User Guide¶

Installation ¶

letsencrypt-auto ¶

letsencrypt-auto is a wrapper which installs some dependencies from your OS standard package repositories (e.g. using apt-get or yum), and for other dependencies it sets up a virtualized Python environment with packages downloaded from PyPI [1]. It also provides automated updates.

To install and run the client, just type…

./letsencrypt-auto

Hint

During the beta phase, Let’s Encrypt enforces strict rate limits on the number of certificates issued for one domain. It is recommended to initially use the test server via –test-cert until you get the desired certificates.

Throughout the documentation, whenever you see references to letsencrypt script/binary, you can substitute in letsencrypt-auto. For example, to get basic help you would type:

./letsencrypt-auto --help

or for full help, type:

./letsencrypt-auto --help all

letsencrypt-auto is the recommended method of running the Let’s Encrypt client beta releases on systems that don’t have a packaged version. Debian, Arch Linux, Gentoo, FreeBSD, and OpenBSD now have native packages, so on those systems you can just install letsencrypt (and perhaps letsencrypt-apache). If you’d like to run the latest copy from Git, or run your own locally modified copy of the client, follow the instructions in the Developer Guide. Some other methods of installation are discussed below.

Plugins ¶

The Let’s Encrypt client supports a number of different “plugins” that can be used to obtain and/or install certificates. Plugins that can obtain a cert are called “authenticators” and can be used with the “certonly” command. Plugins that can install a cert are called “installers”. Plugins that do both can be used with the “letsencrypt run” command, which is the default.

Plugin	Auth	Inst	Notes
apache	Y	Y	Automates obtaining and installing a cert with Apache 2.4 on Debian-based distributions with `libaugeas0` 1.0+.
standalone	Y	N	Uses a “standalone” webserver to obtain a cert. This is useful on systems with no webserver, or when direct integration with the local webserver is not supported or not desired.
webroot	Y	N	Obtains a cert by writing to the webroot directory of an already running webserver.
manual	Y	N	Helps you obtain a cert by giving you instructions to perform domain validation yourself.
nginx	Y	Y	Very experimental and not included in letsencrypt-auto.

Future plugins for IMAP servers, SMTP servers, IRC servers, etc, are likely to be installers but not authenticators.

Apache ¶

If you’re running Apache 2.4 on a Debian-based OS with version 1.0+ of the libaugeas0 package available, you can use the Apache plugin. This automates both obtaining and installing certs on an Apache webserver. To specify this plugin on the command line, simply include --apache.

Webroot ¶

If you’re running a local webserver for which you have the ability to modify the content being served, and you’d prefer not to stop the webserver during the certificate issuance process, you can use the webroot plugin to obtain a cert by including certonly and --webroot on the command line. In addition, you’ll need to specify --webroot-path or -w with the top-level directory (“web root”) containing the files served by your webserver. For example, --webroot-path /var/www/html or --webroot-path /usr/share/nginx/html are two common webroot paths.

If you’re getting a certificate for many domains at once, the plugin needs to know where each domain’s files are served from, which could potentially be a separate directory for each domain. When requested a certificate for multiple domains, each domain will use the most recently specified --webroot-path. So, for instance,

letsencrypt certonly --webroot -w /var/www/example/ -d www.example.com -d example.com -w /var/www/other -d other.example.net -d another.other.example.net

would obtain a single certificate for all of those names, using the /var/www/example webroot directory for the first two, and /var/www/other for the second two.

The webroot plugin works by creating a temporary file for each of your requested domains in ${webroot-path}/.well-known/acme-challenge. Then the Let’s Encrypt validation server makes HTTP requests to validate that the DNS for each requested domain resolves to the server running letsencrypt. An example request made to your web server would look like:

66.133.109.36 - - [05/Jan/2016:20:11:24 -0500] "GET /.well-known/acme-challenge/HGr8U1IeTW4kY_Z6UIyaakzOkyQgPr_7ArlLgtZE8SX HTTP/1.1" 200 87 "-" "Mozilla/5.0 (compatible; Let's Encrypt validation server; +https://www.letsencrypt.org)"

Note that to use the webroot plugin, your server must be configured to serve files from hidden directories. If /.well-known is treated specially by your webserver configuration, you might need to modify the configuration to ensure that files inside /.well-known/acme-challenge are served by the webserver.

Standalone ¶

To obtain a cert using a “standalone” webserver, you can use the standalone plugin by including certonly and --standalone on the command line. This plugin needs to bind to port 80 or 443 in order to perform domain validation, so you may need to stop your existing webserver. To control which port the plugin uses, include one of the options shown below on the command line.

--standalone-supported-challenges http-01 to use port 80

--standalone-supported-challenges tls-sni-01 to use port 443

The standalone plugin does not rely on any other server software running on the machine where you obtain the certificate. It must still be possible for that machine to accept inbound connections from the Internet on the specified port using each requested domain name.

Manual ¶

If you’d like to obtain a cert running letsencrypt on a machine other than your target webserver or perform the steps for domain validation yourself, you can use the manual plugin. While hidden from the UI, you can use the plugin to obtain a cert by specifying certonly and --manual on the command line. This requires you to copy and paste commands into another terminal session, which may be on a different computer.

