NAMED-RRCHECKER(1)

NAME
named-rrchecker - syntax checker for individual DNS resource records

SYNOPSIS

named-rrchecker [-h] [-o origin] [-p] [-u] [-C] [-T] [-P]

DESCRIPTION

named-rrchecker reads a single DNS resource record (RR) from standard input and checks whether it is syntactically correct.

    The input format is a minimal subset of the DNS zone file format. The entire input must be:
        CLASS TYPE RDATA

    •   Input must not start with an owner (domain) name

    •   The CLASS field is mandatory (typically IN).

    •   The TTL field must not be present.

    •   RDATA format is specific to each RRTYPE.

    •   Leading and trailing whitespace in each field is ignored.

Format details can be found in RFC 1035 Section 5.1 <https://datatracker.ietf.org/doc/html/rfc1035.html#section-5.1> under <rr> specification. RFC 3597 <https://datatracker.ietf.org/doc/html/rfc3597.html> format is also accepted in any of the input fields. See Examples.

OPTIONS

    -o origin
        This option specifies the origin to be used when interpreting names in the record: it defaults to root (.). The specified origin is always taken as an absolute name.

    -p  This option prints out the resulting record in canonical form. If there is no canonical form defined, the record is printed in RFC 3597 <https://datatracker.ietf.org/doc/html/rfc3597.html> unknown record format.

    -u  This option prints out the resulting record in RFC 3597 <https://datatracker.ietf.org/doc/html/rfc3597.html> unknown record format.

    -C, -T, -P
        These options do not read input. They print out known classes, standard types, and private type mnemonics. Each item is printed on a separate line. The resulting list of private types may be empty

    -h  This option prints out the help menu.

EXAMPLES

Pay close attention to the echo command line options -e and -n, as they affect whitespace in the input to named-rrchecker.

    echo -n 'IN A 192.0.2.1' | named-rrchecker

        •   Valid input is in RFC 1035 <https://datatracker.ietf.org/doc/html/rfc1035.html> format with no newline at the end of the input.

        •   Return code 0.

    echo -e '\n \n IN\tA 192.0.2.1 \t \n\n ' | named-rrchecker -p

        •   Valid input with leading and trailing whitespace.

        •   Output: IN A 192.0.2.1

        •   Leading and trailing whitespace is not part of the output.

  Relative names and origin

    echo 'IN CNAME target' | named-rrchecker -p

        •   Valid input with a relative name as the CNAME target.

        •   Output: IN CNAME target.

        •   Relative name target from the input is converted to an absolute name using the default origin . (root).

    echo 'IN CNAME target' | named-rrchecker -p -o origin.test

        •   Valid input with a relative name as the CNAME target.

        •   Output: IN CNAME target.origin.test.

        •   Relative name target from the input is converted to an absolute name using the specified origin origin.test

    echo 'IN CNAME target.' | named-rrchecker -p -o origin.test

        •   Valid input with an absolute name as the CNAME target.

        •   Output: IN CNAME target.

        •   The specified origin has no influence if target from the input is already absolute.

  Special characters

Special characters allowed in zone files by RFC 1035 Section 5.1 <https://datatracker.ietf.org/doc/html/rfc1035.html#section-5.1> are accepted.

    echo 'IN CNAME t\097r\get\.' | named-rrchecker -p -o origin.test

        •   Valid input with backslash escapes.

        •   Output: IN CNAME target\..origin.test.

        •   \097 denotes an ASCII value in decimal, which, in this example, is the character a.

        •   \g is converted to a plain g because the g character does not have a special meaning and so the \ prefix does nothing in this case.

        •   \. denotes a literal ASCII dot (here as a part of the CNAME target name). Special meaning of . as the DNS label separator was disabled by the preceding \ prefix.

    echo 'IN CNAME @' | named-rrchecker -p -o origin.test

        •   Valid input with @ used as a reference to the specified origin.

        •   Output: IN CNAME origin.test.

    echo 'IN CNAME \@' | named-rrchecker -p -o origin.test

        •   Valid input with a literal @ character (escaped).

        •   Output: IN CNAME \@.origin.test.

    echo 'IN CNAME prefix.@' | named-rrchecker -p -o origin.test

        •   Valid input with @ used as a reference to the specifed origin.

        •   Output: IN CNAME prefix.\@.origin.test.

        •   @ has special meaning only if it is free-standing.

    echo 'IN A 192.0.2.1; comment' | named-rrchecker -p

        •   Valid input with a trailing comment. Note the lack of whitespace before the start of the comment.

        •   Output: IN A 192.0.2.1

For multi-line examples see the next section.

  Multi-token records

    echo -e 'IN TXT two words \n' | named-rrchecker -p

        •   Valid TXT RR with two unquoted words and trailing whitespace.

        •   Output: IN TXT "two" "words"

        •   Two unquoted words in the input are treated as two <character-string>s per RFC 1035 Section 3.3.14 <https://datatracker.ietf.org/doc/html/rfc1035.html#section-3.3.14>.

