certbot/docs/using.rst

User Guide

Table of Contents

Certbot Commands

Certbot uses a number of different commands (also referred to as "subcommands") to request specific actions such as obtaining, renewing, or revoking certificates. The most important and commonly-used commands will be discussed throughout this document; an exhaustive list also appears near the end of the document.

The certbot script on your web server might be named letsencrypt if your system uses an older package, or certbot-auto if you used an alternate installation method. Throughout the docs, whenever you see certbot, swap in the correct name as needed.

Getting certificates (and choosing plugins)

The Certbot client supports two types of plugins for obtaining and installing certificates.

Authenticators are plugins used with the certonly command to obtain a cert. The authenticator validates that you control the domain(s) you are requesting a cert for, obtains a cert for the specified domain(s), and places the cert in the /etc/letsencrypt directory on your machine. The authenticator does not install the cert (it does not edit any of your server's configuration files to serve the obtained certificate). If you specify multiple domains to authenticate, they will all be listed in a single certificate. To obtain multiple separate certificates you will need to run Certbot multiple times.

Installers are Plugins used with the install command to install a cert. These plugins can modify your webserver's configuration to serve your website over HTTPS using certificates obtained by certbot.

Plugins that do both can be used with the certbot run command, which is the default when no command is specified. The run subcommand can also be used to specify a combination of distinct authenticator and installer plugins.

Plugin	Auth	Inst	Notes	Challenge types (and port)
apache	Y	Y	Automates obtaining and installing a cert with Apache 2.4 on Debian-based distributions with libaugeas0 1.0+.	tls-sni-01 (443)
webroot	Y	N	Obtains a cert by writing to the webroot directory of an already running webserver.	http-01 (80)
nginx	Y	Y	Automates obtaining and installing a cert with Nginx. Alpha release shipped with Certbot 0.9.0.	tls-sni-01 (443)
standalone	Y	N	Uses a "standalone" webserver to obtain a cert. Requires port 80 or 443 to be available. This is useful on systems with no webserver, or when direct integration with the local webserver is not supported or not desired.	http-01 (80) or tls-sni-01 (443)
manual	Y	N	Helps you obtain a cert by giving you instructions to perform domain validation yourself. Additionally allows you to specify scripts to automate the validation task in a customized way.	http-01 (80) or dns-01 (53)

Under the hood, plugins use one of several ACME protocol "Challenges_" to prove you control a domain. The options are http-01 (which uses port 80), tls-sni-01 (port 443) and dns-01 (requiring configuration of a DNS server on port 53, though that's often not the same machine as your webserver). A few plugins support more than one challenge type, in which case you can choose one with --preferred-challenges.

There are also many third-party-plugins available. Below we describe in more detail the circumstances in which each plugin can be used, and how to use it.

Apache

The Apache plugin currently requires an OS with augeas version 1.0; currently it supports modern OSes based on Debian, Fedora, SUSE, Gentoo and Darwin. 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 requesting a certificate for multiple domains, each domain will use the most recently specified --webroot-path. So, for instance,

certbot 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 certbot. 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.

Nginx

The Nginx plugin has been distributed with Certbot since version 0.9.0 and should work for most configurations. Because it is alpha code, we recommend backing up Nginx configurations before using it (though you can also revert changes to configurations with certbot --nginx rollback). You can use it by providing the --nginx flag on the commandline.

certbot --nginx

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 certbot 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.

Additionally you can specify scripts to prepare for validation and perform the authentication procedure and/or clean up after it by using the --manual-auth-hook and --manual-cleanup-hook flags. This is described in more depth in the hooks section.

Third-party plugins

There are also a number of third-party plugins for the client, provided by other developers. Many are beta/experimental, but some are already in widespread use:

Plugin	Auth	Inst	Notes
plesk	Y	Y	Integration with the Plesk web hosting tool
haproxy	Y	Y	Integration with the HAProxy load balancer
s3front	Y	Y	Integration with Amazon CloudFront distribution of S3 buckets
gandi	Y	Y	Integration with Gandi's hosting products and API
varnish	Y	N	Obtain certs via a Varnish server
external	Y	N	A plugin for convenient scripting (See also ticket 2782)
icecast	N	Y	Deploy certs to Icecast 2 streaming media servers
pritunl	N	Y	Install certs in pritunl distributed OpenVPN servers
proxmox	N	Y	Install certs in Proxmox Virtualization servers
postfix	N	Y	STARTTLS Everywhere is becoming a Certbot Postfix/Exim plugin
heroku	Y	Y	Integration with Heroku SSL

If you're interested, you can also write your own plugin <dev-plugin>.

