SSH into docker app as the root user

docker run --rm -v `pwd`:/var/www/html pimcore/pimcore:PHP7.4-fpm composer create-project pimcore/skeleton pm6 "2.8.16"

cd pm6

docker-compose up -d

docker-compose run --rm php vendor/bin/pimcore-install --mysql-host-socket=db --mysql-username=pimcore --mysql-password=pimcore --mysql-database=pimcore

docker-compose run --rm php chown -R www-data:www-data var/*

composer install --no-plugins

COMPOSER_PROCESS_TIMEOUT=20000 composer install

 docker exec -it -u 0 6899f3bfdc70056d5bedc8502bd28bb71afd71f7e8ecc6b0f0d9c9496ac6546d bash
 
 # It is the -u 0 that allows you in as a root user

 docker exec -it -u 0 6899f3bfdc70056d5bedc8502bd28bb71afd71f7e8ecc6b0f0d9c9496ac6546d bash
 
 # It is the -u 0 that allows you in as a root user