环境是centos7.0 并且只安装云锁服务器端软件，之后操作如下：

[root@10-46-35-141 docker]# docker pull ubuntu
Using default tag: latest
Trying to pull repository docker.io/library/ubuntu ...
latest: Pulling from docker.io/library/ubuntu
473ede7ed136: Extracting 32.03 MB/32.03 MB
c46b5fa4d940: Download complete
93ae3df89c92: Download complete
6b1eed27cade: Download complete
latest: Pulling from docker.io/library/ubuntu
473ede7ed136: Extracting 32.03 MB/32.03 MB
c46b5fa4d940: Download complete
93ae3df89c92: Download complete
6b1eed27cade: Download complete
failed to register layer: Error processing tar file(exit status 1): open /etc/init.d/hwclock.sh: permission denied

请问这是怎么回事。谢谢。