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@(#)files.me 6.10 (Berkeley) 4/22/91

.sh 1 "Files .pp The name server uses several files to load its data base. This section covers the files and their formats needed for named. .sh 2 "Boot File" .pp This is the file that is first read when named starts up. This tells the server what type of server it is, which zones it has authority over and where to get its initial data. The default location for this file is /\|etc\|/\|named\|.\|boot\|. However this can be changed by setting the BOOTFILE variable when you compile named or by specifying the location on the command line when named is started up. .sh 3 "Domain" .pp A default domain may be specified for the nameserver using a line such as .(b l domain Berkeley\|.\|Edu .)b .re The name server uses this information when it receives a query for a name without a ``.'' that is not known. When it receives one of these queries, it appends the name in the second field to the query name. This is an obsolete facility which will be removed from future releases. .sh 3 "Directory" .pp The directory line specifies the directory in which the nameserver should run, allowing the other file names in the boot file to use relative path names. .(b l directory /usr/local/domain .)b .re If you have more than a couple of named files to be maintained, you may wish to place the named files in a directory such as /usr/local/domain and adjust the directory command properly. The main purposes of this command are to make sure named is in the proper directory when trying to include files by relative path names with $Include and to allow named to run in a location that is reasonable to dump core if it feels the urge. .sh 3 "Primary Master" .pp The line in the boot file that designates the server as a primary server for a zone looks as follows: .(b l primary Berkeley\|.\|Edu ucbhosts .)b .re The first field specifies that the server is a primary one for the zone stated in the second field. The third field is the name of the file from which the data is read. .sh 3 "Secondary Master" .pp The line for a secondary server is similar to the primary except that it lists addresses of other servers (usually primary servers) from which the zone data will be obtained. .(b l secondary Berkeley\|.\|Edu 128.32.0.10 128.32.0.4 ucbhosts.bak .)b .re The first field specifies that the server is a secondary master server for the zone stated in the second field. The two network addresses specify the name servers that are primary for the zone. The secondary server gets its data across the network from the listed servers. Each server is tried in the order listed until it successfully receives the data from a listed server. If a filename is present after the list of primary servers, data for the zone will be dumped into that file as a backup. When the server is first started, the data are loaded from the backup file if possible, and a primary server is then consulted to check that the zone is still up-to-date. .sh 3 "Caching Only Server" .pp You do not need a special line to designate that a server is a caching server. What denotes a caching only server is the absence of authority lines, such as secondary or primary in the boot file. .pp All servers should have a line as follows in the boot file to prime the name servers cache: .(b l cache . root.cache .)b All cache files listed will be read in at named boot time and any values still valid will be reinstated in the cache and the root nameserver information in the cache files will always be used. For information on cache file see section on Cache Initialization. .sh 3 "Forwarders" Any server can make use of forwarders. A forwarder is another server capable of processing recursive queries that is willing to try resolving queries on behalf of other systems. The forwarders command specifies forwarders by internet address as follows: .(b l forwarders 128.32.0.10 128.32.0.4 .)b .re There are two main reasons for wanting to do so. First, the other systems may not have full network access and may be prevented from sending any IP packets into the rest of the network and therefore must rely on a forwarder which does have access to the full net. The second reason is that the forwarder sees a union of all queries as they pass through his server and therefore he builds up a very rich cache of data compared to the cache in a typical workstation nameserver. In effect, the forwarder becomes a meta-cache that all hosts can benefit from, thereby reducing the total number of queries from that site to the rest of the net. .sh 3 "Slave Mode" .pp Slave mode is used if the use of forwarders is the only possible way to resolve queries due to lack of full net access or if you wish to prevent the nameserver from using other than the listed forwarders. Slave mode is activated by placing the simple command .(b l slave .)b in the bootfile. If slave is used, then you must specify forwarders. When in slave mode, the server will forward each query to each of the forwarders until an answer is found or the list of forwarders is exhausted. .sh 3 "Remote Server" .pp To set up a host that will use a remote server instead of a local server to answer queries, the file /\|etc/\|resolv\|.\|conf needs to be created. This file designates the name servers on the network that should be sent queries. It is not advisable to create this file if you have a local server running. If this file exists it is read almost every time gethostbyname\|() or gethostbyaddr\|() is called. .sh 2 "Cache Initialization" .sh 3 root.cache .pp The name server needs to know the servers that are the authoritative name servers for the root domain of the network. To do this we have to prime the name server's cache with the addresses of these higher authorities. The location of this file is specified in the boot file. This file uses the Standard Resource Record Format (aka. Masterfile Format) covered further on in this paper. .sh 2 "Domain Data Files" .pp There are three standard files for specifying the data for a domain. These are named\|.\|local, hosts and host\|.\|rev. These files use the Standard Resource Record Format covered later in this paper. .sh 3 named\|.\|local .pp This file specifies the address for the local loopback interface, better known as localhost with the network address 127.0.0.1. The location of this file is specified in the boot file. .sh 3 hosts .pp This file contains all the data about the machines in this zone. The location of this file is specified in the boot file. .sh 3 hosts\|.\|rev .pp This file specifies the IN-ADDR\|.\|ARPA domain. This is a special domain for allowing address to name mapping. As internet host addresses do not fall within domain boundaries, this special domain was formed to allow inverse mapping. The IN-ADDR\|.\|ARPA domain has four labels preceding it. These labels correspond to the 4 octets of an Internet address. All four octets must be specified even if an octets is zero. The Internet address 128.32.0.4 is located in the domain 4\|.\|0\|.\|32\|.\|128\|.\|IN-ADDR\|.\|ARPA. This reversal of the address is awkward to read but allows for the natural grouping of hosts in a network. .sh 2 "Standard Resource Record Format" .pp The records in the name server data files are called resource records. The Standard Resource Record Format (RR) is specified in RFC1035. The following is a general description of these records:

