First you have to install the module:

sudo apt install php7.0-mcrypt

and then enable it:

sudo a2enmod mcrypt

Then I got this error which I resolved the following way, per https://stackoverflow.com/questions/48363789/warning-module-mcrypt-ini-file-doesnt-exist-under-etc-php-7-2-mods-available

root@hquapp33:/home/nazadmin# phpenmod mcrypt
WARNING: Module mcrypt ini file doesn’t exist under /etc/php/7.2/mods-available
WARNING: Module mcrypt ini file doesn’t exist under /etc/php/7.2/mods-available
WARNING: Module mcrypt ini file doesn’t exist under /etc/php/7.2/mods-available
root@hquapp33:/home/nazadmin# sudo ln -s /etc/php/7.0/mods-available/mcrypt.ini /etc/php/7.2/mods-available/
root@hquapp33:/home/nazadmin# phpenmod mcrypt
root@hquapp33:/home/nazadmin#

Then I kept going. Then I got an error on the ISPConfig install:

=====================
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=====================
root@hquapp33:/tmp# sudo tar xfz ispconfig.tar.gz
root@hquapp33:/tmp# cd ispconfig3*/install/
root@hquapp33:/tmp/ispconfig3-stable-3.1-87c0dde9b1b19600f4a6ecf32659601fe3859c05/install# sudo php -q install.php
PHP Warning: PHP Startup: Unable to load dynamic library ‘mcrypt.so’ (tried: /usr/lib/php/20170718/mcrypt.so (/usr/lib/php/20170718/mcrypt.so: cannot open shared object file: No such file or directory), /usr/lib/php/20170718/mcrypt.so.so (/usr/lib/php/20170718/mcrypt.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0

——————————————————————————–
_____ ___________ _____ __ _ ____
|_ _/ ___| ___ \ / __ \ / _(_) /__ \
| | \ `–.| |_/ / | / \/ ___ _ __ | |_ _ __ _ _/ /
| | `–. \ __/ | | / _ \| ‘_ \| _| |/ _` | |_ |
_| |_/\__/ / | | \__/\ (_) | | | | | | | (_| | ___\ \
\___/\____/\_| \____/\___/|_| |_|_| |_|\__, | \____/
__/ |
|___/
——————————————————————————–

>> Initial configuration

Operating System: Ubuntu 16.04.4 LTS (Xenial Xerus)

Following will be a few questions for primary configuration so be careful.
Default values are in [brackets] and can be accepted with .
Tap in “quit” (without the quotes) to stop the installer.

Select language (en,de) [en]:

Installation mode (standard,expert) [standard]:

Full qualified hostname (FQDN) of the server, eg server1.domain.tld [hquapp33.nazarene.org]:

No PHP MySQLi functions available. Please ensure that the PHP MySQL module is loaded.root@hquapp33:/tmp/ispconfig3-stable-3.1-87c0dde9b1b19600f4a6ecf32659601fe3859c05/install#
=====================
*******************************
=====================

So I gave up at that point as asked for assistance.

Since there is an issue with mcrypt and …something else (mbstring?) that are now deprecated and no longer work with ISPConfig, we are limited to using PHP 7.0, as the instructions above specify. However, because of an error in the server it was corrected with too-aggressive updates that forced it to be 7.2 before I got to it and performed this procedure.

There was a lot wrong on our end. It took someone who knew what they were doing 4 hours to get to the bottom of this, which I have summarized

Package daemon is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

followed by 20-30 of these kinds: E: Package ‘libapache2-mod-fcgid’ has no installation candidate
E: Package ‘php-auth’ has no installation candidate
E: Unable to locate package mcrypt
E: Unable to locate package libruby….

Any ideas?

According to the error message you get

Address already in use: AH00072: make_sock: could not bind to address [::]: 443
Address already in use: AH00072: make_sock: could not bind to address 0.0.0.0:443

port 443 is already used by another service. Please stop the service running on port 443 and restart Apache again.

Thanks.

$ systemctl status apache2.service
● apache2.service – LSB: Apache2 web server
Loaded: loaded (/etc/init.d/apache2; bad; vendor preset: enabled)
Drop-In: /lib/systemd/system/apache2.service.d
└─apache2-systemd.conf
Active: inactive (dead) since Fri 2017-10-27 15:40:13 BRST; 4min ago
Docs: man: systemd-sysv-generator (8)
Process: 7984 ExecStop = / etc / init.d / apache2 stop (code = exited, status = 0 / SUCCESS)
Process: 7961 ExecStart = / etc / init.d / apache2 start (code = exited, status = 0 / SUCCESS)

Oct 27 15:40:13 server apache2 [7961]: (98) Address already in use: AH00072: make_sock: could not bind to address [::]: 443
Oct 27 15:40:13 server apache2 [7961]: (98) Address already in use: AH00072: make_sock: could not bind to address 0.0.0.0:443
Oct 27 15:40:13 apache2 server [7961]: no listening sockets available, shutting down
Oct 27 15:40:13 apache2 server [7961]: AH00015: Unable to open logs
Oct 27 15:40:13 server apache2 [7961]: Action ‘start’ failed.
Oct 27 15:40:13 apache2 server [7961]: The Apache error log may have more information.
Oct 27 15:40:13 apache2 server [7961]: *
Oct 27 15:40:13 apache2 server [7984]: * Stopping Apache httpd web server apache2
Oct 27 15:40:13 apache2 server [7984]: *
Oct 27 15:40:13 systemd server [1]: Started LSB: Apache2 web server.