snap create-user gets bad username

[Michael Nelson]

ubuntu@dev-xenial3:~⟫ sudo snap create-user <email address hidden>
error: bad user result: cannot create user michael.nelson: adduser failed with exit status 1: adduser: Please enter a username matching the regular expression configured
via the NAME_REGEX[_SYSTEM] configuration variable. Use the `--force-badname'
option to relax this check or reconfigure NAME_REGEX.

ubuntu@dev-xenial3:~⟫ curl -s https://<email address hidden> | jq .username
"michael.nelson"

ubuntu@dev-xenial3:~⟫ grep NAME_REGEX /etc/adduser.conf
#NAME_REGEX="^[a-z][-a-z0-9_]*\$"

Assuming the above commented out NAME_REGEX is the default, then create-user will fail for some usernames which launchpad/SSO allow.

[Michael Nelson (michael.nelson)]

Assuming we don't want people to have to change usernames on SSO/LP (sometimes not even possible, if people have packages published in PPAs - from memory?), I don't (yet) see any other option than to use the username with a period from SSO/LP (which is posix compliant [1]).

But can we be sure usernames with dots will be safe on other distros? (hopefully given it's within the standard). Or what other options are there?

I'd be happy to provide a fix if there's a decided direction.

[1] See points in http://askubuntu.com/questions/405638/what-are-the-disadvantages-of-having-a-dot-in-a-user-name#405668

[Steve Langasek (vorlon)]

adduser has a --force-badname option that overrides this behavior. We should probably switch to using this.

We definitely don't want adduser to be enforcing different username rules than SSO does.