How to fix E: Unable to locate package nodejs in Docker

This is the most common fix. Always run apt-get update immediately before apt-get install in the same RUN command:

FROM ubuntu:22.04

# ❌ WRONG - Separate commands (update gets cached)
RUN apt-get update
RUN apt-get install -y nodejs

# ✅ CORRECT - Combined command
RUN apt-get update && apt-get install -y \
    nodejs \
    curl \
    git

The && operator ensures that if the update fails, the install won't run. This pattern prevents Docker from using a stale cached package index from a previous build.

After installing packages, remove the apt cache to keep your image lean:

RUN apt-get update && apt-get install -y \
    nodejs \
    && rm -rf /var/lib/apt/lists/*

This removes the package lists and prevents them from being stored in the Docker layer. The /var/lib/apt/lists/* directory contains the package index files that apt-get update downloads.

If the error persists, check that the package exists in your Ubuntu version:

1. Check your base image version:

FROM ubuntu:22.04  # Know which version you're using

2. Search for the package on packages.ubuntu.com or test in a temporary container:

docker run -it ubuntu:22.04 bash
apt-get update
apt-cache search nodejs

3. If the package doesn't exist, find the correct name or use a different Ubuntu version:

# nodejs might not be available; use specific version
FROM ubuntu:22.04
RUN apt-get update && apt-get install -y nodejs

# Or install from NodeSource if you need a specific version
RUN curl -fsSL https://deb.nodesource.com/setup_18.x | bash -
RUN apt-get install -y nodejs

Comments and line continuations can break multi-line RUN commands:

# ❌ WRONG - Comment breaks the command
RUN apt-get update && apt-get install -y \
    curl \ # this is curl
    nodejs

# ✅ CORRECT - Comments before the command
# Install build dependencies
RUN apt-get update && apt-get install -y \
    curl \
    nodejs

Make sure:
- Backslashes (\) at the end of each line except the last
- No comments inline with package names
- Proper line continuation without trailing spaces after backslashes

If you suspect Docker's build cache is causing issues, rebuild without cache:

docker build --no-cache -t myapp .

This forces Docker to run all commands fresh, including apt-get update, which will fetch the latest package indexes. Use this as a diagnostic step rather than a permanent solution.