mixed version of the kas-container entrypoint and vscode devcontainer to start bash or execute a random bash command as any user

container-entrypoint

#!/bin/bash

REMOTE_USER=${REMOTE_USER:="builder"}
NEW_UID=${NEW_UID:=1000}
NEW_GID=${NEW_GID:=1000}

eval "$(sed -n "s/${REMOTE_USER}:[^:]*:\([^:]*\):\([^:]*\):[^:]*:\([^:]*\).*/OLD_UID=\1;OLD_GID=\2;HOME_FOLDER=\3/p" /etc/passwd); "	
eval $(sed -n "s/\([^:]*\):[^:]*:${NEW_UID}:.*/EXISTING_USER=\1/p" /etc/passwd); 	
eval $(sed -n "s/\([^:]*\):[^:]*:${NEW_GID}:.*/EXISTING_GROUP=\1/p" /etc/group); 
GOSU=""
if [ -z "$OLD_UID" ]; then
 		echo "Remote user not found in /etc/passwd ($REMOTE_USER).";
elif [ "$OLD_UID" = "$NEW_UID" -a "$OLD_GID" = "$NEW_GID" ]; then
 		echo "UIDs and GIDs are the same ($NEW_UID:$NEW_GID).";
        GOSU="gosu $REMOTE_USER"
elif [ "$OLD_UID" != "$NEW_UID" -a -n "$EXISTING_USER" ]; then
 		echo "User with UID exists ($EXISTING_USER=$NEW_UID).";
elif [ "$OLD_GID" != "$NEW_GID" -a -n "$EXISTING_GROUP" ]; then 		
        echo "Group with GID exists ($EXISTING_GROUP=$NEW_GID).";
else
 		echo "Updating UID:GID from $OLD_UID:$OLD_GID to $NEW_UID:$NEW_GID.";
        sed -i -e "s/\(${REMOTE_USER}:[^:]*:\)[^:]*:[^:]*/\1${NEW_UID}:${NEW_GID}/" /etc/passwd;
        if [ "$OLD_GID" != "$NEW_GID" ]; then
        	sed -i -e "s/\([^:]*:[^:]*:\)${OLD_GID}:/\1${NEW_GID}:/" /etc/group;
        fi;
        chown -R $NEW_UID:$NEW_GID $HOME_FOLDER;
        GOSU="gosu $REMOTE_USER"
fi;

# if you set your working directory to a non existing folder on host, docker will breate it but with root ownership.
# this handles this case by affecting PWD to NEW_ID
if [ $(stat -c '%u' $PWD) -ne $NEW_UID ]; then
    echo "chown $PWD to $NEW_UID"
    chown $NEW_UID:$NEW_GID $PWD
fi;

if [[ -z "$@" ]];
then exec $GOSU bash;
else exec $GOSU bash -c "$@";
fi

# To build
docker build -t bcadet .
# To run
docker run -it -v ${PWD}:/volumes -e USER_ID=$(id -u) -e GROUP_ID=$(id -g) bcadet bash