Symptom

Package manager operations fail with errors indicating that repository signatures cannot be verified.

Cause

Some TLS‑inspecting proxies block access to external GPG keyservers (commonly using port 11371). As a result, package managers cannot retrieve or validate repository signing keys.

Resolution

Download the required repository signing key on the host system and add it via the Dockerfile. For example:

COPY repo-key.gpg /etc/apt/trusted.gpg.d/