Ubuntu 25.10 Questing Quokka: Rust Coreutils, RC Kernel, GNOME 49, X11 Tradeoff

Ubuntu’s next interim release, Questing Quokka (25.10), has entered its User Interface Freeze as Canonical rides a wave of late-cycle engineering changes: Rust-based system utilities moving into the default image, an aggressively modern kernel target that could ship as a release candidate at launch, and a last-minute reversal in GNOME’s approach to the X11/Wayland transition that will shape desktop compatibility for months to come. The net effect is a release that’s simultaneously ambitious and transitional — one that promises measurable gains in performance and safety while also introducing integration and compatibility risks administrators and power users will need to manage carefully. (lists.ubuntu.com) (discourse.ubuntu.com)

Background​

Ubuntu 25.10, codenamed Questing Quokka, is an interim (non-LTS) release scheduled for an October 9, 2025 final. As an interim release it will receive nine months of official support, through July 2026. The project’s development calendar — monthly snapshots, early betas, and clearly stated freeze dates — is intended to give the community predictable checkpoints while allowing Canonical to land newer kernels and userland updates sooner than in LTS cycles. (discourse.ubuntu.com)
The recent announcement that the desktop images are now under UI Freeze formally ends the period where visual or string changes are allowed without special exceptions. That step signals the team is confident in the desktop’s visual coherence and translation stability, and it typically precedes an intensified focus on regression fixes and installer polish. (lists.ubuntu.com)

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What’s changing under the hood​

A move toward Rust: sudo-rs and Rust Coreutils​

Perhaps the most consequential foundation-level change in Questing Quokka is Canonical’s adoption of Rust-based tooling in main — notably sudo-rs as the default sudo implementation and the inclusion of the Rust Coreutils (uutils) in the image. This is not a cosmetic shift; it replaces longtime C implementations of fundamental system utilities with Rust equivalents aiming for memory safety and, in some cases, better throughput.

• sudo-rs has been promoted to the default sudo in Ubuntu daily ISOs for 25.10 after passing inclusion review and meeting parity for many commonly used features (sudoedit support, NOEXEC semantics, AppArmor profile switching, and compatibility with older kernels). Canonical has kept the original C sudo available in the archives as a fallback, and the release notes make it clear the transition is deliberate and staged. (discourse.ubuntu.com)
• The Rust Coreutils project (uutils) shipped version 0.2 in early September, with headline performance claims: several utilities that were previously slower than the GNU equivalents have reportedly overtaken them and, in some cases, shown large improvements in microbenchmarks. The Phoronix coverage highlights notable wins for tools like tr, sort and cat, and reports the project as making rapid progress toward GNU test-suite parity. While daily workflows may not be dramatically faster, this is a material evolution for command-line tooling and signals a wider systems-language shift. (phoronix.com)

Why this matters: memory-safety languages such as Rust help prevent entire classes of vulnerabilities (use-after-free, buffer overflow) which have historically afflicted privileged utilities written in C. Rewriting privileged paths in Rust can reduce the attack surface and improve auditability. However, parity and behavioral exactness are crucial — admin scripts, auditing tooling, and enterprise automation often depend on subtle command semantics that can differ across implementations.

Kernel 6.17: fresh enablement, RC risk​

Canonical’s kernel team has signaled it will target Linux 6.17 for Questing Quokka. The policy of importing the latest upstream kernel available by Feature Freeze allows Ubuntu to ship fresher hardware enablement and new driver stacks, but it carries the trade-off that the kernel may still be at Release Candidate status at the time ISO images are finalized. Canonical’s kernel announcement explicitly warns that 6.17 could be an unstable kernel on release day and may be updated post-release to the final upstream point. This is the classic trade-off between immediacy and long-tail stability. (discourse.ubuntu.com)
Implications:

• Newer hardware (recent GPUs, Wi‑Fi, and SoC support) will be better served out of the box.
• Modules, DKMS drivers, and proprietary drivers (notably GPU drivers) may require rebuilds and additional testing.
• Enterprise deployments and production workstations should plan for rollback options or hold on deploying to critical hosts until first point updates stabilize.

systemd and other core components​

Questing Quokka will ship with systemd 257, even though systemd 258 development and release candidates are in progress. The decision to remain on 257 for the release underscores a conservative approach for core init components where late-stage changes can have far-reaching boot and service-management consequences. This conservative selection reduces risk but also means some newer systemd features won’t be available until later releases. Project and community testing continues on newer systemd versions, but they missed the freeze window for 25.10. (phoronix.com)

