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host2ptr.py Hosts File Parser

This script parses a Unix-style /etc/hosts file to extract valid IP addresses and relevant information to create DNS reverse lookup entries. The script is designed to work specifically with IPv4 addresses and generates PTR records that contain fully qualified domain names (FQDNs).

Features

  • Parses /etc/hosts syntax text file to extract IP addresses and hostnames.
  • Generates PTR records for DNS reverse lookup.
  • Supports adding a default domain to short hostnames.
  • Retains comments from the /etc/hosts file.
  • Outputs the processed data in JSON format.
  • Allows filtering and displaying records by netname.

Requirements

  • Python 3.6+
  • re module (regular expressions, included in the standard library)
  • json module (JSON handling, included in the standard library)
  • ipaddress module (IP address validation, included in the standard library)
  • collections module (defaultdict for grouping records, included in the standard library)

Usage

Usage: ./host2ptr.py <host_file>

  1. Ensure you have a /etc/hosts syntax style file for your input.
  2. Run the script: 
    ./host2ptr.py my-hostfile.txt
  3. The script will generate a JSON file named hostfile-converted-ptr-data.json containing the processed data.

Example Output Format

The JSON output format for a single entry looks like this:

[
    "192.168.36.98",
    {
        "ipaddr": "192.168.36.98",
        "netname": "192.168.36",
        "zonename": "36.168.192.in-addr.arpa",
        "lastoctet": "98",
        "names": [
            "xxxxxxxxxxxxx001",
            "xxxxxxxxxxxxx001.example.com"
        ],
        "hosts": [
            "xxxxxxxxxxxxx001.example.com",
            "xxxxxxxxxxxxx001.example.com"
        ],
        "fqdn": "xxxxxxxxxxxxx001.example.com",
        "comment": "# Comment from hosts file",
        "ptr_record": "98  IN PTR  xxxxxxxxxxxxx001.example.com.    ;Comment from hosts file"
    }
]

gen-zone.py Utility

Zone File Generator

This script reads a JSON file containing PTR record data and generates DNS zone files for reverse DNS lookup.

Requirements

  • Python 3.6+
  • json module (included in the standard library)
  • sys module (included in the standard library)

Usage

Usage: ./gen-zone.py <json_file>

  1. Ensure you have the JSON file output generated by the host2ptr.py utility (typically hostfile-converted-ptr-data.json).
  2. Run the script: 
    ./gen-zone.py hostfile-converted-ptr-data.json
  3. The script will generate zone files named <zonename>.db for each unique zonename found in the JSON file.

Example Input JSON

The input JSON file should be in the following format:

[
  [
    "192.168.36.98",
    {
      "ipaddr": "192.168.36.98",
      "netname": "192.168.36",
      "zonename": "36.168.192.in-addr.arpa",
      "lastoctet": "98",
      "names": [
        "example001",
        "example001.example.com"
      ],
      "hosts": [
        "example001.example.com",
        "example001.example.com"
      ],
      "fqdn": "example001.example.com",
      "comment": "# Comment from hosts file",
      "ptr_record": "98  IN PTR  example001.example.com.    ;Comment from hosts file"
    }
  ],
  [
    "192.168.5.7",
    {
      "ipaddr": "192.168.5.7",
      "netname": "192.168.5",
      "zonename": "5.168.192.in-addr.arpa",
      "lastoctet": "7",
      "names": [
        "example002",
        "example002.example.com"
      ],
      "hosts": [
        "example002.example.com",
        "example002.example.com"
      ],
      "fqdn": "example002.example.com",
      "comment": "# Another comment",
      "ptr_record": "7  IN PTR  example002.example.com.    ;Another comment"
    }
  ]
]

License

This script is provided "as is" without any warranty. Use it at your own risk.

Author

G Fontaine