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 and installers.

Authenticators are plugins used with the certonly command to obtain a certificate. The authenticator validates that you control the domain(s) you are requesting a certificate for, obtains a certificate for the specified domain(s), and places the certificate in the /etc/letsencrypt directory on your machine. The authenticator does not install the certificate (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 certificate. 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 certificate with Apache 2.4 on OSes with `libaugeas0` 1.0+.	tls-sni-01 (443)
webroot	Y	N	Obtains a certificate by writing to the webroot directory of an already running webserver.	http-01 (80)
nginx	Y	Y	Automates obtaining and installing a certificate with Nginx. Shipped with Certbot 0.9.0.	tls-sni-01 (443)
standalone	Y	N	Uses a "standalone" webserver to obtain a certificate. 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)
`DNS plugins <dns_plugins>`	Y	N	This category of plugins automates obtaining a certificate by modifying DNS records to prove you have control over a domain. Doing domain validation in this way is the only way to obtain wildcard certificates from Let's Encrypt.	dns-01 (53)
manual	Y	N	Helps you obtain a certificate 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), dns-01 (53) or tls-sni-01 (443)

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 certificates 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 certificate 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. 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

Use standalone mode to obtain a certificate if you don't want to use (or don't currently have) existing server software. The standalone plugin does not rely on any other server software running on the machine where you obtain the certificate.

To obtain a certificate 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.

--preferred-challenges http to use port 80

--preferred-challenges tls-sni to use port 443

It must still be possible for your machine to accept inbound connections from the Internet on the specified port using each requested domain name.

Note

The --standalone-supported-challenges option has been deprecated since certbot version 0.9.0.

DNS Plugins

If you'd like to obtain a wildcard certificate from Let's Encrypt or run certbot on a machine other than your target webserver, you can use one of Certbot's DNS plugins.

These plugins are still in the process of being packaged by many distributions and cannot currently be installed with certbot-auto. If, however, you are comfortable installing the certificates yourself, you can run these plugins with Docker <docker-user>.

Once installed, you can find documentation on how to use each plugin at:

certbot-dns-cloudflare
certbot-dns-cloudxns
certbot-dns-digitalocean
certbot-dns-dnsimple
certbot-dns-dnsmadeeasy
certbot-dns-google
certbot-dns-luadns
certbot-dns-nsone
certbot-dns-rfc2136
certbot-dns-route53

Manual

If you'd like to obtain a certificate 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 certificate 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.

The manual plugin can use either the http, dns or the tls-sni challenge. You can use the --preferred-challenges option to choose the challenge of your preference.

The http challenge will ask you to place a file with a specific name and specific content in the /.well-known/acme-challenge/ directory directly in the top-level directory (“web root”) containing the files served by your webserver. In essence it's the same as the webroot plugin, but not automated.

When using the dns challenge, certbot will ask you to place a TXT DNS record with specific contents under the domain name consisting of the hostname for which you want a certificate issued, prepended by _acme-challenge.

For example, for the domain example.com, a zone file entry would look like:

_acme-challenge.example.com. 300 IN TXT "gfj9Xq...Rg85nM"

When using the tls-sni challenge, certbot will prepare a self-signed SSL certificate for you with the challenge validation appropriately encoded into a subjectAlternatNames entry. You will need to configure your SSL server to present this challenge SSL certificate to the ACME server using SNI.

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.

Combining plugins

Sometimes you may want to specify a combination of distinct authenticator and installer plugins. To do so, specify the authenticator plugin with --authenticator or -a and the installer plugin with --installer or -i.

For instance, you may want to create a certificate using the webroot plugin for authentication and the apache plugin for installation, perhaps because you use a proxy or CDN for SSL and only want to secure the connection between them and your origin server, which cannot use the tls-sni-01 challenge due to the intermediate proxy.

certbot run -a webroot -i apache -w /var/www/html -d example.com

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 certificates via a Varnish server
external	Y	N	A plugin for convenient scripting (See also ticket 2782)
icecast	N	Y	Deploy certificates to Icecast 2 streaming media servers
pritunl	N	Y	Install certificates in pritunl distributed OpenVPN servers
proxmox	N	Y	Install certificates 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>.

Managing certificates

To view a list of the certificates Certbot knows about, run the certificates subcommand:

certbot certificates

This returns information in the following format:

Found the following certs:
  Certificate Name: example.com
    Domains: example.com, www.example.com
    Expiry Date: 2017-02-19 19:53:00+00:00 (VALID: 30 days)
    Certificate Path: /etc/letsencrypt/live/example.com/fullchain.pem
    Private Key Path: /etc/letsencrypt/live/example.com/privkey.pem

Certificate Name shows the name of the certificate. Pass this name using the --cert-name flag to specify a particular certificate for the run, certonly, certificates, renew, and delete commands. Example:

certbot certonly --cert-name example.com

Re-creating and Updating Existing Certificates

You can use certonly or run subcommands to request the creation of a single new certificate even if you already have an existing certificate with some of the same domain names.