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Desktop: GNOME 49, Wayland, and a retreat on X11​

GNOME 49 is the default, but Wayland-only plans were revised​

Ubuntu’s default desktop for 25.10 will be GNOME 49, and the initial plans to make the distribution Wayland-only on the desktop were thrown into practical relief by GNOME’s own release-candidate behavior.
GNOME’s 49 release candidate re-enabled X11 support in GDM by default after an alpha phase that disabled X11 sessions; maintainers found it difficult to cleanly separate GDM’s X11 launch capability from its broader X11 integration and elected to re-enable support while signaling the longer-term intent to pare back X11 integration in future versions. Canonical’s desktop roadmap had referenced GNOME 49 and a Wayland-first posture, but with GNOME RC modifying GDM’s defaults, Ubuntu has retained the ability for users to run X11 sessions via the login manager, improving compatibility for legacy sessions and third-party desktops. (phoronix.com)
This is notable: GNOME’s path toward Wayland is steady, but the community remains pragmatic when the ecosystem still requires X11 compatibility for certain drivers, toolchains, or legacy applications.

New apps and integration changes in GNOME 49​

GNOME 49 is not just a paint job. The desktop brings new and replaced components that will affect the out-of-the-box experience:

• Showtime replaces Totem as the default movie player.
• Papers replaces Evince as the document viewer in some builds.
• Manuals replaces Devhelp for documentation browsing.
• Ptyxis, a GPU-accelerated terminal emulator tightly integrated with GNOME, is likely to be included. It offers a modern acceleration model similar to Ghostty or Alacritty but with closer GNOME integration.

These choices reflect a pattern: GNOME is modernizing default apps and pushing GPU-accelerated components into the core desktop. For typical desktop users, these changes should feel like increased polish; for admins and power users, they mean re-evaluating workflows that integrate with default apps. (phoronix.com)

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Alternative desktops and the persistence of X11​

Ubuntu’s official flavors remain a refuge for users who prefer non‑GNOME desktops. The Budgie flavor has released Budgie 10.9.3, aligning parts of its stack with GNOME 49 where needed while forking some components to maintain independence. The broader ecosystem is also witnessing work on X11 forks such as XLibre, which aims to clean up and extend X.Org server code rather than abandoning it. These parallel efforts underscore that X11 remains alive for many users and distributions, even as Wayland matures. (github.com)

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Security and privacy: TPM-backed full-disk encryption progress​

Questing Quokka’s release notes and developer discussion reveal work on TPM-backed full-disk encryption (FDE) and recovery-key management. This is an important step for usability — the aim is to ease recovery for encrypted installs while leveraging hardware-backed attestation and secrets storage.
The caveat: the integration of TPM with full-disk encryption is complex. TPM chips vary by vendor, and policy decisions (what to store in TPM, how to handle firmware updates, and recovery key escrow) need careful documentation and optionality. Early reports indicate there are still outstanding bugs, which is typical for such a sensitive feature and explains the cautious wording in the release notes. Administrators should treat TPM-backed FDE as a major convenience once matured, but avoid rushing it into production without validation on target hardware. (ubuntuhandbook.org)

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Performance claims: Rust Coreutils and real-world impact​

Rust Coreutils 0.2’s release notes and independent coverage emphasize substantial performance improvements for specific utilities — some commands that were an order of magnitude slower in early Rust implementations are now faster than their GNU counterparts in lab benchmarks. The improvements reported by the uutils project and covered by Phoronix include microbenchmarks for commands like tr, sort, and base64 where algorithmic changes and Rust’s modern toolchain deliver gains. (phoronix.com)
Important caveats:

• Benchmark context matters. Single-command microbenchmarks don’t always translate to faster real-world shell scripts or I/O-bound workloads where filesystem and kernel behavior dominate.
• Compatibility and edge-case behavior must be confirmed before assuming equivalent semantics across all flags and locales.
• The community must validate tooling behavior within automation, CI pipelines, and system management tooling.

Nevertheless, the safety and performance trajectory is promising: if the Rust tools continue to converge with GNU semantics while preserving or improving throughput, the day where core utilities ship in Rust by default could be close at hand.

