oasis-root

nsd.conf.5 (36612B)

.TH "nsd.conf" "5" "Apr  6, 2021" "NLnet Labs" "nsd 4.3.6"
.\" Copyright (c) 2001\-2008, NLnet Labs. All rights reserved.
.\" See LICENSE for the license.
.SH "NAME"
.B nsd.conf
\- NSD configuration file
.SH "SYNOPSIS"
.B nsd.conf
.SH "DESCRIPTION"
.B 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. 
.PP
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".
.PP
.B Nsd.conf
specifies options for the nsd server, zone files, primaries and 
secondaries.
.SH "EXAMPLE"
An example of a short nsd.conf file is below.
.LP
# Example.com nsd.conf file
.RS 0
# This is a comment.
.RE
.TP
server:
.RS 5
server-count: 1 # use this number of cpu cores
.RE
.RS 5
database: ""  # or use "/var/db/nsd/nsd.db"
.RE
.RS 5
zonelistfile: "/var/db/nsd/zone.list"
.RE
.RS 5
username: nsd
.RE
.RS 5
logfile: "/var/log/nsd.log"
.RE
.RS 5
pidfile: "/run/nsd.pid"
.RE
.RS 5
xfrdfile: "/var/db/nsd/xfrd.state"
.RE
.TP
zone:
.RS 5
name: example.com
.RE
.RS 5
zonefile: /etc/nsd/example.com.zone 
.RE
.TP
zone:
.RS 5
# this server is master, 192.0.2.1 is the secondary.
.RE
.RS 5
name: masterzone.com
.RE
.RS 5
zonefile: /etc/nsd/masterzone.com.zone 
.RE
.RS 5
notify: 192.0.2.1 NOKEY
.RE
.RS 5
provide-xfr: 192.0.2.1 NOKEY
.RE
.TP
zone:
.RS 5
# this server is secondary, 192.0.2.2 is master.
.RE
.RS 5
name: secondzone.com
.RE
.RS 5
zonefile: /etc/nsd/secondzone.com.zone 
.RE
.RS 5
allow-notify: 192.0.2.2 NOKEY
.RE
.RS 5
request-xfr: 192.0.2.2 NOKEY
.RE
.LP
Then, use kill \-HUP to reload changes from master zone files.
And use kill \-TERM to stop the server.
.SH "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. 
.P
At the top level only 
.BR server: ,
.BR key: ,
.BR pattern: ,
.BR zone: ,
and
.B remote-control:
are allowed. These are followed by their attributes or a new top-level keyword. The
.B zone:
attribute is followed by zone options. The 
.B server: 
attribute is followed by global options for the 
.B NSD 
server. A 
.B key: 
attribute is used to define keys for authentication. The
.B pattern:
attribute is followed by the zone options for zones that use the pattern.
.P
Files can be included using the 
.B 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 \fBglob\fR(7).  If no files match the pattern, this
is not an error.
.SS "Server Options"
.LP
The global options (if not overridden from the NSD commandline) are 
taken from the 
.B server: 
clause. There may only be one 
.B server: 
clause.
.TP
.B ip\-address:\fR <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
.BR \-a.
.IP
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.
.IP
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.
.IP
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).
.TP
.B interface:\fR <ip4 or ip6>[@port] [servers] [bindtodevice] [setfib]
Same as ip\-address (for ease of compatibility with unbound.conf).
.TP
.B ip\-transparent:\fR <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.
.TP
.B ip\-freebind:\fR <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.
.TP
.B reuseport:\fR <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.
.TP
.B send\-buffer\-size:\fR <number>
Set the send buffer size for query-servicing sockets.  Set to 0 to use the default settings.
.TP
.B receive\-buffer\-size:\fR <number>
Set the receive buffer size for query-servicing sockets.  Set to 0 to use the default settings.
.TP
.B debug\-mode:\fR <yes or no>
Turns on debugging mode for nsd, does not fork a daemon process. 
Default is no. Same as commandline option
.BR \-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.
.TP
.B do\-ip4:\fR <yes or no>
If yes, NSD listens to IPv4 connections.  Default yes.
.TP
.B do\-ip6:\fR <yes or no>
If yes, NSD listens to IPv6 connections.  Default yes.
.TP
.B database:\fR <filename>
By default 
.I /var/db/nsd/nsd.db
is used. The specified file is used to store the compiled 
zone information. Same as commandline option 
.BR \-f.
If set to "" then no database is used.  This uses less memory but
zone updates are not (immediately) spooled to disk.
.TP
.B zonelistfile:\fR <filename>
By default 
.I /var/db/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.
.TP
.B identity:\fR <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 
.BR \-i .
See hide\-identity to set the server to not respond to such queries.
.TP
.B version:\fR <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.
