Skip to content

Clarify what the ARG instruction actually does during build #6411

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
tonistiigi merged 1 commit into from
Dec 15, 2025
+8 −2
Merged

Clarify what the ARG instruction actually does during build #6411

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 8 additions & 2 deletions frontend/dockerfile/docs/reference.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2430,9 +2430,15 @@ Therefore, to avoid unintended operations in unknown directories, it's best prac
ARG <name>[=<default value>] [<name>[=<default value>]...]
```

The `ARG` instruction defines a variable that users can pass at build-time to
The `ARG` instruction defines a variable that users can pass at build time to
the builder with the `docker build` command using the `--build-arg <varname>=<value>`
flag.
flag. This variable can be used in subsequent instructions such as `FROM`, `ENV`,
`WORKDIR`, and others using the `${VAR}` or `$VAR` template syntax.
It is also passed to all subsequent `RUN` instructions as a build-time
environment variable.

Unlike `ENV`, an `ARG` variable is not embedded in the image and is not available
in the final container.

> [!WARNING]
> It isn't recommended to use build arguments for passing secrets such as
Expand Down