Dockerfile: Bash Script executing flawlessly with ENTRYPOINT, but not with RUN - bash

Question

Project
I am building a docker-compose file for a simple devops stack. One of the tools is Helix Core by Perforce. I am trying to build an Ubuntu Dockerfile, that will install Helix Core and then run it. I have already written a bash script install.sh that when put like this
FROM ubuntu:20.04
COPY ./install.sh /install.sh
ENTRYPOINT["/bin/bash", "/install.sh"]
will work flawlessly.
Breaking Change
The problem is that I need the script to run as a setup step and not every time the container is started. So I tried the following:
FROM ubuntu:20.04
COPY ./install.sh /install.sh
RUN chmod +x /install.sh
SHELL ["/bin/bash", "-c"]
RUN /install.sh
ENTRYPOINT [ "p4d" ]
Problem
Now firstly I do not get any descriptive output in the console. The only thing I get is the default building output.
...
=> CACHED [2/4] COPY ./install.sh /install.sh 0.0s
=> CACHED [3/4] RUN chmod +x /install.sh 0.0s
=> CACHED [4/4] RUN /install.sh 0.0s
=> exporting to image
...
Secondly the script does not seem to execute or fails immediately. (It should take much longer than it does.) Here is the script, it does work in the first Dockerfile, just not in the second.
#!/bin/bash
service_name="${service_name:="master"}"
p4root="${p4root:="/opt/perforce/servers/$service_name"}"
unicode_mode="${unicode_mode:=0}"
case_sensitive="${case_sensitive:=0}"
p4port="${p4port:="1666"}"
super_user_login="${super_user_login:="super"}"
if [ -z "$super_user_password" ]
then
echo "Install aborted!"
echo "Please set 'super_user_password' via environment variable!"
exit
fi
echo "Installing Helix Core..."
echo "Updating Ubuntu..."
apt-get update -y
echo "Installing utilities..."
apt-get install ca-certificates wget gpg curl -y
echo "Downloading public key..."
curl https://package.perforce.com/perforce.pubkey > perforce.pubkey
echo "Adding public key..."
gpg init
gpg -n --import --import-options import-show perforce.pubkey
rm perforce.pubkey
echo "Adding perforce packaging key to keyring..."
wget -qO - https://package.perforce.com/perforce.pubkey | apt-key add -
echo "Adding perforce repository to APT configuration..."
echo "deb http://package.perforce.com/apt/ubuntu focal release" > /etc/apt/sources.list.d/perforce.list
echo "Updating Ubuntu..."
apt-get update -y
echo "Installing..."
apt-get install helix-p4d -y
echo "Install complete! Writing config file..."
/opt/perforce/sbin/configure-helix-p4d.sh $service_name -n -p $p4port -r $p4root -u $super_user_login -P $super_user_password
p4 admin stop
Extra Information
The Dockerfile is being built with docker-compose, but I have already tried out docker build with no success.
My Thoughts
It is my understanding that the only relevant difference between RUN and ENTRYPOINT is, that RUN only executes one time in the lifecycle of a container (in the build phase), while ENTRYPOINT defines the executable that will be started together with the container every time it is started. So I assume the environment that script is called in is the same.
Any ideas to why this behavior occurs and how to fix it are appreciated.

Answer 1

So thanks to #DavidMaze I took another look at something I overlooked before.
You can get output from the build command using --progress (see: Why is docker build not showing any output from commands?)
Problem 1 solved!
From there I found:
#6 [4/4] RUN /install.sh
#6 sha256:26be9fa6818fd9e3a0fb64e95a83b816de790902b1f54da1c123ff19888873ff
#6 0.344 Install aborted!
#6 0.344 Please set 'super_user_password' via environment variable!
#6 DONE 0.4s
Problem 2 identified!
Now... the actual problem is that:
Environment variables and arguments are two different things.
You want environment variables for the execution environment and arguments for the build environment. This webpage explained it to me.
My mistake was trying to use environment variables for the build environment.
Modified dockerfile:
FROM ubuntu:20.04
COPY ./install.sh /install.sh
SHELL ["/bin/bash", "-c"]
RUN chmod +x /install.sh
RUN ["/install.sh", "$super_user_password"]
ENTRYPOINT [ "p4d" ]
and I had to add this line to my script:
super_user_password="$1"
And finally... it works!