NSUPDATE(8) BSD System Manager’s Manual NSUPDATE(8)


nsupdate − update Internet name servers interactively


nsupdate [k keydir:keyname] [d] [v] [filename]


Nsupdate is a program to update Internet domain name servers supporting dynamic update. Nsupdate uses the DNS resolver library to pass messages to a DNS server requesting the additional or deletion of DNS resource records (RRs). Nsupdate reads input from filename or standard input.


      −k’            Sign updates with TSIG.

−d’ Debug mode.

−v’ Virtual circuit - use TCP to communication with server. Default is UDP.


Nsupdate reads input records, one per line, each line contributing a resource record to an update request. All domain names used in a single update request must belong to the same DNS zone. Updates are sent to the master server as defined in the SOA MNAME field. A blank line causes the accumulated records to be formated into a single update request and transmitted to the zone’s authoritative name servers. Additional records may follow, which are formed into additional, completely independent update requests. For the last request to be transmitted, a blank line must end the input.

Records take one of two general forms. Prerequisite records specify conditions that must be satisfied before the request will be processed. Update records specify changes to be made to the DNS database. A update request consists of zero or more prerequisites and one or more updates. Each update request is processed atomically - all prerequisites must be satisfied, then all updates will be performed.

Nsupdate understands the following input record formats:

       prereq nxdomain domain-name Requires that no RR of any type exists withname domain-name.

prereq yxdomain domain-name Requires that at least one RR named domain-name must exist.

prereq nxrrset domain-name [class] type Requires that no RR exists of the specified type and domain-name.

prereq yxrrset domain-name [class] type [data...] Requires that a RR exists of the specified type and domain-name. If data is specified, it must match exactly.

update delete domain-name [class] [type [data...]] Deletes RRs named domain-name. If type (and possibly data) is specified, only matching records will be deleted.

update add domain-name ttl [class] type data... Adds a new RR with specified ttl, type, and data.


The following example illustrates the interactive use of nsupdate to change an IP address by deleting any existing A records for a domain name and then inserting a new one. Since no prerequisites are specified, the new record will be added even if there were no existing records to delete. Note the trailing blank line, required to process the request.

      $ nsupdate
      > update delete test.example.com A
      > update add test.example.com 3600 A

In this example, a CNAME alias is added to the database only if there are no existing A or CNAME records for the domain name.

      $ nsupdate
      > prereq nxrrset www.example.com A
      > prereq nxrrset www.example.com CNAME
      > update add www.example.com 3600 CNAME test.example.com

In this example, the nsupdate will be signed with the key "mykey", which is in the directory "/var/named/keys".

      $ nsupdate -k /var/named/keys:mykey
      > update add ftp.example.com 60 A


       "send error" Typically indicates that the authoritative nameserverscould not be reached

"failed update packet" Typically indicates that the nameserver has rejected the update, either because the nameserver doesn’t support dynamic update, or due to an authentication failure

"res_mkupdate: packet size = size" (and no other messages) The update was successfully received and authenticated by the nameserver. The prerequisites, however, may have prevented the update from actually being performed. The only way to determine if the update was performed is to use debug mode (−d) and examine the status field in the nameserver’s reply.



initial domain name and name server addresses


named(8), resolver(3), resolver(5); RFC-1034, ‘‘Domain Names - Concepts and Facilities’’; RFC-1035, ‘‘Domain Names - Implementation and Specification’’; RFC-2136, Dynamic Updates in the Domain Name System.


Brent Baccala

4th Berkeley Distribution March 5, 1999 4th Berkeley Distribution