NDB(8) NDB(8)
NAME
query, ipquery, mkhash, mkdb, mkhosts, cs, csquery, dns,
dnstcp, dnsquery, dnsdebug, inform - network database
SYNOPSIS
ndb/query [ -am ] [ -f dbfile ] attr value [ rattr ]
ndb/ipquery attr value rattr...
ndb/mkhash file attr
ndb/mkdb
ndb/mkhosts [ domain [ dbfile ] ]
ndb/cs [ -4n ] [ -f dbfile ] [ -x netmtpt ]
ndb/csquery [ -s ] [ server [ addr... ] ]
ndb/dns [ -norRs ] [ -a maxage ] [ -f dbfile ] [ -N target ]
[ -x netmtpt ] [ -z program ]
ndb/dnstcp [ -rR ] [ -f dbfile ] [ -x netmtpt ] [ conn-dir ]
ndb/dnsquery [ -x netmtpt ] [ query [ querytype ]]
ndb/dnsdebug [ -r ] [ -x netmtpt ] [ -f dbfile ] [ [ @server
] domain-name [ type ] ]
ndb/inform [ -x netmtpt ]
DESCRIPTION
The network database holds administrative information used
by network programs such as dhcpd(8), ipconfig(8), con(1),
etc.
Ndb/query searches the database dbfile (/lib/ndb/local by
default) for an attribute of type attr and value value. If
rattr is not specified, all entries matched by the search
are printed. If rattr is specified, the value of the first
pair with attribute rattr of all the matched entries nor-
mally is printed. Under -m and rattr, the values of all
pairs with a rattr attribute within the first matching entry
are printed. Under -a and rattr, all values of pairs with a
rattr attribute within all entries are printed.
Ndb/ipquery uses ndbipinfo (see ndb(2)) to search for the
values of the attributes rattr corresponding to the system
with entries of attribute type attr and value value.
Ndb/inform sends an RFC2136 DNS inform packet to a name-
server to associate the host's IPv4 address with its DNS
name. This is required if the domain's nameserver is a
Microsoft Windows Active Directory controller. The host's
domain name will be sent to the AD controller unless a tuple
of the form inform=xxx is found in the host's ndb entry.
Database maintenance
Ndb/mkhash creates a hash file for all entries with
attribute attr in database file file. The hash files are
used by ndb/query and by the ndb library routines.
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Ndb/mkdb is used in concert with awk(1) scripts to convert
uucp systems files and IP host files into database files.
It is very specific to the situation at Murray Hill.
When the database files change underfoot, ndb/cs and ndb/dns
track them properly. Nonetheless, to keep the database
searches efficient it is necessary to run ndb/mkhash when-
ever the files are modified. It may be profitable to con-
trol this by a frequent cron(8) job.
Ndb/mkhosts generates a BSD style hosts, hosts.txt, and
hosts.equiv files from an ndb data base file specified on
the command line (default /lib/ndb/local). For local rea-
sons the files are called hosts.1127, astro.txt, and
hosts.equiv.
Connection service
Ndb/cs is a server used by dial(2) to translate network
names. It is started at boot time. It finds out what net-
works are configured by looking for /net/*/clone when it
starts. It can also be told about networks by writing to
/net/cs a message of the form:
add net1 net2 ...
Ndb/cs also sets the system name in /dev/sysname if it can
figure it out. The options are:
-f supplies the name of the data base file to use, default
/lib/ndb/local.
-n causes cs to do nothing but set the system name.
-x specifies the mount point of the network.
Ndb/csquery queries ndb/cs to see how it resolves addresses.
Ndb/csquery prompts for addresses and prints what ndb/cs
returns. Server defaults to /net/cs. If any addrs are
specified, ndb/csquery prints their translations and immedi-
ately exits. The exit status will be nil only if all
addresses were successfully translated. The -s flag sets
exit status without printing any results.
Domain name service
Ndb/dns serves ndb/cs and remote systems by translating
Internet domain names. Ndb/dns is started at boot time. By
default dns serves only requests written to /net/dns. Pro-
grams must seek to offset 0 before reading or writing
/net/dns or /net/cs. The options are:
-a sets the maximum time in seconds that an unreferenced
domain name will remain cached. The default is one hour
(3600).
-f supplies the name of the data base file to use, default
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/lib/ndb/local.
-n whenever a DNS zone that we serve changes, send UDP
NOTIFY messages to any dns slaves for that zone (see the
`dnsslave' attribute below).
-N sets the goal for the number of domain names cached to
target rather than the default of 8,000.
-o used with -s, -o causes dns to assume that it straddles
inside and outside networks and that the outside network
is mounted on /net.alt. Queries for inside addresses
will be sent via /net/udp (or /net/tcp in response to
truncated replies) and those for outside addresses via
/net.alt/udp (or /net.alt/tcp). This makes dns suitable
for serving non-Plan-9 systems in an organization with
firewalls, DNS proxies, etc., particularly if they don't
work very well. See `Straddling Server' below for
details.