Nginx ¶

In the future, if you’re running Nginx you can use this plugin to automatically obtain and install your certificate. The Nginx plugin is still experimental, however, and is not installed with letsencrypt-auto. If installed, you can select this plugin on the command line by including --nginx.

Third-party plugins ¶

These plugins are listed at https://github.com/letsencrypt/letsencrypt/wiki/Plugins. If you’re interested, you can also write your own plugin.

Renewal ¶

Note

Let’s Encrypt CA issues short-lived certificates (90 days). Make sure you renew the certificates at least once in 3 months.

The letsencrypt client now supports a renew action to check all installed certificates for impending expiry and attempt to renew them. The simplest form is simply

letsencrypt renew

This will attempt to renew any previously-obtained certificates that expire in less than 30 days. The same plugin and options that were used at the time the certificate was originally issued will be used for the renewal attempt, unless you specify other plugins or options.

If you’re sure that this command executes successfully without human intervention, you can add the command to crontab (since certificates are only renewed when they’re determined to be near expiry, the command can run on a regular basis, like every week or every day); note that the current version provides detailed output describing either renewal success or failure.

The --force-renew flag may be helpful for automating renewal; it causes the expiration time of the certificate(s) to be ignored when considering renewal, and attempts to renew each and every installed certificate regardless of its age. (This form is not appropriate to run daily because each certificate will be renewed every day, which will quickly run into the certificate authority rate limit.)

Note that options provided to letsencrypt renew will apply to every certificate for which renewal is attempted; for example, letsencrypt renew --rsa-key-size 4096 would try to replace every near-expiry certificate with an equivalent certificate using a 4096-bit RSA public key. If a certificate is successfully renewed using specified options, those options will be saved and used for future renewals of that certificate.

An alternative form that provides for more fine-grained control over the renewal process (while renewing specified certificates one at a time), is letsencrypt certonly with the complete set of subject domains of a specific certificate specified via -d flags, like

letsencrypt certonly -d example.com -d www.example.com

(All of the domains covered by the certificate must be specified in this case in order to renew and replace the old certificate rather than obtaining a new one; don’t forget any www. domains! Specifying a subset of the domains creates a new, separate certificate containing only those domains, rather than replacing the original certificate.) The certonly form attempts to renew one individual certificate.

Please note that the CA will send notification emails to the address you provide if you do not renew certificates that are about to expire.

Let’s Encrypt is working hard on improving the renewal process, and we apologize for any inconveniences you encounter in integrating these commands into your individual environment.

Where are my certificates?¶

First of all, we encourage you to use Apache or nginx installers, both which perform the certificate management automatically. If, however, you prefer to manage everything by hand, this section provides information on where to find necessary files.

All generated keys and issued certificates can be found in /etc/letsencrypt/live/$domain. Rather than copying, please point your (web) server configuration directly to those files (or create symlinks). During the renewal, /etc/letsencrypt/live is updated with the latest necessary files.

Note

/etc/letsencrypt/archive and /etc/letsencrypt/keys contain all previous keys and certificates, while /etc/letsencrypt/live symlinks to the latest versions.

The following files are available:

privkey.pem

Private key for the certificate.

Warning

This must be kept secret at all times! Never share it with anyone, including Let’s Encrypt developers. You cannot put it into a safe, however - your server still needs to access this file in order for SSL/TLS to work.

This is what Apache needs for SSLCertificateKeyFile, and nginx for ssl_certificate_key.

cert.pem

Server certificate only.

This is what Apache < 2.4.8 needs for SSLCertificateFile.

chain.pem

All certificates that need to be served by the browser excluding server certificate, i.e. root and intermediate certificates only.

This is what Apache < 2.4.8 needs for SSLCertificateChainFile, and what nginx >= 1.3.7 needs for ssl_trusted_certificate.

fullchain.pem

All certificates, including server certificate. This is concatenation of chain.pem and cert.pem.

This is what Apache >= 2.4.8 needs for SSLCertificateFile, and what nginx needs for ssl_certificate.

For both chain files, all certificates are ordered from root (primary certificate) towards leaf.

Please note, that you must use either chain.pem or fullchain.pem. In case of webservers, using only cert.pem, will cause nasty errors served through the browsers!

Note

All files are PEM-encoded (as the filename suffix suggests). If you need other format, such as DER or PFX, then you could convert using openssl, but this means you will not benefit from automatic renewal!

Configuration file ¶

It is possible to specify configuration file with letsencrypt-auto --config cli.ini (or shorter -c cli.ini). An example configuration file is shown below:

# This is an example of the kind of things you can do in a configuration file.
# All flags used by the client can be configured here. Run Let's Encrypt with
# "--help" to learn more about the available options.

