SSHFS mount in Dockerfile fails unless it's from ENTRYPOINT - docker

Question

I'm attempting to SSHFS from the container to a remote server, with the mount created during the Dockerfile build.
The mount command works if executed in the already running container, and will work if I make the command the entrypoint (but then I have to string on the real entrypoint script on the end with a ; which feels too klugy.)
If I put the command in the Dockerfile with a RUN, it fails with a fuse: device not found, try 'modprobe fuse' first error.
Here's the files...
install.sh
#!/bin/bash
USAGE="install.sh <dir_to_parse> <filetype_to_parse>"
if [ $# -lt 2 ]
then
echo "$USAGE"
exit 1
fi
REMOTE_DIR=$1 FILE_EXTENSION=$2 docker-compose -p '' -f docker-compose.yml up -d --build
docker-compose.yml
version: "3"
services:
source.test:
build:
context: .
dockerfile: ./Dockerfile
image: test.source
container_name: test.source
environment:
ELASTIC_HOST: “http://<redacted>:<redacted>”
REMOTE_SERVER: <redacted>
REMOTE_USER: <redacted>
REMOTE_KEY: /etc/ssl/certs/<redacted>
FEEDER_URL: http://<redacted>/api
MONGOHOST: mongo
WALKDIRS: <redacted>
REMOTE_DIR: ${REMOTE_DIR}
FILE_EXTENSION: ${FILE_EXTENSION}
volumes:
- /etc/ssl/certs/:/etc/ssl/certs/
ports:
- 127.0.0.1:6000:80
cap_add:
- SYS_ADMIN
devices:
- "/dev/fuse:/dev/fuse"
security_opt:
- "apparmor:unconfined"
networks:
default:
external:
name: test
Dockerfile
FROM ubuntu:18.04
RUN apt-get update && apt-get -y install \
fuse \
sshfs
COPY <redacted> /etc/ssl/certs/<redacted>
COPY fuse.conf /etc/fuse.conf
RUN chown root:root /etc/fuse.conf
RUN chmod 644 /etc/fuse.conf
RUN mkdir /mnt/filestobeparsed
# Fails with fuse: device not found
RUN sshfs username#<xxx.xxx.xxx.xxx>:/remote/path /mnt/filestobeparsed -o StrictHostKeyChecking=no,IdentityFile=/etc/ssl/certs/<redacted>,auto_cache,reconnect,transform_symlinks,follow_symlinks,allow_other
ENTRYPOINT tail -f /dev/null
# Works but is klugy
#ENTRYPOINT sshfs username#<xxx.xxx.xxx.xxx>:/remote/path /mnt/filestobeparsed -o StrictHostKeyChecking=no,IdentityFile=/etc/ssl/certs/<redacted>,auto_cache,reconnect,transform_symlinks,follow_symlinks,allow_other; tail -f /dev/null