Document Ubuntu 26.04 Rust Coreutils & sudo-rs changes, add GNU fallback build flag

[Copilot]

Ubuntu 26.04 LTS ships uutils-coreutils (Rust) and sudo-rs (Rust) as defaults, replacing GNU Coreutils and traditional sudo. This has compatibility, licensing, and maturity implications that were previously undocumented.

Documentation (README.md)

• Updated component table to call out Rust-based tooling on 26.04 with link to new section
• Added "Ubuntu 26.04 LTS: Rust Coreutils and sudo-rs" section covering:
  • What changed and why it matters (compatibility, security, licensing: MIT vs GPL-3.0/ISC, maturity)
  • Option 1: Pin to phusion/baseimage:noble-* (Ubuntu 24.04) for GNU tooling
  • Option 2: Build with INSTALL_GNU_COREUTILS=1 to restore GNU variants on 26.04

Build infrastructure

• image/buildconfig — added INSTALL_GNU_COREUTILS flag (default 0)
• image/Dockerfile — exposed as ARG INSTALL_GNU_COREUTILS=0
• image/prepare.sh — on Ubuntu 26.04+, when flag is 1, installs coreutils-gnu and sudo-traditional/sudo-classic if available via apt-cache show probe

# Restore GNU Coreutils + traditional sudo on a 26.04-based build
docker build --build-arg BASE_IMAGE=ubuntu:26.04 \
             --build-arg INSTALL_GNU_COREUTILS=1 \
             image/

Package names (coreutils-gnu, sudo-traditional) are probed at build time and may need adjustment as Ubuntu 26.04 packaging stabilises.

[Copilot]

Pull request overview

Documents Ubuntu 26.04 LTS's shift to Rust-based uutils-coreutils and sudo-rs, and adds an opt-in build flag intended to swap those back for GNU Coreutils / traditional sudo when building on 26.04.

Changes:

• README: new "Ubuntu 26.04 LTS: Rust Coreutils and sudo-rs" section plus a note in the component table, covering compatibility/security/licensing/maturity tradeoffs and two mitigation options.
• Build config & Dockerfile: introduce INSTALL_GNU_COREUTILS (default 0) as a build-time flag.
• prepare.sh: on Ubuntu ≥26.04, when the flag is 1, probe for coreutils-gnu and sudo-traditional/sudo-classic via apt-cache show and install whichever exist.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
README.md	Adds TOC entry, table note, and a new section explaining the 26.04 Rust tooling change with two workarounds.
image/buildconfig	Exports new INSTALL_GNU_COREUTILS variable defaulting to 0.
image/Dockerfile	Declares ARG INSTALL_GNU_COREUTILS=0 with a comment.
image/prepare.sh	Conditionally installs GNU coreutils / traditional sudo on Ubuntu ≥26.04 when the flag is set.

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[Theaxiom]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Applied all review feedback in commit 9e1c464:

• prepare.sh verification (unresolved thread on lines 71-93): Added a post-install ls --version | grep -qi 'gnu coreutils' check. If GNU coreutils aren't active on PATH after installation (e.g. the package installs to a non-default location), the build fails with a clear diagnostic message explaining the issue and pointing to Ubuntu 26.04 packaging as the source to consult.

• README codename/tag (unresolved thread on lines 682-685): Removed the speculative codename "Resolute Ringtail" from the description text, and replaced the non-existent phusion/baseimage:resolute-1.0.0 example tag with the generic placeholder <ubuntu-26.04-version>.

The two previously-resolved items (ARG→env passthrough in Dockerfile, and the error/exit on missing packages) were already in place from the prior commit.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (1)

image/prepare.sh:93

• The replacement package names (coreutils-gnu, sudo-traditional, sudo-classic) used here are speculative — the PR description itself acknowledges they "may need adjustment as Ubuntu 26.04 packaging stabilises." As written, on a real Ubuntu 26.04 system where none of these probed packages exist, INSTALL_GNU_COREUTILS=1 will always fail the build at line 92 with the "ERROR: ... could not be fully installed" message, making the documented flag effectively non-functional. Consider either (a) deferring this code path until the actual package names are confirmed and adding them, or (b) explicitly documenting this as an experimental/forward-looking option that may not work on current 26.04 images, so users aren't surprised when the documented build command fails.