# Use a 4096 bit RSA key instead of 2048
rsa-key-size = 4096

# Uncomment and update to register with the specified e-mail address
# email = foo@example.com

# Uncomment and update to generate certificates for the specified
# domains.
# domains = example.com, www.example.com

# Uncomment to use a text interface instead of ncurses
# text = True

# Uncomment to use the standalone authenticator on port 443
# authenticator = standalone
# standalone-supported-challenges = tls-sni-01

# Uncomment to use the webroot authenticator. Replace webroot-path with the
# path to the public_html / webroot folder being served by your web server.
# authenticator = webroot
# webroot-path = /usr/share/nginx/html

By default, the following locations are searched:

/etc/letsencrypt/cli.ini
$XDG_CONFIG_HOME/letsencrypt/cli.ini (or ~/.config/letsencrypt/cli.ini if $XDG_CONFIG_HOME is not set).

Getting help ¶

If you’re having problems you can chat with us on IRC (#letsencrypt @ Freenode) or get support on our forums.

If you find a bug in the software, please do report it in our issue tracker. Remember to give us as much information as possible:

copy and paste exact command line used and the output (though mind that the latter might include some personally identifiable information, including your email and domains)
copy and paste logs from /var/log/letsencrypt (though mind they also might contain personally identifiable information)
copy and paste letsencrypt --version output
your operating system, including specific version
specify which installation method you’ve chosen

Other methods of installation ¶

Running with Docker ¶

Docker is an amazingly simple and quick way to obtain a certificate. However, this mode of operation is unable to install certificates or configure your webserver, because our installer plugins cannot reach it from inside the Docker container.

You should definitely read the Where are my certificates? section, in order to know how to manage the certs manually. https://github.com/letsencrypt/letsencrypt/wiki/Ciphersuite-guidance provides some information about recommended ciphersuites. If none of these make much sense to you, you should definitely use the letsencrypt-auto method, which enables you to use installer plugins that cover both of those hard topics.

If you’re still not convinced and have decided to use this method, from the server that the domain you’re requesting a cert for resolves to, install Docker, then issue the following command:

sudo docker run -it --rm -p 443:443 -p 80:80 --name letsencrypt \
            -v "/etc/letsencrypt:/etc/letsencrypt" \
            -v "/var/lib/letsencrypt:/var/lib/letsencrypt" \
            quay.io/letsencrypt/letsencrypt:latest auth

and follow the instructions (note that auth command is explicitly used - no installer plugins involved). Your new cert will be available in /etc/letsencrypt/live on the host.

Operating System Packages ¶

FreeBSD

Port: cd /usr/ports/security/py-letsencrypt && make install clean

Package: pkg install py27-letsencrypt

OpenBSD

Port: cd /usr/ports/security/letsencrypt/client && make install clean

Package: pkg_add letsencrypt

Arch Linux

sudo pacman -S letsencrypt letsencrypt-apache

Debian

If you run Debian Stretch or Debian Sid, you can install letsencrypt packages.

sudo apt-get update
sudo apt-get install letsencrypt python-letsencrypt-apache

If you don’t want to use the Apache plugin, you can omit the python-letsencrypt-apache package.

Packages for Debian Jessie are coming in the next few weeks.

Fedora

sudo dnf install letsencrypt

Gentoo

The official Let’s Encrypt client is available in Gentoo Portage. If you want to use the Apache plugin, it has to be installed separately:

emerge -av app-crypt/letsencrypt
emerge -av app-crypt/letsencrypt-apache

Currently, only the Apache plugin is included in Portage. However, if you want the nginx plugin, you can use Layman to add the mrueg overlay which does include the nginx plugin package:

emerge -av app-portage/layman
layman -S
layman -a mrueg
emerge -av app-crypt/letsencrypt-nginx

When using the Apache plugin, you will run into a “cannot find a cert or key directive” error if you’re sporting the default Gentoo httpd.conf. You can fix this by commenting out two lines in /etc/apache2/httpd.conf as follows:

Change

<IfDefine SSL>
LoadModule ssl_module modules/mod_ssl.so
</IfDefine>

#<IfDefine SSL>
LoadModule ssl_module modules/mod_ssl.so
#</IfDefine>

For the time being, this is the only way for the Apache plugin to recognise the appropriate directives when installing the certificate. Note: this change is not required for the other plugins.

Other Operating Systems

OS packaging is an ongoing effort. If you’d like to package Let’s Encrypt client for your distribution of choice please have a look at the Packaging Guide.

From source ¶

Installation from source is only supported for developers and the whole process is described in the Developer Guide.

Warning

Please do not use python setup.py install or python pip install .. Please do not attempt the installation commands as superuser/root and/or without virtual environment, e.g. sudo python setup.py install, sudo pip install, sudo ./venv/bin/.... These modes of operation might corrupt your operating system and are not supported by the Let’s Encrypt team!

Comparison of different methods ¶

Unless you have a very specific requirements, we kindly ask you to use the letsencrypt-auto method. It’s the fastest, the most thoroughly tested and the most reliable way of getting our software and the free SSL certificates!

Beyond the methods discussed here, other methods may be possible, such as installing Let’s Encrypt directly with pip from PyPI or downloading a ZIP archive from GitHub may be technically possible but are not presently recommended or supported.

Footnotes