[Let’s Encrypt](https://letsencrypt.org/) is a service that offers free SSL certificates through an automated API. The most popular Let’s Encrypt client is [EFF](https://www.eff.org/)’s [Certbot](https://certbot.eff.org/) client. Certbot offers a variety of ways to validate your domain, fetch certificates, and automatically configure Apache and Nginx. In this tutorial, we’ll discuss Certbot’s [standalone mode](https://certbot.eff.org/docs/using.html#standalone) and how to use it to secure other types of services, such as a mail server or a message broker like [RabbitMQ](https://www.rabbitmq.com/).

Ubuntu

18.04

### Introduction

[Let's Encrypt](https://letsencrypt.org/) is a service offering free SSL certificates through an automated API. The most popular Let's Encrypt client is [EFF](https://www.eff.org/)'s [Certbot](https://certbot.eff.org/).

Certbot offers a variety of ways to validate your domain, fetch certificates, and automatically configure Apache and Nginx. In this tutorial, we'll discuss Certbot's _standalone_ mode and how to use it to secure other types of services, such as a mail server or a message broker like RabbitMQ.

We won’t discuss the details of SSL configuration, but when you are done you will have a valid certificate that is automatically renewed. Additionally, you will be able to automate reloading your service to pick up the renewed certificate.


## Prerequisites

Before starting this tutorial, you will need:

* An Ubuntu 18.04 server with a non-root, sudo-enabled user and basic firewall set up, as detailed in [this Ubuntu 18.04 server setup tutorial](https://www.digitalocean.com/community/tutorials/initial-server-setup-with-ubuntu-18-04).
* A domain name pointed at your server, which you can accomplish by following “[How to Set Up a Host Name with DigitalOcean](https://www.digitalocean.com/community/tutorials/how-to-set-up-a-host-name-with-digitalocean).” This tutorial will use `<^>example.com<^>` throughout.
* Port 80 **or** 443 must be unused on your server. If the service you're trying to secure is on a machine with a web server that occupies both of those ports, you'll need to use a different mode such as Certbot's [_webroot_ mode](https://certbot.eff.org/docs/using.html#webroot).


## Step 1 — Installing Certbot

Ubuntu includes the Certbot client in their default repository, but it's a bit out of date. Instead, we'll install it from Certbot's official Ubuntu PPA, or *Personal Package Archive*. These are alternative repositories that package more recent or more obscure software. First, add the repository:

```command
sudo add-apt-repository ppa:certbot/certbot
```

You'll need to press `ENTER` to accept. Afterwards, update the package list to pick up the new repository's package information:

```command
sudo apt update
```

And finally, install the `certbot` package:

```command
sudo apt install certbot
```

Now that we have Certbot installed, let's run it to get our certificate.


## Step 2 — Running Certbot

Certbot needs to answer a cryptographic challenge issued by the Let's Encrypt API in order to prove we control our domain. It uses ports `80` (HTTP) or `443` (HTTPS) to accomplish this. Open up the appropriate port in your firewall:

```command
sudo ufw allow <^>80<^>
```

Substitute `443` above if that's the port you're using. `ufw` will output confirmation that your rule was added:

```
[secondary_label Output]
Rule added
Rule added (v6)
```

We can now run Certbot to get our certificate. We'll use the `--standalone` option to tell Certbot to handle the challenge using its own built-in web server. The `--preferred-challenges` option instructs Certbot to use port 80 or port 443. If you're using port 80, you want `--preferred-challenges http`. For port 443 it would be `--preferred-challenges tls-sni`. Finally, the `-d` flag is used to specify the domain you're requesting a certificate for. You can add multiple `-d` options to cover multiple domains in one certificate.

```command
sudo certbot certonly --standalone --preferred-challenges <^>http<^> -d <^>example.com<^>
```

When running the command, you will be prompted to enter an email address and agree to the terms of service. After doing so, you should see a message telling you the process was successful and where your certificates are stored:

```
[secondary_label Output]
IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/<^>example.com<^>/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/<^>example.com<^>/privkey.pem
   Your cert will expire on 2018-10-09. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot
   again. To non-interactively renew *all* of your certificates, run
   "certbot renew"
 - Your account credentials have been saved in your Certbot
   configuration directory at /etc/letsencrypt. You should make a
   secure backup of this folder now. This configuration directory will
   also contain certificates and private keys obtained by Certbot so
   making regular backups of this folder is ideal.
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le
```

We've got our certificates. Let's take a look at what we downloaded and how to use the files with our software.


## Step 3 — Configuring Your Application

Configuring your application for SSL is beyond the scope of this article, as each application has different requirements and configuration options, but let's take a look at what Certbot has downloaded for us. Use `ls` to list out the directory that holds our keys and certificates:

```command
sudo ls /etc/letsencrypt/live/<^>example.com<^>
```

```
[secondary_label Output]
cert.pem  chain.pem  fullchain.pem  privkey.pem  README
```

The `README` file in this directory has more information about each of these files. Most often you'll only need two of these files:

- `privkey.pem`: This is the private key for the certificate. This needs to be kept safe and secret, which is why most of the `/etc/letsencrypt` directory has very restrictive permissions and is accessible by only the **root** user. Most software configuration will refer to this as something similar to `ssl-certificate-key` or `ssl-certificate-key-file`.
- `fullchain.pem`: This is our certificate, bundled with all intermediate certificates. Most software will use this file for the actual certificate, and will refer to it in their configuration with a name like 'ssl-certificate'.

For more information on the other files present, refer to the "[Where are my certificates](https://certbot.eff.org/docs/using.html#where-are-my-certificates)" section of the Certbot docs.

Some software will need its certificates in other formats, in other locations, or with other user permissions. It is best to leave everything in the `letsencrypt` directory, and not change any permissions in there (permissions will just be overwritten upon renewal anyway), but sometimes that's just not an option. In that case, you'll need to write a script to move files and change permissions as needed. This script will need to be run whenever Certbot renews the certificates, which we'll talk about next.


