lego/docs/content/dns/zz_gen_exec.md

title	date	draft	slug	dnsprovider
External program	2019-03-03T16:39:46+01:00	false	exec	since code url v0.5.0 exec /dns/exec

Solving the DNS-01 challenge using an external program.

• Code: exec
• Since: v0.5.0

Here is an example bash command using the External program provider:

EXEC_PATH=/the/path/to/myscript.sh \
lego --email you@example.com --dns exec --domains my.example.org run

Base Configuration

Environment Variable Name	Description
EXEC_MODE	RAW, none
EXEC_PATH	The path of the the external program.

Additional Configuration

Environment Variable Name	Description
EXEC_POLLING_INTERVAL	Time between DNS propagation check.
EXEC_PROPAGATION_TIMEOUT	Maximum waiting time for DNS propagation.
EXEC_SEQUENCE_INTERVAL	Time between sequential requests.

Description

The file name of the external program is specified in the environment variable EXEC_PATH.

When it is run by lego, three command-line parameters are passed to it: The action ("present" or "cleanup"), the fully-qualified domain name and the value for the record.

For example, requesting a certificate for the domain 'my.example.org' can be achieved by calling lego as follows:

EXEC_PATH=./update-dns.sh \
	lego --email you@example.com \
	--dns exec \
	--domains my.example.org run

It will then call the program './update-dns.sh' with like this:

./update-dns.sh "present" "_acme-challenge.my.example.org." "MsijOYZxqyjGnFGwhjrhfg-Xgbl5r68WPda0J9EgqqI"

The program then needs to make sure the record is inserted. When it returns an error via a non-zero exit code, lego aborts.

When the record is to be removed again, the program is called with the first command-line parameter set to cleanup instead of present.

If you want to use the raw domain, token, and keyAuth values with your program, you can set EXEC_MODE=RAW:

EXEC_MODE=RAW \
EXEC_PATH=./update-dns.sh \
	lego --email you@example.com \
	--dns exec \
	--domains my.example.org run

It will then call the program ./update-dns.sh like this:

./update-dns.sh "present" "my.example.org." "--" "some-token" "KxAy-J3NwUmg9ZQuM-gP_Mq1nStaYSaP9tYQs5_-YsE.ksT-qywTd8058G-SHHWA3RAN72Pr0yWtPYmmY5UBpQ8"

Commands

{{% notice note %}} The -- is because the token MAY start with a -, and the called program may try and interpret a - as indicating a flag. In the case of urfave, which is commonly used, you can use the -- delimiter to specify the start of positional arguments, and handle such a string safely. {{% /notice %}}

Present

Mode	Command
default	myprogram present -- <FQDN> <record>
RAW	myprogram present -- <domain> <token> <key_auth>

Cleanup

Mode	Command
default	myprogram cleanup -- <FQDN> <record>
RAW	myprogram cleanup -- <domain> <token> <key_auth>