- Docker inspect layer size install#
- Docker inspect layer size Patch#
- Docker inspect layer size software#
- Docker inspect layer size series#
Docker inspect layer size install#
It’s tempting to install wget, vim, netcat, and other tools into your container for testing purposes, but your final image should not contain these. If there are slow commands that would have to be run again frequently if you combine your RUN commands together, split up that slow command into its own, just be sure to clean up properly. It’s a lot easier to clean up all your installed development packages, temporary files, and build artifacts if they all happen together instead of having to do it at each stage.ĭon’t overdo the act of condensing all the commands into one though.
Try to combine as many RUN commands together to prevent new layers from being created. If you write a temporary file, delete that temporary file inside the same command. When running a command, perform all cleanup in the same command otherwise the layer with all the junk will exist in your image.
You’ve likely seen all of these somewhere before, but for completeness, I’m adding them to this post. When you start off with a 300MB image, your image is going to stay above 300MB even if you delete the entire file system. Using recommended practices, it’s impossible to have your final image smaller than your starting point because every command creates a new layer. Alpine versions of most of these images are a really good starting point and are usually at least 3x smaller than the debian-slim counterparts. Check the tags for the image you need, and find one that is acceptable for your usage.
Docker inspect layer size software#
There are many existing images that will get you the software you need for your project, such as the node, php, and python images. When creating your Dockerfile, start from the smallest image possible but don’t repeat yourself. Those folders contain the layer’s file system and metadata such as environment variables, command, and entrypoint. You’ll see each layer saved in a folder identified by its checksum. The other directives in the file still create new layers, but they only modify metadata which will amount to a negligible change to the image size.Ī simple way to see how an image is built is to simply use docker save and then inspect the TAR file it produced. Almost all directives in your Dockerfile will create a new layer, but the ones you want to focus most on are ADD, COPY and RUN.
Docker inspect layer size series#
The image is built in series from each layer, either adding, removing, or changing permissions of files (that last point is very important to remember later on).Ī layer is a set of changes to apply to the previous layer.
Docker inspect layer size Patch#
Other than being an output line in your terminal from which containers can be created, an image is a union file system that is built in layers, essentially performing a patch from each layer. This helps reduce possible issues down the line with unnecessary packages, libraries, and tools that you don’t need. When you think about your docker image size, it forces you into using only the libraries and tools required for your app to run isolated inside of its container. Disk space is cheap but the IO cost behind it can be expensive. Along with the time saved when deploying, you are also saving disk space. Containers are meant to be as lightweight and small as possible.
When deploying your apps, the time difference between a 3GB and a 150MB image is very noticeable. The size of the image may not seem too important to some, but there are many benefits to having smaller docker images.Ī smaller image will allow you to upload and download the images faster. Even if you remove unnecessary files and packages, you’ll still see your image size be much larger than expected. With Docker, it’s easy to end up with images many times larger than they need to be.