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Manual Reference Pages  -  NDB (7)


ndb - Network database




The network database consists of files describing machines known to the local installation and machines known publicly. The files comprise multi-line tuples made up of attribute/value pairs of the form attr=value or sometimes just attr. Each line starting without white space starts a new tuple. Lines starting with # are comments.

The file /lib/ndb/local is the root of the database. Other files are included in the database if a tuple with an attribute-value pair of attribute database and no value exists in /lib/ndb/local. Within the database tuple, each pair with attribute file identifies a file to be included in the database. The files are searched in the order they appear. For example:
declares the database to be composed of the three files /lib/ndb/common, /lib/ndb/local, and /lib/ndb/global. By default, /lib/ndb/local is searched before the others. However, /lib/ndb/local may be included in the database to redefine its ordering.
Within tuples, pairs on the same line bind tighter than pairs on different lines.
Programs search the database directly using the routines in ndb(3). The routine ndbipinfo imposes structure on the otherwise flat database by using knowledge specific to the network. The internet is made up of networks which can be subnetted multiple times. A network must have an ipnet attribute and is uniquely identified by the values of its ip and ipmask attributes. If the ipmask is missing, the relevant Class A, B or C one is used.
A search for an attribute associated with a network or host starts at the lowest level, the entry for the host or network itself, and works its way up, bit by bit, looking at entries for nets/subnets that include the network or host. The search ends when the attribute is found. For example, consider at the following entries:
ipnet=murray-hill ip= ipmask=
        dns= ipnet=plan9 ip= ipmask= ip= sys=anna
Here anna is on the subnet plan9 which is in turn on the class B net murray-hill. Assume that we’re searching for anna’s NTP and SMTP servers. The search starts by looking for an entry with sys=anna. We find the anna entry. Since it has an pair, we’re done looking for that attribute. To fulfill the NTP request, we continue by looking for networks that include anna’s IP address. We lop off the right most one bit from anna’s address and look for an ipnet= entry with ip= Not finding one, we drop another bit and look for an ipnet= entry with ip= There is such an entry and it has the pair,, ending our search.
A number of attributes are meaningful to programs and thus reserved. They are:
sys system name
dom Internet domain name
ip Internet address
ether Ethernet address
bootf file to download for initial bootstrap
ipnet Internet network name
ipmask Internet network mask
ipgw Internet gateway
auth authentication server to be used
  authentication domain. Plan 9 supports multiple authentication domains. To specify an authentication server for a particular domain, add a tuple containing both auth and authdom attributes and values.
fs file server to be used
tcp a TCP service name
udp a UDP service name
il an IL service name
port a TCP, UDP, or IL port number
  a TCP service that can be called only by ports numbered less that 1024
proto a protocol supported by a host.
  a domain name that ndb/dns adds onto any unrooted names when doing a search There may be multiple dnsdomain pairs.
dns a DNS server to use (for DNS and DHCP)
ntp an NTP server to use (for DHCP)
smtp an SMTP server to use (for DHCP)
time a time server to use (for DHCP)
wins a Windows name server (for DHCP)
mx mail exchanger (for DNS and DHCP)
soa start of area (for DNS)


A tuple for the CPU server, spindle.

sys = spindle
        ip= ether=080069020677

Entries for the network mh-astro-net and its subnets.

ipnet=mh-astro-net ip= ipmask= ipnet=unix-room ip=
        ipgw= ipnet=third-floor ip=

Mappings between TCP service names and port numbers.

tcp=sysmon     port=401 tcp=rexec      port=512   restricted tcp=9fs        port=564


  first database file searched


ndb(1), ndb(3)
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