COPY

Dockerfile - line 2

COPY hello.sh /

This instruction tells Docker to copy a file (or files) from the source host file system (which in this case is your machine's file system) to the destination directory in the container file system.

You can only copy files from the source directory containing your Dockerfile and any of its subdirectories.

You could have also written /hello.sh and this would still work since hello.sh is at the root of your build context, but making it look like an absolute path unnecessary and potentially confusing.

The COPY instruction can be used to rename the file. For example,

COPY hello.sh /app

would copy hello.sh to the root directory and rename it to app.

The following does not rename the file, but instead copies it to the /app directory (and creates the directory if it doesn't exist):

COPY hello.sh /app/

You can copy to any arbitrary path (and it will be created) and rename the file:

COPY hello.sh /path/to/scripts/app.sh

Finally, you can copy to destination paths that are relative to the current working directory, as specified using the WORKDIR instruction.

WORKDIR /app
COPY hello.sh .

The path for WORKDIR does not need to exist. The WORKDIR instruction is useful when you need to run a number of commands in a specific directory.