我尝试在amazone linux上安装postgresql-server，但它失败了：
[ec2-user@ip-xyz ~]$ sudo yum install postgresql-server
Loaded plugins: priorities, update-motd, upgrade-helper
amzn-main/latest | 2.1 kB 00:00
amzn-updates/latest | 2.3 kB 00:00
961 packages excluded due to repository priority protections
Resolving Dependencies
--> Running transaction check
---> Package postgresql93-server.x86_64 0:9.3.12-1PGDG.rhel7 will be installed
--> Processing Dependency: systemd-units for package: postgresql93-server-9.3.12-1PGDG.rhel7.x86_64
--> Processing Dependency: systemd-units for package: postgresql93-server-9.3.12-1PGDG.rhel7.x86_64
--> Finished Dependency Resolution
Error: Package: postgresql93-server-9.3.12-1PGDG.rhel7.x86_64 (pgdg93)
Requires: systemd-units
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
似乎存在未满足要求的问题。
我该如何解决这个问题：Error: Package: postgresql93-server-9.3.12-1PGDG.rhel7.x86_64 (pgdg93)
Requires: systemd-units