Question 210420 in Ubuntu Question posted in
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Ubuntu – I can't create folder in Dockerfile

I have this in my Dockerfile:

FROM mcr.microsoft.com/mssql/server:latest

RUN mkdir -p /new-folder

Since the latests release of the image (07/13/2023), I get this error:

mkdir: cannot create directory ‘/new-folder’: Permission denied

If I change the image to the previous one (mcr.microsoft.com/mssql/server:2022-CU5-ubuntu-20.04) it works well again.

So I have 2 questions:

  1. What can I do in my Dockerfile to enable folder creation with the latest image?
  2. Is it possible to see the Dockerfile of that SQLServer image, to understand this breaking change?
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2

Answers


  1. 0

    Change WORKDIR to a directory you actually have permission to create folders in.

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  2. 0

    This is not working because / is owned by root while you’re trying to create a folder with the default user that is the user of the parent image.

    You have to create the folder as root user:

    FROM mcr.microsoft.com/mssql/server:latest
USER root
RUN mkdir -p /newfolder

    then, if you want to change user, you should add the commands to create a new user, change the permission of that folder and set the new user. In this case, your Dockerfile becomes like that:

    FROM mcr.microsoft.com/mssql/server:latest
USER root
RUN mkdir -p /newfolder
RUN useradd -r newuser
RUN chown newuser:newuser /newfolder
USER newuser
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