There are few basic anologies
Docker Images
Image Layering is accomplished by Union Mounts. Instead of mounting one file system like root , it allows to mount multiple file system on top of each other. plus they combine all of the layers into a single view.
Note
You can see the relationship between image layers by tree command
You can see the same relationship by the directory structure as well
I think /diff/ has actual data
See how different layers have different part of filesystem
You can run
Docker Images
- List of everything that is in our containers
- And Instructions how to build it
- They launch docker containers.
- They comprise of multiple layers
- stored locally at /var/lib/docker/
ex /var/lib/docker/aufs - Are generally much smaller in size than OS ( as made of layers )
- Single Image may be shared by multiple containers.
- Whenever conflicts in layers , highest ones always wins.
Image Layering is accomplished by Union Mounts. Instead of mounting one file system like root , it allows to mount multiple file system on top of each other. plus they combine all of the layers into a single view.
Note
- top r/w image will be of different size based on different amount of work done.
- rootfs of container is always read only
- in normal linux boot scenario rootfs gets mounted as readonly , then later in process get remounted as readwrite.
- the top writable layer gives look and feel of r/w rootfs. ( i think its because of rule in case of conflict higher layer always gets priority )
- all containers in a sungle system share the kernel of hostOS ( this makes no difference to us as a developer or admin )
You can see the relationship between image layers by tree command
You can see the same relationship by the directory structure as well
I think /diff/ has actual data
See how different layers have different part of filesystem
You can run
- docker pull -a fedora
- docker images fedora
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