Building an image via Dockerfile (creating a folder in /dev) - node.js

Question

I am trying to build an image and following error occurs:
npm ERR! code ENOENT
npm ERR! syscall open
npm ERR! path /dev/lab3/package.json
npm ERR! errno -2
npm ERR! enoent ENOENT: no such file or directory, open '/dev/lab3/package.json'
npm ERR! enoent This is related to npm not being able to find a file.
npm ERR! enoent
Here we have Dockerfile:
FROM node:latest
WORKDIR /dev/lab3
COPY server.js .
COPY package.json .
RUN mkdir /files
ADD ./files /files
RUN npm install
CMD ["npm", "start"]
Look at df -h:
root#279f05c372ce:/dev# df -h
Filesystem Size Used Avail Use% Mounted on
overlay 118G 13G 99G 11% /
tmpfs 64M 0 64M 0% /dev
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup
shm 64M 0 64M 0% /dev/shm
/dev/sda5 118G 13G 99G 11% /etc/hosts
tmpfs 3.9G 0 3.9G 0% /proc/acpi
tmpfs 3.9G 0 3.9G 0% /proc/scsi
tmpfs 3.9G 0 3.9G 0% /sys/firmware
My assumption - while building an image, WORKDIR sets /dev/lab3 for working directory. /dev is tmpfs filesystem (temporary), so when next layers of image are created (COPY server.js and COPY package.json) there is no /lab3 folder.
Could you confirm this ? Or there is other explaination?

Answer 1

The /dev folder is for devices (like hard drives and ttys) in Linux. User applications do no belong there. Docker manages this directory because some special devices are expected in Linux (e.g. /dev/zero and /dev/random) so it configures an in memory filesystem (tmpfs) and mounts that in the container filesystem namespace. When you mount a directory in Linux, files and directories in the underlying filesystem are hidden for as long as that mount exists (in this case, for the lifetime of the container).