If a certificate is requested with run or certonly specifying a certificate name that already exists, Certbot updates the existing certificate. Otherwise a new certificate is created and assigned the specified name.

The --force-renewal, --duplicate, and --expand options control Certbot's behavior when re-creating a certificate with the same name as an existing certificate. 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 domain must be explicitly specified via -d. If successful, this certificate is 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 renewing a specific individual certificate.

--duplicate tells Certbot to create a separate, unrelated certificate with the same domains as an existing certificate. This certificate is saved completely separately from the prior one. Most users will not need to issue this command in normal circumstances.

--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. With the --expand option, use the -d option to specify all existing domains and one or more new domains.

Example:

certbot --expand -d existing.com,example.com,newdomain.com

If you prefer, you can specify the domains individually like this:

certbot --expand -d existing.com -d example.com -d newdomain.com

Consider using --cert-name instead of --expand, as it gives more control over which certificate is modified and it lets you remove domains as well as adding them.

--allow-subset-of-names tells Certbot to continue with certificate 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.

Changing a Certificate's Domains

The --cert-name flag can also be used to modify the domains a certificate contains, by specifying new domains using the -d or --domains flag. If certificate example.com previously contained example.com and www.example.com, it can be modified to only contain example.com by specifying only example.com with the -d or --domains flag. Example:

certbot certonly --cert-name example.com -d example.com

The same format can be used to expand the set of domains a certificate contains, or to replace that set entirely:

certbot certonly --cert-name example.com -d example.org,www.example.org

Revoking certificates

If your account key has been compromised or you otherwise need to revoke a certificate, use the revoke command to do so. Note that the revoke command takes the certificate path (ending in cert.pem), not a certificate name or domain. Example:

certbot revoke --cert-path /etc/letsencrypt/live/CERTNAME/cert.pem

You can also specify the reason for revoking your certificate by using the reason flag. Reasons include unspecified which is the default, as well as keycompromise, affiliationchanged, superseded, and cessationofoperation:

certbot revoke --cert-path /etc/letsencrypt/live/CERTNAME/cert.pem --reason keycompromise

Additionally, if a certificate is a test certificate obtained via the --staging or --test-cert flag, that flag must be passed to the revoke subcommand. Once a certificate is revoked (or for other certificate management tasks), all of a certificate's relevant files can be removed from the system with the delete subcommand:

certbot delete --cert-name example.com

Note

If you don't use delete to remove the certificate completely, it will be renewed automatically at the next renewal event.

Note

Revoking a certificate will have no effect on the rate limit imposed by the Let's Encrypt server.

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.

As of version 0.10.0, Certbot 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 command attempts 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 only renews certificates that are near expiry it can be run as frequently as you want - since it will usually take no action.

The renew command includes hooks for running commands or scripts before or after a certificate is renewed. For example, if you have a single certificate obtained using the standalone plugin, you might need to stop the webserver before renewing so standalone can bind to the necessary ports, and then restart it after the plugin is finished. Example:

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

If a hook exits with a non-zero exit code, the error will be printed to stderr but renewal will be attempted anyway. A failing hook doesn't directly cause Certbot to exit with a non-zero exit code, but since Certbot exits with a non-zero exit code when renewals fail, a failed hook causing renewal failures will indirectly result in a non-zero exit code. Hooks will only be run if a certificate is due for renewal, so you can run the above command frequently without unnecessarily stopping your webserver.

--pre-hook and --post-hook hooks run before and after every renewal attempt. If you want your hook to run only after a successful renewal, use --deploy-hook in a command like this.

certbot renew --deploy-hook /path/to/deploy-hook-script

For example, if you have a daemon that does not read its certificates as the root user, a deploy hook like this can copy them to the correct location and apply appropriate file permissions.