Re-running Certbot

Running Certbot with the certonly or run commands always requests the creation of a single new certificate, even if you already have an existing certificate with some of the same domain names. The --force-renewal, --duplicate, and --expand options control Certbot's behavior in this case. If you don't specify a requested behavior, Certbot may ask you what you intended.

--force-renewal tells Certbot to request a new certificate with the same domains as an existing certificate. (Each and every domain must be explicitly specified via -d.) If successful, this certificate will be saved alongside the earlier one and symbolic links (the "live" reference) will be updated to point to the new certificate. This is a valid method of explicitly requesting the renewal of a specific individual certificate.

--duplicate tells Certbot to create a separate, unrelated certificate with the same domains as an existing certificate. This certificate will be saved completely separately from the prior one. Most users probably do not want this behavior.

--expand tells Certbot to update an existing certificate with a new certificate that contains all of the old domains and one or more additional new domains.

--allow-subset-of-names tells Certbot to continue with cert generation if only some of the specified domain authorizations can be obtained. This may be useful if some domains specified in a certificate no longer point at this system.

Whenever you obtain a new certificate in any of these ways, the new certificate exists alongside any previously-obtained certificates, whether or not the previous certificates have expired. The generation of a new certificate counts against several rate limits that are intended to prevent abuse of the ACME protocol, as described here.

Renewing certificates

Note

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

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

certbot 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. Unlike certonly, renew acts on multiple certificates and always takes into account whether each one is near expiry. Because of this, renew is suitable (and designed) for automated use, to allow your system to automatically renew each certificate when appropriate. Since renew will only renew certificates that are near expiry it can be run as frequently as you want - since it will usually take no action.

You can also specify hooks to be run before or after a certificate is renewed. For example, if you have only a single cert and you obtained it using the standalone plugin, it will be used by default when renewing. In that case you may want to use a command like this to renew your certificate.

certbot renew --pre-hook "service nginx stop" --post-hook "service nginx start"

This will stop Nginx so standalone can bind to the necessary ports and then restart Nginx after the plugin is finished. The hooks will only be run if a certificate is due for renewal, so you can run this command frequently without unnecessarily stopping your webserver. More information about renewal hooks can be found by running certbot --help renew.

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). In that case, you are likely to want to use the -q or --quiet quiet flag to silence all output except errors.

If you are manually renewing all of your certificates, the --force-renewal flag may be helpful; 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 certbot renew will apply to every certificate for which renewal is attempted; for example, certbot 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 certbot certonly with the complete set of subject domains of a specific certificate specified via -d flags. You may also want to include the -n or --noninteractive flag to prevent blocking on user input (which is useful when running the command from cron).

certbot certonly -n -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.) When run with a set of domains corresponding to an existing certificate, the certonly command attempts to renew that 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.

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

Certbot command-line options

Certbot supports a lot of command line options. Here's the full list, from certbot --help all:

cli-help.txt

Where are my certificates?

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 Certbot 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.

fullchain.pem

All certificates, including server certificate (aka leaf certificate or end-entity certificate). The server certificate is the first one in this file, followed by any intermediates.

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

cert.pem and chain.pem (less common)

cert.pem contains the server certificate by itself, and chain.pem contains the additional intermediate certificate or certificates that web browsers will need in order to validate the server certificate. If you provide one of these files to your web server, you must provide both of them, or some browsers will show "This Connection is Untrusted" errors for your site, some of the time.

Apache < 2.4.8 needs these for SSLCertificateFile. and SSLCertificateChainFile, respectively.

If you're using OCSP stapling with Nginx >= 1.3.7, chain.pem should be provided as the ssl_trusted_certificate to validate OCSP responses.

Note

All files are PEM-encoded. If you need other format, such as DER or PFX, then you could convert using openssl. You can automate that with --renew-hook if you're using automatic renewal.

Pre and Post Validation Hooks

Certbot allows for the specification fo pre and post validation hooks when run in manual mode. The flags to specify these scripts are --manual-auth-hook and --manual-cleanup-hook respectively and can be used as such:

certbot certonly --manual --manual-auth-hook /path/to/http/authenticator.sh --manual-cleanup-hook /path/to/http/cleanup.sh -d secure.example.com

This will run the authenticator.sh script, attempt the validation, and then run the cleanup.sh script. Additionally certbot will pass three environment variables to these scripts:

• CERTBOT_DOMAIN: The domain being authenticated
• CERTBOT_VALIDATION: The validation string
• CERTBOT_TOKEN: Resource name part of the HTTP-01 challenge (HTTP-01 only)

