DOMAIN.SYS(8) XR32 REFERENCE MANUAL 27/1/2013
NAME
DOMAIN.SYS -- Hostname Resolution File.
DESCRIPTION
This optional file is used to "resolve" host names such as
"g8jvm.ampr.org" and aliases such as "lgsbbs" into their
corresponding IP addresses.
It is the first place XR32 looks when resolving a hostname.
If the file is not present, or the hostname is not found in
in the file, XR32 queries a DNS (Domain Name Server) to
obtain the information (in order for this to work, either
Windows or XR32 must have a network connection to a DNS).
If no DNS is available, and the hostname is not found in
DOMAIN.SYS, you will have to enter the full IP address of
the target host when using the PING, TELNET, TTY, and FINGER
commands.
Name resolution using a radio-based DNS is quite slow, so if
you are using this mode you should add entries to this file
for frequently contacted hosts whose addresses are stable.
Externally resolved names are added automatically to
DOMAIN.SYS at regular intervals, and expired entries are
purged.
FILE FORMAT
Each host is listed on a separate line. Each field must be
separated by one or more spaces or tabs. Comments, spaces,
tabs and blank lines are permissible to aid clarity. The
records are case-insensitive, but most people use lower case
for hostnames. The format of each record is as follows:
<hostname> [ttl] IN A <ip-address>
<alias> [ttl] IN CNAME <hostname>
<hostname> [ttl] IN MX [pref] <hostname>
The first form maps a hostname to an IP address, and the
second and third forms map alternative hostnames to a host
that is already defined.
For example, the IP address for the GB7PZT mailbox is
44.131.91.2 so it would have an Internet Address (IN A)
record like so:
gb7pzt IN A 44.131.91.2
But gb7pzt is also known locally as "pztbbs", and "kdrbbs".
There is nothing to stop you adding further "IN A" records
for gb7pzt, one for each alias, but you could instead use
the second form shown above, the CNAME or "Canonical Name"
record like so:
pztbbs. IN CNAME gb7pzt
kdrbbs. IN CNAME gb7pzt
Thus if the user types "TEL pztbbs" or "TEL kdrbbs", the
gb7pzt record is used. This removes the need to keep
repeating the IP address in multiple "A" records, and makes
it easier if the IP address is changed.
The MX or "Mail Exchange" records are usually used for
defining alternate names for mail servers, but as XRouter is
not concerned with mail you can use them in the same way as
CNAME entries, although there would be no point in doing so.
The format of the additional records would be:
pztbbs. IN MX gb7pzt
kdrbbs. IN MX gb7pzt
The optional "preference" field of MX records is ignored.
The optional [ttl] field in all types of entry is the
"time to live" of the entry in seconds, used to expire
records whose addresses are liable to change. If omitted or
set to zero, the record has an unlimited lifetime.
In order to simplify the file, the ".ampr.org" is usually
omitted from the records, and appended automatically when
the file is read. However, hostnames which contain or end
with a dot will not be extended in this manner. Thus
"gb7pzt" would be extended to "gb7pzt.ampr.org", whereas
"lgs." and "ns.cyberphile.co.uk" would not be modified.
NOTES
Although DOMAIN.SYS was originally designed to be simpler
than the more standard DOMAIN.TXT format, Xrouter is capable
of understanding both formats, so you may use an existing
DOMAIN.TXT simply by renaming it to DOMAIN.SYS.
FILES
DOMAIN.SYS is located in the same directory as XR32.EXE.
LIMITATIONS
XRouter's DNS server currently responds only to type A
queries.
SEE ALSO
DNS(1) -- DNS Configuration Commands.
DOMAIN.SYS(8) END OF DOCUMENT
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