Dear Qubes Community,
We're pleased to announce that the third [release candidate (RC)](#what-is-a-release-candidate) for Qubes OS 4.2.0 is now available for [testing](Testing new releases and updates | Qubes OS). The ISO and associated [verification files](Verifying signatures | Qubes OS) are available on the [downloads](Download Qubes OS | Qubes OS) page.
## Explanation for the early RC
We [announced RC2](Qubes OS 4.2.0-rc2 is available for testing | Qubes OS) approximately one week ago. Normally, RC2 would have been tested for [approximately five weeks](Version scheme | Qubes OS) before we announced RC3. However, RC2 contained several bugs (listed below), some of which prevented certain users from testing it. These bugs have been fixed in RC3. We've decided to release RC3 early, as an exception to our usual policy, in order to get these fixes out as quickly as possible so that more users can test 4.2 for longer before the eventual stable release.
## Main changes from RC2 to RC3
- Fixed: ["Installer in R4.2 does not warn about incompatible hardware" (#8345)](Installer in R4.2 does not warn about incompatible hardware · Issue #8345 · QubesOS/qubes-issues · GitHub)
- Fixed: ["Wi-Fi firmware missing from default templates on 4.2.0-rc2 ISO" (#8452)](Wi-Fi firmware missing from default templates on 4.2.0-rc2 ISO · Issue #8452 · QubesOS/qubes-issues · GitHub)
- Fixed: ["Qubes R4.2.0-rc2 cannot be installed on legacy BIOS system" (#8462)](Qubes R4.2.0-rc2 cannot be installed on legacy BIOS system · Issue #8462 · QubesOS/qubes-issues · GitHub)
- Fixed: ["R4.2 (rc1, rc2) unable to boot on Thinkpad T430 when UEFI is enabled" (#8464)](R4.2 (rc1, rc2) unable to boot on Thinkpad T430 when UEFI is enabled · Issue #8464 · QubesOS/qubes-issues · GitHub)
For an overview of major changes from Qubes 4.1 to 4.2, please see the [Qubes OS 4.2.0 release notes](Qubes OS 4.2.0 release notes | Qubes OS).
## When is the stable release?
That depends on the number of bugs discovered in this RC and their severity. As explained in our [release schedule](Version scheme | Qubes OS) documentation, our usual process after issuing a new RC is to collect bug reports, triage the bugs, and fix them. This usually takes around five weeks, depending on the bugs discovered. If warranted, we then issue a new RC that includes the fixes and repeat the whole process again. We continue this iterative procedure until we're left with an RC that's good enough to be declared the stable release. No one can predict, at the outset, how many iterations will be required (and hence how many RCs will be needed before a stable release), but we tend to get a clearer picture of this with each successive RC, which we share in this section in each RC announcement.
At this point, we can say that there will be at least one more RC after this one.
## Testing Qubes 4.2.0-rc3
Thank you to everyone who tested the previous Qubes 4.2.0 RCs! Due to your efforts, this new RC includes fixes for several bugs that were present in the previous RCs.
If you're willing to [test](Testing new releases and updates | Qubes OS) this new RC, you can help us improve the eventual stable release by [reporting any bugs you encounter](Issue tracking | Qubes OS). We encourage experienced users to join the [testing team](Joining the Testing Team).
A full list of issues affecting Qubes 4.2.0 is available [here](Issues · QubesOS/qubes-issues · GitHub). We strongly recommend [updating Qubes OS](How to update | Qubes OS) immediately after installation in order to apply all available bug fixes.
## Upgrading to Qubes 4.2.0-rc3
If you're currently running any Qubes 4.2.0 RC, you can upgrade to the latest RC by [updating normally](How to update | Qubes OS). However, please note that there have been some recent template changes, which are detailed in the [Qubes OS 4.2.0 release notes](Qubes OS 4.2.0 release notes | Qubes OS).
If you're currently on Qubes 4.1 and wish to test 4.2, please see [how to upgrade to Qubes 4.2](How to upgrade to Qubes 4.2 | Qubes OS), which details both clean installation and in-place upgrade options. As always, we strongly recommend [making a full backup](How to back up, restore, and migrate | Qubes OS) beforehand.
## Reminder: new signing key for Qubes OS 4.2
As a reminder, we published the following special announcement in [Qubes Canary 032](Qubes Canary 032 | Qubes OS) on 2022-09-14:
We plan to create a new Release Signing Key (RSK) for Qubes OS 4.2. Normally, we have only one RSK for each major release. However, for the 4.2 release, we will be using Qubes Builder version 2, which is a complete rewrite of the Qubes Builder. Out of an abundance of caution, we would like to isolate the build processes of the current stable 4.1 release and the upcoming 4.2 release from each other at the cryptographic level in order to minimize the risk of a vulnerability in one affecting the other. We are including this notice as a canary special announcement since introducing a new RSK for a minor release is an exception to our usual RSK management policy.
As always, we encourage you to [authenticate](Qubes security pack (qubes-secpack) | Qubes OS) this canary by [verifying its PGP signatures](Verifying signatures | Qubes OS). Specific instructions are also included in the [canary announcement](Qubes Canary 032 | Qubes OS).
As with all Qubes signing keys, we also encourage you to [authenticate](Verifying signatures | Qubes OS) the new Qubes OS Release 4.2 Signing Key, which is available in the [Qubes Security Pack (qubes-secpack)](Qubes security pack (qubes-secpack) | Qubes OS) as well as on the [downloads](Download Qubes OS | Qubes OS) page under the Qubes OS 4.2.0-rc3 ISO.
## What is a release candidate?
A release candidate (RC) is a software build that has the potential to become a stable release, unless significant bugs are discovered in testing. RCs are intended for more advanced (or adventurous!) users who are comfortable testing early versions of software that are potentially buggier than stable releases. You can read more about Qubes OS [supported releases](Supported releases | Qubes OS) and the [version scheme](Version scheme | Qubes OS) in our documentation.
This announcement is also available on the Qubes website: