discrimination between tags containing one '/' and repository names is weak.
multiple '/' characters in tags is not possible (should be).
Example:
$ docker info
Containers: 0
Running: 0
Paused: 0
Stopped: 0
Images: 50
Storage Driver: sdc
SDCAccount: gregzuro
Logging Driver: json-file
Plugins:
Volume:
Network:
Swarm:
NodeID:
Is Manager: false
Node Address:
Security Options:
Kernel Version: 3.12.0-1-amd64
Operating System: SmartDataCenter
OSType: linux
Architecture: x86_64
CPUs: 0
Total Memory: 0 B
Name: us-west-1
ID: ad77aa84-aaef-4ebc-b68f-36725427c008
Docker Root Dir:
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
WARNING: No kernel memory limit support
WARNING: No oom kill disable support
WARNING: No cpu cfs quota support
WARNING: No cpu cfs period support
WARNING: No cpu shares support
WARNING: No cpuset support
WARNING: bridge-nf-call-iptables is disabled
WARNING: bridge-nf-call-ip6tables is disabled
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
consul 0.7.2 2b13d9b85f83 2 days ago 0 B
vault 0.6.4 7543e293bb89 5 days ago 0 B
grafana/grafana 4.0.1 d0aaace0748e 2 weeks ago 0 B
influxdb 1.0.2-alpine b5d995eee90d 9 weeks ago 0 B
$ docker tag 7543e293bb89 a
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
consul 0.7.2 2b13d9b85f83 2 days ago 0 B
a latest 7543e293bb89 5 days ago 0 B
vault 0.6.4 7543e293bb89 5 days ago 0 B
grafana/grafana 4.0.1 d0aaace0748e 2 weeks ago 0 B
influxdb 1.0.2-alpine b5d995eee90d 9 weeks ago 0 B
$ docker tag 7543e293bb89 a/b
Error response from daemon: invalid repository namespace, must be between 2 and 255 characters: a (3d7e59bb-33fc-42ef-8060-89add308f839)
$ docker tag 7543e293bb89 aa/b
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
consul 0.7.2 2b13d9b85f83 2 days ago 0 B
aa/b latest 7543e293bb89 5 days ago 0 B
a latest 7543e293bb89 5 days ago 0 B
vault 0.6.4 7543e293bb89 5 days ago 0 B
grafana/grafana 4.0.1 d0aaace0748e 2 weeks ago 0 B
influxdb 1.0.2-alpine b5d995eee90d 9 weeks ago 0 B
$ docker tag 7543e293bb89 aa/b/c
Error response from daemon: invalid repository name, may only contain [a-z0-9_.-] characters: b/c (f43c5a21-c515-422a-ad60-72f6db72356d)
tl;dr:
Example: