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.

Firstly, please install Git and run the following commands:

git clone https://github.com/letsencrypt/letsencrypt
cd letsencrypt

Note

On RedHat/CentOS 6 you will need to enable the EPEL repository before install.

To install and run the client you just need to 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, 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.
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.

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

Webroot

If you’re running a webserver that you don’t want to stop to use standalone, 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 root directory of 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, each domain will use the most recent --webroot-path. So for instance:

letsencrypt certonly --webroot -w /var/www/example/ -d www.example.com -d example.com -w /var/www/eg -d eg.is -d www.eg.is

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

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.

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.

In order to renew certificates simply call the letsencrypt (or letsencrypt-auto) again, and use the same values when prompted. You can automate it slightly by passing necessary flags on the CLI (see --help all), or even further using the Configuration file. The --renew-by-default flag may be helpful for automating renewal. If you’re sure that UI doesn’t prompt for any details you can add the command to crontab (make it less than every 90 days to avoid problems, say every month).

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 automating the renewal process. Until the tool is ready, we are sorry for the inconvenience!

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.

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

[1]By using this virtualized Python environment (virtualenv) we don’t pollute the main OS space with packages from PyPI!