## Step 4 — Handling Certbot Automatic Renewals

Let's Encrypt's certificates are only valid for ninety days. This is to encourage users to automate their certificate renewal process. The `certbot` package we installed takes care of this for us by adding a renew script to `/etc/cron.d`. This script runs twice a day and will renew any certificate that's within thirty days of expiration.

With our certificates renewing automatically, we still need a way to run other tasks after a renewal. We need to at least restart or reload our server to pick up the new certificates, and as mentioned in Step 3 we may need to manipulate the certificate files in some way to make them work with the software we're using. This is the purpose of Certbot's `renew_hook` option.

To add a `renew_hook`, we update Certbot's renewal config file. Certbot remembers all the details of how you first fetched the certificate, and will run with the same options upon renewal. We just need to add in our hook. Open the config file with you favorite editor:

```command
sudo nano /etc/letsencrypt/renewal/example.com.conf
```

A text file will open with some configuration options. Add your hook on the last line:

```
[label /etc/letsencrypt/renewal/example.com.conf]
renew_hook = <^>systemctl reload rabbitmq<^>
```

Update the command above to whatever you need to run to reload your server or run your custom file munging script. Usually, on Ubuntu, you’ll mostly be using `systemctl` to reload a service. Save and close the file, then run a Certbot dry run to make sure the syntax is ok:

```command
sudo certbot renew --dry-run
```

If you see no errors, you're all set. Certbot is set to renew when necessary and run any commands needed to get your service using the new files.


## Conclusion

In this tutorial, we've installed the Certbot Let's Encrypt client, downloaded an SSL certificate using standalone mode, and enabled automatic renewals with renew hooks. This should give you a good start on using Let's Encrypt certificates with services other than your typical web server.

For more information, please refer to [Certbot's documentation](https://certbot.eff.org/docs/).





Certbot offers a variety of ways to validate your domain, fetch certificates, and automatically configure Apache and Nginx. In this tutorial, we'll discuss Certbot's standalone mode and how to use it to secure other types of services, such as a mail server or a message broker like RabbitMQ.

How To Use Certbot Standalone Mode to Retrieve Let's Encrypt SSL Certificates on Ubuntu 18.04

How To Use Certbot Standalone Mode to Retrieve Let's Encrypt SSL Certificates

16.04

### Introduction

[Let's Encrypt](https://letsencrypt.org/) is a service offering free SSL certificates through an automated API. The most popular Let's Encrypt client is [EFF](https://www.eff.org/)'s [Certbot](https://certbot.eff.org/).

Certbot offers a variety of ways to validate your domain, fetch certificates, and automatically configure Apache and Nginx. In this tutorial, we'll discuss Certbot's _standalone_ mode and how to use it to secure other types of services, such as a mail server or a message broker like RabbitMQ.

We won’t discuss the details of SSL configuration, but when you are done you will have a valid certificate that is automatically renewed. Additionally, you will be able to automate reloading your service to pick up the renewed certificate.


## Prerequisites

Before starting this tutorial, you will need:

* An Ubuntu 16.04 server with a non-root, sudo-enabled user and basic firewall set up, as detailed in [this Ubuntu 16.04 server setup tutorial](https://www.digitalocean.com/community/tutorials/initial-server-setup-with-ubuntu-16-04).
* A domain name pointed at your server, which you can accomplish by following “[How to Set Up a Host Name with DigitalOcean](https://www.digitalocean.com/community/tutorials/how-to-set-up-a-host-name-with-digitalocean).” This tutorial will use `<^>example.com<^>` throughout.
* Port 80 **or** 443 must be unused on your server. If the service you're trying to secure is on a machine with a web server that occupies both of those ports, you'll need to use a different mode such as Certbot's [_webroot_ mode](https://certbot.eff.org/docs/using.html#webroot).


## Step 1 — Installing Certbot

Ubuntu includes the Certbot client in their default repository, but it's a bit out of date. Instead, we'll install it from Certbot's official Ubuntu PPA, or *Personal Package Archive*. These are alternative repositories that package more recent or more obscure software. First, add the repository:

```command
sudo add-apt-repository ppa:certbot/certbot
```

You'll need to press `ENTER` to accept. Afterwards, update the package list to pick up the new repository's package information:

```command
sudo apt-get update
```

And finally, install the `certbot` package:

```command
sudo apt-get install certbot
```

Now that we have Certbot installed, let's run it to get our certificate.


## Step 2 — Running Certbot

Certbot needs to answer a cryptographic challenge issued by the Let's Encrypt API in order to prove we control our domain. It uses ports `80` (HTTP) or `443` (HTTPS) to accomplish this. Open up the appropriate port in your firewall:

```command
sudo ufw allow <^>80<^>
```

Substitute `443` above if that's the port you're using. `ufw` will output confirmation that your rule was added:

```
[secondary_label Output]
Rule added
Rule added (v6)
```

We can now run Certbot to get our certificate. We'll use the `--standalone` option to tell Certbot to handle the challenge using its own built-in web server. The `--preferred-challenges` option instructs Certbot to use port 80 or port 443. If you're using port 80, you want `--preferred-challenges http`. For port 443 it would be `--preferred-challenges tls-sni`. Finally, the `-d` flag is used to specify the domain you're requesting a certificate for. You can add multiple `-d` options to cover multiple domains in one certificate.

```command
sudo certbot certonly --standalone --preferred-challenges <^>http<^> -d <^>example.com<^>
```

When running the command, you will be prompted to enter an email address and agree to the terms of service. After doing so, you should see a message telling you the process was successful and where your certificates are stored:

```
[secondary_label Output]
IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at
   /etc/letsencrypt/live/example.com/fullchain.pem. Your cert will
   expire on 2017-10-23. To obtain a new or tweaked version of this
   certificate in the future, simply run certbot again with the
   "certonly" option. To non-interactively renew *all* of your
   certificates, run "certbot renew"
 - Your account credentials have been saved in your Certbot
   configuration directory at /etc/letsencrypt. You should make a
   secure backup of this folder now. This configuration directory will
   also contain certificates and private keys obtained by Certbot so
   making regular backups of this folder is ideal.
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le
```

We've got our certificates. Let's take a look at what we downloaded and how to use the files with our software.


