Docker - how to set up compose for local webserver - docker

Question

I have a docker compose file in a local folder on my mac. I have also another folder /src which should act as the root element. The docker-compose file looks like this:
version: '2'
services:
fpm:
image: sbusso/php-fpm-ion
nginx:
image: nginx:stable
ports:
- "80:80"
links:
- fpm
- db
db:
image: orchardup/mysql
ports:
- 3306:3306
environment:
MYSQL_ROOT_PASSWORD: root
MYSQL_DATABASE: myproject
I understand what we are doing here, but I am missing the solution that /src is taken as the root and I think I need to set up an lsync service which syncs between local and my docker container. So I found this one, but it is not working properly - the root /src is not taken into account. I just want to type localhost in my browser and it should open the /src folder.
version: '2'
services:
fpm:
image: sbusso/php-fpm-ion
links:
- sync
volumes_from:
- sync
db:
image: orchardup/mysql
ports:
- 3306:3306
environment:
MYSQL_ROOT_PASSWORD: root
MYSQL_DATABASE: myproject
links:
- sync
volumes_from:
- sync
nginx:
image: nginx:stable
ports:
- "80:80"
links:
- sync
volumes_from:
- sync
sync:
image: zeroboh/lsyncd
volumes:
- /var/www/html
- ./src:/src:Z
- ./docker-config/nginx:/etc/nginx/conf.d
- /var/lib/php/session
- ./docker-config/lrsync/lrsync.lua:/etc/lrsync/lrsync.lua
- ./sync:/sync
What I do understand is that every image that is loaded links the sync service into it. What I do not understand is why every image needs a volumes_from and that the syntax in sync explicitly says - can somebody help me, setting this up correctly?
Thanks

Answer 1

volumes_from imports volumes from another container
By default, each container has no volumes. You can define local volumes using the volumes attribute, but the volumes are only used in that container. In order for other containers to make use of them, those containers must import the volumes using volumes_from, pointing to the name of one or more containers. All volumes in those named containers are then made available in the current container.
The Z volume label indicates a private volume
You are mounting the /src volume using this:
volumes:
- ./src:/src:Z
That's fine, except you are also using volumes_from, and your question indicates that you specifically wanted to share /src. But by using the Z label, you have told Docker to make this a private volume.
From the documentation:
Volume labels
Labeling systems like SELinux require that proper labels are placed on volume content mounted into a container. Without a label, the security system might prevent the processes running inside the container from using the content. By default, Docker does not change the labels set by the OS.
To change a label in the container context, you can add either of two suffixes :z or :Z to the volume mount. These suffixes tell Docker to relabel file objects on the shared volumes. The z option tells Docker that two containers share the volume content. As a result, Docker labels the content with a shared content label. Shared volume labels allow all containers to read/write content. The Z option tells Docker to label the content with a private unshared label. Only the current container can use a private volume.
In this case, "current container" is sync, so only that container may use the volume. The others may not use it.