Ubuntu Manpage: nsd.conf - NSD configuration file

NAME

       nsd.conf - NSD configuration file

SYNOPSIS

       nsd.conf

DESCRIPTION

       Nsd.conf  is  used  to  configure  nsd(8). The file format has attributes and values. Some
       attributes have attributes inside them. The notation is: attribute: value.

       Comments start with # and last to  the  end  of  line.  Empty  lines  are  ignored  as  is
       whitespace  at  the  beginning  of  a line. Quotes can be used, for names with spaces, eg.
       "file name.zone".

       Nsd.conf specifies options for the nsd server, zone files, primaries and secondaries.

EXAMPLE

       An example of a short nsd.conf file is below.

       # Example.com nsd.conf file
       # This is a comment.

       server:
            server-count: 1 # use this number of cpu cores
            database: ""  # or use "/var/lib/nsd/nsd.db"
            zonelistfile: "/var/lib/nsd/zone.list"
            username: nsd
            logfile: "/var/log/nsd.log"
            pidfile: "/run/nsd/nsd.pid"
            xfrdfile: "/var/lib/nsd/xfrd.state"

       zone:
            name: example.com
            zonefile: /etc/nsd/example.com.zone

       zone:
            # this server is master, 192.0.2.1 is the secondary.
            name: masterzone.com
            zonefile: /etc/nsd/masterzone.com.zone
            notify: 192.0.2.1 NOKEY
            provide-xfr: 192.0.2.1 NOKEY

       zone:
            # this server is secondary, 192.0.2.2 is master.
            name: secondzone.com
            zonefile: /etc/nsd/secondzone.com.zone
            allow-notify: 192.0.2.2 NOKEY
            request-xfr: 192.0.2.2 NOKEY

       Then, use kill -HUP to reload changes from master zone files.  And use kill -TERM to  stop
       the server.

FILE FORMAT

There must be whitespace between keywords. Attribute keywords end with a colon ':'. An
attribute is followed by its containing attributes, or a value.

At the top level only server:, key:, pattern:, zone:, tls-auth:, and remote-control: are
allowed. These are followed by their attributes or a new top-level keyword. The zone:
attribute is followed by zone options. The server: attribute is followed by global options
for the NSD server. A key: attribute is used to define keys for authentication. The
pattern: attribute is followed by the zone options for zones that use the pattern. A tls-
auth: attribute is used to define credentials for authenticating an outgoing TLS
connection used for XFR-over-TLS.

Files can be included using the include: directive. It can appear anywhere, and takes a
single filename as an argument. Processing continues as if the text from the included file
was copied into the config file at that point. If a chroot is used an absolute filename
is needed (with the chroot prepended), so that the include can be parsed before and after
application of the chroot (and the knowledge of what that chroot is). You can use '*' to
include a wildcard match of files, eg. "foo/nsd.d/*.conf". Also '?', '{}', '[]', and '~'
work, see glob(7). If no files match the pattern, this is not an error.

Server Options
The global options (if not overridden from the NSD commandline) are taken from the server:
clause. There may only be one server: clause.

ip-address: <ip4 or ip6>[@port] [servers] [bindtodevice] [setfib]
NSD will bind to the listed ip-address. Can be given multiple times to bind
multiple ip-addresses. Optionally, a port number can be given. If none are given
NSD listens to the wildcard interface. Same as commandline option -a.

To limit which NSD server(s) listen on the given interface, specify one or more
servers separated by whitespace after <ip>[@port]. Ranges can be used as a
shorthand to specify multiple consecutive servers. By default every server will
listen.

If an interface name is used instead of ip4 or ip6, the list of IP addresses
associated with that interface is picked up and used at server start.

For servers with multiple IP addresses that can be used to send traffic to the
internet, list them one by one, or the source address of replies could be wrong.
This is because if the udp socket associates a source address of 0.0.0.0 then the
kernel picks an ip-address with which to send to the internet, and it picks the
wrong one. Typically needed for anycast instances. Use ip-transparent to be able
to list addresses that turn on later (typical for certain load-balancing).

interface: <ip4 or ip6>[@port] [servers] [bindtodevice] [setfib]
Same as ip-address (for ease of compatibility with unbound.conf).

ip-transparent: <yes or no>
Allows NSD to bind to non local addresses. This is useful to have NSD listen to IP
addresses that are not (yet) added to the network interface, so that it can answer
immediately when the address is added. Default is no.

ip-freebind: <yes or no>
Set the IP_FREEBIND option to bind to nonlocal addresses and interfaces that are
down. Similar to ip-transparent. Default is no.

