Error response from daemon: pull access denied for xxx , repository does not exist or may require 'docker login'

问题

拉取镜像时出现如下提示:

root@ubuntu:~# docker search zabbix-proxy-sqlite3
NAME                                          DESCRIPTION                                     STARS               OFFICIAL            AUTOMATED
zabbix/zabbix-proxy-sqlite3                   Zabbix proxy with SQLite3 database support      32                                      [OK]
zeduperes/zabbix-proxy-sqlite3-alpine     
...
root@ubuntu:~# docker pull zabbix-proxy-sqlite3
Using default tag: latest
Error response from daemon: pull access denied for zabbix-proxy-sqlite3, repository does not exist or may require 'docker login': denied: requested access to the resource is denied

理论上从 docker hub 拉取镜像时是不需要的登录, 所以就只有一个原因: repository does not exist,
于是我指定了仓库的用户名, 重新拉取

latest: Pulling from zabbix/zabbix-proxy-sqlite3
df20fa9351a1: Pull complete 
1414a6c7d595: Pull complete 
54e29d68e62a: Pull complete 
30d6c368b026: Pull complete 
Digest: sha256:4f24c537906ba53ff7955de954281404045aaf649d77dda41b50da2d206ceb41
Status: Downloaded newer image for zabbix/zabbix-proxy-sqlite3:latest
docker.io/zabbix/zabbix-proxy-sqlite3:latest

这里涉及了一个基础知识

docker hub 的两种仓库

1. 顶层仓库, 由docker hub 自己管理
2. 用户仓库, 由开发人员创建维护, 命名构成: 用户名/仓库名, 例如: zabbix/zabbix-proxy-sqlite3