ACME-CLIENT(1) | General Commands Manual | ACME-CLIENT(1)

# NAME

`acme-client` — ACME client

# SYNOPSIS

`acme-client` | [`-Fnrv`] [`-f` configfile] handle

# DESCRIPTION

`acme-client` is an Automatic Certificate Management Environment (ACME) client: it looks in its configuration for a domain section corresponding to the handle given as command line argument and uses that configuration to retrieve an X.509 certificate which can be used to provide domain name validation (i.e. prove that the domain is who it says it is). The certificates are typically used to provide HTTPS for web servers, but can be used in any situation where domain name validation is required (such as mail servers).

If the certificate already exists and is close to expiry, `acme-client` attempts to renew the certificate. For certificates with a lifetime of more than 10 days, this is done when less than a third of the lifetime remains. Otherwise, renewal is done when half the lifetime has expired.

In order to prove that the client has access to the domain, a challenge is issued by the signing authority. `acme-client` implements the “http-01” challenge type, where a file is created within a directory accessible by a locally run web server. The default challenge directory /var/www/acme can be served by httpd(8) with this location block, which will properly map response challenges:

    location "/.well-known/acme-challenge/*" {
    	root "/acme"
    	request strip 2
    }

The options are as follows:

`-F`
  Force certificate renewal, regardless of remaining lifetime.
`-f` configfile
  Specify an alternative configuration file.
`-n`
  No operation: check and print configuration.
`-r`
  Revoke the X.509 certificate.
`-v`
  Verbose operation. Specify twice to also trace communication and data transfers.
handle
  The handle of the domain section of the configuration that contains the details of the certificate to be created, renewed or revoked.

# FILES

/etc/acme
  Private keys for `acme-client`.
/etc/acme-client.conf
  Default configuration.
/var/www/acme
  Default challengedir.

# EXIT STATUS

`acme-client` returns 0 if certificates were changed (revoked or updated), 1 on failure, or 2 if the certificates didn't change (up to date).

# EXAMPLES

Example configuration files for `acme-client` and httpd(8) are provided in /etc/examples/acme-client.conf and /etc/examples/httpd.conf.

To generate a certificate for example.com and use it to provide HTTPS, create acme-client.conf and httpd.conf and run:

`# acme-client -v example.com && rcctl reload httpd`

A cron(8) job can renew the certificate as necessary. On renewal, httpd(8) is reloaded:

    ~ * * * * acme-client example.com && rcctl reload httpd

# SEE ALSO

openssl(1), acme-client.conf(5), httpd.conf(5), ssl(8)

# STANDARDS

R. Barnes, J. Hoffman-Andrews, D. McCarney, and J. Kasten, Automatic Certificate Management Environment (ACME), RFC 8555, March 2019.

# HISTORY

The `acme-client` utility first appeared in OpenBSD 6.1.

# AUTHORS

The `acme-client` utility was written by Kristaps Dzonsons <kristaps@bsd.lv>.

# CAVEATS

The usual ACME service providers are notoriously picky about authenticating rules, and yield fairly long time-outs after just a few invalid attempts. It is strongly suggested to first validate a configuration with a staging server before moving an official certificate validation workflow to crontab(5) status.

September 18, 2025 | Debian