## Step 3 — Configuring Your Application

Configuring your application for SSL is beyond the scope of this article, as each application has different requirements and configuration options, but let's take a look at what Certbot has downloaded for us. Use `ls` to list out the directory that holds our keys and certificates:

```command
sudo ls /etc/letsencrypt/live/<^>example.com<^>
```

```
[secondary_label Output]
cert.pem  chain.pem  fullchain.pem  privkey.pem  README
```

The `README` file in this directory has more information about each of these files. Most often you'll only need two of these files:

- `privkey.pem`: This is the private key for the certificate. This needs to be kept safe and secret, which is why most of the `/etc/letsencrypt` directory has very restrictive permissions and is accessible by only the **root** user. Most software configuration will refer to this as something similar to `ssl-certificate-key` or `ssl-certificate-key-file`.
- `fullchain.pem`: This is our certificate, bundled with all intermediate certificates. Most software will use this file for the actual certificate, and will refer to it in their configuration with a name like 'ssl-certificate'.

For more information on the other files present, refer to the "[Where are my certificates](https://certbot.eff.org/docs/using.html#where-are-my-certificates)" section of the Certbot docs.

Some software will need its certificates in other formats, in other locations, or with other user permissions. It is best to leave everything in the `letsencrypt` directory, and not change any permissions in there (permissions will just be overwritten upon renewal anyway), but sometimes that's just not an option. In that case, you'll need to write a script to move files and change permissions as needed. This script will need to be run whenever Certbot renews the certificates, which we'll talk about next.


## Step 4 — Handling Certbot Automatic Renewals

Let's Encrypt's certificates are only valid for ninety days. This is to encourage users to automate their certificate renewal process. The `certbot` package we installed takes care of this for us by adding a renew script to `/etc/cron.d`. This script runs twice a day and will renew any certificate that's within thirty days of expiration.

With our certificates renewing automatically, we still need a way to run other tasks after a renewal. We need to at least restart or reload our server to pick up the new certificates, and as mentioned in Step 3 we may need to manipulate the certificate files in some way to make them work with the software we're using. This is the purpose of Certbot's `renew_hook` option.

To add a `renew_hook`, we update Certbot's renewal config file. Certbot remembers all the details of how you first fetched the certificate, and will run with the same options upon renewal. We just need to add in our hook. Open the config file with you favorite editor:

```command
sudo nano /etc/letsencrypt/renewal/example.com.conf
```

A text file will open with some configuration options. Add your hook on the last line:

```
[label /etc/letsencrypt/renewal/example.com.conf]
renew_hook = <^>systemctl reload rabbitmq<^>
```

Update the command above to whatever you need to run to reload your server or run your custom file munging script. Usually, on Ubuntu, you’ll mostly be using `systemctl` to reload a service. Save and close the file, then run a Certbot dry run to make sure the syntax is ok:

```command
sudo certbot renew --dry-run
```

If you see no errors, you're all set. Certbot is set to renew when necessary and run any commands needed to get your service using the new files.


## Conclusion

In this tutorial, we've installed the Certbot Let's Encrypt client, downloaded an SSL certificate using standalone mode, and enabled automatic renewals with renew hooks. This should give you a good start on using Let's Encrypt certificates with services other than your typical web server.

For more information, please refer to [Certbot's documentation](https://certbot.eff.org/docs/).




How To Use Certbot Standalone Mode to Retrieve Let's Encrypt SSL Certificates on Ubuntu 16.04

Debian

### Introduction

[Let's Encrypt](https://letsencrypt.org/) is a service offering free SSL certificates through an automated API. The most popular Let's Encrypt client is [EFF](https://www.eff.org/)'s [Certbot](https://certbot.eff.org/).

Certbot offers a variety of ways to validate your domain, fetch certificates, and automatically configure Apache and Nginx. In this tutorial, we'll discuss Certbot's _standalone_ mode and how to use it to secure other types of services, such as a mail server or a message broker like RabbitMQ.

We won’t discuss the details of SSL configuration, but when you are done you will have a valid certificate that is automatically renewed. Additionally, you will be able to automate reloading your service to pick up the renewed certificate.


## Prerequisites

Before starting this tutorial, you will need:

* A Debian 9 server with a non-root, sudo-enabled user and basic firewall set up, as detailed in [this Debian 9 server setup tutorial](https://www.digitalocean.com/community/tutorials/initial-server-setup-with-debian-9).
* A domain name pointed at your server, which you can accomplish by following “[How to Set Up a Host Name with DigitalOcean](https://www.digitalocean.com/community/tutorials/how-to-set-up-a-host-name-with-digitalocean).” This tutorial will use `<^>example.com<^>` throughout.
* Port 80 **or** 443 must be unused on your server. If the service you're trying to secure is on a machine with a web server that occupies both of those ports, you'll need to use a different mode such as Certbot's [_webroot_ mode](https://certbot.eff.org/docs/using.html#webroot) or DNS-based challenge mode.


## Step 1 — Installing Certbot

Debian 9 includes the Certbot client in their default repository, and it should be up-to-date enough for basic use. If you need to do DNS-based challenges or use other newer Certbot features, you should instead install from the `stretch-backports` repo as instructed by [the official Certbot documentation](https://certbot.eff.org/lets-encrypt/debianstretch-other).

