WordPress Access denied for user root with MySQL container

Solution:

I have solved it by deleting everything and try starting it up again.

docker rm -v spawning-pool # -v Remove the volumes associated with the container

Remove the volume too

docker volume rm hatchery

Then I created the containers again

# create the volume
docker volume create hatchery

# MySQL instance
docker run -it -d --restart on-failure -v hatchery:/var/lib/mysql \
           -e MYSQL_ROOT_PASSWORD=Kerrigan \
           -e MYSQL_DATABASE=zerglings --name spawning-pool mysql

# creating wordpress
docker run -d --name lair -p 8080:80 --link spawning-pool:mysql \
           -e WORDPRESS_DB_HOST=mysql -e WORDPRESS_DB_NAME=zerglings 
           -e WORDPRESS_DB_PASSWORD=Kerrigan wordpress