[root@centos6 ~]#  # CentOS 6.x の場合
[root@centos6 ~]# rpm -ivh http://nginx.org/packages/centos/6/noarch/RPMS/nginx-release-centos-6-0.el6.ngx.noarch.rpm

http://dl.iuscommunity.org/pub/ius/stable/CentOS/6/i386/ius-release-1.0-13.ius.centos6.noarch.rpm を取得中
警告: /var/tmp/rpm-tmp.99sX6T: ヘッダ V4 DSA/SHA1 Signature, key ID 9cd4953f: NOKEY
準備中...                ########################################### [100%]
   1:ius-release            ########################################### [100%]

[root@centos7 ~]# # CentOS 7.xの場合
[root@centos7 ~]# rpm -ivh http://nginx.org/packages/centos/7/noarch/RPMS/nginx-release-centos-7-0.el7.ngx.noarch.rpm
http://nginx.org/packages/centos/7/noarch/RPMS/nginx-release-centos-7-0.el7.ngx.noarch.rpm を取得中
警告: /var/tmp/rpm-tmp.kBFF5W: ヘッダー V4 RSA/SHA1 Signature、鍵 ID 7bd9bf62: NOKEY
準備しています...              ################################# [100%]
更新中 / インストール中...
   1:nginx-release-centos-7-0.el7.ngx ################################# [100%]
		

[root@centos ~]#  # CentOS 6.x の場合
[root@centos ~]#  cp -n /etc/yum.repos.d/nginx.repo /etc/yum.repos.d/nginx.repo.org && sed -e 's@packages@packages/mainline@' /etc/yum.repos.d/nginx.repo.org > /etc/yum.repos.d/nginx.repo
[root@centos ~]#