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/common, /lib/ndb/local, and /lib/ndb/global. By
default, /lib/ndb/local is searched before the others. How-
ever, /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(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 rele-
vant 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 net-
work 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:
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NDB(6) NDB(6)
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 look-
ing for that attribute. To fulfill the NTP request, we con-
tinue 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 $ fol-
lowed 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 `AAAA'
record.
ether Ethernet address (must be lower-case hexadeci-
mal). 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
ipnet Internet network name
ipmask Internet network mask
ipgw Internet gateway
auth authentication server to be used
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NDB(6) NDB(6)
authdom authentication domain. Plan 9 supports multiple
authentication domains. To specify an authenti-
cation 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 protocol
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 consulting 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
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NDB(6) NDB(6)
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 ALSO
dial(2), ndb(2), ndb(8), dhcpd(8), ipconfig(8), con(1)
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