Intro: Here is a 1-to-1 copy of the article on how to install certbot in Ubuntu 16.04 and Debian Stretch
Ubuntu 16.04 HOWTO:
Install
On Ubuntu systems, the Certbot team maintains a PPA. Once you add it to your list of repositories all you’ll need to do is apt-get the following packages.
$ sudo apt-get update
$ sudo apt-get install software-properties-common
$ sudo add-apt-repository ppa:certbot/certbot
$ sudo apt-get update
$ sudo apt-get install certbot
Advanced Get Started
Certbot supports a number of different “plugins” that can be used to obtain and/or install certificates.
Since your server architecture doesn’t yet support automatic installation you’ll have to use the certonly command to obtain your certificate.
$ sudo certbot certonly
This will allow you interactively select the plugin and options used to obtain your certificate. If you already have a webserver running, we recommend choosing the “webroot” plugin.
Alternatively, you can specify more information on the command line.
To obtain a cert using the “webroot” plugin, which can work with the webroot directory of any webserver software:
$ sudo certbot certonly --webroot -w /var/www/example -d example.com -d www.example.com -w /var/www/thing -d thing.is -d m.thing.is
This command will obtain a single cert for example.com, www.example.com, thing.is, and m.thing.is; it will place files below /var/www/example to prove control of the first two domains, and under /var/www/thing for the second pair.
Note:
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.
To obtain a cert using a built-in “standalone” webserver (you may need to temporarily stop your existing webserver, if any) for example.com and www.example.com:
$ sudo certbot certonly --standalone -d example.com -d www.example.com
Automating renewal
The Certbot packages on your system come with a cron job that will renew your certificates automatically before they expire. Since Let’s Encrypt certificates last for 90 days, it’s highly advisable to take advantage of this feature. You can do automatic renewal for your certificates by running this command:
$ sudo certbot renew
Debian Stretch(9.0) HOWTO:
Install
Since Certbot is packaged for your system, all you’ll need to do is apt-get the following packages.
First you’ll have to follow the instructions here to enable the Stretch backports repo, if you have not already done so.
For this run:
$ sudo echo "deb http://ftp.debian.org/debian stretch-backports main" >> /etc/apt/sources.list
$ sudo apt-get update
$ sudo apt-get install certbot -t stretch-backports
Advanced Get Started
Certbot supports a number of different “plugins” that can be used to obtain and/or install certificates.
Since your server architecture doesn’t yet support automatic installation you’ll have to use the certonly command to obtain your certificate.
$ sudo certbot certonly
This will allow you interactively select the plugin and options used to obtain your certificate. If you already have a webserver running, we recommend choosing the “webroot” plugin.
Alternatively, you can specify more information on the command line.
To obtain a cert using the “webroot” plugin, which can work with the webroot directory of any webserver software:
$ sudo certbot certonly --webroot -w /var/www/example -d example.com -d www.example.com -w /var/www/thing -d thing.is -d m.thing.is
This command will obtain a single cert for example.com, www.example.com, thing.is, and m.thing.is; it will place files below /var/www/example to prove control of the first two domains, and under /var/www/thing for the second pair.
Note:
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.
To obtain a cert using a built-in “standalone” webserver (you may need to temporarily stop your existing webserver, if any) for example.com and www.example.com:
$ sudo certbot certonly --standalone -d example.com -d www.example.com
Automating renewal
The Certbot packages on your system come with a cron job that will renew your certificates automatically before they expire. Since Let’s Encrypt certificates last for 90 days, it’s highly advisable to take advantage of this feature. You can do renewal for your certificates by running this command:
$ sudo certbot renew