Under CentOS7 use Sonatype Nexus3 build Docker private warehouse

Relevant information:

　　Sonatype Nexus3 official website: https://www.sonatype.com/download-oss-sonatype

　　Sonatype Nexus3 Docker Hub Address: https://hub.docker.com/r/sonatype/nexus3/

　　Sonatype Nexus3 some introduction and use: https://yeasy.gitbooks.io/docker_practice/repository/nexus3_registry.html

　　This article Reference article: https://www.cnblogs.com/holdengong/archive/2019/09/05/11468290.html

⒈ installation Docker (requirement)

　　Please refer https://www.cnblogs.com/fanqisoft/p/10439620.html install Docker