ref: 60cbbb123b106f7f31495514326a2b0bbcb0d75d
dir: /sys/man/6/ndb/
.TH NDB 6
.SH NAME
ndb \- Network database
.SH DESCRIPTION
.PP
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
.IB attr = value
or sometimes just
.IR attr .
Each line starting without white space starts a new tuple.
Lines starting with
.B #
are comments.
.PP
The file
.B /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
.B database
and no value exists in
.BR /lib/ndb/local
.
Within the
.B database
tuple,
each pair with attribute
.B file
identifies a file to be included in the database. The files are searched
in the order they appear.
For example:
.IP
.EX
database=
file=/lib/ndb/common
file=/lib/ndb/local
file=/lib/ndb/global
.EE
.PP
declares the database to be composed of the three files
.BR /lib/ndb/common ,
.BR /lib/ndb/local ,
and
.BR /lib/ndb/global .
By default,
.B /lib/ndb/local
is searched before the others.
However,
.B /lib/ndb/local
may be included in the
.B database
to redefine its ordering.
.PP
Within tuples, pairs on the same line bind tighter than
pairs on different lines.
.PP
Programs search the database directly using the routines in
.IR ndb (2)
or indirectly using
.B ndb/cs
and
.B ndb/dns
(see
.IR ndb (8)).
Both
.B ndb/cs
and the routine
.I 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
.B ipnet
attribute and is uniquely identified by the values of its
.B ip
and
.B ipmask
attributes. If the
.B ipmask
is missing, the relevant Class A, B or C one is used.
.LP
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:
.IP
.EX
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
.EE
.LP
Here
.B anna
is on the subnet
.B plan9
which is in turn on the class B net
.BR murray-hill .
Assume that we're searching for
.BR anna 's
.B NTP
and
.B SMTP
servers.
The search starts by looking for an entry with
.BR sys=anna .
We find the anna entry. Since it has an
.B 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
.B ipnet=
entry with
.BR ip=135.104.9.4 .
Not finding one, we drop another bit and look for an
.B ipnet=
entry with
.BR ip=135.104.9.0 .
There is
such an entry and it has the pair,
.BR ntp=oncore.cs.bell-labs.com ,
ending our search.
.PP
.I Ndb/cs
can be made to perform such network aware
searches by using metanames in the dialstring.
A metaname is a
.I $
followed by an attribute name.
.I Ndb/cs
looks up the attribute relative to the system it is running
on. Thus, with the above example, if a program called
.IP
.EX
dial("tcp!$smtp!smtp", 0, 0, 0);
.EE
.LP
the dial would connect to the SMTP port of
.BR smtp2.cs.bell-labs.com .
.PP
A number of attributes are meaningful to programs and thus
reserved.
They are:
.TF dnsdomain
.TP
.B sys
system name (a short name)
.TP
.B dom
Internet fully-qualified domain name
.TP
.B ip
Internet address,
v4 or v6.
.TP
.B ipv6
IPv6 Internet address.
For DNS, an
.L AAAA
record.
.TP
.B ether
Ethernet address
(must be lower-case hexadecimal).
Beware that for machines with multiple
.B ether
attributes,
.I dhcpd
may expect requests to come from the address in the first
.B ether
attribute.
.TP
.B bootf
file to download for initial bootstrap;
.B /386/9bootpxe
to boot a PC via PXE.
.TP
.B tftp
an TFTP server to use for PXE bootstrap
.TP
.B ipnet
Internet network name
.TP
.B ipmask
Internet network mask
.TP
.B ipgw
Internet gateway (ip address)
.TP
.B auth
authentication server to be used
.TP
.B authdom
authentication domain. Plan 9 supports multiple authentication
domains. To specify an authentication server for a particular domain,
add a tuple containing both
.B auth
and
.B authdom
attributes and values.
.TP
.B fs
file server to be used
.TP
.B tcp
a TCP service name
.TP
.B udp
a UDP service name
.TP
.B port
a TCP or UDP port number
.TP
.B restricted
a TCP service that can be called only by ports numbered
less than 1024
.TP
.B proto
a protocol supported by a host.
The pair
.B proto=il
was needed by
.I cs
(see
.IR ndb (8))
in tuples for hosts that supported the IL protocol
.TP
.B dnsdomain
a domain name that
.I ndb/dns
adds onto any unrooted names when doing a search.
There may be multiple
.B dnsdomain
pairs.
.TP
.B dns
a DNS server to use (for DNS and DHCP)
.TP
.B ntp
an NTP server to use (for DHCP)
.TP
.B smtp
an SMTP server to use (for DHCP)
.TP
.B time
a time server to use (for DHCP)
.TP
.B wins
a Windows name server (for DHCP)
.TP
.B mx
mail exchanger (for DNS and DHCP);
also
.BR pref .
.TP
.B srv
service location (for DNS);
also
.BR pri ,
.B weight
and
.BR port .
.TP
.B soa
start of area (for DNS)
.PD
.PP
.I Cs
defers to
.I dns
to translate dotted names to IP addresses,
only consulting the database files if
.I dns
cannot translate the name.
.PP
.I Cs
allows network entries with
.B sys
and
.B dom
attributes but no
.B ip
attribute.
Searches for the system name are resolved
by looking up the domain name with
.IR dns .
.PP
The file
.B /lib/ndb/auth
is used during authentication to decide who has the power to `speak for' other
users; see
.IR authsrv (6).
.SH EXAMPLES
.LP
A tuple for the CPU server, spindle.
.LP
.EX
sys=spindle
dom=spindle.research.bell-labs.com
bootf=/mips/9powerboot
ip=135.104.117.32 ether=080069020677
.EE
.LP
Entries for the network
.B mh-astro-net
and its subnets.
.LP
.EX
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
.EE
.LP
Mappings between TCP service names and port numbers.
.LP
.EX
.ta \w'\fLtcp=sysmonxxxxx'u \w'\fLtcp=sysmonxxxxxport=512xxx'u
tcp=sysmon port=401
tcp=rexec port=512 restricted
tcp=9fs port=564
.EE
.SH FILES
.TF /lib/ndb/local
.TP
.B /lib/ndb/local
first database file searched
.SH "SEE ALSO"
.IR con (1),
.IR dial (2),
.IR ndb (2),
.IR booting (8),
.IR dhcpd (8),
.IR ipconfig (8),
.IR ndb (8)