● postgresql-11.service - PostgreSQL 11 database server
   Loaded: loaded (/usr/lib/systemd/system/postgresql-11.service; disabled; vendor preset: disabled)
   Active: active (running) since Sun 2019-02-17 22:37:04 CST; 2s ago