/path/to/deploy-hook-script

#!/bin/sh

set -e

for domain in $RENEWED_DOMAINS; do
        case $domain in
        example.com)
                daemon_cert_root=/etc/some-daemon/certs

                # Make sure the certificate and private key files are
                # never world readable, even just for an instant while
                # we're copying them into daemon_cert_root.
                umask 077

                cp "$RENEWED_LINEAGE/fullchain.pem" "$daemon_cert_root/$domain.cert"
                cp "$RENEWED_LINEAGE/privkey.pem" "$daemon_cert_root/$domain.key"

                # Apply the proper file ownership and permissions for
                # the daemon to read its certificate and key.
                chown some-daemon "$daemon_cert_root/$domain.cert" \
                        "$daemon_cert_root/$domain.key"
                chmod 400 "$daemon_cert_root/$domain.cert" \
                        "$daemon_cert_root/$domain.key"

                service some-daemon restart >/dev/null
                ;;
        esac
done

You can also specify hooks by placing files in subdirectories of Certbot's configuration directory. Assuming your configuration directory is /etc/letsencrypt, any executable files found in /etc/letsencrypt/renewal-hooks/pre, /etc/letsencrypt/renewal-hooks/deploy, and /etc/letsencrypt/renewal-hooks/post will be run as pre, deploy, and post hooks respectively when any certificate is renewed with the renew subcommand. These hooks are run in alphabetical order and are not run for other subcommands. (The order the hooks are run is determined by the byte value of the characters in their filenames and is not dependent on your locale.)

Hooks specified in the command line, configuration file <config-file>, or renewal configuration files <renewal-config-file> are run as usual after running all hooks in these directories. One minor exception to this is if a hook specified elsewhere is simply the path to an executable file in the hook directory of the same type (e.g. your pre-hook is the path to an executable in /etc/letsencrypt/renewal-hooks/pre), the file is not run a second time. You can stop Certbot from automatically running executables found in these directories by including --no-directory-hooks on the command line.

More information about 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.

Many of the certbot clients obtained through a distribution come with automatic renewal out of the box, such as Debian and Ubuntu versions installed through apt, CentOS/RHEL 7 through EPEL, etc. See Automated Renewals for more details.

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 specific 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 to improve the renewal process, and we apologize for any inconvenience you encounter in integrating these commands into your individual environment.

Note

certbot renew exit status will only be 1 if a renewal attempt failed. This means certbot renew exit status will be 0 if no certificate needs to be updated. If you write a custom script and expect to run a command only after a certificate was actually renewed you will need to use the --post-hook since the exit status will be 0 both on successful renewal and when renewal is not necessary.

Modifying the Renewal Configuration File

When a certificate is issued, by default Certbot creates a renewal configuration file that tracks the options that were selected when Certbot was run. This allows Certbot to use those same options again when it comes time for renewal. These renewal configuration files are located at /etc/letsencrypt/renewal/CERTNAME.

For advanced certificate management tasks, it is possible to manually modify the certificate's renewal configuration file, but this is discouraged since it can easily break Certbot's ability to renew your certificates. If you choose to modify the renewal configuration file we advise you to test its validity with the certbot renew --dry-run command.

Warning

Modifying any files in /etc/letsencrypt can damage them so Certbot can no longer properly manage its certificates, and we do not recommend doing so.

For most tasks, it is safest to limit yourself to pointing symlinks at the files there, or using --deploy-hook to copy / make new files based upon those files, if your operational situation requires it (for instance, combining certificates and keys in different way, or having copies of things with different specific permissions that are demanded by other programs).

If the contents of /etc/letsencrypt/archive/CERTNAME are moved to a new folder, first specify the new folder's name in the renewal configuration file, then run certbot update_symlinks to point the symlinks in /etc/letsencrypt/live/CERTNAME to the new folder.

If you would like the live certificate files whose symlink location Certbot updates on each run to reside in a different location, first move them to that location, then specify the full path of each of the four files in the renewal configuration file. Since the symlinks are relative links, you must follow this with an invocation of certbot update_symlinks.

For example, say that a certificate's renewal configuration file previously contained the following directives:

archive_dir = /etc/letsencrypt/archive/example.com
cert = /etc/letsencrypt/live/example.com/cert.pem
privkey = /etc/letsencrypt/live/example.com/privkey.pem
chain = /etc/letsencrypt/live/example.com/chain.pem
fullchain = /etc/letsencrypt/live/example.com/fullchain.pem

The following commands could be used to specify where these files are located:

mv /etc/letsencrypt/archive/example.com /home/user/me/certbot/example_archive
sed -i 's,/etc/letsencrypt/archive/example.com,/home/user/me/certbot/example_archive,' /etc/letsencrypt/renewal/example.com.conf
mv /etc/letsencrypt/live/example.com/*.pem /home/user/me/certbot/
sed -i 's,/etc/letsencrypt/live/example.com,/home/user/me/certbot,g' /etc/letsencrypt/renewal/example.com.conf
certbot update_symlinks

Automated Renewals

Many Linux distributions provide automated renewal when you use the packages installed through their system package manager. The following table is an incomplete list of distributions which do so, as well as their methods for doing so.

If you are not sure whether or not your system has this already automated, refer to your distribution's documentation, or check your system's crontab (typically in /etc/crontab/ and /etc/cron.*/* and systemd timers (systemctl list-timers).