reuseport: <yes or no>
Use the SO_REUSEPORT socket option, and create file descriptors for every server in
the server-count. This improves performance of the network stack. Only really
useful if you also configure a server-count higher than 1 (such as, equal to the
number of cpus). The default is no. It works on Linux, but does not work on
FreeBSD, and likely does not work on other systems.

send-buffer-size: <number>
Set the send buffer size for query-servicing sockets. Set to 0 to use the default
settings.

receive-buffer-size: <number>
Set the receive buffer size for query-servicing sockets. Set to 0 to use the
default settings.

debug-mode: <yes or no>
Turns on debugging mode for nsd, does not fork a daemon process. Default is no.
Same as commandline option -d. If set to yes it does not fork and stays in the
foreground, which can be helpful for commandline debugging, but is also used by
certain server supervisor processes to ascertain that the server is running.

do-ip4: <yes or no>
If yes, NSD listens to IPv4 connections. Default yes.

do-ip6: <yes or no>
If yes, NSD listens to IPv6 connections. Default yes.

database: <filename>
By default '/var/lib/nsd/nsd.db' is used. The specified file is used to store the
compiled zone information. Same as commandline option -f. If set to "" then no
database is used. This uses less memory but zone updates are not (immediately)
spooled to disk.

zonelistfile: <filename>
By default /var/lib/nsd/zone.list is used. The specified file is used to store the
dynamically added list of zones. The list is written to by NSD to add and delete
zones. It is a text file with a zone-name and pattern-name on each line. This
file is used for the nsd-control addzone and delzone commands.

identity: <string>
Returns the specified identity when asked for CH TXT ID.SERVER. Default is the
name as returned by gethostname(3). Same as commandline option -i. See
hide-identity to set the server to not respond to such queries.

version: <string>
Returns the specified version string when asked for CH TXT version.server, and
version.bind queries. Default is the compiled package version. See hide-version
to set the server to not respond to such queries.

nsid: <string>
Add the specified nsid to the EDNS section of the answer when queried with an NSID
EDNS enabled packet. As a sequence of hex characters or with ascii_ prefix and
then an ascii string. Same as commandline option -I.

logfile: <filename>
Log messages to the logfile. The default is to log to stderr and syslog (with
facility LOG_DAEMON). Same as commandline option -l.

log-only-syslog: <yes or no>
Log messages only to syslog. Useful with systemd so that print to stderr does not
cause duplicate log strings in journald. Before syslog has been opened, the server
uses stderr. Stderr is also used if syslog is not available. Default is no.

server-count: <number>
Start this many NSD servers. Default is 1. Same as commandline option -N.

cpu-affinity: <number> <number> ...
Overall CPU affinity for NSD server(s). Default is no affinity. -n.

server-N-cpu-affinity: <number>
Bind NSD server specified by N to a specific core. Default is to have affinity set
to every core specified in cpu-affinity. This setting only takes effect if
cpu-affinity is enabled. -n

xfrd-cpu-affinity: <number>
Bind xfrd to a specific core. Default is to have affinity set to every core
specified in cpu-affinity. This setting only takes effect if cpu-affinity is
enabled. -n

tcp-count: <number>
The maximum number of concurrent, active TCP connections by each server. Default
is 100. Same as commandline option -n.

tcp-reject-overflow: <yes or no>
If set to yes, TCP connections made beyond the maximum set by tcp-count will be
dropped immediately (accepted and closed). Default is no.

tcp-query-count: <number>
The maximum number of queries served on a single TCP connection. Default is 0,
meaning there is no maximum.

tcp-timeout: <number>
Overrides the default TCP timeout. This also affects zone transfers over TCP. The
default is 120 seconds.

tcp-mss: <number>
Maximum segment size (MSS) of TCP socket on which the server responds to queries.
Value lower than common MSS on Ethernet (1220 for example) will address path MTU
problem. Note that not all platform supports socket option to set MSS
(TCP_MAXSEG). Default is system default MSS determined by interface MTU and
negotiation between server and client.

outgoing-tcp-mss: <number>
Maximum segment size (MSS) of TCP socket for outgoing XFR request to other
nameservers. Value lower than common MSS on Ethernet (1220 for example) will
address path MTU problem. Note that not all platform supports socket option to set
MSS (TCP_MAXSEG). Default is system default MSS determined by interface MTU and
negotiation between NSD and other servers.

xfrd-tcp-max: <number>
Number of sockets for xfrd to use for outgoing zone transfers. Default 128.
Increase it to allow more zone transfer sockets, like to 256. To save memory, this
can be lowered, set it lower together with some other settings to have reduced
memory footprint for NSD. xfrd-tcp-max: 32 and xfrd-tcp-pipeline: 128 and rrl-size:
1000

This reduces memory footprint, other memory usage is caused mainly by the
server-count setting, the number of server processes, and the tcp-count setting,
which keeps buffers per server process, and by the size of the zone data.