        •   Trailing whitespace is omitted from the last <character-string>.

    echo -e 'IN TXT "two words" \n' | named-rrchecker -p

        •   Valid TXT RR with one character-string and trailing whitespace.

        •   Output: IN TXT "two words"

    echo -e 'IN TXT "problematic newline\n"' | named-rrchecker -p

        •   Invalid input - the closing " is not detected before the end of the line.

    echo 'IN TXT "with newline\010"' | named-rrchecker -p

        •   Valid input with an escaped newline character inside character-string.

        •   Output: IN TXT "with newline\010"

    echo -e 'IN TXT ( two\nwords )' | named-rrchecker -p

        •   Valid multi-line input with line continuation allowed inside optional parentheses in the RDATA field.

        •   Output: IN TXT "two" "words"

    echo -e 'IN TXT ( two\nwords ; misplaced comment )' | named-rrchecker -p

        •   Invalid input - comments, starting with ";", are ignored by the parser, so the closing parenthesis should be before the semicolon.

    echo -e 'IN TXT ( two\nwords ; a working comment\n )' | named-rrchecker -p

        •   Valid input - the comment is terminated with a newline.

        •   Output: IN TXT "two" "words"

    echo 'IN HTTPS 1 . alpn="h2,h3"' | named-rrchecker -p

        •   Valid HTTPS record

        •   Output: IN HTTPS 1 . alpn="h2,h3"

    echo -e 'IN HTTPS ( 1 \n . \n alpn="dot")port=853' | named-rrchecker -p

        •   Valid HTTPS record with individual sub-fields split across multiple lines using RFC 1035 Section 5.1 <https://datatracker.ietf.org/doc/html/rfc1035.html#section-5.1> parentheses syntax to group data that crosses a line boundary.

        •   Note the missing whitespace between the closing parenthesis and adjacent tokens.

        •   Output: IN HTTPS 1 . alpn="dot" port=853

  Unknown type handling

    echo 'IN A 192.0.2.1' | named-rrchecker -u

        •   Valid input in RFC 1035 <https://datatracker.ietf.org/doc/html/rfc1035.html> format.

        •   Output in RFC 3957 <https://datatracker.ietf.org/doc/html/rfc3957.html> format: CLASS1 TYPE1 \# 4 C0000201

    echo 'CLASS1 TYPE1 \# 4 C0000201' | named-rrchecker -p

        •   Valid input in RFC 3597 <https://datatracker.ietf.org/doc/html/rfc3597.html> format.

        •   Output in RFC 1035 <https://datatracker.ietf.org/doc/html/rfc1035.html> format: IN A 192.0.2.1

    echo 'IN A \# 4 C0000201' | named-rrchecker -p

        •   Valid input with class and type in RFC 1035 <https://datatracker.ietf.org/doc/html/rfc1035.html> format and rdata in RFC 3597 <https://datatracker.ietf.org/doc/html/rfc3597.html> format.

        •   Output in RFC 1035 <https://datatracker.ietf.org/doc/html/rfc1035.html> format: IN A 192.0.2.1

    echo 'IN HTTPS 1 . key3=\001\000' | named-rrchecker -p

        •   Valid input with RFC 9460 <https://datatracker.ietf.org/doc/html/rfc9460.html> syntax for an unknown key3 field. Syntax \001\000 produces two octets with values 1 and 0, respectively.

        •   Output: IN HTTPS 1 . port=256

        •   key3 matches the standardized key name port.

        •   Octets 1 and 0 were decoded as integer values in big-endian encoding.

    echo 'IN HTTPS 1 . key3=\001' | named-rrchecker -p

        •   Invalid input - the length of the value for key3 (i.e. port) does not match the known standard format for that parameter in the SVCB RRTYPE.

    echo 'IN HTTPS 1 . port=\001\000' | named-rrchecker -p

        •   Invalid input - the key port, when specified using its standard mnemonic name, must use standard key-specific syntax.

  Meta values

    echo 'IN AXFR' | named-rrchecker

        •   Invalid input - AXFR is a meta type, not a genuine RRTYPE.

    echo 'ANY A 192.0.2.1' | named-rrchecker

        •   Invalid input - ANY is meta class, not a true class.

    echo 'A 192.0.2.1' | named-rrchecker

        •   Invalid input - the class field is missing, so the parser would try and fail to interpret the RRTYPE A as the class.

RETURN CODES

    0   The whole input was parsed as one syntactically valid resource record.

    1   The input is not a syntactically valid resource record, or the given type is not supported, or either/both class and type are meta-values, which should not appear in zone files.

SEE ALSO

RFC 1034 <https://datatracker.ietf.org/doc/html/rfc1034.html>, RFC 1035 <https://datatracker.ietf.org/doc/html/rfc1035.html>, RFC 3957 <https://datatracker.ietf.org/doc/html/rfc3957.html>, named(8) <#std-iscman-named>.

Author
Internet Systems Consortium

Copyright
2026, Internet Systems Consortium