0. Log out of Roundcube! This is necessary for proper setup of the databases later.

1a. Download the last release of RCMCardDAV here:
  https://github.com/blind-coder/rcmcarddav/releases/tag/v3.0.3
  Extract the archive and rename the extracted directory to 'carddav'.

1b. Copy/Clone the whole RCMCardDAV plugin directory to roundcubemail/plugins/ and rename
the directory to 'carddav'. 

2. Only if you are installing a git clone, change to the directory
roundcubemail/plugins/carddav/ and install the dependencies using composer:
	php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
	php -r "if (hash_file('SHA384', 'composer-setup.php') === '544e09ee996cdf60ece3804abc52599c22b1f40f4323403c44d44fdfdd586475ca9813a858088ffbc1f233e9b180f061') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
	php composer-setup.php
	php -r "unlink('composer-setup.php');"
	php composer.phar install

3. Change to the plugin directory roundcubemail/plugins/carddav and copy the
file 'config.inc.php.dist' to 'config.inc.php' to create the initial plugin
configuration file.

4. If necessary, customize the default plugin settings in the file created in
step 3.

5. Make sure that the file and directory ownership match the user which is used
to run your web server, e.g.:
	chown -R wwwrun  roundcubemail/plugins/carddav
	chgrp -R nogroup roundcubemail/plugins/carddav

6. Install the curl and mbstring php extensions if not already present:
  apt-get install php7.0-{mbstring,curl} # on Debian

7. Add 'carddav' to the $rcmail_config['plugins'] array in
roundcubemail/config/main.inc.php

8. Login to Roundcube and set-up your first CardDAV address book by accessing
'Settings -> Settings -> CardDAV'