ubuntu-distro: Update Dockerfile

- Split installation & configuration into 2 separate RUN commands.
- Add comments in Dockerfile.

Signed-off-by: Chirag Shilwant <c-shilwant@ti.com>

ubuntu-distro/Dockerfile

@@ -1,14 +1,23 @@
+# Using ubuntu:22.04 as the base image
 FROM amd64/ubuntu:22.04
+
+# Installing packages needed for Yocto & SDK Makefile builds
 RUN export DEBIAN_FRONTEND=noninteractive; apt-get update && \
          apt-get install -y --no-install-recommends file build-essential autoconf automake bison flex libssl-dev bc u-boot-tools swig python3 python3-pip wget device-tree-compiler python3-dev dosfstools fdisk sudo && \
          pip3 install jsonschema pyelftools PyYAML Mako && \
          apt-get -f -y install git diffstat texinfo gawk chrpath socat doxygen dos2unix mono-devel mono-complete curl python3-distutils repo pseudo python3-sphinx \
-         g++-multilib libc6-dev-i386 jq git-lfs pigz zstd liblz4-tool cpio file zstd lz4 locales && \
-         locale-gen en_US en_US.UTF-8 && \
+         g++-multilib libc6-dev-i386 jq git-lfs pigz zstd liblz4-tool cpio file zstd lz4 locales \
+
+# Set locale's and reconfigure to use bash as the default shell for /bin/sh.
+RUN export DEBIAN_FRONTEND=noninteractive; locale-gen en_US en_US.UTF-8 && \
          echo "dash dash/sh boolean false" | debconf-set-selections && \
          dpkg-reconfigure dash && addgroup --gid 786 tisdk && \
+         # Add user tisdk with uid & gid as 786.
          adduser --disabled-password --uid 786 --gid 786 --gecos "" --home /home/tisdk --shell /bin/bash tisdk && \
+         # Add tisdk to sudoers & make it passwordless
          adduser tisdk sudo && usermod -aG sudo tisdk && echo "tisdk ALL=(ALL) NOPASSWD:ALL" >> /etc/sudoers && \
          export LC_ALL="en_US.UTF-8" && export LC_CTYPE="en_US.UTF-8" && export LC_NUMERIC="en_US.UTF-8" && \
          rm -rf /var/lib/apt/lists/*
+
+# Set default user as tisdk         
 USER tisdk