我试图使用以下命令拉出Fedora docker镜像,但它失败了,最新版本未找到存储库docker.io/library/fedora错误：

# docker pull fedora
Using default tag: latest
latest: Pulling from library/fedora
62b0615068df: Pull complete 
cd1e9127a3f8: Verifying Checksum 
Pulling repository docker.io/library/fedora
Tag latest not found in repository docker.io/library/fedora

但是,当我使用明确指定的最新标记将其拉出时,它成功了.

docker pull fedora:latest
latest: Pulling from library/fedora
cd1e9127a3f8: Pull complete 
Digest: sha256:52db7a1a18f173622a9b1a75354c7266220bffb7187c4880590805af0d7679d6
Status: Downloaded newer image for fedora:latest

为了进一步理解这一点,我试图拉动CentOS docker镜像.但是,在CentOS的情况下,我没有看到这种行为：

docker pull centos
Using default tag: latest
latest: Pulling from library/centos
Digest: sha256:1a62cd7c773dd5c6cf08e2e28596f6fcc99bd97e38c9b324163e0da90ed27562
Status: Downloaded newer image for centos:latest

版本信息

# cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 7.2 (Maipo)
# docker -v
Docker version 1.9.1,build a34a1d5

有人可以帮我理解这种行为吗？