xfrd-tcp-pipeline: <number>
Number of simultaneous outgoing zone transfers that are possible on the tcp sockets
of xfrd. Max is 65536, default is 128.

ipv4-edns-size: <number>
Preferred EDNS buffer size for IPv4. Default 1232.

ipv6-edns-size: <number>
Preferred EDNS buffer size for IPv6. Default 1232.

pidfile: <filename>
Use the pid file instead of the platform specific default, usually
/run/nsd/nsd.pid. Same as commandline option -P. With "" there is no pidfile, for
some startup management setups, where a pidfile is not useful to have.

port: <number>
Answer queries on the specified port. Default is 53. Same as commandline option -p.

statistics: <number>
If not present no statistics are dumped. Statistics are produced every number
seconds. Same as commandline option -s.

chroot: <directory>
NSD will chroot on startup to the specified directory. Note that if elsewhere in
the configuration you specify an absolute pathname to a file inside the chroot, you
have to prepend the chroot path. That way, you can switch the chroot option on and
off without having to modify anything else in the configuration. Set the value to
"" (the empty string) to disable the chroot. By default "" is used. Same as
commandline option -t.

username: <username>
After binding the socket, drop user privileges and assume the username. Can be
username, id or id.gid. Same as commandline option -u.

zonesdir: <directory>
Change the working directory to the specified directory before accessing zone
files. Also, NSD will access database, zonelistfile, logfile, pidfile, xfrdfile,
xfrdir, server-key-file, server-cert-file, control-key-file and control-cert-file
relative to this directory. Set the value to "" (the empty string) to disable the
change of working directory. By default "/etc/nsd" is used.

difffile: <filename>
Ignored, for compatibility with NSD3 config files.

xfrdfile: <filename>
The soa timeout and zone transfer daemon in NSD will save its state to this file.
State is read back after a restart. The state file can be deleted without too much
harm, but timestamps of zones will be gone. If it is configured as "", the state
file is not used, all slave zones are checked for updates upon startup. For more
details see the section on zone expiry behavior of NSD. Default is
/var/lib/nsd/xfrd.state.

xfrdir: <directory>
The zone transfers are stored here before they are processed. A directory is
created here that is removed when NSD exits. Default is /tmp.

xfrd-reload-timeout: <number>
If this value is -1, xfrd will not trigger a reload after a zone transfer. If
positive xfrd will trigger a reload after a zone transfer, then it will wait for
the number of seconds before it will trigger a new reload. Setting this value
throttles the reloads to once per the number of seconds. The default is 1 second.

verbosity: <level>
This value specifies the verbosity level for (non-debug) logging. Default is 0. 1
gives more information about incoming notifies and zone transfers. 2 lists soft
warnings that are encountered. 3 prints more information.

Verbosity 0 will print warnings and errors, and other events that are important to
keep NSD running.

Verbosity 1 prints additionally messages of interest. Successful notifies,
successful incoming zone transfer (the zone is updated), failed incoming zone
transfers or the inability to process zone updates.

Verbosity 2 prints additionally soft errors, like connection resets over TCP. And
notify refusal, and axfr request refusals.

hide-version: <yes or no>
Prevent NSD from replying with the version string on CHAOS class queries. Default
is no.

hide-identity: <yes or no>
Prevent NSD from replying with the identity string on CHAOS class queries. Default
is no.

drop-updates: <yes or no>
If set to yes, drop received packets with the UPDATE opcode. Default is no.

use-systemd: <yes or no>
This option is deprecated and ignored. If compiled with libsystemd, NSD signals
readiness to systemd and use of the option is not necessary.

log-time-ascii: <yes or no>
Log time in ascii, if "no" then in seconds epoch. Default is yes. This chooses
the format when logging to file. The printout via syslog has a timestamp formatted
by syslog.

round-robin: <yes or no>
Enable round robin rotation of records in the answer. This changes the order of
records in the answer and this may balance load across them. The default is no.

minimal-responses: <yes or no>
Enable minimal responses for smaller answers. This makes packets smaller. Extra
data is only added for referrals, when it is really necessary. This is different
from the --enable-minimal-responses configure time option, that reduces packets,
but exactly to the fragmentation length, the nsd.conf option reduces packets as
small as possible. The default is no.

confine-to-zone: <yes or no>
If set to yes, additional information will not be added to the response if the apex
zone of the additional information does not match the apex zone of the initial
query (E.G. CNAME resolution). Default is no.

refuse-any: <yes or no>
Refuse queries of type ANY. This is useful to stop query floods trying to get
large responses. Note that rrl ratelimiting also has type ANY as a ratelimiting
type. It sends truncation in response to UDP type ANY queries, and it allows TCP
type ANY queries like normal. The default is no.