{name} {ttl} addr-class Record Type Record Specific data

Resource records have a standard format shown above. The first field is always the name of the domain record and it must always start in column 1. For some RR's the name may be left blank; in that case it takes on the name of the previous RR. The second field is an optional time to live field. This specifies how long this data will be stored in the data base. By leaving this field blank the default time to live is specified in the Start Of Authority resource record (see below). The third field is the address class; currently, only one class is supported: IN for internet addresses and other information. The fourth field states the type of the resource record. The fields after that are dependent on the type of the RR. Case is preserved in names and data fields when loaded into the name server. All comparisons and lookups in the name server data base are case insensitive. .bl .b The following characters have special meanings: .ip . A free standing dot in the name field refers to the current domain. .ip @ A free standing @ in the name field denotes the current origin. .ip ".\|." Two free standing dots represent the null domain name of the root when used in the name field. .ip "\\\X" Where X is any character other than a digit (0-9), quotes that character so that its special meaning does not apply. For example, ``\e.'' can be used to place a dot character in a label. .ip "\\\DDD" Where each D is a digit, is the octet corresponding to the decimal number described by DDD. The resulting octet is assumed to be text and is not checked for special meaning. .ip "( )" Parentheses are used to group data that crosses a line. In effect, line terminations are not recognized within parentheses. .ip ";" Semicolon starts a comment; the remainder of the line is ignored. .ip "*" An asterisk signifies wildcarding. .pp Most resource records will have the current origin appended to names if they are not terminated by a ``.''. This is useful for appending the current domain name to the data, such as machine names, but may cause problems where you do not want this to happen. A good rule of thumb is that, if the name is not in the domain for which you are creating the data file, end the name with a ``.''. .sh 3 $INCLUDE .pp An include line begins with $INCLUDE, starting in column 1, and is followed by a file name. This feature is particularly useful for separating different types of data into multiple files. An example would be: .(b l $INCLUDE /usr/named/data/mailboxes .)b The line would be interpreted as a request to load the file /usr/named/data/mailboxes. The $INCLUDE command does not cause data to be loaded into a different zone or tree. This is simply a way to allow data for a given zone to be organized in separate files. For example, mailbox data might be kept separately from host data using this mechanism. .sh 3 $ORIGIN .pp The origin is a way of changing the origin in a data file. The line starts in column 1, and is followed by a domain origin. This is useful for putting more then one domain in a data file. .sh 3 "SOA - Start Of Authority" .(b L

