encountered two fedora 6 issues - underscore in host name, :*: in passwd file prevented logins

[Ben Scott]

On 1/8/07, Todd Littlefield <t.littlefield at comcast.net> wrote:
> If I remember correctly, underscores are not allowed in names.  Only
> a-z, 0-9 and the hyphen character are acceptable.

  Right.  Internet names should contain only those characters, and
begin and end with a letter or number (dashes in the middle only).
Originally, they had to begin with a letter, but then some jerk
founded a major network company called "3Com".  ;-)

> I can't quote the RFC, but someone here probably can ;-)

  RFC-1123, "Requirements for Internet Hosts", which Incorporated
RFC-952, "DoD Internet host table specification", by reference.  Yes,
I had to look that up.  :)  I remembered the title of the first one
and was able to Google it.

  It's interesting to note that, as far as the DNS protocol is
concerned, labels (the parts between dots) can contain any character
except the dot and NUL.  The restrictions were put in place to make
the Internet more friendly to various systems.

-- Ben