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Deployment guidance: testing, rollback, and checklist​

For home users, enthusiasts, and administrators planning to test or deploy Ubuntu 25.10, the combination of new tooling and a modern kernel requires a practical, staged approach:

• Create bootable daily/snapshot ISOs and test on non-production hardware first.
• Validate critical workflows (backup/restore, disk encryption unlock, sudo behavior, automation scripts).
• For systems running DKMS modules (NVIDIA, VirtualBox, ZFS), build and test the modules against the target kernel candidate. Keep an older kernel entry in GRUB for rollbacks.
• If you depend on advanced sudo features (I/O logging, sudoreplay, LDAP sudoers), verify whether those features are present in sudo-rs in your snapshot; plan to keep the GNU sudo package available until you confirm parity. Canonical retains the original sudo in archives to ease this transition. (discourse.ubuntu.com)
• Treat TPM-backed FDE as an experimental feature until bug reports stabilize — test full recovery scenarios, firmware update flows, and cross-device migrations.
• Consider a staged rollout for fleets: pilot group (test hardware variability), wider pilot (non-critical workstations), then production.

A focused pre-upgrade checklist:

• Backup system and configuration files.
• Snapshot VM images or create full disk images for rollback.
• Test login managers, GPU drivers, and display stack under both Wayland and X11 sessions.
• Validate any compliance or audit tooling that integrates with sudo or logs privileged command execution.

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Strengths, risks, and strategic implications​

Strengths​

• Security-first modernization: Rewriting privileged utilities in Rust can materially reduce memory-safety bugs and the resulting vulnerability surface.
• Fresher hardware support: Targeting newer kernels gives immediate access to driver and platform improvements, especially for new GPUs and silicon families.
• User-visible polish: GNOME 49 brings modernized apps, GPU-accelerated terminals, and improved multimedia and color-management features.

Risks​

• Integration parity: Behavioral differences in Rust implementations of core utilities and sudo may surprise legacy scripts, configuration management, and compliance tooling.
• Kernel RC at release: Shipping with a Release Candidate kernel increases the chance of late regressions; vendors with proprietary drivers may be affected.
• Operational cost: Admins will need to validate DKMS rebuilds, Secure Boot signing, and rollback strategies, increasing pre-deployment testing overhead.

Strategic implications​

• Canonical’s decisions reflect a broader Linux ecosystem trend: moving safety-critical code to memory-safe languages, accelerating hardware enablement schedules, and nudging the desktop ecosystem toward Wayland while pragmatically supporting X11 for compatibility.
• Enterprises with long change-control cycles will likely delay mass adoption until the first stable point updates arrive, whereas early-adopter workstations and developers stand to benefit from improved hardware support and performance.

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What to watch between now and release​

• Final upstream 6.17 kernel timing and any canonical decision to delay or replace the kernel with a later stable patch.
• Completion of integration tests and the resolution of key sudo-rs gaps (I/O logging, sudoreplay parity, LDAP-backed sudoers).
• GNOME 49 stable release notes and the final behavior of GDM regarding Wayland/X11 defaults, which may influence the default session choices in 25.10 images.
• Reports from early daily-image testers and Canonical’s bug-tracker flags for TPM-backed FDE bugs.

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Conclusion​

Ubuntu 25.10 Questing Quokka is shaping up to be an important evolutionary release: secure-by-design decisions like adopting sudo-rs and shipping Rust Coreutils align Ubuntu with a long-term risk-reduction strategy, while the decision to target Linux 6.17 demonstrates Canonical’s commitment to timely hardware enablement. GNOME 49’s last-minute re-enablement of X11 in GDM underscores the pragmatic compromises required when an ecosystem transitions away from decades-old infrastructure.
For users and administrators, the release offers real benefits — from potential micro-performance wins to better hardware support — but it also raises operational questions that warrant a deliberate testing posture. The short support window for this interim release (nine months) and the proximity to the 26.04 LTS development cycle mean the community’s testing and bug reports over the coming weeks will be crucial in smoothing the path to longer-term stability.
In short: Questing Quokka is ambitious and modernizing, and it will reward careful testing and staged adoption. The move toward Rust in system-level tooling is likely to be the most consequential change not just for this release, but for Ubuntu’s security posture going forward. (phoronix.com)

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Source: theregister.com Ubuntu 25.10 'Questing Quokka' in UI freeze as release nears