Why Installing Laravel 5.7 on ubuntu I have fork failed - Cannot allocate memory in error

Installing Laravel 5.7 app on ubunutu 16 under LEMP/ASW I got error :

$ composer install
Cannot create cache directory /home/ubuntu/.composer/cache/repo/https---packagist.org/, or directory is not writable. Proceeding without cache
Cannot create cache directory /home/ubuntu/.composer/cache/files/, or directory is not writable. Proceeding without cache
Loading composer repositories with package information
Updating dependencies (including require-dev)

PHP Fatal error:  Uncaught ErrorException: proc_open(): fork failed - Cannot allocate memory in /usr/share/php/Symfony/Component/Console/Application.php:943
Stack trace:
#0 [internal function]: Composer\Util\ErrorHandler::handle(2, 'proc_open(): fo...', '/usr/share/php/...', 943, Array)
#1 /usr/share/php/Symfony/Component/Console/Application.php(943): proc_open('stty -a | grep ...', Array, NULL, NULL, NULL, Array)
#2 /usr/share/php/Symfony/Component/Console/Application.php(751): Symfony\Component\Console\Application->getSttyColumns()
#3 /usr/share/php/Symfony/Component/Console/Application.php(712): Symfony\Component\Console\Application->getTerminalDimensions()
#4 /usr/share/php/Symfony/Component/Console/Application.php(645): Symfony\Component\Console\Application->getTerminalWidth()
#5 /usr/share/php/Symfony/Component/Console/Application.php(127): Symfony\Component\Console\Application->renderException(Object(RuntimeException), Object(Symfony\Component\Console\Output\StreamOutput))
#6 /usr/share/php/Composer/Console/Application. in /usr/share/php/Symfony/Component/Console/Application.php on line 943

Fatal error: Uncaught ErrorException: proc_open(): fork failed - Cannot allocate memory in /usr/share/php/Symfony/Component/Console/Application.php:943
Stack trace:
#0 [internal function]: Composer\Util\ErrorHandler::handle(2, 'proc_open(): fo...', '/usr/share/php/...', 943, Array)
#1 /usr/share/php/Symfony/Component/Console/Application.php(943): proc_open('stty -a | grep ...', Array, NULL, NULL, NULL, Array)
#2 /usr/share/php/Symfony/Component/Console/Application.php(751): Symfony\Component\Console\Application->getSttyColumns()
#3 /usr/share/php/Symfony/Component/Console/Application.php(712): Symfony\Component\Console\Application->getTerminalDimensions()
#4 /usr/share/php/Symfony/Component/Console/Application.php(645): Symfony\Component\Console\Application->getTerminalWidth()
#5 /usr/share/php/Symfony/Component/Console/Application.php(127): Symfony\Component\Console\Application->renderException(Object(RuntimeException), Object(Symfony\Component\Console\Output\StreamOutput))
#6 /usr/share/php/Composer/Console/Application. in /usr/share/php/Symfony/Component/Console/Application.php on line 943

I suppose that is memory lack error

phpinfo shows me :

memory_limit    2056M   2056M
$ uname -a
Linux serge 4.15.0-51-generic #55-Ubuntu SMP Wed May 15 14:27:21 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux


$ free
              total        used        free      shared  buff/cache   available
Mem:        1014384      224744      454504       13848      335136      611300
Swap:       1048572           0     1048572

$ whoami
ubuntu

I think this memory must be enough for my app, but why error ? Which parameters have I to pay attention at ?

Thanks!

via Chebli Mohamed