Use `apt` to install the `certbot` package:

```command
sudo apt install certbot
```

You may test your install by asking `certbot` to output its version number:

```command
certbot --version
```

```
[secondary_label Output]
certbot 0.28.0
```

Now that we have Certbot installed, let's run it to get our certificate.


## Step 2 — Running Certbot

Certbot needs to answer a cryptographic challenge issued by the Let's Encrypt API in order to prove we control our domain. It uses ports `80` (HTTP) or `443` (HTTPS) to accomplish this. Open up the appropriate port in your firewall:

```command
sudo ufw allow <^>80<^>
```

Substitute `443` above if that's the port you're using. `ufw` will output confirmation that your rule was added:

```
[secondary_label Output]
Rule added
Rule added (v6)
```

We can now run Certbot to get our certificate. We'll use the `--standalone` option to tell Certbot to handle the challenge using its own built-in web server. The `--preferred-challenges` option instructs Certbot to use port 80 or port 443. If you're using port 80, you want `--preferred-challenges http`. For port 443 it would be `--preferred-challenges tls-sni`. Finally, the `-d` flag is used to specify the domain you're requesting a certificate for. You can add multiple `-d` options to cover multiple domains in one certificate.

```command
sudo certbot certonly --standalone --preferred-challenges <^>http<^> -d <^>example.com<^>
```

When running the command, you will be prompted to enter an email address and agree to the terms of service. After doing so, you should see a message telling you the process was successful and where your certificates are stored:

```
[secondary_label Output]
IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/<^>example.com<^>/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/<^>example.com<^>/privkey.pem
   Your cert will expire on 2019-08-28. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot
   again. To non-interactively renew *all* of your certificates, run
   "certbot renew"
 - Your account credentials have been saved in your Certbot
   configuration directory at /etc/letsencrypt. You should make a
   secure backup of this folder now. This configuration directory will
   also contain certificates and private keys obtained by Certbot so
   making regular backups of this folder is ideal.
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le
```

We've got our certificates. Let's take a look at what we downloaded and how to use the files with our software.


## Step 3 — Configuring Your Application

Configuring your application for SSL is beyond the scope of this article, as each application has different requirements and configuration options, but let's take a look at what Certbot has downloaded for us. Use `ls` to list out the directory that holds our keys and certificates:

```command
sudo ls /etc/letsencrypt/live/<^>example.com<^>
```

```
[secondary_label Output]
cert.pem  chain.pem  fullchain.pem  privkey.pem  README
```

The `README` file in this directory has more information about each of these files. Most often you'll only need two of these files:

- `privkey.pem`: This is the private key for the certificate. This needs to be kept safe and secret, which is why most of the `/etc/letsencrypt` directory has very restrictive permissions and is accessible by only the **root** user. Most software configuration will refer to this as something similar to `ssl-certificate-key` or `ssl-certificate-key-file`.
- `fullchain.pem`: This is our certificate, bundled with all intermediate certificates. Most software will use this file for the actual certificate, and will refer to it in their configuration with a name like 'ssl-certificate'.

For more information on the other files present, refer to the "[Where are my certificates](https://certbot.eff.org/docs/using.html#where-are-my-certificates)" section of the Certbot docs.

Some software will need its certificates in other formats, in other locations, or with other user permissions. It is best to leave everything in the `letsencrypt` directory, and not change any permissions in there (permissions will just be overwritten upon renewal anyway), but sometimes that's just not an option. In that case, you'll need to write a script to move files and change permissions as needed. This script will need to be run whenever Certbot renews the certificates, which we'll talk about next.


## Step 4 — Handling Certbot Automatic Renewals

Let's Encrypt's certificates are only valid for ninety days. This is to encourage users to automate their certificate renewal process. The `certbot` package we installed takes care of this for us by adding a renew script to `/etc/cron.d`. This script runs twice a day and will renew any certificate that's within thirty days of expiration.

With our certificates renewing automatically, we still need a way to run other tasks after a renewal. We need to at least restart or reload our server to pick up the new certificates, and as mentioned in Step 3 we may need to manipulate the certificate files in some way to make them work with the software we're using. This is the purpose of Certbot's `renew_hook` option.

To add a `renew_hook`, we update Certbot's renewal config file. Certbot remembers all the details of how you first fetched the certificate, and will run with the same options upon renewal. We just need to add in our hook. Open the config file with you favorite editor:

```command
sudo nano /etc/letsencrypt/renewal/example.com.conf
```

A text file will open with some configuration options. Add your hook on the last line:

```
[label /etc/letsencrypt/renewal/example.com.conf]
renew_hook = <^>systemctl reload rabbitmq<^>
```

Update the command above to whatever you need to run to reload your server or run your custom file munging script. Usually, on Debian, you’ll mostly be using `systemctl` to reload a service. Save and close the file, then run a Certbot dry run to make sure the syntax is ok:

```command
sudo certbot renew --dry-run
```

If you see no errors, you're all set. Certbot is set to renew when necessary and run any commands needed to get your service using the new files.


## Conclusion

In this tutorial, we've installed the Certbot Let's Encrypt client, downloaded an SSL certificate using standalone mode, and enabled automatic renewals with renew hooks. This should give you a good start on using Let's Encrypt certificates with services other than your typical web server.

For more information, please refer to [Certbot's documentation](https://certbot.eff.org/docs/).


Let's Encrypt is a service offering free SSL certificates through an automated API. The most popular Let's Encrypt client is EFF's Certbot. Certbot offers a variety of ways to validate your...

How To Use Certbot Standalone Mode to Retrieve Let's Encrypt SSL Certificates on Debian 9

CentOS

### Introduction

[Let's Encrypt](https://letsencrypt.org/) is a service offering free SSL certificates through an automated API. The most popular Let's Encrypt client is [EFF](https://www.eff.org/)'s [Certbot](https://certbot.eff.org/).