.TP
.B nsid:\fR <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
.BR \-I .
.TP
.B logfile:\fR <filename>
Log messages to the logfile. The default is to log to stderr and 
syslog (with facility LOG_DAEMON). Same as commandline option 
.BR \-l .
.TP
.B log\-only\-syslog:\fR <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.
.TP
.B server\-count:\fR <number>
Start this many NSD servers. Default is 1. Same as commandline 
option 
.BR \-N .
.TP
.B cpu\-affinity:\fR <number> <number> ...
Overall CPU affinity for NSD server(s). Default is no affinity.
.BR \-n .
.TP
.B server\-N\-cpu\-affinity:\fR <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.
.BR \-n
.TP
.B xfrd\-cpu\-affinity:\fR <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.
.BR \-n
.TP
.B tcp\-count:\fR <number>
The maximum number of concurrent, active TCP connections by each server. 
Default is 100. Same as commandline option
.BR \-n .
.TP
.B tcp\-reject\-overflow:\fR <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.
.TP
.B tcp\-query\-count:\fR <number>
The maximum number of queries served on a single TCP connection.
Default is 0, meaning there is no maximum.
.TP
.B tcp\-timeout:\fR <number>
Overrides the default TCP timeout. This also affects zone transfers over TCP.
The default is 120 seconds.
.TP
.B tcp-mss:\fR <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.
.TP
.B outgoing\-tcp\-mss:\fR <number>
Maximum segment size (MSS) of TCP socket for outgoing XFR request
to other namesevers. 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.
.TP
.B ipv4\-edns\-size:\fR <number>
Preferred EDNS buffer size for IPv4.  Default 1232.
.TP
.B ipv6\-edns\-size:\fR <number>
Preferred EDNS buffer size for IPv6.  Default 1232.
.TP
.B pidfile:\fR <filename>
Use the pid file instead of the platform specific default, usually 
.IR /run/nsd.pid. 
Same as commandline option 
.BR \-P .
With "" there is no pidfile, for some startup management setups,
where a pidfile is not useful to have.
.TP
.B port:\fR <number>
Answer queries on the specified port. Default is 53. Same as 
commandline option 
.BR \-p .
.TP
.B statistics:\fR <number>
If not present no statistics are dumped. Statistics are produced 
every number seconds. Same as commandline option 
.BR \-s .
.TP
.B chroot:\fR <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 \fBchroot\fR 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 "\fI\fR" is used. Same as
commandline option 
.BR \-t .
.TP
.B username:\fR <username>
After binding the socket, drop user privileges and assume the 
username. Can be username, id or id.gid. Same as commandline option 
.BR \-u .
.TP
.B zonesdir:\fR <directory>
Change the working directory to the specified directory before accessing
zone files. Also, NSD will access \fBdatabase\fR, \fBzonelistfile\fR,
\fBlogfile\fR, \fBpidfile\fR, \fBxfrdfile\fR, \fBxfrdir\fR,
\fBserver-key-file\fR, \fBserver-cert-file\fR, \fBcontrol-key-file\fR and
\fBcontrol-cert-file\fR
relative to this directory. Set the value to "" (the empty string)
to disable the change of working directory. By default "\fI/etc/nsd/zone\fR"
is used.
.TP
.B difffile:\fR <filename>
Ignored, for compatibility with NSD3 config files. 
.TP
.B xfrdfile:\fR <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
.IR /var/db/nsd/xfrd.state .
.TP
.B xfrdir:\fR <directory>
The zone transfers are stored here before they are processed.  A directory
is created here that is removed when NSD exits.  Default is
.IR /tmp .
.TP
.B xfrd\-reload\-timeout:\fR <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.
.TP
.B verbosity:\fR <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.
.IP
Verbosity 0 will print warnings and errors, and other events that are
important to keep NSD running.
.IP
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.
.IP
Verbosity 2 prints additionally soft errors, like connection resets over TCP.
And notify refusal, and axfr request refusals.
.TP
.B hide\-version:\fR <yes or no>
Prevent NSD from replying with the version string on CHAOS class 
queries.  Default is no.
.TP
.B hide\-identity:\fR <yes or no>
Prevent NSD from replying with the identity string on CHAOS class 
queries.  Default is no.
.TP
.B drop\-updates:\fR <yes or no>
If set to yes, drop received packets with the UPDATE opcode.  Default is no.
.TP
.B use\-systemd:\fR <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.
.TP
.B log\-time\-ascii:\fR <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.
.TP
.B round\-robin:\fR <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.
.TP
.B minimal\-responses:\fR <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.
.TP
.B confine\-to\-zone:\fR <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. 
.TP
.B refuse\-any:\fR <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.
.TP
.B zonefiles\-check:\fR <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.
