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| | | = Support for two boot mode variants in Fedora Cloud Images = |
| = Make btrfs the default file system for desktop variants = | |
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| == Summary == | | == Summary == |
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| For laptop and workstation installs of Fedora, we want to provide file system features to users in a transparent fashion. We want to add new features, while reducing the amount of expertise needed to deal with situations like [https://pagure.io/fedora-workstation/issue/152 running out of disk space.] Btrfs is well adapted to this role by design philosophy, let's make it the default.
| | With recent changes in public cloud bringing widespread support for the use of UEFI boot, it would beneficial to add hybrid boot support, unifying the classic and uefi boot in the same fedora cloud base images. |
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| == Owners == | | == Owner == |
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| * Name: [[User:Chrismurphy|Chris Murphy]], [[User:Ngompa|Neal Gompa]], [[User:Josef|Josef Bacik]], [[User:Salimma|Michel Alexandre Salim]], [[User:Dcavalca|Davide Cavalca]], [[User:eeickmeyer|Erich Eickmeyer]], [[User:ignatenkobrain|Igor Raits]], [[User:Raveit65|Wolfgang Ulbrich]], [[User:Zsun|Zamir SUN]], [[User:rdieter|Rex Dieter]], [[User:grinnz|Dan Book]], [[User:nonamedotc|Mukundan Ragavan]] | | * Name: [[User:Davdunc|David Duncan]], [[User:Chrismurphy|Chris Murphy]], [[User:Josef|Josef Bacik]], [[User:Salimma|Michel Alexandre Salim]], [[User:Dcavalca|Davide Cavalca]], [[User:Ngompa|Neal Gompa]], [[User:Dustymabe|Dusty Mabe]], [[User:Malmond|Matthew Almond]] |
| * Email: chrismurphy@fedoraproject.org, ngompa13@gmail.com, josef@toxicpanda.com, michel@michel-slm.name, dcavalca@fb.com, erich@ericheickmeyer.com, ignatenkobrain@fedoraproject.org, fedora@raveit.de, zsun@fedoraproject.org, rdieter@gmail.com, grinnz@gmail.com, nonamedotc@gmail.com | | * Email: davdunc@amazon.com, chrismurphy@fedoraproject.org, josef@toxicpanda.com, michel@michel-slm.name, dcavalca@fb.com, ngompa13@gmail.com, dusty@dustymabe.com, malmond@fb.com |
| <!--- UNCOMMENT only for Changes with assigned Shepherd (by FESCo)
| | * Products: Fedora Cloud Edition |
| * FESCo shepherd: [[User:FASAccountName| Shehperd name]] <email address> | | * Responsible WGs: Fedora Cloud WG |
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| * Products: All desktop editions, spins, and labs
| | == Current status == |
| * Responsible WGs: Workstation Working Group, KDE Special Interest Group
| | [[Category:ChangePageIncomplete]] |
| | <!-- When your change proposal page is completed and ready for review and announcement --> |
| | <!-- remove Category:ChangePageIncomplete and change it to Category:ChangeReadyForWrangler --> |
| | <!-- The Wrangler announces the Change to the devel-announce list and changes the category to Category:ChangeAnnounced (no action required) --> |
| | <!-- After review, the Wrangler will move your page to Category:ChangeReadyForFesco... if it still needs more work it will move back to Category:ChangePageIncomplete--> |
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| == Current status ==
| | <!-- Select proper category, default is Self Contained Change --> |
| [[Category:ChangeAcceptedF33]]
| | <!-- Category:SelfContainedChange--> |
| [[Category:SystemWideChange]] | | [[Category:SystemWideChange]] |
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| * Targeted release: [[Releases/33 | Fedora 33 ]] | | * Targeted release: [[Releases/35|Fedora Linux 35]] |
| * Last updated: <!-- this is an automatic macro — you don't need to change this line --> {{REVISIONYEAR}}-{{REVISIONMONTH}}-{{REVISIONDAY2}} | | * Last Updated: <!-- this is an automatic macro — you don't need to change this line --> {{REVISIONYEAR}}-{{REVISIONMONTH}}-{{REVISIONDAY2}} |
| <!-- After the change proposal is accepted by FESCo, tracking bug is created in Bugzilla and linked to this page
| | * FESCo Issue: ''Pending'' |
| Bugzilla states meaning as usual:
| | * Tracker bug: <will be assigned by the Wrangler> |
| ASSIGNED -> accepted by FESCo with on going development
| | * Release notes tracker: <will be assigned by the Wrangler> |
| MODIFIED -> change is substantially done and testable
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| ON_QA -> change is code completed and could be tested in the Beta release (optionally by QA)
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| CLOSED as NEXTRELEASE -> change is completed and verified and will be delivered in next release under development
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| * FESCo issue: [https://pagure.io/fesco/issue/2429 #2429] | |
| * Tracker bug: [https://bugzilla.redhat.com/show_bug.cgi?id=1851166 #1851166] | |
| * Release notes tracker: [https://pagure.io/fedora-docs/release-notes/issue/530 #530] | |
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| == Detailed Description == | | == Detailed Description == |
| | The cloud base will be created with multiple partitions and a GPT label instead of one single partition and implicit mbr |
| | The partitions will be: |
| | 1. An EFI System partition |
| | 1. A BIOS boot partition |
| | 1. A general data partition |
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| Fedora desktop edition/spin variants will switch to using Btrfs as the filesystem by default for new installs. Labs derived from these variants inherit this change, and other editions may opt into this change.
