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content/blog/docker-image-bash.md

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+---
+title: "Advanced Docker Image Construction with Bash"
+date: 2019-12-26T21:01:37-05:00
+draft: false
+images: []
+---
+
+On current versions of Docker, you can't mount volumes during image construction. This poses an issue for me as I don't want to replicate gigabytes of data already existing on my disk when it won't appear on the final build. Therefore, instead of building an image with a traditional Dockerfile, we're going to use a bash script on a running base image container and export the filesystem to create the image from.
+
+So first run the base image with the mounts that you want
+
+```bash
+docker run -v /mnt:/mnt -td --name containername baseimage /bin/bash
+```
+
+Then copy whatever `setup` script you have and execute it on the running container
+
+```bash
+docker cp setup containername:/setup
+docker exec -it containername /setup
+```
+
+Once the setup script finalizes, we can export the container filesystem into a file called `image.tar`
+
+```bash
+docker export --output="image.tar" containername
+```
+
+Once we've exported the filesystem, we can get rid of the existing container
+
+```bash
+docker stop containername && docker rm containername
+```
+
+Now create a `Dockerfile` with the following:
+
+```dockerfile
+FROM scratch
+ADD image.tar /
+CMD ["bin/bash"]
+```
+
+Now you can create the image by building the Dockerfile
+
+```bash
+docker build -t finalimagename .
+```
+