Here are a few letsencrypt commands that I’ve found useful in the past few months of trying it out.

Installation:

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

Note: for a few Debian installations, you can also install with:

apt-get install letsencrypt python-letsencrypt-apache

Other OS’s are also supported. See https://letsencrypt.readthedocs.org/en/latest/using.html#operating-system-packages for details!

Generating new keys on Apache:

./letsencrypt-auto run --apache -d domain1 -d domain2 -d domain3

Loading pre-generated keys from a backup into a new installation:

#Need to have backed up /etc/letsencrypt/ to some 
# backup location. This will grab private keys, 
# public certs, symlinks to them, everything.
# More help at https://letsencrypt.readthedocs.org/en/latest/using.html#where-are-my-certificates 
#
#Simply running the command, even to load help, 
# will bootstrap dependency installations and set 
# up the Python scripts if they haven't been set up 
# already. 
./letsencrypt-auto --help all

cp -R /path/to/backup/letsencrypt/* /etc/letsencrypt/

./letsencrypt-auto --install -d -d -d --cert-path /etc/letsencrypt/live/domain1/cert.pem --key-path /etc/letsencrypt/live/domain1/privkey.pem --fullchain-path /etc/letsencrypt/live/domain1/fullchain.pem

Renewing the keys (keeping them the same, but extending the expiration date another 90 days):

#Special bash scripts intended for datestamp 
# checking to refrain from renewing certs
# younger than 60 days old are no longer 
# needed in LE version 0.4. Simply run the 
# following: 
./letsencrypt-auto renew