User guide

Installation

Warning

It is strongly advised with pip to install Lexicon in a Python virtual environment, in order to avoid interference between Python modules preinstalled on your system as OS packages and modules installed by pip (see https://docs.python-guide.org/dev/virtualenvs/).

To use lexicon as a CLI application, do the following:

$ pip install dns-lexicon

Some providers (like Route53 and TransIP) require additional dependencies. You can install the provider specific dependencies separately:

$ pip install dns-lexicon[route53]

To install lexicon with the additional dependencies of every provider, do the following:

$ pip install dns-lexicon[full]

You can also install the latest version from the repository directly.

$ pip install git+https://github.com/AnalogJ/lexicon.git

and with Route 53 provider dependencies:

$ pip install git+https://github.com/AnalogJ/lexicon.git#egg=dns-lexicon[route53]

Note

As an alternative you can also install Lexicon using the OS packages available for major Linux distributions (see lexicon or dns-lexicon package in https://pkgs.org/download/lexicon).

Usage

$ lexicon -h
usage: lexicon [-h] [--version] [--delegated DELEGATED] [--config-dir CONFIG_DIR] [--resolve-zone-name]
              {aliyun,...,zonomi}
              ...

Create, Update, Delete, List DNS entries

positional arguments:
  {aliyun,...,zonomi}
                        specify the DNS provider to use
    aliyun              aliyun provider
    ...
    zonomi              zonomi provider

optional arguments:
  -h, --help            show this help message and exit
  --version             show the current version of lexicon
  --delegated DELEGATED
                        specify the delegated domain (may not needed if --resolve-zone-name is set)
  --config-dir CONFIG_DIR
                        specify the directory where to search lexicon.yml and lexicon_[provider].yml configuration files (default: current directory).
  --resolve-zone-name   trigger an active resolution of the zone name for the given domain using DNS queries

Using the lexicon CLI is pretty simple:

# setup provider environmental variables:
export LEXICON_CLOUDFLARE_USERNAME="myusername@example.com"
export LEXICON_CLOUDFLARE_TOKEN="cloudflare-api-token"

# list all TXT records on cloudflare
lexicon cloudflare list example.com TXT

# create a new TXT record on cloudflare
lexicon cloudflare create www.example.com TXT --name="_acme-challenge.www.example.com." --content="challenge token"

# delete a  TXT record on cloudflare
lexicon cloudflare delete www.example.com TXT --name="_acme-challenge.www.example.com." --content="challenge token"
lexicon cloudflare delete www.example.com TXT --identifier="cloudflare record id"

Configuration

Authentication

Most supported DNS services provide an API token, however each service implements authentication differently. Lexicon attempts to standardize authentication around the following CLI flags:

--auth-username - For DNS services that require it, this is usually the account id or email address
--auth-password - For DNS services that do not provide an API token, this is usually the account password
--auth-token - This is the most common auth method, the API token provided by the DNS service

You can see all the --auth-* flags for a specific service by reading the DNS service specific help: lexicon cloudflare -h

Environmental variables

Instead of providing authentication information via the CLI, you can also specify them via environmental variables. Every DNS service and auth flag maps to an environmental variable as follows: LEXICON_{DNS Provider Name}_{Auth Type}

So instead of specifying --auth-username and --auth-token flags when calling lexicon cloudflare ..., you could instead set the LEXICON_CLOUDFLARE_USERNAME and LEXICON_CLOUDFLARE_TOKEN environmental variables.

Injection of Lexicon general options also works with environment variables, using the LEXICON_ prefix: for instance LEXICON_DELEGATED can be used to setup the --delegated option (see next paragraph for the purpose of this option).

LEXICON_DELEGATED=foo.example.com

Resolution of the zone name

Given the provided domain, Lexicon must determine what is the actual zone name that needs to be queried.

If the decision is “easy” for second-level domains (like example.com), it is not the case for higher level domains. For instance example.com DNS zone could declare a delegation of subdomain sub.example.com to another DNS zone. In this case, a request done to sub.example.com must correctly that the zone name is sub.example.com and not example.com.

Lexicon provides two ways to deal with this situation.

TLDextract & `--delegate`

By default the tldextract library is used by Lexicon to guess the actual zone name from well known top-level domains (aka TLDs). This works well for second-level domains, like guessing that zone name for www.domain.net is domain.net.

Lexicon stores tldextract cache by default in ~/.lexicon_tld_set where ~ is the current user’s home directory. You can change this path using the TLDEXTRACT_CACHE_PATH environment variable.

For instance, to store tldextract cache in /my/path/to/tld_cache, you can invoke Lexicon like this from a Linux shell:

TLDEXTRACT_CACHE_PATH=/my/path/to/tld_cache lexicon myprovider create www.example.net TXT ...

For higher-level domains, like sub.domain.net defined to a specific DNS zone, Lexicon would improperly guess that the zone name is domain.net. To instruct Lexicon here, please use the --delegated flag with the actual zone name.

For instance:

# Create the TXT entry "bar" on FQDN "foo.sub.domain.net" in DNS zone of domain "sub.domain.net"
lexicon --delegated=sub.domain.net cloudflare create sub.domain.net TXT --name=foo --content=bar

Use of `--resolve-zone-name`

A more modern approach introduced with Lexicon 3.17.0 is to leverage dnspython capacities to lookup on the DNS servers what is the actual zone name of a given domain. In this case tldextract is not used.

In the example given to the previous section, Lexicon will then be able to directly guess that the zone name is sub.domain.net and not domain.net.

This option is disabled by default. To activate it, you can pass the flag --resolve-zone-name to Lexicon.

For instance:

# Create the TXT entry "bar" on FQDN "foo.sub.domain.net" in DNS zone of domain "sub.domain.net"
lexicon --resolve-zone-name cloudflare create sub.domain.net TXT --name=foo --content=bar

In most cases, the --delegated flag is not needed. However you can still use it if needed to override the resolved zone name.

Integration

Lexicon can be integrated with various tools and process to help handling DNS records.

Let’s Encrypt instructions

Lexicon has an example dehydrated hook file that you can use for any supported provider. All you need to do is set the PROVIDER env variable.

PROVIDER=cloudflare dehydrated --cron --hook dehydrated.default.sh --challenge dns-01

Lexicon can also be used with Certbot and the included Certbot hook file (requires configuration).

Docker

There is an included example Dockerfile that can be used to automatically generate certificates for your website.