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

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

Savio Mathew

Next >> Lab #7: RUN instruction