状况1：
[octopus@pc3 ~]$ sudo service postgresql start
Redirecting to /bin/systemctl start postgresql.service
Job for postgresql.service failed. See "systemctl status postgresql.service" and "journalctl -xe" for details.
状况2：
[octopus@pc3 ~]$ psql
psql: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
其实问题的根源是我今天在执行sudo dnf update时无意中发现的：
Total 116 kB/s | 75 MB 10:58
Delta RPMs reduced 258.5 MB of updates to 74.7 MB (71.1% saved)
Running transaction check
Transaction check succeeded.
Running transaction test
Error: Transaction check error:
file /usr/share/doc/postgresql/README.rpm-dist conflicts between attempted installs of postgresql-9.4.4-1.fc22.i686 and postgresql-9.4.4-1.fc22.x86_64
Error Summary
这是因为出现了conflicts，系统中同时安装了postgresql-9.4.4-1.fc22.i686 and postgresql-9.4.4-1.fc22.x86_64两个版本而出错。因此只需卸载其中一个版本即可。
[octopus@pc3 ~]$ sudo dnf remove postgresql-9.4.3-1.fc22.x86_64
Dependencies resolved.
Package Arch Version Repository Size
Removing:
postgresql x86_64 9.4.3-1.fc22 @System 3.8 M
postgresql-devel x86_64 9.4.3-1.fc22 @System 4.3 M
postgresql-docs x86_64 9.4.3-1.fc22 @System 23 M
postgresql-server x86_64 9.4.3-1.fc22 @System 17 M
postgresql-upgrade x86_64 9.4.3-1.fc22 @System 9.1 M
Transaction Summary
Remove 5 Packages
Installed size: 58 M
Is this ok [y/N]: n
Operation aborted.
[octopus@pc3 ~]$ sudo dnf remove postgresql-9.4.3-1.fc22.i686
Dependencies resolved.
Package Arch Version Repository Size
Removing:
postgresql i686 9.4.3-1.fc22 @System 3.7 M
Transaction Summary
Remove 1 Package
Installed size: 3.7 M
Is this ok [y/N]: y
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
Erasing: postgresql-9.4.3-1.fc22.i686 1/1
Verifying: postgresql-9.4.3-1.fc22.i686 1/1
Removed:
postgresql.i686 9.4.3-1.fc22
Complete!
因为卸载postgresql-9.4.3-1.fc22.i686时只卸载一样东西，而卸载postgresql-9.4.3-1.fc22.x86_64需要卸载所有的有关psql的东西。所以只卸载i686那个不完整版本。执行：
sudo dnf remove postgresql-9.4.3-1.fc22.i686
然后升级数据库：
[octopus@pc3 ~]$ sudo postgresql-setup --upgrade
* Upgrading database.
* Upgraded OK.
WARNING: The configuration files were replaced by default configuration.
WARNING: The previous configuration and data are stored in folder
WARNING: /var/lib/pgsql/data-old.
* See /var/lib/pgsql/upgrade_postgresql.log for details.
[octopus@pc3 ~]$ sudo service postgresql start
Redirecting to /bin/systemctl start postgresql.service
启动成功！问题已解决。
CentOS 6.5下PostgreSQL故障切换实现：http://www.linuxdiyf.com/linux/12605.html
Linux安装PostgreSQL 9.4：http://www.linuxdiyf.com/linux/12237.html
在Linux下面卸载与重新安装PostgreSQL(rpm包)：http://www.linuxdiyf.com/linux/7288.html
Ubuntu下手动编译安装PostgreSQL9.1和pgAdmin3：http://www.linuxdiyf.com/linux/2161.html
Fedora安装PostgreSQL 8.4.11：http://www.linuxdiyf.com/linux/3854.html