name {ttl} addr-class SOA Origin Person in charge

@ IN SOA ucbvax.Berkeley.Edu. kjd.ucbvax.Berkeley.Edu. (

1\|.\|1 ; Serial

10800 ; Refresh

1800 ; Retry

3600000 ; Expire

86400 ) ; Minimum

.)b The Start of Authority, SOA, record designates the start of a zone. The name is the name of the zone. Origin is the name of the host on which this data file resides. Person in charge is the mailing address for the person responsible for the name server. The serial number is the version number of this data file, this number should be incremented whenever a change is made to the data. The name server cannot handle numbers over 9999 after the decimal point. The refresh indicates how often, in seconds, a secondary name servers is to check with the primary name server to see if an update is needed. The retry indicates how long, in seconds, a secondary server is to retry after a failure to check for a refresh. Expire is the upper limit, in seconds, that a secondary name server is to use the data before it expires for lack of getting a refresh. Minimum is the default number of seconds to be used for the time to live field on resource records. There should only be one SOA record per zone. .sh 3 "NS - Name Server"

{name} {ttl} addr-class NS Name servers name

IN NS ucbarpa\|.\|Berkeley\|.\|Edu.

The Name Server record, NS, lists a name server responsible for a given domain. The first name field lists the domain that is serviced by the listed name server. There should be one NS record for each Primary Master server for the domain. .sh 3 "A - Address"

{name} {ttl} addr-class A address

ucbarpa IN A 128.32.0.4

IN A 10.0.0.78

The Address record, A, lists the address for a given machine. The name field is the machine name and the address is the network address. There should be one A record for each address of the machine. .sh 3 "HINFO - Host Information"

This lists the hardware and operating system that are running at

the listed host.

It should be noted that only a single space separates the hardware info

and the operating system info.

If you want to include a space in the machine name you must quote the name.

There should be one HINFO record for each host.

.(b L

.sh 3 "WKS - Well Known Services"

{name} {ttl} addr-class WKS address protocol list of services IN WKS 128.32.0.10 UDP who route timed domain IN WKS 128.32.0.10 TCP ( echo telnet discard sunrpc sftp uucp-path systat daytime netstat qotd nntp link chargen ftp auth time whois mtp pop rje finger smtp supdup hostnames domain nameserver ) The Well Known Services record, WKS, describes the well known services supported by a particular protocol at a specified address. The list of services and port numbers come from the list of services specified in /etc/services. There should be only one WKS record per protocol per address. .)b .sh 3 "CNAME - Canonical Name" An alias should be the only record associated with the alias name; all other resource records should be associated with the canonical name and not with the alias. Any resource records that include a domain name as their value (e.g. NS or MX) should list the canonical name, not the alias. .sh 3 "PTR - Domain Name Pointer" PTR names should be unique to the zone. .sh 3 "MB - Mailbox" This lists the machine where a user wants to receive mail. The name field is the users login; the machine field denotes the machine to which mail is to be delivered. Mail Box names should be unique to the zone. (These records are currently for experimental use only.) .sh 3 "MR - Mail Rename Name" The name field lists the alias for the name listed in the fourth field, which should have a corresponding MB record. (These records are currently for experimental use only.) .sh 3 "MINFO - Mailbox Information" This resource record is usually associated with a mail group Mail Group, but may be used with a Mail Box record. The name specifies the name of the mailbox. The requests field is where mail such as requests to be added to a mail group should be sent. The maintainer is a mailbox that should receive error messages. This is particularly appropriate for mailing lists when errors in members names should be reported to a person other than the sender. (These records are currently for experimental use only.) .sh 3 "MG - Mail Group Member" (These records are currently for experimental use only.) An example for setting up a mailing list is as follows: In the first example, above, Seismo\|.\|CSS\|.\|GOV\|. is a mail gateway that knows how to deliver mail to Munnari\|.\|OZ\|.\|AU\|. but other machines on the network can not deliver mail directly to Munnari. These two machines may have a private connection or use a different transport medium. The preference value is the order that a mailer should follow when there is more then one way to deliver mail to a single machine. See RFC974 for more detailed information. .pp Wildcard names containing the character ``*'' may be used for mail routing with MX records. There are likely to be servers on the network that simply state that any mail to a domain is to be routed through a relay. Second example, above, all mail to hosts in the domain IL is routed through RELAY.CS.NET. This is done by creating a wildcard resource record, which states that *.IL has an MX of RELAY.CS.NET. .sh 2 "Sample Files" .pp The following section contains sample files for the name server. This covers example boot files for the different types of servers and example domain data base files.