BeforeUp 0.4.3

BeforeUp 0.4.3 is the first stable release of the read-only Docker Compose preflight and deployment-change checker for native Linux Docker Engine setups.

What it checks

• Docker Compose configuration resolution, host-port ownership and collisions, missing local bind sources and build contexts, and Docker disk headroom.
• Differences between a proposed Compose project and its currently running services: published ports, bind mounts/volumes, declared environment values and image references. Sensitive values and resolved bind-source paths are not printed.
• Optional JSON output and strict warning exit codes for scripting.

Install

• Debian/Ubuntu: download the appropriate .deb asset and SHA256SUMS, verify the checksum, and install with sudo apt install ./beforeup_0.4.3_amd64.deb (or the ARM64 package).
• Other Linux: use the static linux_amd64 or linux_arm64 archive after verifying its checksum.
• Run beforeup check -f compose.yaml or beforeup compare -f compose.yaml.

Requirements and limitations
Docker CLI with Compose v2, the Linux ss command, and permission to inspect the target Docker Engine. BeforeUp never performs up, down, build, pull or Docker cleanup. A successful preflight does not guarantee successful deployment or application health.

Rootless writable binds, Docker Desktop for Linux, SELinux-enforcing hosts, some dual-stack setups, replicated services and ARM64 real-device installation are not independently qualified. See docs/platform-support.md for exactly what was tested. The ARM64 package is cross-built, not install-tested on ARM64 hardware.

Validation: 57 Go tests, race checks, a 14-case Compose matrix, a disposable real Docker comparison, package install/remove on Debian 13 and Ubuntu 24.04/26.04, and executable startup across ten Linux distribution images. The last two do not imply full Docker Engine compatibility on those distributions.