      # Install GNU Coreutils if available (package name may vary by Ubuntu release).
      # 'coreutils-gnu' is the expected package name for the GNU implementation
      # when uutils-coreutils is the default.
      if apt-cache show coreutils-gnu > /dev/null 2>&1; then
        $minimal_apt_get_install coreutils-gnu
        GNU_COREUTILS_INSTALLED=1
      fi
      # Install traditional sudo if available (package name may vary).
      # 'sudo-traditional' or similar may be provided alongside 'sudo-rs'.
      if apt-cache show sudo-traditional > /dev/null 2>&1; then
        $minimal_apt_get_install sudo-traditional
        TRADITIONAL_SUDO_INSTALLED=1
      elif apt-cache show sudo-classic > /dev/null 2>&1; then
        $minimal_apt_get_install sudo-classic
        TRADITIONAL_SUDO_INSTALLED=1
      fi
      if [ "$GNU_COREUTILS_INSTALLED" -ne 1 ] || [ "$TRADITIONAL_SUDO_INSTALLED" -ne 1 ]; then
        echo "*** ERROR: INSTALL_GNU_COREUTILS=1 was requested, but the requested replacements could not be fully installed." >&2
        if [ "$GNU_COREUTILS_INSTALLED" -ne 1 ]; then
          echo "*** ERROR: No GNU coreutils replacement package was found (tried: coreutils-gnu)." >&2
        fi
        if [ "$TRADITIONAL_SUDO_INSTALLED" -ne 1 ]; then
          echo "*** ERROR: No traditional sudo replacement package was found (tried: sudo-traditional, sudo-classic)." >&2
        fi
        exit 1
      fi

[Theaxiom]

@copilot Please address all open comments on all open threads in this PR and synthesize the solution based on the inputs.

[Copilot]

@copilot Please address all open comments on all open threads in this PR and synthesize the solution based on the inputs.

All open threads are now addressed in commit af5f71b:

Open thread (README.md:684-693) — Rewrote the speculative Dockerfile snippet. Instead of hard-coding coreutils-gnu sudo-traditional (package names that may not exist), the section now shows a docker run discovery step using apt-cache search to find the real package names first, followed by a Dockerfile example with explicit <gnu-coreutils-pkg> / <traditional-sudo-pkg> placeholders so readers understand they must substitute confirmed names before use.

The previously-resolved threads were already addressed in prior commits:

• prepare.sh:64 — case statement replaced [ -eq ] arithmetic test (safe under set -e for non-numeric inputs)
• prepare.sh:75-103 — build exits with a clear error if packages aren't found or GNU coreutils aren't active on PATH after installation
• Dockerfile:14 — ARG is passed inline to the RUN command so the env var reaches the script
• README.md:643-647 — wording softened; codename and speculative tag removed

[PikachuEXE]

Making changes and testing locally (with 24.04 & 26.04
Should we remove the sudo part from README though since sudo is absent in docker image (and setuser is already present to reduce the need for sudo)

Edit 1: commands used to test

make build NAME=joe/stretch QEMU_ARCH=amd64 PLATFORM=linux/amd64
docker run -it --rm joe/stretch:noble-1.0.2 bash

make build NAME=joe/stretch QEMU_ARCH=amd64 PLATFORM=linux/amd64 VERSION=resolute-1.0.0 BASE_IMAGE=ubuntu:26.04
docker run -it --rm joe/stretch:resolute-1.0.0 bash

docker build --no-cache -t joe/stretch:resolute-1.0.0-gnu --build-arg BASE_IMAGE=ubuntu:26.04 --build-arg QEMU_ARCH=amd64 --build-arg INSTALL_GNU_COREUTILS=1 --platform linux/amd64 --rm image
docker run -it --rm joe/stretch:resolute-1.0.0-gnu bash

[Theaxiom]

@PikachuEXE sure, let's make sure the docs are aligned. 👍

[PikachuEXE]

Updated
sudo-rs left for ubuntu 26.04 but also mentioned it's absent in Docker image

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (2)

image/prepare.sh:78

• apt-get remove ... coreutils-from-uutils is executed unconditionally when the flag is enabled. If Ubuntu 26.04 ends up using a different package name (as the PR description suggests might happen), this will hard-fail the build. Consider probing for the package first (e.g., via apt-cache show / dpkg -s) and emitting a clear error that includes the expected package name(s) when it's not present.

    if [ "$INSTALL_GNU_COREUTILS_NORMALIZED" = "1" ]; then
      echo "*** Removing Rust to restore GNU Coreutils..."
      # GNU Coreutils can only be installed by removing `coreutils-from-uutils`
      apt-get remove -y --allow-remove-essential coreutils-from-uutils
      # Verify that GNU coreutils are now the active implementation on PATH.

image/prepare.sh:86

• The failure message says "coreutils-from-gnu was installed" but this script never installs that package (it only removes coreutils-from-uutils). This makes the error misleading if the PATH check fails. Adjust the message to describe the actual action taken (e.g., removal of coreutils-from-uutils) and what the user should do next.

      if ! ls --version 2>&1 | grep -qi 'gnu coreutils'; then
        echo "*** ERROR: coreutils-from-gnu was installed but GNU coreutils are not active on PATH." >&2
        echo "*** 'ls --version' does not report 'GNU coreutils'." >&2
        echo "*** The package may place binaries outside the default PATH or require" >&2
        echo "*** manual update-alternatives configuration. Check Ubuntu 26.04 packaging." >&2
        exit 1

[Theaxiom]

@PikachuEXE if you are happy with this, you can merge it. 👍

Re-review requested.