If you are behind a proxy, Docker (and apt ) needs to know about it. You’ll need to configure your proxy settings in /etc/apt/apt.conf.d/proxy.conf .

Most people see this error because of a typo or an incorrect variable in their package manager’s source list. Docker’s repository structure is very specific: ://docker.com[distro]/[version] .

If you’re seeing this within the Docker Desktop app, it usually means the internal engine can’t reach the update server. Restart Docker Desktop.