Automatic Target Architecture on Debian

Custom images generated from config dockerfile or pre-build keys will export CROSS_DEB_ARCH, which allows you to install packages from Ubuntu/Debian repositories without having to specify the exact architecture. You can find an example of this here.

Custom Images

cross provides default Docker images for the targets listed in the README. However, it can't cover every single use case out there.

Adding Dependencies to Existing Images

If you simply need to install a dependency availaible in ubuntus package manager, see target.TARGET.pre-build:

toml

[target.x86_64-unknown-linux-gnu]
pre-build = [
    "dpkg --add-architecture $CROSS_DEB_ARCH",
    "apt-get update && apt-get install --assume-yes libssl-dev:$CROSS_DEB_ARCH"
]

For FreeBSD targets, a few helper scripts are available for use in target.TARGET.pre-build:

toml

[target.x86_64-unknown-freebsd]
pre-build = ["""
export FREEBSD_MIRROR=$(/freebsd-fetch-best-mirror.sh) &&
/freebsd-setup-packagesite.sh &&
/freebsd-install-package.sh xen-tools
"""]

Custom Dockerfile

For other targets, or when the default image is not enough, you can use the target.{{TARGET}}.dockerfile field in Cross.toml to use a custom Docker image for a specific target:

NOTE: Refer to the build.dockerfile section of the configuration for tips when writing your own Dockerfile.

toml

[target.aarch64-unknown-linux-gnu]
dockerfile = "Dockerfile"

cross will build and use the image that was built instead of the default image.

Custom Image

If there is a pre-built image for your specific target, you can use the target.{{TARGET}}.image field in Cross.toml to use that instead:

toml

[target.aarch64-unknown-linux-gnu]
image = "my/image:tag"

In thie case, cross will use a image named my/image:tag instead of the default one. Normal Docker behavior applies, so:

Docker will first look for a local image named my/image:tag
If it doesn't find a local image, then it will look in Docker Hub.
If only image:tag is specified, then Docker won't look in Docker Hub.
If only tag is omitted, then Docker will use the latest tag.