Certbot offers a variety of ways to validate your domain, fetch certificates, and automatically configure Apache and Nginx. In this tutorial, we'll discuss Certbot's _standalone_ mode and how to use it to secure other types of services, such as a mail server or a message broker like RabbitMQ.

We won’t discuss the details of SSL configuration, but when you are done you will have a valid certificate that is automatically renewed. Additionally, you will be able to automate reloading your service to pick up the renewed certificate.


## Prerequisites

Before starting this tutorial, you will need:

* An CentOS 7 server with a non-root, sudo-enabled user, as detailed in [this CentOS 7 initial server setup tutorial](https://www.digitalocean.com/community/tutorials/initial-server-setup-with-centos-7).
* A domain name pointed at your server, which you can accomplish by following “[How to Set Up a Host Name with DigitalOcean](https://www.digitalocean.com/community/tutorials/how-to-set-up-a-host-name-with-digitalocean).” This tutorial will use `<^>example.com<^>` throughout.
* Port 80 **or** 443 must be unused on your server. If the service you're trying to secure is on a machine with a web server that occupies both of those ports, you'll need to use a different mode such as Certbot's [_webroot_ mode](https://certbot.eff.org/docs/using.html#webroot).


## Step 1 — Installing Certbot

Certbot is packaged in an extra repository called _Extra Packages for Enterprise Linux_ (EPEL). To enable this repository on CentOS 7, run the following `yum` command:

```command
sudo yum --enablerepo=extras install epel-release
```

Afterwards, the `certbot` package can be installed with `yum`:

```command
sudo yum install certbot
```

You may confirm your install was successful by calling the `certbot` command:

```command
certbot --version
```

```
[secondary_label Output]
certbot 0.31.0
```

Now that we have Certbot installed, let's run it to get our certificate.


## Step 2 — Running Certbot

Certbot needs to answer a cryptographic challenge issued by the Let's Encrypt API in order to prove we control our domain. It uses ports `80` (HTTP) or `443` (HTTPS) to accomplish this. If you're using a firewall, open up the appropriate port now. For `firewalld` this would be something like the following:

```command
sudo firewall-cmd --add-service=http
sudo firewall-cmd --runtime-to-permanent
```

Substitute `https` for `http` above if you're using port 443.

We can now run Certbot to get our certificate. We'll use the `--standalone` option to tell Certbot to handle the challenge using its own built-in web server. The `--preferred-challenges` option instructs Certbot to use port 80 or port 443. If you're using port 80, you want `--preferred-challenges http`. For port 443 it would be `--preferred-challenges tls-sni`. Finally, the `-d` flag is used to specify the domain you're requesting a certificate for. You can add multiple `-d` options to cover multiple domains in one certificate.

```command
sudo certbot certonly --standalone --preferred-challenges <^>http<^> -d <^>example.com<^>
```

When running the command, you will be prompted to enter an email address and agree to the terms of service. After doing so, you should see a message telling you the process was successful and where your certificates are stored:

```
[secondary_label Output]
IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/<^>example.com<^>/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/<^>example.com<^>/privkey.pem
   Your cert will expire on 2018-10-09. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot
   again. To non-interactively renew *all* of your certificates, run
   "certbot renew"
 - Your account credentials have been saved in your Certbot
   configuration directory at /etc/letsencrypt. You should make a
   secure backup of this folder now. This configuration directory will
   also contain certificates and private keys obtained by Certbot so
   making regular backups of this folder is ideal.
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le
```

We've got our certificates. Let's take a look at what we downloaded and how to use the files with our software.


## Step 3 — Configuring Your Application

Configuring your application for SSL is beyond the scope of this article, as each application has different requirements and configuration options, but let's take a look at what Certbot has downloaded for us. Use `ls` to list out the directory that holds our keys and certificates:

```command
sudo ls /etc/letsencrypt/live/<^>example.com<^>
```

```
[secondary_label Output]
cert.pem  chain.pem  fullchain.pem  privkey.pem  README
```

The `README` file in this directory has more information about each of these files. Most often you'll only need two of these files:

- `privkey.pem`: This is the private key for the certificate. This needs to be kept safe and secret, which is why most of the `/etc/letsencrypt` directory has very restrictive permissions and is accessible by only the **root** user. Most software configuration will refer to this as something similar to `ssl-certificate-key` or `ssl-certificate-key-file`.
- `fullchain.pem`: This is our certificate, bundled with all intermediate certificates. Most software will use this file for the actual certificate, and will refer to it in their configuration with a name like 'ssl-certificate'.

For more information on the other files present, refer to the "[Where are my certificates](https://certbot.eff.org/docs/using.html#where-are-my-certificates)" section of the Certbot docs.

Some software will need its certificates in other formats, in other locations, or with other user permissions. It is best to leave everything in the `letsencrypt` directory, and not change any permissions in there (permissions will just be overwritten upon renewal anyway), but sometimes that's just not an option. In that case, you'll need to write a script to move files and change permissions as needed. This script will need to be run whenever Certbot renews the certificates, which we'll talk about next.


## Step 4 — Enabling Automatic Certificate Renewal

Let's Encrypt's certificates are only valid for ninety days. This is to encourage users to automate their certificate renewal process. The `certbot` package we installed includes a systemd timer to check for renewals twice a day, but it is disabled by default. Enable the timer by running the following command:

```command
sudo systemctl enable --now certbot-renew.timer
```

```
[secondary_label Output]
Created symlink from /etc/systemd/system/timers.target.wants/certbot-renew.timer to /usr/lib/systemd/system/certbot-renew.timer.
```

You may verify the status of the timer using `systemctl`:

```command
sudo systemctl status certbot-renew.timer
```

```
[secondary_label Output]
● certbot-renew.timer - This is the timer to set the schedule for automated renewals
   Loaded: loaded (/usr/lib/systemd/system/certbot-renew.timer; enabled; vendor preset: disabled)
   <^>Active: active (waiting)<^> since Fri 2019-05-31 15:10:10 UTC; 48s ago
```

The timer should be active. Certbot will now automatically renew any certificates on this server whenever necessary.


