CODEWITHSUNDEEP
docker
Keeto
Keeto

Reputation: 4198

Changing the default command of base docker images

I downloaded the ubuntu base image from the docker hub. Now I am trying to build a new image based on the ubuntu image. However, I want the default command for the ubuntu image to be "/bin/bash -c" instead of "/bin/sh" so as when I use RUN in my Dockerfile, it accesses bash instead of sh. Notice I am talking about the default command of the same image, not the image I am trying to build.

Upvotes: 19

Views: 22447

Answers (4)

Suryansh Rajan
Suryansh Rajan

Reputation: 11

RUN chsh -s /bin/bash Add this in you docker file and the complete commands mentioned below this line will be executed with bash

Upvotes: 0

Cymmer John
Cymmer John

Reputation: 255

maybe this can help:

SHELL ["/bin/bash", "-c"]

Reference: https://github.com/moby/moby/issues/7281#issuecomment-389440503

Upvotes: 11

dsdenes
dsdenes

Reputation: 1035

You can use:

RUN ["/bin/bash", "-c", "<command>"]

Upvotes: 3

ivant
ivant

Reputation: 3919

I don't think there is a default command in the ubuntu image. When you run

$ docker run ubuntu echo hi
hi

it runs ["/bin/echo", "hi"]. You can verify that by running

$ docker run ubuntu set
2014/06/20 08:38:54 exec: "set": executable file not found in $PATH

set is built-in command in shell, but docker tries to run it as an external one.

If you want to change the default shell from dash to bash, you can create an image with the fixed symlink. Here's a dockerfile:

FROM ubuntu
RUN ln -sf /bin/bash /bin/sh

[EDIT]

I just realized what you're talking about. I don't know if you can change the default for RUN command, but you can explicitly use /bin/bash like this:

RUN /bin/bash -c ...

Upvotes: 7

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