Combine FTP server and Node.js in one docker container

I want to build a container that contains FTP server (e.g. pure-ftpd) and next to that, a Node.js application that watches the incoming folder when files get dropped (and sends them elsewhere).

I am fairly new to docker, and I cannot figure out how to get this configured so I have an environment / docker image that I can deploy many times.

My dockerfile:

FROM stilliard/pure-ftpd

# e.g. this command should change to config ftp correctly, but now it even doesn't start the server:
RUN /run.sh -c 30 -C 10 -l puredb:/etc/pure-ftpd/pureftpd.pdb -E -j -R -P $PUBLICHOST -p 30000:30059 -e FTP_USER_NAME=bob -e FTP_USER_PASS=12345 -e FTP_USER_HOME=/home/bob
FROM node:10
COPY package*.json ./

RUN mkdir /incoming
RUN npm install

COPY . .
CMD ["node","start.js"]

I believe my issue is the double RUN instead of CMD, but I cannot do 2 CMD’s.
Anyway, any pointers in the right direction would help me.

Source: StackOverflow