## Step 5 — Running Tasks When Certificates are Renewed

Now that our certificates are renewing automatically, we need a way to run certain tasks after a renewal. We need to at least restart or reload our server to pick up the new certificates, and as mentioned in Step 3 we may need to manipulate the certificate files in some way to make them work with the software we're using. This is the purpose of Certbot's `renew_hook` option.

To add a `renew_hook`, we update Certbot's renewal config file. Certbot remembers all the details of how you first fetched the certificate, and will run with the same options upon renewal. We just need to add in our hook. Open the config file with you favorite editor:

```command
sudo vi /etc/letsencrypt/renewal/example.com.conf
```

A text file will open with some configuration options. Add your hook on the last line:

```
[label /etc/letsencrypt/renewal/example.com.conf]
renew_hook = <^>systemctl reload rabbitmq<^>
```

Update the command above to whatever you need to run to reload your server or run your custom file munging script. Usually, on CentOS, you’ll mostly be using `systemctl` to reload a service. Save and close the file, then run a Certbot dry run to make sure the syntax is ok:

```command
sudo certbot renew --dry-run
```

If you see no errors, you're all set. Certbot is set to renew when necessary and run any commands needed to get your service using the new files.


## Conclusion

In this tutorial, we've installed the Certbot Let's Encrypt client, downloaded an SSL certificate using standalone mode, and enabled automatic renewals with renew hooks. This should give you a good start on using Let's Encrypt certificates with services other than your typical web server.

For more information, please refer to [Certbot's documentation](https://certbot.eff.org/docs/).


How To Use Certbot Standalone Mode to Retrieve Let's Encrypt SSL Certificates on CentOS 7

### Introduction

[Let's Encrypt](https://letsencrypt.org/) is a service that offers free SSL certificates through an automated API. The most popular Let's Encrypt client is [EFF](https://www.eff.org/)'s [Certbot](https://certbot.eff.org/) client.

Certbot offers a variety of ways to validate your domain, fetch certificates, and automatically configure [Apache](https://httpd.apache.org/) and [Nginx](https://www.nginx.com/). In this tutorial, we'll discuss Certbot's [_standalone_ mode](https://certbot.eff.org/docs/using.html#standalone) and how to use it to secure other types of services, such as a mail server or a message broker like [RabbitMQ](https://www.rabbitmq.com/).

We won’t discuss the details of SSL configuration, but when you are done you will have a valid certificate that is automatically renewed. Additionally, you will be able to automate reloading your service to pick up the renewed certificate.

## Prerequisites

Before starting this tutorial, you will need:

* A Debian 10 server, a non-root user with `sudo` privileges, and a basic firewall, as detailed in [this Debian 10 server setup tutorial](https://www.digitalocean.com/community/tutorials/initial-server-setup-with-debian-10).
* A domain name pointed at your server, which you can accomplish by following this [documentation](https://www.digitalocean.com/docs/networking/dns/) on creating DNS records on DigitalOcean. 
* Port `80` **or** `443` must be **unused** on your server. If the service you're trying to secure is on a machine with a web server that occupies both of those ports, you'll need to use a different mode such as Certbot's [_webroot_ mode](https://certbot.eff.org/docs/using.html#webroot) or DNS-based challenge mode.


## Step 1 — Installing Certbot

Debian 10 includes the Certbot client in their default repository, and it should be up-to-date enough for basic use. If you need to do DNS-based challenges or use other newer Certbot features, you should instead install from the `buster-backports` repo as instructed by [the official Certbot documentation](https://certbot.eff.org/lets-encrypt/debianstretch-other).

Update your package list:

```command
sudo apt update
```

Use `apt` to install the `certbot` package:

```command
sudo apt install certbot
```

You can test your installation by asking `certbot` to output its version number:

```command
certbot --version
```
```
[secondary_label Output]
certbot <^>0.31.0<^>
```
Now that we have Certbot installed, let's run it to get our certificate.

## Step 2 — Running Certbot

Certbot needs to answer a cryptographic challenge issued by the Let's Encrypt API in order to prove we control our domain. It uses ports `80` (HTTP) or `443` (HTTPS) to accomplish this. Open up the appropriate port in your firewall:

```command
sudo ufw allow <^>80<^>
```
Substitute `443` above if that's the port you're using. `ufw` will output confirmation that your rule was added:
```
[secondary_label Output]
Rule added
Rule added (v6)
```
We can now run Certbot to get our certificate. We'll use the `--standalone` option to tell Certbot to handle the challenge using its own built-in web server. The `--preferred-challenges` option instructs Certbot to use port `80` or port `443`. If you're using port `80`, you will use the `--preferred-challenges http` option. For port `443`, use `--preferred-challenges tls-sni`. Finally, we'll use the `-d` flag to specify the domain we're requesting a certificate for. You can add multiple `-d` options to cover multiple domains in one certificate.

We will use the `--preferred-challenges http` option to demonstrate, but you should use the option that makes sense for your use case. Run the following command with your preferred options to get your certificate:

```command
sudo certbot certonly --standalone --preferred-challenges <^>http<^> -d <^>your_domain<^>
```

When running the command, you will be prompted to enter an email address and agree to the terms of service. After doing so, you should see a message telling you the process was successful and where your certificates are stored:

```
[secondary_label Output]
IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/<^>your_domain<^>/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/<^>your_domain<^>/privkey.pem
   Your cert will expire on 2019-08-28. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot
   again. To non-interactively renew *all* of your certificates, run
   "certbot renew"
 - Your account credentials have been saved in your Certbot
   configuration directory at /etc/letsencrypt. You should make a
   secure backup of this folder now. This configuration directory will
   also contain certificates and private keys obtained by Certbot so
   making regular backups of this folder is ideal.
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le
```
We've got our certificates. Let's take a look at what we downloaded and how to use the files with our software.