zonefiles-check: <yes or no>
Make NSD check the mtime of zone files on start and sighup. If you disable it it
starts faster (less disk activity in case of a lot of zones). The default is yes.
The nsd-control reload command reloads zone files regardless of this option.

zonefiles-write: <seconds>
Write changed secondary zones to their zonefile every N seconds. If the zone
(pattern) configuration has "" zonefile, it is not written. Zones that have
received zone transfer updates are written to their zonefile. Default is 0
(disabled) when there is a database, and 3600 (1 hour) when database is "". The
database also commits zone transfer contents. You can configure it away from the
default by putting the config statement for zonefiles-write: after the database:
statement in the config file.

rrl-size: <numbuckets>
This option gives the size of the hashtable. Default 1000000. More buckets use more
memory, and reduce the chance of hash collisions.

rrl-ratelimit: <qps>
The max qps allowed (from one query source). Default is on (with a suggested 200
qps). If set to 0 then it is disabled (unlimited rate), also set the
whitelist-ratelimit to 0 to disable ratelimit processing. If you set verbosity to
2 the blocked and unblocked subnets are logged. Blocked queries are blocked and
some receive TCP fallback replies. Once the rate limit is reached, NSD begins
dropping responses. However, one in every "rrl-slip" number of responses is
allowed, with the TC bit set. If slip is set to 2, the outgoing response rate will
be halved. If it's set to 3, the outgoing response rate will be one-third, and so
on. If you set rrl-slip to 10, traffic is reduced to 1/10th. Ratelimit options
rrl-ratelimit, rrl-size and rrl-whitelist-ratelimit are updated when nsd-control
reconfig is done (also the zone-specific ratelimit options are updated).

rrl-slip: <numpackets>
This option controls the number of packets discarded before we send back a SLIP
response (a response with "truncated" bit set to one). 0 disables the sending of
SLIP packets, 1 means every query will get a SLIP response. Default is 2, cuts
traffic in half and legit users have a fair chance to get a +TC response.

rrl-ipv4-prefix-length: <subnet>
IPv4 prefix length. Addresses are grouped by netblock. Default 24.

rrl-ipv6-prefix-length: <subnet>
IPv6 prefix length. Addresses are grouped by netblock. Default 64.

rrl-whitelist-ratelimit: <qps>
The max qps for query sorts for a source, which have been whitelisted. Default on
(with a suggested 2000 qps). With the rrl-whitelist option you can set specific
queries to receive this qps limit instead of the normal limit. With the value 0
the rate is unlimited.

answer-cookie: <yes or no>
Enable to answer to requests containing DNS Cookies as specified in RFC7873.
Default is no.

cookie-secret: <128 bit hex string>
Servers in an anycast deployment need to be able to verify each other's DNS
Server Cookies. For this they need to share the secret used to construct and
verify the DNS Cookies. Default is a 128 bits random secret generated at startup
time. This option is ignored if a cookie-secret-file is present. In that case the
secrets from that file are used in DNS Cookie calculations.

cookie-secret-file: <filename>
File from which the secrets are read used in DNS Cookie calculations. When this
file exists, the secrets in this file are used and the secret specified by the
cookie-secret option is ignored. Default is /etc/nsd/nsd_cookiesecrets.txt

The content of this file must be manipulated with the add_cookie_secret,
drop_cookie_secret and activate_cookie_secret commands to the nsd-control(8) tool.
Please see that manpage how to perform a safe cookie secret rollover.

tls-service-key: <filename>
If enabled, the server provides TLS service on TCP sockets with the TLS service
port number. The port number (853) is configured with tls-port. To turn it on,
create an interface: option line in config with @port appended to the IP-address.
This creates the extra socket on which the DNS over TLS service is provided.

The file is the private key for the TLS session. The public certificate is in the
tls-service-pem file. Default is "", turned off. Requires a restart (a reload is
not enough) if changed, because the private key is read while root permissions are
held and before chroot (if any).

tls-service-pem: <filename>
The public key certificate pem file for the tls service. Default is "", turned off.

tls-service-ocsp: <filename>
The ocsp pem file for the tls service, for OCSP stapling. Default is "", turned
off. An external process prepares and updates the OCSP stapling data. Like this,
openssl ocsp -no_nonce \
-respout /path/to/ocsp.pem \
-CAfile /path/to/ca_and_any_intermediate.pem \
-issuer /path/to/direct_issuer.pem \
-cert /path/to/cert.pem \
-url "$( openssl x509 -noout -text -in /path/to/cert.pem | grep 'OCSP - URI:'
| cut -d: -f2,3 )"

tls-port: <number>
The port number on which to provide TCP TLS service, default is 853, only
interfaces configured with that port number as @number get DNS over TLS service.

tls-cert-bundle: <filename>
If null or "", the default verify locations are used. Set it to the certificate
bundle file, for example "/etc/pki/tls/certs/ca-bundle.crt". These certificates are
used for authenticating Transfer over TLS (XoT) connections.

