我尝试安装，但看到错误
Error: Package: mysql-community-server-5.7.17-1.el7.x86_64 (mysql57-community)
Requires: systemd
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
我还删除了所有以前的安装。我怎样才能解决这个问题？