NAMED-RRCHECKER(1)

NAMED-RRCHECKER(1) | BIND 9 | 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

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