Remote Control
The remote-control: clause is used to set options for using the nsd-control(8) tool to
give commands to the running NSD server. It is disabled by default, and listens for
localhost by default. It uses TLS over TCP where the server and client authenticate to
each other with self-signed certificates. The self-signed certificates can be generated
with the nsd-control-setup tool. The key files are read by NSD before the chroot and
before dropping user permissions, so they can be outside the chroot and readable by the
superuser only.

control-enable: <yes or no>
Enable remote control, default is no.

control-interface: <ip4 or ip6 | interface name | absolute path>
NSD will bind to the listed addresses to service control requests (on TCP). Can be
given multiple times to bind multiple ip-addresses. Use 0.0.0.0 and ::0 to service
the wildcard interface. If none are given NSD listens to the localhost 127.0.0.1
and ::1 interfaces for control, if control is enabled with control-enable.

If an interface name is used instead of ip4 or ip6, the list of IP addresses
associated with that interface is picked up and used at server start.

With an absolute path, a unix local named pipe is used for control. The file is
created with user and group that is configured and access bits are set to allow
members of the group access. Further access can be controlled by setting
permissions on the directory containing the control socket file. The key and cert
files are not used when control is via the named pipe, because access control is
via file and directory permission.

control-port: <number>
The port number for remote control service. 8952 by default.

server-key-file: <filename>
Path to the server private key, by default /etc/nsd/nsd_server.key. This file is
generated by the nsd-control-setup utility. This file is used by the nsd server,
but not by nsd-control.

server-cert-file: <filename>
Path to the server self signed certificate, by default /etc/nsd/nsd_server.pem.
This file is generated by the nsd-control-setup utility. This file is used by the
nsd server, and also by nsd-control.

control-key-file: <filename>
Path to the control client private key, by default /etc/nsd/nsd_control.key. This
file is generated by the nsd-control-setup utility. This file is used by
nsd-control.

control-cert-file: <filename>
Path to the control client certificate, by default /etc/nsd/nsd_control.pem. This
certificate has to be signed with the server certificate. This file is generated
by the nsd-control-setup utility. This file is used by nsd-control.

Pattern Options
The pattern: clause is used to denote a set of options to apply to some zones. The same
zone options as for a zone are allowed.

name: <string>
The name of the pattern. This is a (case sensitive) string. The pattern names
that start with "_implicit_" are used internally for zones that have no pattern
(they are defined in nsd.conf directly).

include-pattern: <pattern-name>
The options from the given pattern are included at this point in this pattern. The
referenced pattern must be defined above this one.

<zone option>: <value>
The zone options such as zonefile, allow-query, allow-notify, request-xfr,
allow-axfr-fallback, notify, notify-retry, provide-xfr, store-ixfr, ixfr-number,
ixfr-size, create-ixfr, zonestats, and outgoing-interface can be given. They are
applied to the patterns and zones that include this pattern.

Zone Options
For every zone the options need to be specified in one zone: clause. The access control
list elements can be given multiple times to add multiple servers. These elements need to
be added explicitly.

For zones that are configured in the nsd.conf config file their settings are hardcoded (in
an implicit pattern for themselves only) and they cannot be deleted via delzone, but
remove them from the config file and repattern.

name: <string>
The name of the zone. This is the domain name of the apex of the zone. May end with
a '.' (in FQDN notation). For example "example.com", "sub.example.net.". This
attribute must be present in each zone.

zonefile: <filename>
The file containing the zone information. If this attribute is present it is used
to read and write the zone contents. If the attribute is absent it prevents writing
out of the zone.

The string is processed so that one string can be used (in a pattern) for a lot of
different zones. If the label or character does not exist the percent-character is
replaced with a period for output (i.e. for the third character in a two letter
domain name).

%s is replaced with the zone name.

%1 is replaced with the first character of the zone name.

%2 is replaced with the second character of the zone name.

%3 is replaced with the third character of the zone name.

%z is replaced with the toplevel domain name of the zone.

%y is replaced with the next label under the toplevel domain.

%x is replaced with the next-next label under the toplevel domain.

allow-query: <ip-spec> <key-name | NOKEY | BLOCKED>
Access control list. When at least one allow-query option is specified, then the
in the allow-query options specified addresses are are allowed to query the server
for the zone. Queries from unlisted or specifically BLOCKED addresses are
discarded. If NOKEY is given no TSIG signature is required. BLOCKED supersedes
other entries, other entries are scanned for a match in the order of the
statements. Without allow-query options, queries are allowed from any IP address
without TSIG key (which is the default).

