I am not able to install mbstring using docker file - php

Question

Hi i am new to docker.
I have cloned my laravel code from
https://github.com/laravel/laravel/tree/8.x
and followed the steps provided in given below link.
https://www.digitalocean.com/community/tutorials/how-to-set-up-laravel-nginx-and-mysql-with-docker-compose
But still, mbstring is not installed in my project with php 8 version as my laravel project is compatible with a higher version than 7.2 but when i tried mbstring with 7.2 version it was easyly installed. i want to install mbstring with php 8 version.
Given below is my docker file. please have a look at it.
FROM php:8.0.3-fpm-buster
# Copy composer.lock and composer.json
COPY composer.lock composer.json /var/www/
# Set working directory
WORKDIR /var/www
# Install dependencies
RUN apt-get update && apt-get install -y \
build-essential \
libpng-dev \
libjpeg62-turbo-dev \
libfreetype6-dev \
locales \
zip \
jpegoptim optipng pngquant gifsicle \
vim \
unzip \
git \
curl
# Clear cache
RUN apt-get clean && rm -rf /var/lib/apt/lists/*
# Install extensions
RUN docker-php-ext-install pdo_mysql mbstring zip exif pcntl
RUN docker-php-ext-configure gd --with-gd --with-freetype-dir=/usr/include/ --with-jpeg-dir=/usr/include/ --with-png-dir=/usr/include/
RUN docker-php-ext-install gd
# Install composer
RUN curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer
# Add user for laravel application
RUN groupadd -g 1000 www
RUN useradd -u 1000 -ms /bin/bash -g www www
# Copy existing application directory contents
COPY . /var/www
# Copy existing application directory permissions
COPY --chown=www:www . /var/www
# Change current user to www
USER www
# Expose port 9000 and start php-fpm server
EXPOSE 9000
CMD ["php-fpm"]

Answer 1

FROM php:8-fpm
# Copy composer.lock and composer.json
COPY composer.lock composer.json /var/www/
# Set working directory
WORKDIR /var/www
ADD https://github.com/mlocati/docker-php-extension-installer/releases/latest/download/install-php-extensions /usr/local/bin/
RUN chmod +x /usr/local/bin/install-php-extensions && sync && \
install-php-extensions mbstring pdo_mysql zip exif pcntl gd
#previous code
# Install dependencies
RUN apt-get update && apt-get install -y \
build-essential \
libpng-dev \
libjpeg62-turbo-dev \
libfreetype6-dev \
locales \
zip \
jpegoptim optipng pngquant gifsicle \
vim \
unzip \
git \
curl
# Clear cache
RUN apt-get clean && rm -rf /var/lib/apt/lists/*
# Install extensions
#RUN docker-php-ext-install
#RUN docker-php-ext-configure gd --with-gd --with-freetype-dir=/usr/include/ --with-jpeg-dir=/usr/include/ --with-png-dir=/usr/include/
# Install composer
RUN curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer
# Add user for laravel application
RUN groupadd -g 1000 www
RUN useradd -u 1000 -ms /bin/bash -g www www
RUN php artisan key:generate
# Copy existing application directory contents
COPY . /var/www
# Copy existing application directory permissions
COPY --chown=www:www . /var/www
# Change current user to www
USER www
# Expose port 9000 and start php-fpm server
EXPOSE 9000
CMD ["php-fpm"]
Try this..

Answer 2

What follows is more appropriate as a comment, but I have an insufficient reputation to comment.
Adarsh Hiwrale's excellent suggestion mostly worked for me, but I had to rearrange a few lines to avoid a race condition.
That is, the reordered lines are necessary for anyone starting from scratch who is building for the first time because they will not yet have a partial Docker build that can execute RUN php artisan key:generate.
My revision follows with comments indicating what was modified and why.
FROM php:8-fpm
# Copy composer.lock and composer.json
COPY composer.lock composer.json /var/www/
# Set working directory
WORKDIR /var/www
ADD https://github.com/mlocati/docker-php-extension-installer/releases/latest/download/install-php-extensions /usr/local/bin/
RUN chmod +x /usr/local/bin/install-php-extensions && sync && \
install-php-extensions mbstring pdo_mysql zip exif pcntl gd
#previous code
# Install dependencies
RUN apt-get update && apt-get install -y \
build-essential \
libpng-dev \
libjpeg62-turbo-dev \
libfreetype6-dev \
locales \
zip \
jpegoptim optipng pngquant gifsicle \
vim \
unzip \
git \
curl
# Clear cache
RUN apt-get clean && rm -rf /var/lib/apt/lists/*
# Install extensions
#RUN docker-php-ext-install
#RUN docker-php-ext-configure gd --with-gd --with-freetype-dir=/usr/include/ --with-jpeg-dir=/usr/include/ --with-png-dir=/usr/include/
# Install composer
RUN curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer
# Add user for laravel application
RUN groupadd -g 1000 www
RUN useradd -u 1000 -ms /bin/bash -g www www
# BEGIN MODIFICATIONS to Adarsh Hiwrate's suggested code
# Copy existing application directory contents
# The following line is redundant (predundant?) because of the line which copies the required items with the correct permissions.
# COPY . /var/www
# Copy existing application directory permissions
COPY --chown=www:www . /var/www
# This has to come after the above copy, otherwise the code will not yet be available in the container.
RUN php artisan key:generate
# END MODIFICATIONS to Adarsh Hiwrate's suggested code
# Change current user to www
USER www
# Expose port 9000 and start php-fpm server
EXPOSE 9000
CMD ["php-fpm"]