Shim file

A shim file is a small program that helps Linux boot on systems with Secure Boot, a UEFI feature that only runs trusted, signed software. Microsoft signs the shim, which then loads the Linux bootloader (like GRUB), bypassing Secure Boot restrictions. You don't need shims in your physical boots—it's a tech term, not about feet! Users can add their own keys (MOK) for custom software. Recent 2024 updates fixed a shim vulnerability (CVE-2023-40547), but caused boot issues for some, requiring updates or disabling Secure Boot temporarily. Shims add security but also complexity and reliance on Microsoft, which some criticize.