-r act as a resolver only: send `recursive' queries, asking
the other servers to complete lookups. If present,
/env/DNSSERVER must be a space-separated list of such
DNS servers' IP addresses, otherwise optional ndb(6) dns
attributes name DNS servers to forward queries to.
-R ignore the `recursive' bit on incoming requests. Do not
complete lookups on behalf of remote systems.
-s also answer domain requests sent to UDP port 53.
-x specifies the mount point of the network.
-z whenever we receive a UDP NOTIFY message, run program
with the domain name of the area as its argument.
When the -r option is specified, the servers used come from
the dns attribute in the database. For example, to specify
a set of dns servers that will resolve requests for systems
on the network mh-net:
ipnet=mh-net ip=135.104.0.0 ipmask=255.255.0.0
dns=ns1.cs.bell-labs.com
dns=ns2.cs.bell-labs.com
dom=ns1.cs.bell-labs.com ip=135.104.1.11
dom=ns2.cs.bell-labs.com ip=135.104.1.12
The server for a domain is indicated by a database entry
containing both a dom and a ns attribute.
dom=
ns=A.ROOT-SERVERS.NET
ns=B.ROOT-SERVERS.NET
ns=C.ROOT-SERVERS.NET
dom=A.ROOT-SERVERS.NET ip=198.41.0.4
dom=B.ROOT-SERVERS.NET ip=128.9.0.107
dom=C.ROOT-SERVERS.NET ip=192.33.4.12
The last three lines provide a mapping for the server names
to their ip addresses. This is only a hint and will be
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superseded from whatever is learned from servers owning the
domain.
Authoritative Name Servers
You can also serve a subtree of the domain name space from
the local database. You indicate subtrees that you would
like to serve by adding an soa= attribute to the root entry.
For example, the Bell Labs CS research domain is:
dom=cs.bell-labs.com soa=
refresh=3600 ttl=3600
ns=plan9.bell-labs.com
ns=ns1.cs.bell-labs.com
ns=ns2.cs.bell-labs.com
mb=presotto@plan9.bell-labs.com
mx=mail.research.bell-labs.com pref=20
mx=plan9.bell-labs.com pref=10
dnsslave=nslocum.cs.bell-labs.com
dnsslave=vex.cs.bell-labs.com
Here, the mb entry is the mail address of the person respon-
sible for the domain (default postmaster). The mx entries
list mail exchangers for the domain name and refresh and ttl
define the area refresh interval and the minimum TTL for
records in this domain. The dnsslave entries specify slave
DNS servers that should be notified when the domain changes.
The notification also requires the -n flag.
Reverse Domains
You can also serve reverse lookups (returning the name that
goes with an IP address) by adding an soa= attribute to the
entry defining the root of the reverse space.
For example, to provide reverse lookup for all addresses in
starting with `135.104' or `fd00::', ndb must contain a
record like:
dom=104.135.in-addr.arpa soa=
dom=d.f.ip6.arpa soa= # special case, rfc 4193
refresh=3600 ttl=3600
ns=plan9.bell-labs.com
ns=ns1.cs.bell-labs.com
ns=ns2.cs.bell-labs.com
Notice the form of the reverse address. For IPv4, it's the
bytes of the address range you are serving reversed and
expressed in decimal, and with `.in-addr.arpa' appended.
For IPv6, it's the nibbles (4-bit fields) of the address
range you are serving reversed and expressed in hexadecimal,
and with `.ip6.arpa' appended. These are the standard forms
for a domain name in a PTR record.
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If such an soa entry exists in the database, reverse
addresses will automatically be generated from any IP
addresses in the database that are under this root. For
example
dom=ns1.cs.bell-labs.com ip=135.104.1.11
will automatically create both forward and reverse entries
for ns1.cs.bell-labs.com. Unlike other DNS servers, there's
no way to generate inconsistent forward and reverse entries.
Classless reverse delegation
Following RFC 2317, it is possible to serve reverse DNS data
for IPv4 subnets smaller than /24. Declare the non-/24 sub-
net, the reverse domain and the individual systems.
For example, this is how to serve RFC-2317 ptr records for
the subnet `65.14.39.128/123'.
ipnet=our-t1 ip=65.14.39.128 ipmask=/123
dom=128.39.14.65.in-addr.arpa soa=
refresh=3600 ttl=3600
ns=ns1.our-domain.com
ns=ns2.our-domain.com
ip=65.14.39.129 dom=router.our-domain.com
Delegating Name Service Authority
Delegation of a further subtree to another set of name
servers is indicated by an soa=delegated attribute.
dom=bignose.cs.research.bell-labs.com
soa=delegated
ns=anna.cs.research.bell-labs.com
ns=dj.cs.research.bell-labs.com
Nameservers within the delegated domain (as in this example)
must have their IP addresses listed elsewhere in ndb files.
