Problema Dockerfile

Step 3/8 : ENV PORT 3000
 ---> Running in 101c2e920caf
 ---> 844fa3fc86d3
Removing intermediate container 101c2e920caf
Step 4/8 : COPY . /var/www
 ---> 727582b95b08
Removing intermediate container 7c78e74cf387
Step 5/8 : WORKDIR /var/www
 ---> 8d6c6e701f2b
Removing intermediate container bb29aa0ef4e8
Step 6/8 : RUN npm install
 ---> Running in b29653e06b62
npm notice created a lockfile as package-lock.json. You should commit this file.
npm WARN volume-exemplo@1.0.0 No description
npm WARN volume-exemplo@1.0.0 No repository field.

Olá Galera , segui os passos das aulas e estou recebendo o seguinte erro npm notice created a lockfile as package-lock.json. You should commit this file.

Meu Dockerfile

FROM node:latest
MAINTAINER Daniel
ENV PORT=3000
COPY . /var/www
WORKDIR /var/www
RUN npm install
ENTRYPOINT npm start
EXPOSE $PORT

Meu comando

sudo docker build -f Dockerfile -t daniel/node1 .

Só que não funcionou não.