Public/static directory lost in multistage docker build. What build assets to copy?

[malimccalla]

Using a simple next js set up (same as custom-server-typescript but with an added public directory) I am trying to build and run it within a docker container. I can get everything working with this Dockerfile

FROM node:latest
WORKDIR /app

COPY ./package.json ./package.json
COPY ./yarn.lock ./yarn.lock

RUN yarn install

COPY . .

RUN yarn build

CMD ["yarn", "start"]

However my app requires a multistage build so I am trying to copy over the build assets with this Dockerfile

## BUILD PHASE ##
FROM node:latest as builder
WORKDIR /app

COPY ./package.json ./package.json
COPY ./yarn.lock ./yarn.lock

RUN yarn install

COPY . .

RUN yarn run build

## RUN PHASE ##
FROM node:lts-alpine
WORKDIR /app

COPY --from=builder /app/package.json .
COPY --from=builder /app/yarn.lock .

RUN yarn install --production

COPY --from=builder /app/.next ./.next
COPY --from=builder /app/dist ./dist
# Do I need to copy something else from the build output here???

ENV NODE_ENV production
EXPOSE 3000

CMD ["yarn", "start"]

This appears to work just fine at first but files within my public directory are no longer being served when ran. I'm wondering if I need to copy over some additional folders besides the dist and .next to get my static/public assets working.

[malimccalla]

Solved my issue. I needed to copy over the public directory as well, i just assumed it would be built with the project. For anyone that may find it helpful, here is my final working Dockerfile (I have a yarn workspace)

## BUILD PHASE ##
FROM node:latest as builder
WORKDIR /app

COPY ./lerna.json .
COPY ./package.json .
COPY ./yarn.lock .
COPY ./tsconfig.json .
COPY ./packages/www/package.json ./packages/www/package.json
COPY ./packages/shared/package.json ./packages/shared/package.json

# Will use cache unless any of the above files have changed
RUN yarn install

# Copy the source code to be built
COPY ./packages/www/ ./packages/www/
COPY ./packages/shared/ ./packages/shared/

RUN yarn run build:www

## RUN PHASE ##
FROM node:lts-alpine
WORKDIR /app

COPY --from=builder /app/package.json .
COPY --from=builder /app/packages/www/package.json ./packages/www/package.json
COPY --from=builder /app/packages/shared/package.json ./packages/shared/package.json

RUN yarn install --production

COPY --from=builder /app/packages/shared/dist /app/packages/shared/dist

COPY --from=builder /app/packages/www/dist /app/packages/www/dist
COPY --from=builder /app/packages/www/public /app/packages/www/public
COPY --from=builder /app/packages/www/.next /app/packages/www/.next

WORKDIR /app/packages/www

ENV NODE_ENV production
EXPOSE 3000

CMD ["node", "dist/server.js"]

[cjimmy]

A note for those seeing this in 2025. When you configure output: "standalone" in next.config.js (as it does in the example containerized app), public is intentionally not copied over. See docs.