Wildcards, MX and CNAME records
Wild-carded domain names can also be used. For example, to
specify a mail forwarder for all Bell Labs research systems:
dom=*.research.bell-labs.com
mx=research.bell-labs.com
`Cname' aliases may be established by adding a cname
attribute giving the real domain name; the name attached to
the dom attribute is the alias. `Cname' aliases are
severely restricted; the aliases may have no other
attributes than dom and are daily further restricted in
their use by new RFCs.
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cname=anna.cs.bell-labs.com dom=www.cs.bell-labs.com
makes www.... a synonym for the canonical name anna.....
Straddling Server
Many companies have an inside network protected from outside
access with firewalls. They usually provide internal `root'
DNS servers (of varying reliability and correctness) that
serve internal domains and pass on DNS queries for outside
domains to the outside, relaying the results back and cach-
ing them for future use. Some companies don't even let DNS
queries nor replies through their firewalls at all, in
either direction.
In such a situation, running dns -so on a machine that
imports access to the outside network via /net.alt from a
machine that straddles the firewalls, or that straddles the
firewalls itself, will let internal machines query such a
machine and receive answers from outside nameservers for
outside addresses and inside nameservers for inside
addresses, giving the appearance of a unified domain name
space, while bypassing the corporate DNS proxies or fire-
walls. This is different from running dns -s and dns -sRx
/net.alt -f /lib/ndb/external on the same machine, which
keeps the inside and outside namespaces entirely separate.
Under -o, several sys names are significant: inside-dom,
inside-ns, and outside-ns. Inside-dom should contain a
series of dom pairs naming domains internal to the organiza-
tion. Inside-ns should contain a series of ip pairs naming
the internal DNS `root' servers. Outside-ns should contain
a series of ip pairs naming the external DNS servers to con-
sult.
Zone Transfers and TCP
Dnstcp is invoked, usually from /rc/bin/service/tcp53, to
answer DNS queries with long answers via TCP, notably to
transfer a zone within the database dbfile (default
/lib/ndb/local) to its invoker on the network at netmtpt
(default /net). Standard input will be read for DNS
requests and the DNS answers will appear on standard output.
Recursion is disabled by -R; acting as a pure resolver is
enabled by -r. If conn-dir is provided, it is assumed to be
a directory within netmtpt/tcp and is used to find the
caller's address.
DNS Queries and Debugging
Ndb/dnsquery can be used to query ndb/dns to see how it
resolves requests. Ndb/dnsquery prompts for commands of the
form
domain-name request-type
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where request-type can be ip, ipv6, mx, ns, cname, ptr....
In the case of the inverse query type, ptr, dnsquery will
reverse the ip address and tack on the .in-addr.arpa if nec-
essary.
Ndb/dnsdebug is like ndb/dnsquery but bypasses the local
server. It communicates via UDP (and sometimes TCP) with
the domain name servers in the same way that the local
resolver would and displays all packets received. The query
can be specified on the command line or can be prompted for.
The queries look like those of ndb/dnsquery with one addi-
tion. Ndb/dnsdebug can be directed to query a particular
name server by the command @name-server. From that point
on, all queries go to that name server rather than being
resolved by dnsdebug. The @ command returns query resolution
to dnsdebug. Finally, any command preceded by a @name-server
sets the name server only for that command.
Normally dnsdebug uses the /net interface and the database
file /lib/ndb/local. The -f option supplies the name of the
data base file to use. The -r option is the same as for
ndb/dns. The -x option directs dnsdebug to use the /net.alt
interface and /lib/ndb/external database file.
EXAMPLES
Look up helix in ndb.
% ndb/query sys helix
sys=helix dom=helix.research.bell-labs.com bootf=/mips/9powerboot
ip=135.104.117.31 ether=080069020427
Look up plan9.bell-labs.com and its IP address in the DNS.
% ndb/dnsquery
> plan9.bell-labs.com ip
plan9.bell-labs.com ip 204.178.31.2
> 204.178.31.2 ptr
2.31.178.204.in-addr.arpa ptr plan9.bell-labs.com
2.31.178.204.in-addr.arpa ptr ampl.com
>
Print the names of all systems that boot via PXE.
% ndb/query -a bootf /386/9pxeload sys
FILES
/env/DNSSERVER resolver's DNS servers' IP addresses.
/lib/ndb/local first database file searched
/lib/ndb/local.* hash files for /lib/ndb/local
/srv/cs service file for ndb/cs
/net/cs where /srv/cs gets mounted
/srv/dns service file for ndb/dns
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/net/dns where /srv/dns gets mounted
SOURCE
/sys/src/cmd/ndb
SEE ALSO
ndb(2), ndb(6)
BUGS
Ndb databases are case-sensitive; ethernet addresses must be
in lower-case hexadecimal.
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