Rust coreutils cp incompatibility broke Ubuntu image builds and forced a revert to GNU cp

Category: Dev tools
Status: confirmed
Sources: Phoronix, Ubuntu rust-coreutils update, HN discussion
Summary: A difference in how the uutils (Rust) coreutils cp handles the -L argument broke Ubuntu image builds, failing the live-media ISO construction path. The regression was marked critical on Launchpad, and Ubuntu reverted the affected build step to the GNU coreutils cp while an upstream fix proposed to uutils remained unmerged at the time of the report on 2026-07-03. Ubuntu switched to Rust coreutils by default in 25.10, and subtle behavioral gaps against GNU coreutils continue to surface in individual commands.
Why it matters: A flagship distribution replacing GNU userland with a Rust rewrite exposes the migration cost directly: a single argument-handling gap in one command halted image production and forced a per-command fallback rather than a clean cutover.
Follow-up: Track the upstream uutils cp fix merging and whether Ubuntu re-enables Rust cp in the image-build path.