.TP
.B zonefiles\-write:\fR <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.
.TP
.B tls\-service\-key:\fR <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.
.IP
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).
.TP
.B tls\-service\-pem:\fR <filename>
The public key certificate pem file for the tls service. Default is "", turned off.
.TP
.B tls\-service\-ocsp:\fR <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,
.RS 9
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 )"
.RE
.TP
.B tls\-port:\fR <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.
.SS "Remote Control"
The
.B remote\-control:
clause is used to set options for using the \fInsd\-control\fR(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
\fInsd\-control\-setup\fR 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.
.TP
.B control\-enable:\fR <yes or no>
Enable remote control, default is no.
.TP
.B control\-interface:\fR <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.
.IP
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.
.IP
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.
.TP
.B control\-port:\fR <number>
The port number for remote control service. 8952 by default.
.TP
.B server\-key\-file:\fR <filename>
Path to the server private key, by default
.IR /etc/nsd/nsd_server.key .
This file is generated by the \fInsd\-control\-setup\fR utility.
This file is used by the nsd server, but not by \fInsd\-control\fR.
.TP
.B server\-cert\-file:\fR <filename>
Path to the server self signed certificate, by default
.IR /etc/nsd/nsd_server.pem .
This file is generated by the \fInsd\-control\-setup\fR utility.
This file is used by the nsd server, and also by \fInsd\-control\fR.
.TP
.B control\-key\-file:\fR <filename>
Path to the control client private key, by default
.IR /etc/nsd/nsd_control.key .
This file is generated by the \fInsd\-control\-setup\fR utility.
This file is used by \fInsd\-control\fR.
.TP
.B control\-cert\-file:\fR <filename>
Path to the control client certificate, by default
.IR /etc/nsd/nsd_control.pem .
This certificate has to be signed with the server certificate.
This file is generated by the \fInsd\-control\-setup\fR utility.
This file is used by \fInsd\-control\fR.
.SS "Pattern Options"
The
.B 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.
.TP
.B name:\fR <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).
.TP
.B include\-pattern:\fR <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.
.TP
.B <zone option>:\fR <value>
The zone options such as
.BR zonefile ,
.BR allow\-query ,
.BR allow\-notify ,
.BR request\-xfr ,
.BR allow\-axfr\-fallback ,
.BR notify ,
.BR notify\-retry ,
.BR provide\-xfr ,
.BR zonestats ,
and
.B outgoing\-interface 
can be given.  They are applied to the patterns and zones that include
this pattern.
.SS "Zone Options"
.LP 
For every zone the options need to be specified in one 
.B zone: 
clause. The access control list elements can be given multiple 
times to add multiple servers. These elements need to be added
explicitly.
.LP
For zones that are configured in the \fInsd.conf\fR 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.
.TP
.B name:\fR <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.
.TP
.B zonefile:\fR <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.
.IP
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).
.IP
.B %s\fR is replaced with the zone name.
.IP
.B %1\fR is replaced with the first character of the zone name.
.IP
.B %2\fR is replaced with the second character of the zone name.
.IP
.B %3\fR is replaced with the third character of the zone name.
.IP
.B %z\fR is replaced with the toplevel domain name of the zone.
.IP
.B %y\fR is replaced with the next label under the toplevel domain.
.IP
.B %x\fR is replaced with the next-next label under the toplevel domain.
.TP
.B allow\-query:\fR <ip\-spec> <key\-name | NOKEY | BLOCKED>
Access control list.  When at least one \fBallow\-query\fR option is
specified, then the in the \fBallow\-query\fR 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
\fBallow\-query\fR options, queries are allowed from any IP address
without TSIG key (which is the default).
.P
.RS
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.
.RE
.TP
.B allow\-notify:\fR <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.
.P
.RS
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.
.RE
.TP
.B request\-xfr:\fR [AXFR|UDP] <ip\-address> <key\-name | NOKEY>
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.
.P
.RS
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.
.P
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.
.RE
.TP
.B allow\-axfr\-fallback:\fR <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.
.TP
.B size\-limit\-xfr:\fR <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.
.TP
.B notify:\fR <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).
.TP
.B notify\-retry:\fR <number>
This option should be accompanied by notify. It sets the number of retries
when sending notifies.
.TP
.B provide\-xfr:\fR <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).
.P
.RS
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.
.RE
.TP
.B outgoing\-interface:\fR <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). 
.P
.RS
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.
.RE
.TP
.B max\-refresh\-time:\fR <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.
.TP
.B min\-refresh\-time:\fR <seconds>
Limit refresh time for secondary zones.
.TP
.B max\-retry\-time:\fR <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.
.TP
.B min\-retry\-time:\fR <seconds>
Limit retry time for secondary zones.
.TP
.B min\-expire\-time:\fR <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.
