How to Add user when creating docker image from alpine base image

Question

I want to add user www-data as my default user when I run my container in bash mode.

Currently, when I type WHOAMI then it's showing root as user, but I need www-data as user, how to do this in docker.

This is my docker file:

    FROM php:7.2-fpm-alpine

LABEL maintainer="y.ghorecha@abc.de" \
      muz.customer="xxx" \
      muz.product="WIDC" \
      container.mode="production"

#https://pkgs.alpinelinux.org/packages
RUN apk add --no-cache --virtual .deps autoconf tzdata build-base libzip-dev mysql-dev gmp-dev \
            libxml2-dev libpng-dev zlib-dev freetype-dev jpeg-dev icu-dev openldap-dev libxslt-dev &&\
    docker-php-ext-install zip xml mbstring json intl gd pdo pdo_mysql iconv soap \
                           dom gmp fileinfo sockets bcmath mysqli ldap xsl &&\
    echo 'date.timezone="Europe/Berlin"' >> "${PHP_INI_DIR}"/php.ini &&\
    cp /usr/share/zoneinfo/Europe/Berlin /etc/localtime &&\
    echo 'Europe/Berlin' > /etc/timezone &&\
    apk del .deps &&\
    apk add --no-cache libzip mysql libxml2 libpng zlib freetype jpeg icu gmp git subversion libxslt openldap \
            apache2 apache2-ldap apache2-proxy libreoffice openjdk11-jre ghostscript msttcorefonts-installer \
            terminus-font ghostscript-fonts &&\
    ln -s /usr/lib/apache2 /usr/lib/apache2/modules &&\
    ln -s /usr/sbin/httpd /etc/init.d/httpd &&\
    update-ms-fonts

# imap setup
RUN apk --update --virtual build-deps add imap-dev
RUN apk add imap
RUN docker-php-ext-install imap

# copy all codebase
COPY ./ /var/www

# SSH setup
RUN apk update && \
    apk add --no-cache \
    openssh-keygen \
    openssh

# copy Azure specific files
COPY backend/build/azure/backend/ /var/www/backend/

# User owner setup
RUN chown -R www-data:www-data /var/www/

# Work directory setup
WORKDIR /var/www

# copy apache httpd.conf file
COPY httpd.conf /etc/apache2/httpd.conf

# copy crontabs for root user
COPY backend/data/CRONTAB/production/crontab.txt /etc/crontabs/www-data

# SSH Key setup
RUN mkdir -p /home/www-data/.ssh
RUN chown -R www-data:www-data /home/www-data/

#https://github.com/docker-library/httpd/blob/3ebff8dadf1e38dbe694ea0b8f379f6b8bcd993e/2.4/alpine/httpd-foreground
#https://github.com/docker-library/php/blob/master/7.2/alpine3.10/fpm/Dockerfile

CMD ["/bin/sh", "-c", "rm -f /usr/local/apache2/logs/httpd.pid && /usr/sbin/crond start && httpd -DBACKGROUND && php-fpm"]

Please advice on above.

Answer 1

I'd start with first checking if the www-data user even exits in the image. Execute in the running container something like:

sudo cat /etc/passwd | grep www-data

If the user does exist then add the USER www-data directive to the Dockerfile after all commands that do installs, create directories, change permissions, etc. It would be required to also add USER 0 at the beginning to switch to the root user for those commands if the base image doesn't run as root. Looking at the Dockerfile I'd suggest to add USER www-data before the CMD directive.

If the www-data user doesn't exist then it has to be added first. The commands for Alpine Linux are addgroup andadduser . Something like these if the user id for www-data is to be 33 and the group it belongs to is also named www-data and has id of 33:

RUN addgroup -S -g 33 www-data \
 && adduser -S -D -u 33 -s /sbin/nologin -h /var/www -G www-data www-data

Add the above just before RUN chown -R www-data:www-data /var/www/ , or make it a single RUN directive:

RUN addgroup -S -g 33 www-data \
 && adduser -S -D -u 33 -s /sbin/nologin -h /var/www -G www-data www-data \
 && chown -R www-data:www-data /var/www/

Answer 2

You can add this line to you dockerfile in order to become the www-data user

USER www-data

This can be either added

• in the end of your file (if you want at to become that user before the script exits), or
• in the beginning if you want to perform your actions within the docker file as this user.