02 March 2018 1 comment Docker
tl;dr; Watch out for
no such file or directory when building Docker images
First I tried to use
▶ docker-compose build ui Building ui Step 1/8 : FROM node:9 ---> 29831ba76d93 Step 2/8 : ADD ui/package.json /package.json ERROR: Service 'ui' failed to build: ADD failed: stat /var/lib/docker/tmp/docker-builder079614651/ui/package.json: no such file or directory
What the heck? Did I typo the name in the
docker-compose.yml directive for this was:
yaml ui: build: context: . dockerfile: ui/Dockerfile environment: - NODE_ENV=development ports: - "3000:3000" - "35729:35729" volumes: - $PWD/ui:/app command: start
I don't know if it's the awesomest way to do
docker-compose but I did copy this exactly from a different (working!) project. That other project called the web stuff
frontend instead of
ui in this project.
Dockerfile looked like this:
FROM node:9 ADD ./ui/package.json ./ ADD ./ui/package-lock.json ./ RUN npm install EXPOSE 3000 EXPOSE 35729 CMD [ "npm", "start" ]
Let's try without
docker-compose. Or rather, do with
docker-compose does for me automatically.
▶ docker build ui -f ui/Dockerfile Sending build context to Docker daemon 158.2MB Step 1/8 : FROM node:9 ---> 29831ba76d93 Step 2/8 : ADD ui/package.json /package.json ADD failed: stat /var/lib/docker/tmp/docker-builder001494654/ui/package.json: no such file or directory
So I thought I perhaps have misunderstood how relative paths worked. I tried EVERYTHING!
I tried changing to
docker build . -f ui/Dockerfile. No luck.
I tried all sorts of combinations of this with also changing the line to
ADD ui/package.json ... or
ADD /ui/package.json ... or
ADD ./package.json ... or
ADD package.json .... Nothing worked.
Finally I got it to work by doing
▶ cd ui ▶ docker build . -f Dockerfile
but for that to work I had to remove all references of the directory name
ui in the
Dockerfile. Nice, but this is not going to work in
since that starts outside the directory
So then I learned about contexts in docker. Well, I skimmed the docs rapidly. To keep things clean it's a good idea to do things within the directory that matters. So I made this change in the
ui: build: context: ui dockerfile: Dockerfile environment: - NODE_ENV=development ports: - "3000:3000" - "35729:35729" volumes: - $PWD/ui:/app command: start
Still doesn't work! 😫 Still various variations of
no such file or directory.
Turns out, in
projectroot/.dockerignore it had
ui/ as a line entry!!!
I believe this project used to do some of the Python stuff with Docker and the React web app was done "locally" on the host. And since the
ui/node_modules directory is so huge someone decided it was smart of avoid Docker mounting that.
.ui/node_modules and now everything works. I can build it with plain
docker-compose from outside the directory.
Perhaps I should have spent the time I spent writing this blog post to instead file a structured GitHub issue on Docker itself somewhere. I.e. that it should have warned be better. Any takers?