通过“注册ISO”功能导入阿里云的一个镜像，出现如下报错信息：
查看资源域的信息：
2、查看日志
Jan 17 06:25:01 cloudstack-new-02 server: WARN [o.a.c.alerts] (RemoteHostEndPoint-1:ctx-6d1f1c4f) (logid:9193f818) alertType:: 28 // dataCenterId:: 1 // podId:: null // clusterId:: null // message:: Failed to register template: 2baea0b9-4148-4e8c-b08a-fe5d211c6353 with error: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target Jan 17 06:25:01 cloudstack-new-02 server: ERROR [o.a.c.s.i.BaseImageStoreDriverImpl] (RemoteHostEndPoint-1:ctx-6d1f1c4f) (logid:9193f818) Failed to register template: 2baea0b9-4148-4e8c-b08a-fe5d211c6353 with error: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
根据提示，是认证相关的信息，这个时候我无意中尝试了下163的镜像，然后导入163的镜像，提示正常。
3、对比URL
网易163的镜像链接：http://mirrors.163.com/centos/7/isos/x86_64/CentOS-7-x86_64-Minimal-1708.iso
阿里云的镜像链接：https://mirrors.aliyun.com/centos/7/isos/x86_64/CentOS-7-x86_64-Minimal-1708.iso
原来163的镜像使用的http协议，而阿里云的是https，将阿里云的链接地址改为http://mirrors.aliyun.com/centos/7/isos/x86_64/CentOS-7-x86_64-Minimal-1708.iso，然后重新导入，问题解决。
原文：http://blog.51cto.com/molewan/2061970