NDB(6)NDB(6)NAME
ndb - Network database
DESCRIPTION
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:
database=
file=/lib/ndb/common
file=/lib/ndb/local
file=/lib/ndb/global
declares the database to be composed of the three files /lib/ndb/com‐
mon, /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 dif‐
ferent lines.
Programs search the database directly using the routines in ndb(2) or
indirectly using ndb/cs and ndb/dns (see ndb(8)). Both ndb/cs and the
routine ndbipinfo impose 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 the following entries:
ipnet=murray-hill ip=135.104.0.0 ipmask=255.255.0.0
dns=135.104.10.1
ntp=ntp.cs.bell-labs.com
ipnet=plan9 ip=135.104.9.0 ipmask=255.255.255.0
ntp=oncore.cs.bell-labs.com
smtp=smtp1.cs.bell-labs.com
ip=135.104.9.6 sys=anna dom=anna.cs.bell-labs.com
smtp=smtp2.cs.bell-labs.com
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 smtp=smtp2.cs.bell-labs.com 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=135.104.9.4. Not finding one, we drop another bit
and look for an ipnet= entry with ip=135.104.9.0. There is such an
entry and it has the pair, ntp=oncore.cs.bell-labs.com, ending our
search.
Ndb/cs can be made to perform such network aware searches by using
metanames in the dialstring. A metaname is a $ followed by an
attribute name. Ndb/cs looks up the attribute relative to the system
it is running on. Thus, with the above example, if a program called
dial("tcp!$smtp!smtp", 0, 0, 0);
the dial would connect to the SMTP port of smtp2.cs.bell-labs.com.
A number of attributes are meaningful to programs and thus reserved.
They are:
sys system name (a short name)
dom Internet fully-qualified domain name
ip Internet address, v4 or v6.
ipv6 IPv6 Internet address. For DNS, an record.
ether Ethernet address (must be lower-case hexadecimal). Beware that
for machines with multiple ether attributes, dhcpd may expect
requests to come from the address in the first ether attribute.
bootf file to download for initial bootstrap; /386/9boot to boot a PC
via PXE.
ipnet Internet network name
ipmask Internet network mask
ipgw Internet gateway
auth authentication server to be used
authdom
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
port a TCP or UDP port number
restricted
a TCP service that can be called only by ports numbered less
that 1024
proto a protocol supported by a host. The pair proto=il was needed by
cs (see ndb(8)) in tuples for hosts that supported the IL proto‐
col
dnsdomain
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); also pref.
srv service location (for DNS); also pri, weight and port.
soa start of area (for DNS)
Cs defers to dns to translate dotted names to IP addresses, only con‐
sulting the database files if dns cannot translate the name.
Cs allows network entries with sys and dom attributes but no ip
attribute. Searches for the system name are resolved by looking up the
domain name with dns.
The file /lib/ndb/auth is used during authentication to decide who has
the power to `speak for' other users; see authsrv(6).
EXAMPLES
A tuple for the CPU server, spindle.
sys=spindle
dom=spindle.research.bell-labs.com
bootf=/mips/9powerboot
ip=135.104.117.32 ether=080069020677
Entries for the network mh-astro-net and its subnets.
ipnet=mh-astro-net ip=135.104.0.0 ipmask=255.255.255.0
fs=bootes.research.bell-labs.com
ipgw=r70.research.bell-labs.com
auth=p9auth.research.bell-labs.com
ipnet=unix-room ip=135.104.117.0
ipgw=135.104.117.1
ipnet=third-floor ip=135.104.51.0
ipgw=135.104.51.1
Mappings between TCP service names and port numbers.
tcp=sysmon port=401
tcp=rexec port=512 restricted
tcp=9fs port=564
FILES
/lib/ndb/local
first database file searched
SEE ALSOcon(1), dial(2), ndb(2), 9boot(8), booting(8), dhcpd(8), ipconfig(8),
ndb(8)NDB(6)