.TP
.B zonestats:\fR <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.
.TP
.B include\-pattern:\fR <pattern\-name>
The options from the given pattern are included at this point.
The referenced pattern must be defined above this zone.
.TP
.B multi\-master\-check:\fR <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.
.SS "Key Declarations"
The 
.B key: 
clause establishes a key for use in access control lists. It has 
the following attributes.
.TP
.B name:\fR <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.
.TP
.B algorithm:\fR <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).
.TP
.B secret:\fR <base64 blob>
The base64 encoded shared secret. It is possible to put the 
.B secret:
declaration (and base64 blob) into a different file, and then to
.B 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.
.SS DNSTAP Logging Options
DNSTAP support, when compiled in, is enabled in the \fBdnstap:\fR section.
This starts a collector process that writes the log information to the
destination.
.TP
.B dnstap-enable:\fR <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.
.TP
.B dnstap-socket-path:\fR <file name>
Sets the unix socket file name for connecting to the server that is
listening on that socket.  Default is "".
.TP
.B dnstap-send-identity:\fR <yes or no>
If enabled, the server identity is included in the log messages.
Default is no.
.TP
.B dnstap-send-version:\fR <yes or no>
If enabled, the server version if included in the log messages.
Default is no.
.TP
.B dnstap-identity:\fR <string>
The identity to send with messages, if "" the hostname is used.
Default is "".
.TP
.B dnstap-version:\fR <string>
The version to send with messages, if "" the package version is used.
Default is "".
.TP
.B dnstap-log-auth-query-messages:\fR <yes or no>
Enable to log auth query messages.  Default is no.
These are client queries to NSD.
.TP
.B dnstap-log-auth-response-messages:\fR <yes or no>
Enable to log auth response messages.  Default is no.
These are responses from NSD to clients.
.SH "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'. 
.SS "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. 
.P
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.
.P
Here is an example of a slave zone in BIND9 syntax.
.P
# Config file for example.org
options {
.RS 5
dnssec\-enable yes;
.RE
.RS 0
};
.RE
.LP
key tsig.example.org. {
.RS 5
algorithm hmac\-md5;
.RE
.RS 5
secret "aaaaaabbbbbbccccccdddddd";
.RE
};
.LP
server 162.0.4.49 {
.RS 5
keys { tsig.example.org. ; };
.RE
};
.LP
zone "example.org" {
.RS 5
type slave;
.RE
.RS 5
file "secondary/example.org.signed";
.RE
.RS 5
masters { 162.0.4.49; };
.RE
};
.P
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.
.LP
# Config file for example.org
.RS 0
key:
.RE
.RS 5
name: tsig.example.org.
.RE
.RS 5
algorithm: hmac\-md5
.RE
.RS 5
secret: "aaaaaabbbbbbccccccdddddd"
.RE
.LP
zone:
.RS 5
name: "example.org"
.RE
.RS 5
zonefile: "secondary/example.org.signed"
.RE
.RS 5
# the master is allowed to notify and will provide zone data.
.RE
.RS 5
allow\-notify: 162.0.4.49 NOKEY 
.RE
.RS 5
request\-xfr: 162.0.4.49 tsig.example.org.
.RE
.P
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.
.P
It is possible to specify extra allow\-notify lines for addresses 
that are also allowed to send notifications to this slave server.
.SS "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.
.P
Here is an example of a master zone in BIND9 syntax.
.LP
zone "example.nl" {
.RS 5
type master;
.RE
.RS 5
file "example.nl";
.RE
};
.LP
In NSD syntax this becomes:
.LP
zone:
.RS 5
name: "example.nl"
.RE
.RS 5
zonefile: "example.nl"
.RE
.RS 5
# allow anybody to request xfr.
.RE
.RS 5
provide\-xfr: 0.0.0.0/0 NOKEY
.RE
.RS 5
provide\-xfr: ::0/0 NOKEY
.RE
.P
.RS 5
# to list a slave server you would in general give
.RE
.RS 5
# provide\-xfr: 1.2.3.4 tsig\-key.name.
.RE
.RS 5
# notify: 1.2.3.4 NOKEY
.RE
.SS "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.
.SH "FILES"
.TP
/var/db/nsd/nsd.db
default
.B NSD
database
.TP
/etc/nsd/nsd.conf
default
.B NSD
configuration file
.SH "SEE ALSO" 
\fInsd\fR(8), \fInsd\-checkconf\fR(8), \fInsd\-control\fR(8)
.SH "AUTHORS"
.B NSD
was written by NLnet Labs and RIPE NCC joint team. Please see 
CREDITS file in the distribution for further details.
.SH "BUGS"
.B nsd.conf
is parsed by a primitive parser, error messages may not be to the 
point.