## Step 3 — Configuring Your Application

Configuring your application for SSL is beyond the scope of this article, as each application has different requirements and configuration options, but let's take a look at what Certbot has downloaded for us. Use `ls` to list out the directory that holds your keys and certificates:

```command
sudo ls /etc/letsencrypt/live/<^>your_domain<^>
```
You will see the following output:

```
[secondary_label Output]
cert.pem  chain.pem  fullchain.pem  privkey.pem  README
```

The `README` file in this directory has more information about each of these files. Most often you'll only need two of these files:

- `privkey.pem`: This is the private key for the certificate. This needs to be kept safe and secret, which is why most of the `/etc/letsencrypt` directory has very restrictive permissions and is accessible by only the **root** user. Most software configuration will refer to this as `ssl-certificate-key` or `ssl-certificate-key-file`.
- `fullchain.pem`: This is our certificate, bundled with all intermediate certificates. Most software will use this file for the actual certificate, and will refer to it in their configuration with a name like `ssl-certificate`.

For more information on the other files present, refer to the [Where are my certificates?](https://certbot.eff.org/docs/using.html#where-are-my-certificates) section of the Certbot docs.

Some software will need its certificates in other formats or locations, or with other user permissions. It is best to leave everything in the `letsencrypt` directory, and not change any permissions there (permissions will just be overwritten upon renewal anyway), but sometimes that's not an option. In that case, you'll need to write a script to move files and change permissions as needed. This script will need to be run whenever Certbot renews the certificates, which we'll talk about next.

## Step 4 — Handling Certbot Automatic Renewals

Let's Encrypt certificates are only valid for ninety days. This is to encourage users to automate the certificate renewal process. The `certbot` package we installed takes care of this for us by adding a renew script to `/etc/cron.d`. This script runs twice a day and will renew any certificate that's within thirty days of expiring.

With our certificates renewing automatically, we still need a way to run other tasks after a renewal. We need to at least restart or reload our server to pick up the new certificates, and as mentioned in Step 3 we may need to manipulate the certificate files in some way to make them work with the software we're using. This is the purpose of Certbot's [`renew_hook`](https://certbot.eff.org/docs/api/hooks.html?highlight=renew_hook#certbot.hooks.renew_hook) option.

To add a `renew_hook`, we need to update Certbot's renewal config file. Certbot remembers all the details of how you first fetched the certificate, and will run with the same options upon renewal. We just need to add in our hook. Open the config file with your favorite editor:

```command
sudo nano /etc/letsencrypt/renewal/<^>your_domain<^>.conf
```

A text file will open with some configuration options. Add your hook on the last line. In this case, we're using an example that would reload a `rabbitmq` service:

```
[label /etc/letsencrypt/renewal/your_domain.conf]
renew_hook = <^>systemctl reload rabbitmq<^>
```

Update the command above to whatever you need to run to reload your server or run your custom file munging script. On Debian, you’ll usually use `systemctl` to reload a service. 

Save and close the file, then run a Certbot dry run to make sure the syntax is ok:

```command
sudo certbot renew --dry-run
```

If you see no errors, you're all set. Certbot is set to renew when necessary and run any commands needed to get your service using the new files.


## Conclusion

In this tutorial, we've installed the Certbot Let's Encrypt client, downloaded an SSL certificate using standalone mode, and enabled automatic renewals with renew hooks. This should give you a good start on using Let's Encrypt certificates with services other than your typical web server.

For more information, please refer to [Certbot's documentation](https://certbot.eff.org/docs/).


Let's Encrypt is a service offering free SSL certificates through an automated API. In this tutorial, we'll discuss Certbot's _standalone_ mode and how to use it to secure other types of services, such as a mail server or a message broker like RabbitMQ, on Debian 10.

How To Use Certbot Standalone Mode to Retrieve Let's Encrypt SSL Certificates on Debian 10

20.04

### Introduction

[Let's Encrypt](https://letsencrypt.org/) is a service offering free SSL certificates through an automated API. The most popular Let's Encrypt client is [EFF](https://www.eff.org/)'s [Certbot](https://certbot.eff.org/).

Certbot offers a variety of ways to validate your domain, fetch certificates, and automatically configure Apache and Nginx. In this tutorial, we'll discuss Certbot's _standalone_ mode and how to use it to secure other types of services, such as a mail server or a message broker like RabbitMQ.

We won’t discuss the details of SSL configuration, but when you are done you will have a valid certificate that is automatically renewed. Additionally, you will be able to automate reloading your service to pick up the renewed certificate.


## Prerequisites

Before starting this tutorial, you will need:

* An Ubuntu 20.04 server with a non-root, sudo-enabled user and basic firewall set up, as detailed in [this Ubuntu 20.04 server setup tutorial](https://www.digitalocean.com/community/tutorials/initial-server-setup-with-ubuntu-20-04).
* A domain name pointed at your server. If you are using a DigitalOcean Droplet, you can accomplish this by following our [Domains and DNS](https://docs.digitalocean.com/products/networking/dns/) documentation. This tutorial will use `<^>your_domain<^>` throughout.
* Port 80 **or** 443 must be unused on your server. If the service you're trying to secure is on a machine with a web server that occupies both of those ports, you'll need to use a different mode such as Certbot's [_webroot_ mode](https://certbot.eff.org/docs/using.html#webroot).