The ip-spec is either a plain IP address (IPv4 or IPv6), or can be a subnet of the
form 1.2.3.4/24, or masked like 1.2.3.4&255.255.255.0 or a range of the form
1.2.3.4-1.2.3.25. Note the ip-spec ranges do not use spaces around the /, &, @ and
- symbols.

allow-notify: <ip-spec> <key-name | NOKEY | BLOCKED>
Access control list. The listed (primary) address is allowed to send notifies to
this (secondary) server. Notifies from unlisted or specifically BLOCKED addresses
are discarded. If NOKEY is given no TSIG signature is required. BLOCKED supersedes
other entries, other entries are scanned for a match in the order of the
statements.

The ip-spec is either a plain IP address (IPv4 or IPv6), or can be a subnet of the
form 1.2.3.4/24, or masked like 1.2.3.4&255.255.255.0 or a range of the form
1.2.3.4-1.2.3.25. A port number can be added using a suffix of @number, for
example 1.2.3.4@5300 or 1.2.3.4/24@5300 for port 5300. Note the ip-spec ranges do
not use spaces around the /, &, @ and - symbols.

request-xfr: [AXFR|UDP] <ip-address> <key-name | NOKEY> [tls-auth-name]
Access control list. The listed address (the master) is queried for AXFR/IXFR on
update. A port number can be added using a suffix of @number, for example
1.2.3.4@5300. The specified key is used during AXFR/IXFR. If tls-auth-name is
included, the specified tls-auth clause will be used to perform authenticated XFR-
over-TLS.

If the AXFR option is given, the server will not be contacted with IXFR queries but
only AXFR requests will be made to the server. This allows an NSD secondary to have
a master server that runs NSD. If the AXFR option is left out then both IXFR and
AXFR requests are made to the master server.

If the UDP option is given, the secondary will use UDP to transmit the IXFR
requests. You should deploy TSIG when allowing UDP transport, to authenticate
notifies and zone transfers. Otherwise, NSD is more vulnerable for Kaminsky-style
attacks. If the UDP option is left out then IXFR will be transmitted using TCP.

If a tls-auth-name is given then TLS (by default on port 853) will be used for all
zone transfers for the zone. If authentication of the master based on the specified
tls-auth authentication information fails, the XFR request will not be sent.
Support for TLS 1.3 is required for XFR-over-TLS.

allow-axfr-fallback: <yes or no>
This option should be accompanied by request-xfr. It (dis)allows NSD (as secondary)
to fallback to AXFR if the primary name server does not support IXFR. Default is
yes.

size-limit-xfr: <number>
This option should be accompanied by request-xfr. It specifies XFR temporary file
size limit. It can be used to stop very large zone retrieval, that could otherwise
use up a lot of memory and disk space. If this option is 0, unlimited. Default
value is 0.

notify: <ip-address> <key-name | NOKEY>
Access control list. The listed address (a secondary) is notified of updates to
this zone. A port number can be added using a suffix of @number, for example
1.2.3.4@5300. The specified key is used to sign the notify. Only on secondary
configurations will NSD be able to detect zone updates (as it gets notified itself,
or refreshes after a time).

notify-retry: <number>
This option should be accompanied by notify. It sets the number of retries when
sending notifies.

provide-xfr: <ip-spec> <key-name | NOKEY | BLOCKED>
Access control list. The listed address (a secondary) is allowed to request AXFR
from this server. Zone data will be provided to the address. The specified key is
used during AXFR. For unlisted or BLOCKED addresses no data is provided, requests
are discarded. BLOCKED supersedes other entries, other entries are scanned for a
match in the order of the statements. NSD provides AXFR for its secondaries, but
IXFR is not implemented (IXFR is implemented for request-xfr, but not for
provide-xfr).

outgoing-interface: <ip-address>
Access control list. The listed address is used to request AXFR|IXFR (in case of a
secondary) or used to send notifies (in case of a primary).

