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docker buildThe command allows us to create a Docker image from a Dockerfile. It also allows us to build an image from a context that references a set of files located in a location specified by a PATH or URL.

A Dockerfile, on the other hand, is just a read-only text document that contains instructions that will be called when assembling our Docker image. A Docker image is the set of instructions, application code, dependencies, tools, and libraries that we use to build a Docker container.

This article demonstrates how to use docker buildthe command with multiple parameters.

docker buildCommands with multiple parameters

docker buildCommands are usually executed in a terminal or command line.

grammar:

docker build [options] <directory path or URL>

PATH or URL refers to a set of files in a context, which may include resources such as a pre-packaged tarball context, a plain text file, or even a git repository. If all files are stored in a local directory, that is, the same directory as the Dockerfile, we can choose to use .as the path.

This path specifies the file used for the build context on the docker daemon.

docker build .

We can pass multiple parameters during build under options parameter. Using –build-argtag, we can set the values ​​which can be set by the user at build time.

However, we first need to define a in our Dockerfile ARGinstruction, and then use --build-argthe tag to build the image. We can access this build-time variable like regular environment variables; however, they do not persist after the image is built.

Although the ARG directive has limited scope, it can be declared before specifying the base image. We can also --build-argpass multiple build arguments by passing each argument separately using a separate tag.

grammar:

docker build -t <image-name>:<tag> --build-arg <key1>=<value1> --build-arg <key2>=<value2> .

We have a simple Dockerfile that defines some ARGvalues ​​in the following example. In this case, we have not set their default values.

The Docker file is as follows.

#  base image
FROM python

ARG language
ARG name
# Set your working directory
WORKDIR /var/www/

# Copy the necessary files
COPY ./app.py /var/www/app.py

# Install the necessary packages
RUN pip install -r /var/www/requirements.txt

RUN echo "Hello $language Developer"
MAINTAINER Isaac Tonyloi

-build-argTherefore, we should use tags to pass values ​​when building images .

~/my-app$ docker build --build-arg language=Java .

Building the image using the above command will print messages alongside other files Hello Java Developeras shown below.

                                                                                                           0.0s
 => [5/6] RUN pip install -r /var/www/requirements.txt                                                                                                                      100.4s
 => [6/6] RUN echo "Hello Java Developer"                                                                                                                                     4.4s
 => exporting to image                                                                                                                                                        3.8s
 => => exporting layers                                                                                                                                                       2.8s
 => => writing image sha256:22fa358b711d2ea3a1d72e59f062f6c7c38b414bdb253fb8d0def20222cadd93

We can also use multiple --build-argtags to docker builduse with multiple commands.

/my-app$ docker build \
> --build-arg language=Java \
> --build-arg name=Tonyloi \
> .

This will print the message below and next to other messages. Although this is very basic, this is how you pass multiple commands when building a Docker image from a Dockerfile.

Output:

 => [2/2] RUN echo "Hello Java Developer and my name is Tonyloi"                                                                                                              3.3s
 => exporting to image                                                                                                                                                        3.0s
 => => exporting layers                                                                                                                                                       2.0s
 => => writing image sha256:d4d7c3b18aa9422be2990f5381a5423a18867dda8090dd4a4f166efc4e7c4ba2