CODEWITHSUNDEEP
dockerdockerfile
ealeon
ealeon

Reputation: 12462

Dockerfile overriding env var at "docker run" time

Dockerfile

FROM ubuntu
ENV UID "1234"
ENV USERNAME "default"

RUN addgroup $USERNAME && useradd -u $UID -g $USERNAME -ms /bin/bash $USERNAME
CMD ["/usr/bin/id", "-u", "myname"]

and running docker via:

docker build -t setuser .    
docker run -e UID=5555 -e USERNAME=myname setuser

OUTPUT

/usr/bin/id: 'myname': no such user

this error tells me that useradd in Dockerfile was not executed during "docker run" time.

how could I achieve this?

CMD ["/usr/bin/id", "-u", "default"] works but i want to be able to supply the UID and USERNAME at run time, not at Dockerfile build time

Upvotes: 1

Views: 1658

Answers (2)

Shahriar
Shahriar

Reputation: 13804

To elaborate Henry's answer

Following portion of your Dockerfile executed when you build your image.

FROM ubuntu
ENV UID "1234"
ENV USERNAME "default"

RUN addgroup $USERNAME && useradd -u $UID -g $USERNAME -ms /bin/bash $USERNAME

So, this time, UID=1234 & USERNAME=default are set.

When you run your image, It starts with ENTRYPOINT & CMD. It has no effect on RUN addgroup $USERNAME ...

So you need to run a script to use your passing ENV.

#!/bin/bash

addgroup $USERNAME && useradd -u $UID -g $USERNAME -ms /bin/bash $USERNAME

id -u $USERNAME

Here, your passing ENV values will be used.

Upvotes: 5

Henry
Henry

Reputation: 43798

The useradd was executed when the image was created. If you want to run some commands when the container is started put them into a script that is executed at start time.

Upvotes: 1

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