docker - Restrictions regarding naming image

Question

I have questions regarding restrictions about naming images. I search online and saw different issue and answers.

which special characters are not allowed in docker image name? (e.g. '*', '$', ',', '_' ...) Is it possible to use uppercase char for image name?

Answer 1

From https://github.com/docker/distribution/blob/master/reference/regexp.go:

// nameComponentRegexp restricts registry path component names to start
// with at least one letter or number, with following parts able to be
// separated by one period, one or two underscore and multiple dashes.

This applies to the image name itself.

• The regex for the letters is all lower case, no upper case letters.
• You can include a hostname and an optional port number after a colon at the very beginning.
• You can include a path between the hostname and image name with slashes /, and each element of the path has the same restrictions as the image name itself.
• After the image name, you can append a tag after a colon or a digest after an @.

Expressed with the common bracketed notation:

[somehost.com[:1234]][/some-path/to/the]image-name[:myTag1.2.3]
[somehost.com[:1234]][/some-path/to/the]image-name[@ca468b84b84846e84...]