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SDB:Why should username, hostname and domainname be written

tagline: openSUSE sitesinden

Version: 1.0 -

Applicable to
SuSE version: all
Kernel version: all
XFree86 version: all

Unfortunately problems are constantly appearing in the network area, because the naming standards for username, hostnane and domainname are not conformed. This is why here are summarized the most important guidelines concerning the small writing.

The username

The username has, as far as the upper and lowercase are concerned, can be rather various. However, some mail exchange protocols exist (e.g. POP3, see RFC 1725), that behave indifferent to the upper and lowercase. Consequently, it is appropriate to use always a lowercase username.

The hostname

RFC 1178: `Choosing a Name for Your Computer'

A quote from it:

Don't expect case to be preserved.
Upper and lowercase characters look the same to a great deal of
internet software, often under the assumption that it is doing
you a favor.  It may seem appropriate to capitalize a name the
same way you might do it in English, but convention dictates
that computer names appear all lowercase.  (And it saves
holding down the shift key.)

Consequently it is very strongly recommended to write the hostname in lowercase, since some protocols, particularly NIS, ignore capital letters.

The domainname

RFC 2065: `Domain Name System Security Extensions'

A quote from it:

For purposes of DNS security, the canonical form for an RR is the RR
with domain names (1) fully expanded (no name compression via
pointers), (2) all domain name letters set to lower case, and (3) the
original TTL substituted for the current TTL.
RFC 2065

obliges as well to a domain name's lowercase writing. Even when numerous operators do not conform these convention, this should be any reason for imitations.