Dockerfile

# Use Ubuntu 22.04 as base
FROM ubuntu:22.04

# Install cURL, Python 3, sudo, unbuffer and the package for "add-apt-repository"
RUN apt update && apt install -y curl python3 sudo expect-dev software-properties-common

# Download Install FEX script to temp file
RUN curl --silent https://raw.githubusercontent.com/FEX-Emu/FEX/main/Scripts/InstallFEX.py --output /tmp/InstallFEX.py

# FEX installer has to install RootFS on the user we want to run the program
# Run as steam user, auto answer yes for all prompts and auto extract on "FEXRootFSFetcher"
# also makes it run with unbuffer because it's fucking shit (TLDR wants to run under zenity when we don't have a display, isatty call being stupid)
RUN sed -i 's@\["FEXRootFSFetcher"\]@"sudo -u steam bash -c \\"unbuffer FEXRootFSFetcher -y -x\\"", shell=True@g' /tmp/InstallFEX.py

# Run verification on steam user
RUN sed -i 's@\["FEXInterpreter", "/usr/bin/uname", "-a"\]@"sudo -u steam bash -c \\"FEXInterpreter /usr/bin/uname -a\\"", shell=True@g' /tmp/InstallFEX.py

# Create user steam
RUN useradd -m steam

# Run Install FEX and remove the temp file
RUN python3 /tmp/InstallFEX.py && rm /tmp/InstallFEX.py

# Change user to steam
USER steam

# Go to /home/steam/Steam
WORKDIR /home/steam/Steam

# Download and extract SteamCMD
RUN curl -sqL "https://steamcdn-a.akamaihd.net/client/installer/steamcmd_linux.tar.gz" | tar zxvf -

# Copy init-server.sh to container
COPY --chmod=755 ./init-server.sh /home/steam/init-server.sh

# Set up some default environment variables
ENV ALWAYS_UPDATE_ON_START=true \
    MULTITHREAD_ENABLED=true \
    COMMUNITY_SERVER=false

# Run it
ENTRYPOINT /home/steam/init-server.sh