NDB/DNS

ndb/dns(8) can provide an authoritative name server.

To run the server at bootup, add this line to either /cfg/$sysname/termrc or /cfg/$sysname/cpurc:

ndb/dns -nsR

• The flag -s allows the DNS server to answer requests sent to UDP port 53.
• The flag -r allows ndb/dns to act as a resolver.
• The flag -n causes the server to send UDP NOTIFY messages to DNS slaves.
• The flag -R causes ndb/dns to ignore recursive lookups on behalf of remote systems. This can help prevent DDoS amplification attacks.

Note: Networking must be configured before running ndb/dns(8). Otherwise, you might see the following errors:

ndb/dns: can't read my ip address

Next, add records to /lib/ndb/local, similar to the following:

sys=example dom=example.com
	ether=f2b2b3daeb89
	ip=198.51.100.2 ipmask=255.255.255.0 ipgw=198.51.100.1
	ntp=pool.ntp.org
	dns=198.51.100.1
	auth=198.51.100.1
	authdom=example.com

dom=example.com soa=
	refresh=300 ttl=300
	ns=ns1.example.com
	ns=ns2.example.com
	ip=198.51.100.2
	dnsslave=ns2.example.com
	mb=postmaster@example.com
	mx=mail.example.com pref=5
	txt="v=spf1 mx -all"

sys=ns1 dom=ns1.example.com ip=198.51.100.2
sys=ns2 dom=ns2.example.com ip=198.51.100.2
sys=mail dom=mail.example.com ip=198.51.100.2
sys=_dmarc dom=_dmarc.example.com txt="v=DMARC1; p=none"
dom=p9auth.example.com
	cname=example.com

dom=2.100.51.198.in-addr.arpa soa=
	refresh=300 ttl=300
	ns=ns1.example.com
	ns=ns2.example.com

Replace 198.51.100.1, 198.51.100.2, example.com, and postmaster@example.com with your actual values.

Note: ndb may be sensitive to poorly formatted whitespace. If ndb is not recognizing your tuples properly, double check your whitespace.

Note: Make sure to define your tuple for sys=example.com in /lib/ndb/local right after the definition for localhost, before other tuples. Otherwise, the system might use the wrong subnet mask, causing routing issues.

To refresh cs and dns after an update to /lib/ndb/local:

; echo -n refresh > /net/cs
; echo -n refresh > /net/dns

Suppose you have a server example.com, and you want to delegate subdomain.example.com.

In example.com, you need to have something like this in /lib/ndb/local:

dom=subdomain.example.com soa=delegated
	ns=ns1.subdomain.example.com
	ns=ns2.subdomain.example.com
	dom=ns1.subdomain.example.com ip=198.51.100.3
	dom=ns2.subdomain.example.com ip=198.51.100.4

Then, in subdomain.example.com, add this to /lib/ndb/local:

sys=ns1 dom=ns1.subdomain.example.com ip=198.51.100.3
sys=ns2 dom=ns2.subdomain.example.com ip=198.51.100.4

dom=subdomain.example.com soa=
	refresh=300 ttl=300
	ns=ns1.subdomain.example.com
	ns=ns2.subdomain.example.com
	ip=198.51.100.3
	dnsslave=ns2.subdomain.example.com
	mb=username@subdomain.example.com
	mx=mail.subdomain.example.com
	txt="v=spf1 mx -all"

dom=3.100.51.198.in-addr.arpa soa=
	refresh=300 ttl=300
	ns=ns1.subdomain.example.com
	ns=ns2.subdomain.example.com

DNS ERRORS

Occasionally, this error may occur:

dns: file does not exist: /fd/0:3: < can't open: $user: '$user' directory entry not found
/fd/0:4: /net/net/clone: '/net/net/clone' dns: file does not exist

This may mean either cs or ndb is dead. Both can be restarted with:

; ndb/cs
; kill dns | rc
; ndb/dns

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Last modified Tue Mar 3 03:54:23 PST 2026

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