The ip-address is a plain IP address (IPv4 or IPv6). A port number can be added
using a suffix of @number, for example 1.2.3.4@5300.

store-ixfr: <yes or no>
If enabled, IXFR contents are stored and provided to the set of clients specified
in the provide-xfr statement. Default is no. IXFR contents is a smaller set of
changes that differ between zone versions, where an AXFR contains the full contents
of the zone.

ixfr-number: <number>
The number of IXFR versions to store for this zone, at most. Default is 5.

ixfr-size: <number>
The max storage to use for IXFR versions for this zone, in bytes. Default is
1048576. A value of 0 means unlimited, if you want to turn off IXFR storage, use
the store-ixfr option. NSD does not elide IXFR contents from versions that add and
remove the same data, that merges version changes together to shorten the data, but
leaves the data and change sequence as it was transmitted by another server.

create-ixfr: <yes or no>
If enabled, IXFR data is created when a zonefile is read by the server. Also set
store-ixfr enabled, so that the contents are stored, when you use this. Default is
off. If the server is not running, the nsd-checkzone -i option can be used to
create an IXFR file. When an IXFR is created, the server spools a version of the
zone to a temporary file, at the location where the ixfr files are stored. This
creates IXFR data when the zone is read from file, but not when a zone is read by
AXFR transfer from a server, because then the topmost server that originates the
data is the one place where ixfr differences are computed and those differences are
then transmitted verbatim to all the other servers.

max-refresh-time: <seconds>
Limit refresh time for secondary zones. This is the timer which checks to see if
the zone has to be refetched when it expires. Normally the value from the SOA
record is used, but this option restricts that value.

min-refresh-time: <seconds>
Limit refresh time for secondary zones.

max-retry-time: <seconds>
Limit retry time for secondary zones. This is the timer which retries after a
failed fetch attempt for the zone. Normally the value from the SOA record is used,
followed by an exponential backoff, but this option restricts that value.

min-retry-time: <seconds>
Limit retry time for secondary zones.

min-expire-time: <seconds or refresh+retry+1>
Limit expire time for secondary zones. The value can be expressed either by a
number of seconds, or the string "refresh+retry+1". With the latter the expire
time will be lower bound to the refresh plus the retry value from the SOA record,
plus 1. The refresh and retry values will be subject to the bounds configured with
max-refresh-time, min-refresh-time, max-retry-time and min-retry-time if given.

zonestats: <name>
When compiled with --enable-zone-stats NSD can collect statistics per zone. This
name gives the group where statistics are added to. The groups are output from
nsd-control stats and stats_noreset. Default is "". You can use "%s" to use the
name of the zone to track its statistics. If not compiled in, the option can be
given but is ignored.

include-pattern: <pattern-name>
The options from the given pattern are included at this point. The referenced
pattern must be defined above this zone.

rrl-whitelist: <rrltype>
This option causes queries of this rrltype to be whitelisted, for this zone. They
receive the whitelist-ratelimit. You can give multiple lines, each enables a new
rrltype to be whitelisted for the zone. Default has none whitelisted. The rrltype
is the query classification that the NSD RRL employs to make different types not
interfere with one another. The types are logged in the loglines when a subnet is
blocked (in verbosity 2). The RRL classification types are: nxdomain, error,
referral, any, rrsig, wildcard, nodata, dnskey, positive, all.

multi-master-check: <yes or no>
Default no. If enabled, checks all masters for the last version. It uses the
higher version of all the configured masters. Useful if you have multiple masters
that have different version numbers served.

Key Declarations
The key: clause establishes a key for use in access control lists. It has the following
attributes.

name: <string>
The key name. Used to refer to this key in the access control list. The key name
has to be correct for tsig to work. This is because the key name is output on the
wire.

algorithm: <string>
Authentication algorithm for this key. Such as hmac-md5, hmac-sha1, hmac-sha224,
hmac-sha256, hmac-sha384 and hmac-sha512. Can also be abbreviated as 'sha1',
'sha256'. Default is sha256. Algorithms are only available when they were
compiled in (available in the crypto library).

secret: <base64 blob>
The base64 encoded shared secret. It is possible to put the secret: declaration
(and base64 blob) into a different file, and then to include: that file. In this
way the key secret and the rest of the configuration file, which may have different
security policies, can be split apart. The content of the secret is the agreed
base64 secret content. To make it up, enter a password (its length must be a
multiple of 4 characters, A-Za-z0-9), or use dev-random output through a base64
encode filter.

TLS Auth Declarations
The tls-auth: clause establishes authentication attributes to use when authenticating the
far end of an outgoing TLS connection used in access control lists for XFR-over-TLS. It
has the following attributes.

name: <string>
The tls-auth name. Used to refer to this TLS authentication information in the
access control list.

auth-domain-name: <string>
The authentication domain name as defined in RFC8310.

client-cert: <file name of clientcert.pem>
If you want to use mutual TLS authentication, this is where the client certificates
can be configured that NSD uses to connect to the upstream server to download the
zone. The client public key pem cert file can be configured here. Also configure a
private key with client-key.

client-key: <file name of clientkey.key>
If you want to use mutual TLS authentication, the private key file can be
configured here for the client authentication.

client-key-pw: <string>
If the client-key file uses a password to decrypt the key before it can be used,
then the password can be specified here as a string. It is possible to include
other config files with the include: option, and this can be used to move that
sensitive data to another file, if you wish.

