following the steps in the documentation here:
https://confluence.ez.no/display/EZP52/Installing+eZ+Publish+on+a+Linux-UNIX+based+system

when the "php composer.phar install" runs, without GD the process stops with message:

Installing dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

Problem 1

• ezsystems/ezpublish-kernel 5.2.0 requires ext-gd * -> the requested PHP extension gd is missing from your system.
• ezsystems/ezpublish-kernel 5.2.0 requires ext-gd * -> the requested PHP extension gd is missing from your system.
• Installation request for ezsystems/ezpublish-kernel ~5.2.0 -> satisfiable by ezsystems/ezpublish-kernel[5.2.0].

however, imagemagic is installed, and the requirements docs state:
"ImageMagick supports more formats than GD and usually produces better results (better scaling, etc.). The setup wizard will automatically detect the pre-installed image conversion system(s)."

until version 5.2, the composer.phar was not required to run. now it appears that without both imagemagick and GD the composer will not complete.

Steps to reproduce:

There are several ways to verify this. If GD is not installed, run composer install:

php composer.phar install

If GD is already installed:

1. Edit gd.ini:

sudo gedit /etc/php5/apache2/conf.d/gd.ini

2. Comment out gd extension:

; configuration for php GD module
;extension=gd.so

Then save and close the file.

3. Restart apache:

sudo service apache2 reload

4. Run composer install:

php composer.phar install

Also verified when updating symfony:

php -d memory_limit=-1 composer.phar update --no-dev --prefer-dist symfony/symfony -vv