Menu
I have been reading about Docker, and one of the first things that I read about docker was that it runs images in a read-only manner. This has raised this question in my mind, what happens if I need users to upload files? In that case where would the file go (are they appended to the image)? or in other words, how to handle uploaded files?
821
Docker also supports containers storing files in-memory on the host machine. Such files are not persisted. If you're running Docker on Linux, tmpfs mount is used to store files in the host's system memory. If you're running Docker on Windows, named pipe is used to store files in the host's system memory.
Docker uses storage drivers to store image layers, and to store data in the writable layer of a container. The container's writable layer does not persist after the container is deleted, but is suitable for storing ephemeral data that is generated at runtime.
Docker supports several storage drivers, using a pluggable architecture. The storage driver controls how images and containers are stored and managed on your Docker host. After you have read the storage driver overview, the next step is to choose the best storage driver for your workloads.
If you use the default storage driver overlay2, then your Docker images are stored in /var/lib/docker/overlay2 . There, you can find different files that represent read-only layers of a Docker image and a layer on top of it that contains your changes.
Docker containers are meant to be immutable and replaceable - you should be able to stop a container and replace it with a newer version without any ill effects. It's bad practice to store any configuration or operational data inside the container.
The situation you describe with file uploads would typically be resolved with a volume, which mounts a folder from the host filesystem into the container. Any modifications performed by the container to the mounted folder would persist on the host filesystem. When the container is replaced, the folder is re-mounted when the new container is started.
It may be helpful to read up on volumes: https://docs.docker.com/storage/volumes/
77
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
