| NDB(7) | NDB(7)
| 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. 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=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.
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 `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 `il` an IL service name `port` a TCP, UDP, or IL port number `restricted` a TCP service that can be called only by ports numbered less that 1024 `proto` a protocol supported by a host. `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) `soa` start of area (for DNS)
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 proto=il
`
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
| `/build/plan9port/pkg/plan9port/usr/local/plan9port/ndb/local`
| first database file searched
SEE ALSO
| ndb(1), ndb(3)