That is an excellent question. I'm guessing you're meaning connecting to
an AD back-end.
We've had beaucoup problems historically with that; AD itself is not case
sensitive, but Kerberos client on Linux very much is.
Our (Windows-based) erstwhile AD admins love them some camel-case user
principal names. And we're Linux engineers, so AD is not in our span of
control. We're merely consumers of it.
We'd used other AD integration tools where you have an explicit option to
"map samAcccountName or UPN to lower case". Then -- regardless of the case
that your AD admin used for user name, it gets mapped in Linux to lower
I'm looking at our SSSD deployments. They seem to do this auto-magically.
whatever case I use to log in, it gets accepted and it consistently maps
the login name to lower case.
That's good for us, but I'd guess some companies wouldn't like this -- now
the Linux account name doesn't match the Kerberos principal name.