## Step 1 — Installing Certbot

Certbot recommends using their *snap* package for installation. Snap packages work on nearly all Linux distributions, but they require that you've installed snapd first in order to manage snap packages. Ubuntu 20.04 comes with support for snaps out of the box, so you can start by making sure your snapd core is up to date:

```command
sudo snap install core; sudo snap refresh core
```

If you're working on a server that previously had an older version of certbot installed, you should remove it before going any further:

```command
sudo apt remove certbot
```

After that, you can install the `certbot` package:

```command
sudo snap install --classic certbot
```

Finally, you can link the `certbot` command from the snap install directory to your path, so you'll be able to run it by just typing `certbot`. This isn't necessary with all packages, but snaps tend to be less intrusive by default, so they don't conflict with any other system packages by accident:

```command
sudo ln -s /snap/bin/certbot /usr/bin/certbot
```

Now that we have Certbot installed, let's run it to get our certificate.


## Step 2 — Running Certbot

Certbot needs to answer a cryptographic challenge issued by the Let's Encrypt API in order to prove we control our domain. It uses ports `80` (HTTP) or `443` (HTTPS) to accomplish this. Open up the appropriate port(s) in your firewall:

```command
sudo ufw allow <^>443<^>
```

```
[secondary_label Output]
Rule added
Rule added (v6)
```

We can now run Certbot to get our certificate. We'll use the `--standalone` option to tell Certbot to handle the challenge using its own built-in web server. Finally, the `-d` flag is used to specify the domain you're requesting a certificate for. You can add multiple `-d` options to cover multiple domains in one certificate.

```command
sudo certbot certonly --standalone -d <^>your_domain<^>
```

When running the command, you will be prompted to enter an email address and agree to the terms of service. After doing so, you should see a message telling you the process was successful and where your certificates are stored:

```
[secondary_label Output]
IMPORTANT NOTES:
Successfully received certificate.
Certificate is saved at: /etc/letsencrypt/live/<^>your_domain<^>/fullchain.pem
Key is saved at: /etc/letsencrypt/live/<^>your_domain<^>/privkey.pem
This certificate expires on 2022-02-10.
These files will be updated when the certificate renews.
Certbot has set up a scheduled task to automatically renew this certificate in the background.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
If you like Certbot, please consider supporting our work by:
* Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate
* Donating to EFF: https://eff.org/donate-le
```

You should now have your certificates. In the next step, we will inspect some of the files that we downloaded and learn about their functionality.  


## Step 3 — Configuring Your Application

Configuring your application for SSL is beyond the scope of this article, as each application has different requirements and configuration options, but let's take a look at what Certbot has downloaded for us. Use `ls` to list out the directory that holds our keys and certificates:

```command
sudo ls /etc/letsencrypt/live/<^>your_domain<^>
```

```
[secondary_label Output]
cert.pem  chain.pem  fullchain.pem  privkey.pem  README
```

The `README` file in this directory has more information about each of these files. Most often you'll only need two of these files:

- `privkey.pem`: This is the private key for the certificate. This needs to be kept safe and secret, which is why most of the `/etc/letsencrypt` directory has very restrictive permissions and is accessible by only the **root** user. Most software configuration will refer to this as something similar to `ssl-certificate-key` or `ssl-certificate-key-file`.
- `fullchain.pem`: This is our certificate, bundled with all intermediate certificates. Most software will use this file for the actual certificate, and will refer to it in their configuration with a name like 'ssl-certificate'.

For more information on the other files present, refer to the "[Where are my certificateshttps://eff-certbot.readthedocs.io/en/stable/using.html#where-are-my-certificates)" section of the Certbot docs.

Some software will need its certificates in other formats, in other locations, or with other user permissions. It is best to leave everything in the `letsencrypt` directory, and not change any permissions in there (permissions will just be overwritten upon renewal anyway), but sometimes that's just not an option. In that case, you'll need to write a script to move files and change permissions as needed. This script will need to be run whenever Certbot renews the certificates, which we'll talk about next.


## Step 4 — Handling Certbot Automatic Renewals

Let's Encrypt's certificates are only valid for ninety days. This is to encourage users to automate their certificate renewal process. The `certbot` package we installed takes care of this for us by adding a renew script to `/etc/cron.d`. This script runs twice a day and will renew any certificate that's within thirty days of expiration.

With our certificates renewing automatically, we still need a way to run other tasks after a renewal. We need to at least restart or reload our server to pick up the new certificates, and as mentioned in Step 3 we may need to manipulate the certificate files in some way to make them work with the software we're using. This is the purpose of Certbot's `renew_hook` option.

To add a `renew_hook`, we update Certbot's renewal config file. Certbot remembers all the details of how you first fetched the certificate, and will run with the same options upon renewal. We just need to add in our hook. Open the config file with you favorite editor:

```command
sudo nano /etc/letsencrypt/renewal/<^>your_domain<^>.conf
```

A text file will open with some configuration options. You can add a hook on the last line that will reload any web-facing services, making them use the renewed certificate:

```
[label /etc/letsencrypt/renewal/<^>your_domain<^>.conf]
renew_hook = <^>systemctl reload your_service<^>
```

Update the command above to whatever you need to run to reload your server or run your custom file munging script. Usually, on Ubuntu, you’ll mostly be using `systemctl` to reload a service. Save and close the file, then run a Certbot dry run to make sure the syntax is ok:

```command
sudo certbot renew --dry-run
```

If you see no errors, you're all set. Certbot is set to renew when necessary and run any commands needed to get your service using the new files.


## Conclusion

In this tutorial, we've installed the Certbot Let's Encrypt client, downloaded an SSL certificate using standalone mode, and enabled automatic renewals with renew hooks. This should give you a good start on using Let's Encrypt certificates with services other than your typical web server.

For more information, please refer to [Certbot's documentation](https://eff-certbot.readthedocs.io/en/stable/).


How To Use Certbot Standalone Mode to Retrieve Let's Encrypt SSL Certificates on Ubuntu 20.04

Senior DevOps Technical Writer

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