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Why do you need to write a Dockerfile?
However, writing a Dockerfile is a more consistent and repeatable way to build your own images. A Dockerfile is a text file that has a series of instructions on how to build your image. It supports a simple set of commands that you need to use in your Dockerfile. You create a Dockerfile with the required instructions.
What is a Dockerfile and why do we need it?
The Dockerfile is essentially the build instructions to build the image. The advantage of a Dockerfile over just storing the binary image (or a snapshot/template in other virtualization systems) is that the automatic builds will ensure you have the latest version available.
What is difference between run and CMD in Dockerfile?
9 Answers. RUN is an image build step, the state of the container after a RUN command will be committed to the container image. A Dockerfile can have many RUN steps that layer on top of one another to build the image. CMD is the command the container executes by default when you launch the built image.
What happens when you run a Dockerfile?
When Docker starts it runs any initializers via reexec, if any, then it parses the flags for the Docker executable via the mflag package. This packages lives under pkg/mgflag and is aliased as flag. At this point it can print out version information if necessary or enable debug mode and debug logging.
How to run bash in a dockerfile?
If you are using an old Docker version and don’t have access to SHELL, this will work so long as you don’t need anything from .bashrc (which is a rare case in Dockerfiles): Note the -i is needed to make bash read the rcfile at all. This runs perfectly fine for building CentOS 6.6 Docker container, but gave issues in Debian containers
How to run a Git script in Docker?
Considering your script ( bootstrap.sh: a couple of git config –global commands), it would be best to RUN that script once in your Dockerfile, but making sure to use the right user (the global git config file is %HOME%/.gitconfig, which by default is the /root one)
How to write dockerfile from stdin or Docker build?
The syntax uses the -f (or –file) option to specify the Dockerfile to use, using a hyphen (-) as filename to instruct Docker to read the Dockerfile from stdin: docker build [OPTIONS] -f- PATH
How to change the default shell in Docker?
Using SHELL instruction, you can change default shell for subsequent RUN instructions in Dockerfile: SHELL [“/bin/bash”, “-c”] Now, default shell has changed and you don’t need to explicitly define it in every RUN instruction. RUN “source file” # now translates to: RUN /bin/bash -c “source file”