cross-rs/cross · error

using both `CROSS_CONTAINER_OPTS` and `DOCKER_OPTS`.

Error message

using both `CROSS_CONTAINER_OPTS` and `DOCKER_OPTS`.

What it means

Warning emitted when the user has set both CROSS_CONTAINER_OPTS and DOCKER_OPTS in the environment. CROSS_CONTAINER_OPTS is the supported, engine-agnostic variable; DOCKER_OPTS is the older Docker-only one. Setting both is ambiguous because only one can take effect, so cross warns and proceeds rather than silently ignoring the configuration.

Solutions

1. Unset DOCKER_OPTS and keep only CROSS_CONTAINER_OPTS so the options apply regardless of the container engine used
2. If you specifically rely on DOCKER_OPTS semantics, remove CROSS_CONTAINER_OPTS to silence the warning
3. Move the shared options into cross's configuration file instead of environment variables to avoid the conflict

When it happens

Trigger: Thrown at src/docker/shared.rs:1034 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of cross-rs/cross@8c1a8aa4b6 (2026-09-13). Data as JSON: /api/errors/6b44095edeae5955. Report an issue: GitHub.

Appendix: source

Thrown at src/docker/shared.rs:1034

            .args([
                "-e",
                &format!("CROSS_RUST_SYSROOT={}", dirs.sysroot_mount_path()),
            ])
            .args(["-e", "CARGO_TARGET_DIR=/target"])
            .args(["-e", &cross_runner]);
        if options.command_variant.uses_zig() {
            // otherwise, zig has a permission error trying to create the cache
            self.args(["-e", "XDG_CACHE_HOME=/target/.zig-cache"]);
        }
        self.add_configuration_envvars();

        if let Some(username) = id::username().wrap_err("could not get username")? {
            self.args(["-e", &format!("USER={username}")]);
        }

        if let Ok(value) = env::var("CROSS_CONTAINER_OPTS") {
            if env::var("DOCKER_OPTS").is_ok() {
                msg_info.warn("using both `CROSS_CONTAINER_OPTS` and `DOCKER_OPTS`.")?;
            }
            self.args(&Engine::parse_opts(&value)?);
        } else if let Ok(value) = env::var("DOCKER_OPTS") {
            // FIXME: remove this when we deprecate DOCKER_OPTS.
            self.args(&Engine::parse_opts(&value)?);
        };

        let (major, minor, patch) = match options.rustc_version.as_ref() {
            Some(version) => (version.major, version.minor, version.patch),
            // no toolchain version available, always provide the oldest
            // compiler available. this isn't a major issue because
            // linking with libgcc will not include symbols found in
            // the builtins.
            None => (1, 0, 0),
        };
        self.args(["-e", &format!("CROSS_RUSTC_MAJOR_VERSION={}", major)]);
        self.args(["-e", &format!("CROSS_RUSTC_MINOR_VERSION={}", minor)]);
        self.args(["-e", &format!("CROSS_RUSTC_PATCH_VERSION={}", patch)]);

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