What causes "attempted to create already existing container." in cross-rs/cross?

Remove the stale container: `docker rm -f ` (or `cross clean`), then rerun.

attempted to create already existing container.

Error message

attempted to create already existing container.

What it means

cross's `create` function refuses to create a Docker container when a container with the same target name already exists. Before creating, it checks whether the container is already present; the bail happens in the else branch when the container exists but is not in a reusable running/created state the function accepts. This is an explicit guard against duplicating build containers.

Solutions

Remove the stale container: `docker rm -f <container>` (or `cross clean`), then rerun.
Check for a concurrently running cross process and wait for it to finish.
Use a different container name/id via CARGO_TARGET/cross config to avoid the collision.

Example fix

// before
$ cross build --target aarch64-unknown-linux-gnu
error: attempted to create already existing container.
// after
$ docker ps -a --filter name=cross   # find stale container
$ docker rm -f cross-aarch64-unknown-linux-gnu
$ cross build --target aarch64-unknown-linux-gnu

Defensive patterns

Strategy: retry

Validate before calling

const { execSync } = require('child_process');
function containerExists(name) {
  try {
    execSync(`docker ps -a --filter name=^/${name}$ --format '{{.Names}}'`, { stdio: 'pipe' });
    return true;
  } catch { return false; }
}

Try / catch

try {
  await create(container);
} catch (e) {
  if (String(e.message).includes('already existing container')) {
    await removeContainer(container); // docker rm -f
    return create(container); // retry once after cleanup
  }
  throw e;
}

Prevention

Clean up leftover cross containers after interrupted builds (docker rm -f).
Avoid running multiple cross builds concurrently against the same target.
Add a pre-build step that checks for and removes stale containers.

When it happens

Trigger: Calling `create` when a container with the same name already exists on the Docker daemon (e.g. `cross build` after a previous run left a stale container behind, or a concurrently running cross invocation created it first).

Common situations: A previous cross build was killed without cleaning up its container; running cross in parallel from multiple processes; container name collisions from custom `CROSS_CONTAINER_OPTS` naming.

Understand the failure class

Background: "already exists" / EEXIST / FileAlreadyExistsException: what the 'file already exists' error means and how to fix it — this error's family across 37 libraries.

Related errors

AI-assisted analysis of cross-rs/cross@8c1a8aa4b6 (2026-09-13). Data as JSON: /api/errors/7a76941723734dd7. Report an issue: GitHub.

Appendix: source

Thrown at src/docker/shared.rs:555

            exists: AtomicBool::new(false),
        }
    }

    pub fn create(engine: Engine, name: String) -> Result<()> {
        // SAFETY: guarded by an atomic swap
        unsafe {
            #[allow(static_mut_refs)]
            if !CHILD_CONTAINER.exists.swap(true, Ordering::SeqCst) {
                CHILD_CONTAINER.info = Some(ChildContainerInfo {
                    engine,
                    name,
                    timeout: NO_TIMEOUT,
                    color_choice: ColorChoice::Never,
                    verbosity: Verbosity::Quiet,
                });
                Ok(())
            } else {
                eyre::bail!("attempted to create already existing container.");
            }
        }
    }

    // the static functions have been placed by the internal functions to
    // verify the internal functions are wrapped in atomic load/stores.

    pub fn exists(&self) -> bool {
        self.exists.load(Ordering::SeqCst)
    }

    pub fn exists_static() -> bool {
        // SAFETY: an atomic load.
        #[allow(static_mut_refs)]
        unsafe {
            CHILD_CONTAINER.exists()
        }
    }

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