Lab #6: WORKDIR instruction
The WORKDIR directive in Dockerfile defines the working directory for the rest of the instructions in the Dockerfile. The WORKDIR instruction wont create a new layer in the image but will add metadata to the image config. If the WORKDIR doesn’t exist, it will be created even if it’s not used in any subsequent Dockerfile instruction. you can have multiple WORKDIR in same Dockerfile. If a relative path is provided, it will be relative to the previous WORKDIR instruction.
WORKDIR /path/to/workdir
If no WORKDIR is specified in the Dockerfile then the default path is /. The WORKDIR instruction can resolve environment variables previously set in Dockerfile using ENV.
Pre-requisite:
Tested Infrastructure
| Platform | Number of Instance | Reading Time |
|---|---|---|
| Play with Docker | 1 | 5 min |
Pre-requisite
- Create an account with DockerHub
- Open PWD Platform on your browser
- Click on Add New Instance on the left side of the screen to bring up Alpine OS instance on the right side
Assignment
- Dockerfile with WORKDIR instruction
- WORKDIR with Relative path
- WORKDIR with Absolute path
- WORKDIR with environment variables as path
Dockerfile with WORKDIR instruction
Dockerfile
FROM alpine:3.9.3
LABEL maintainer="Collabnix"
WORKDIR /opt
Building Docker image
$ docker build -t workdir:v1 .
Testing current WORKDIR by running container
$ docker run -it workdir:v1 pwd
WORKDIR with relative path
Dockerfile
FROM alpine:3.9.3
LABEL maintainer="Collabnix"
WORKDIR /opt
RUN echo "Welcome to Docker Labs" > opt.txt
WORKDIR folder1
RUN echo "Welcome to Docker Labs" > folder1.txt
WORKDIR folder2
RUN echo "Welcome to Docker Labs" > folder2.txt
Building Docker image
$ docker build -t workdir:v2 .
Testing current WORKDIR by running container
$ docker run -it workdir:v2 pwd
WORKDIR with Absolute path
Dockerfile
FROM alpine:3.9.3
LABEL maintainer="Collabnix"
WORKDIR /opt/folder1
RUN echo "Welcome to Docker Labs" > opt.txt
WORKDIR /var/tmp/
Building Docker image
$ docker build -t workdir:v3 .
Testing current WORKDIR by running container
$ docker run -it workdir:v3 pwd
WORKDIR with environment variables as path
Dockerfile
FROM alpine:3.9.3
LABEL maintainer="Collabnix"
ENV DIRPATH /myfolder
WORKDIR $DIRPATH
Building Docker image
$ docker build -t workdir:v4 .
Testing current WORKDIR by running container
$ docker run -it workdir:v4 pwd
Contributor
Next » Lab #7: RUN instruction