Distributions with Automated Renewal

Distribution Name	Distribution Version	Automation Method
CentOS	EPEL 7	systemd
Debian	jessie	cron, systemd
Debian	stretch	cron, systemd
Debian	testing/sid	cron, systemd
Fedora	26	systemd
Fedora	27	systemd
RHEL	EPEL 7	systemd
Ubuntu	17.10	cron, systemd
Ubuntu	certbot PPA	cron, systemd

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 --deploy-hook if you're using automatic renewal.

Pre and Post Validation Hooks

Certbot allows for the specification of 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 follows:

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 relevant environment variables to these scripts:

CERTBOT_DOMAIN: The domain being authenticated
CERTBOT_VALIDATION: The validation string (HTTP-01 and DNS-01 only)
CERTBOT_TOKEN: Resource name part of the HTTP-01 challenge (HTTP-01 only)
CERTBOT_CERT_PATH: The challenge SSL certificate (TLS-SNI-01 only)
CERTBOT_KEY_PATH: The private key associated with the aforementioned SSL certificate (TLS-SNI-01 only)
CERTBOT_SNI_DOMAIN: The SNI name for which the ACME server expects to be presented the self-signed certificate located at $CERTBOT_CERT_PATH (TLS-SNI-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

Changing the ACME Server

By default, Certbot uses Let's Encrypt's initial production server at https://acme-v01.api.letsencrypt.org/. You can tell Certbot to use a different CA by providing --server on the command line or in a configuration file <config-file> with the URL of the server's ACME directory. For example, if you would like to use Let's Encrypt's new ACMEv2 server, you would add --server https://acme-v02.api.letsencrypt.org/directory to the command line. Certbot will automatically select which version of the ACME protocol to use based on the contents served at the provided URL.

If you use --server to specify an ACME CA that implements a newer version of the spec, you may be able to obtain a certificate for a wildcard domain. Some CAs (such as Let's Encrypt) require that domain validation for wildcard domains must be done through modifications to DNS records which means that the dns-01 challenge type must be used. To see a list of Certbot plugins that support this challenge type and how to use them, see plugins.

Lock Files

When processing a validation Certbot writes a number of lock files on your system to prevent multiple instances from overwriting each other's changes. This means that be default two instances of Certbot will not be able to run in parallel.

Since the directories used by Certbot are configurable, Certbot will write a lock file for all of the directories it uses. This include Certbot's --work-dir, --logs-dir, and --config-dir. By default these are /var/lib/letsencrypt, /var/logs/letsencrypt, and /etc/letsencrypt respectively. Additionally if you are using Certbot with Apache or nginx it will lock the configuration folder for that program, which are typically also in the /etc directory.

Note that these lock files will only prevent other instances of Certbot from using those directories, not other processes. If you'd like to run multiple instances of Certbot simultaneously you should specify different directories as the --work-dir, --logs-dir, and --config-dir for each instance of Certbot that you would like to run.

Configuration file

Certbot accepts a global configuration file that applies its options to all invocations of Certbot. Certificate specific configuration choices should be set in the .conf files that can be found in /etc/letsencrypt/renewal.

By default no cli.ini file is created, after creating one it is possible to specify the location of this 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).

Since this configuration file applies to all invocations of certbot it is incorrect to list domains in it. Listing domains in cli.ini may prevent renewal from working. Additionally due to how arguments in cli.ini are parsed, options which wish to not be set should not be listed. Options set to false will instead be read as being set to true by older versions of Certbot, since they have been listed in the config file.

Log Rotation

By default certbot stores status logs in /var/log/letsencrypt. By default certbot will begin rotating logs once there are 1000 logs in the log directory. Meaning that once 1000 files are in /var/log/letsencrypt Certbot will delete the oldest one to make room for new logs. The number of subsequent logs can be changed by passing the desired number to the command line flag --max-log-backups.

Note

Some distributions, including Debian and Ubuntu, disable certbot's internal log rotation in favor of a more traditional logrotate script. If you are using a distribution's packages and want to alter the log rotation, check /etc/logrotate.d/ for a certbot rotation script.

Certbot command-line options

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

cli-help.txt

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: (#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

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User Guide

Certbot Commands

Getting certificates (and choosing plugins)

Apache

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Standalone

DNS Plugins

Manual

Combining plugins

Third-party plugins

Managing certificates

Re-creating and Updating Existing Certificates

Changing a Certificate's Domains

Revoking certificates

Renewing certificates

Modifying the Renewal Configuration File

Automated Renewals

Where are my certificates?

Pre and Post Validation Hooks

Changing the ACME Server

Lock Files

Configuration file

Log Rotation

Certbot command-line options

Getting help