DNSTAP Logging Options
DNSTAP support, when compiled in, is enabled in the dnstap: section. This starts a
collector process that writes the log information to the destination.

dnstap-enable: <yes or no>
If dnstap is enabled. Default no. If yes, it connects to the dnstap server and if
any of the dnstap-log-..-messages options is enabled it sends logs for those
messages to the server.

dnstap-socket-path: <file name>
Sets the unix socket file name for connecting to the server that is listening on
that socket. Default is "/var/run/nsd-dnstap.sock".

dnstap-send-identity: <yes or no>
If enabled, the server identity is included in the log messages. Default is no.

dnstap-send-version: <yes or no>
If enabled, the server version if included in the log messages. Default is no.

dnstap-identity: <string>
The identity to send with messages, if "" the hostname is used. Default is "".

dnstap-version: <string>
The version to send with messages, if "" the package version is used. Default is
"".

dnstap-log-auth-query-messages: <yes or no>
Enable to log auth query messages. Default is no. These are client queries to
NSD.

dnstap-log-auth-response-messages: <yes or no>
Enable to log auth response messages. Default is no. These are responses from NSD
to clients.

NSD CONFIGURATION FOR BIND9 HACKERS

BIND9 is a name server implementation with its own configuration file format,
named.conf(5). BIND9 types zones as 'Master' or 'Slave'.

Slave zones
For a slave zone, the master servers are listed. The master servers are queried for zone
data, and are listened to for update notifications. In NSD these two properties need to
be configured separately, by listing the master address in allow-notify and request-xfr
statements.

In BIND9 you only need to provide allow-notify elements for any extra sources of
notifications (i.e. the operators), NSD needs to have allow-notify for both masters and
operators. BIND9 allows additional transfer sources, in NSD you list those as request-xfr.

Here is an example of a slave zone in BIND9 syntax.

# Config file for example.org options {
dnssec-enable yes;
};

key tsig.example.org. {
algorithm hmac-md5;
secret "aaaaaabbbbbbccccccdddddd";
};

server 162.0.4.49 {
keys { tsig.example.org. ; };
};

zone "example.org" {
type slave;
file "secondary/example.org.signed";
masters { 162.0.4.49; };
};

For NSD, DNSSEC is enabled automatically for zones that are signed. The dnssec-enable
statement in the options clause is not needed. In NSD keys are associated with an IP
address in the access control list statement, therefore the server{} statement is not
needed. Below is the same example in an NSD config file.

# Config file for example.org
key:
name: tsig.example.org.
algorithm: hmac-md5
secret: "aaaaaabbbbbbccccccdddddd"

zone:
name: "example.org"
zonefile: "secondary/example.org.signed"
# the master is allowed to notify and will provide zone data.
allow-notify: 162.0.4.49 NOKEY
request-xfr: 162.0.4.49 tsig.example.org.

Notice that the master is listed twice, once to allow it to send notifies to this slave
server and once to tell the slave server where to look for updates zone data. More
allow-notify and request-xfr lines can be added to specify more masters.

It is possible to specify extra allow-notify lines for addresses that are also allowed to
send notifications to this slave server.

Master zones
For a master zone in BIND9, the slave servers are listed. These slave servers are sent
notifications of updated and are allowed to request transfer of the zone data. In NSD
these two properties need to be configured separately.

Here is an example of a master zone in BIND9 syntax.

zone "example.nl" {
type master;
file "example.nl";
};

In NSD syntax this becomes:

zone:
name: "example.nl"
zonefile: "example.nl"
# allow anybody to request xfr.
provide-xfr: 0.0.0.0/0 NOKEY
provide-xfr: ::0/0 NOKEY

# to list a slave server you would in general give
# provide-xfr: 1.2.3.4 tsig-key.name.
# notify: 1.2.3.4 NOKEY

Other
NSD is an authoritative only DNS server. This means that it is meant as a primary or
secondary server for zones, providing DNS data to DNS resolvers and caches. BIND9 can
function as an authoritative DNS server, the configuration options for that are compared
with those for NSD in this section. However, BIND9 can also function as a resolver or
cache. The configuration options that BIND9 has for the resolver or caching thus have no
equivalents for NSD.

FILES

       "/var/lib/nsd/nsd.db"
              default NSD database

       /etc/nsd/nsd.conf
              default NSD configuration file

AUTHORS

       NSD  was  written  by  NLnet  Labs and RIPE NCC joint team. Please see CREDITS file in the
       distribution for further details.

BUGS

       nsd.conf is parsed by a primitive parser, error messages may not be to the point.