XRPi Documentation - Sysop Commands

DNS

Command

DNS -- Domain Name Server commands.

Synopsis

DNS {<add | drop> <ipaddr>} | <list>

Description

The DNS commands are used to add and delete Domain Name Servers from the DNS list, and to display the list.

Domain Name Servers are external TCP/IP hosts which are used to resolve host names, for example "bbc.co.uk", into IP addresses, when the information is not found locally in DOMAIN.SYS.

In order for XRPi to use this process, it needs to know the IP addresses of suitable DNS's. These are usually specified in XROUTER.CFG.

If no servers are specified, XRPi will use the domain resolution services provided by Linux.

The "Split DNS" system used by XRPi allows private domains to be resolved using their own servers.

Options

1. "DNS ADD <ipaddr> [domain]" adds the name server whose IP address is specified by <ipaddr> to the server list.

   The [domain] argument may be specified with or without a trailing dot. e.g. ".ampr.org" or ".ampr.org.".

   If [domain] is specified, the name server will only be used to resolve hostnames in that domain, and the hostnames in that domain will only be resolved using that server and no others.

   For example: "DNS=44.131.91.245 .ampr.org." tells XRPi to exclusively use the server 44.131.91.245 to resolve all ampr.org hostnames. That server will not be used to resolve hosts outside the ampr.org domain, and ampr.org will not be resolved using any other server.

2. "DNS DROP <ipaddr>" deletes the nameserver specified by <ipaddr> from the server list.

3. "DNS LIST" displays the list of domain name servers.

Examples

DNS ADD 44.131.91.245 .ampr.org.
DNS ADD 62.31.117.22
DNS DROP 44.131.88.73

Files

Domain servers are usually specified in XROUTER.CFG using one or more "DNS=<ipaddr> [domain]" directives. Alternatively, the DNS ADD command may be used in BOOTCMDS.SYS. Omit the directives to force the use of the Linux resolver.

History

This command, and the DNS server / client were necessary in DOS XRouter, but have less relevance in XRPi because Linux can provide Domain Resolution services.

However, the facilities were not deleted when the code was ported to XRPi, because it is conceivable that (a) someone might wish to use an external DNS via SLIP or PPP or RF because Linux has no Internet connection (Imagine a node on a remote site, with no internet connection), or (b) they may wish to act as a DNS for TCP/IP over radio, or (c) they wish to use a different DNS to the one Linux is using.

Note

If XRPi obtains its IP address via DHCP or PPP, it will automatically obtain primary and secondary DNS addresses, and remove them from the list when the lease terminates.

Availability

Sysop-only.