Run a cassandra in a docker with preloaded data

docker-compose.yml

version: "2"

services:
  cassandra:
    build: docker/cassandra
    ports:
      - "9042:9042"
      - "7199:7199"

Dockerfile

FROM cassandra:3.1.1

RUN mkdir -p /tmp/var/lib/cassandra /etc/cassandra \
	&& chown -R cassandra:cassandra /tmp/var/lib/cassandra /etc/cassandra \
	&& chmod 777 /tmp/var/lib/cassandra /etc/cassandra

RUN sed -i "s~/var/lib/cassandra~/tmp/var/lib/cassandra~g" /etc/cassandra/cassandra.yaml

COPY *.cql /tmp/

RUN cassandra \
    && while [ $(cqlsh -e "USE system" || echo 1) ]; do sleep 0.5; done \
    && echo 'waited for cassandra startup and now setting up myprojectname keyspace...' \
    && cqlsh localhost 9042 -f /tmp/keyspace.cql \
    && echo 'creating schemas...' \
    && cqlsh localhost 9042 -f /tmp/schema.cql \
    && echo 'insert some values...' \
    && cqlsh localhost 9042 -f /tmp/insert.cql \
    && echo 'flushing cassandra...' \
    && nodetool flush myprojectname \
    && echo 'done!'

HEALTHCHECK --interval=1s --timeout=1s --retries=1 CMD cqlsh -e "USE myprojectname"

RUN chmod -R 777 /tmp/var/lib/cassandra /etc/cassandra

insert.cql

INSERT INTO myprojectname.tenant(columnname) VALUES ('myvalue');

keyspace.cql

CREATE KEYSPACE IF NOT EXISTS myprojectname
    with replication = {'class': 'SimpleStrategy', 'replication_factor': 3};

Makefile

docker-compose --project-name projectname up -d --build cassandra
./wait-for-docker.sh 'projectname_cassandra_1'

schema.cql

CREATE TABLE myprojectname.tablename (
    columnname text,
    PRIMARY KEY(columnname)
);

wait-for-docker.sh

printf "Waiting for $1 to become available ..."

for i in $(seq 1 40); do
    health=$(docker inspect --format "{{json .State.Health.Status }}" $1)
    if [[ ${health} == "\"healthy\"" ]]; then
        echo ''
        echo "$1 is up"
        exit 0
    fi
    sleep 1
    printf '.'
done
echo ''
echo "$1 took too long to start up. Failing."
exit 1

In the dockerfile:
RUN chmod -R 777 /tmp/var/lib/cassandra /etc/cassandra

what is this doing?

I'm intrigued by this approach but not getting to work yet in my case.