Additionally for cleanup:

• CERTBOT_AUTH_OUTPUT: Whatever the auth script wrote to stdout

Example usage for HTTP-01:

certbot certonly --manual --preferred-challenges=http --manual-auth-hook /path/to/http/authenticator.sh --manual-cleanup-hook /path/to/http/cleanup.sh -d secure.example.com

/path/to/http/authenticator.sh

#!/bin/bash
echo $CERTBOT_VALIDATION > /var/www/htdocs/.well-known/acme-challenge/$CERTBOT_TOKEN

/path/to/http/cleanup.sh

#!/bin/bash
rm -f /var/www/htdocs/.well-known/acme-challenge/$CERTBOT_TOKEN

Example usage for DNS-01 (Cloudflare API v4) (for example purposes only, do not use as-is)

certbot certonly --manual --preferred-challenges=dns --manual-auth-hook /path/to/dns/authenticator.sh --manual-cleanup-hook /path/to/dns/cleanup.sh -d secure.example.com

/path/to/dns/authenticator.sh

#!/bin/bash

# Get your API key from https://www.cloudflare.com/a/account/my-account
API_KEY="your-api-key"
EMAIL="your.email@example.com"

# Strip only the top domain to get the zone id
DOMAIN=$(expr match "$CERTBOT_DOMAIN" '.*\.\(.*\..*\)')

# Get the Cloudflare zone id
ZONE_EXTRA_PARAMS="status=active&page=1&per_page=20&order=status&direction=desc&match=all"
ZONE_ID=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones?name=$DOMAIN&$ZONE_EXTRA_PARAMS" \
     -H     "X-Auth-Email: $EMAIL" \
     -H     "X-Auth-Key: $API_KEY" \
     -H     "Content-Type: application/json" | python -c "import sys,json;print(json.load(sys.stdin)['result'][0]['id'])")

# Create TXT record
CREATE_DOMAIN="_acme-challenge.$CERTBOT_DOMAIN"
RECORD_ID=$(curl -s -X POST "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/dns_records" \
     -H     "X-Auth-Email: $EMAIL" \
     -H     "X-Auth-Key: $API_KEY" \
     -H     "Content-Type: application/json" \
     --data '{"type":"TXT","name":"'"$CREATE_DOMAIN"'","content":"'"$CERTBOT_VALIDATION"'","ttl":120}' \
             | python -c "import sys,json;print(json.load(sys.stdin)['result']['id'])")
# Save info for cleanup
if [ ! -d /tmp/CERTBOT_$CERTBOT_DOMAIN ];then
        mkdir -m 0700 /tmp/CERTBOT_$CERTBOT_DOMAIN
fi
echo $ZONE_ID > /tmp/CERTBOT_$CERTBOT_DOMAIN/ZONE_ID
echo $RECORD_ID > /tmp/CERTBOT_$CERTBOT_DOMAIN/RECORD_ID

# Sleep to make sure the change has time to propagate over to DNS
sleep 25

/path/to/dns/cleanup.sh

#!/bin/bash

# Get your API key from https://www.cloudflare.com/a/account/my-account
API_KEY="your-api-key"
EMAIL="your.email@example.com"

if [ -f /tmp/CERTBOT_$CERTBOT_DOMAIN/ZONE_ID ]; then
        ZONE_ID=$(cat /tmp/CERTBOT_$CERTBOT_DOMAIN/ZONE_ID)
        rm -f /tmp/CERTBOT_$CERTBOT_DOMAIN/ZONE_ID
fi

if [ -f /tmp/CERTBOT_$CERTBOT_DOMAIN/RECORD_ID ]; then
        RECORD_ID=$(cat /tmp/CERTBOT_$CERTBOT_DOMAIN/RECORD_ID)
        rm -f /tmp/CERTBOT_$CERTBOT_DOMAIN/RECORD_ID
fi

# Remove the challenge TXT record from the zone
if [ -n "${ZONE_ID}" ]; then
    if [ -n "${RECORD_ID}" ]; then
        curl -s -X DELETE "https://api.cloudflare.com/client/v4/zones/$ZONE_ID/dns_records/$RECORD_ID" \
                -H "X-Auth-Email: $EMAIL" \
                -H "X-Auth-Key: $API_KEY" \
                -H "Content-Type: application/json"
    fi
fi

Configuration file

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

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, we recommend posting on the Let's Encrypt Community Forum.

You can also chat with us on IRC: (#certbot @ OFTC) or (#letsencrypt @ freenode).

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 certbot --version output
• your operating system, including specific version
• specify which installation method you've chosen