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| The change is based on the installer's custom partitioning Btrfs preset. It's been well tested for 7 years.
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| '''''Current partitioning'''''<br />
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| <span style="color: tomato">vg/root</span> LV mounted at <span style="color: tomato">/</span> and a <span style="color: tomato">vg/home</span> LV mounted at <span style="color: tomato">/home</span>. These are separate file system volumes, with separate free/used space.
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| '''''Proposed partitioning'''''<br />
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| <span style="color: tomato">root</span> subvolume mounted at <span style="color: tomato">/</span> and <span style="color: tomato">home</span> subvolume mounted at <span style="color: tomato">/home</span>. Subvolumes don't have size, they act mostly like directories, space is shared.
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| '''''Unchanged'''''<br />
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| <span style="color: tomato">/boot</span> will be a small ext4 volume. A separate boot is needed to boot dm-crypt sysroot installations; it's less complicated to keep the layout the same, regardless of whether sysroot is encrypted. There will be no automatic snapshots/rollbacks.
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| If you select to encrypt your data, LUKS (dm-crypt) will be still used as it is today (with the small difference that Btrfs is used instead of LVM+Ext4). There is upstream work on getting native encryption for Btrfs that will be considered once ready and is subject of a different change proposal in a future Fedora release.
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| === Optimizations (Optional) ===
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| The detailed description above is the proposal. It's intended to be a minimalist and transparent switch. It's also the same as was [[Features/F16BtrfsDefaultFs|proposed]] (and [https://lwn.net/Articles/446925/ accepted]) for Fedora 16. The following optimizations improve on the proposal, but are not critical. They are also transparent to most users. The general idea is agree to the base proposal first, and then consider these as enhancements. NOTE: These optimizations will not be used by default in Fedora 33, but are available for opt-in adoption and evaluation.
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| ==== Boot on Btrfs ====
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| * Instead of a 1G ext4 boot, create a 1G Btrfs boot.
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| * Advantage: Makes it possible to include in a snapshot and rollback regime. GRUB has stable support for Btrfs for 10+ years.
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| * Scope: Contingent on bootloader and installer team review and approval. blivet should use <code>mkfs.btrfs --mixed</code>.
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| ==== Compression ====
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| * Enable transparent compression using zstd on select directories: <span style="color: tomato">/usr</span>, <span style="color: tomato">/var/lib/flatpak</span>, <span style="color: tomato">~/.local/share/flatpak</span>
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| * Advantage: Saves space and significantly increase the lifespan of flash-based media by reducing write amplification. It may improve performance in some instances.
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| * Scope: Contingent on installer team review and approval to enhance anaconda to perform the installation using <code>mount -o compress=zstd</code>, then set the proper XATTR for each directory. The XATTR can't be set until after the directories are created via: rsync, rpm, or unsquashfs based installation.
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| ==== Additional subvolumes ====
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| * <span style="color: tomato">/var/log/</span>, <span style="color: tomato">/var/lib/libvirt/images</span> and <span style="color: tomato">~/.local/share/gnome-boxes/images/</span> will use separate subvolumes.
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| * Advantage: Makes it easier to excluded them from snapshots, rollbacks, and send/receive. (Btrfs snapshotting is not recursive, it stops at a nested subvolume.)
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| * Scope: Anaconda knows how to do this already, just change the kickstart to add additional subvolumes (minus the subvolume in <span style="color: tomato">~/</span>. GNOME Boxes will need enhancement to detect that the user home is on Btrfs and create <span style="color: tomato">~/.local/share/gnome-boxes/images/</span> as a subvolume.
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| == Feedback == | | == Feedback == |
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| ==== Red Hat doesn't support Btrfs? Can Fedora do this? ====
| | <!-- Pending discussion after proposal is wrangled --> |
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| Red Hat supports Fedora well, in many ways. But Fedora already works closely with, and depends on, upstreams. And this will be one of them. That's an important consideration for this proposal. The community has a stake in ensuring it is supported. Red Hat will never support Btrfs if Fedora rejects it. Fedora necessarily needs to be first, and make the persuasive case that it solves more problems than alternatives. Feature owners believe it does, hands down.
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| The Btrfs community has users that have been using it for most of the past decade at scale. It's been the default on openSUSE (and SUSE Linux Enterprise) since 2014, and Facebook has been using it for all their OS and data volumes, in their data centers, for almost as long. Btrfs is a mature, well-understood, and battle-tested file system, used on both desktop/container and server/cloud use-cases. We do have developers of the Btrfs filesystem maintaining and supporting the code in Fedora, one is a Change owner, so issues that are pinned to Btrfs can be addressed quickly.
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| ==== What about device-mapper alternatives? ====
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| dm-thin (thin provisioning): [https://pagure.io/fedora-workstation/issue/152 Issue #152] still happens, because the installer won't over provision by default. It still requires manual intervention by the user to identify and resolve the problem. Upon growing a file system on dm-thin, the pool is over committed, and file system sizes become a fantasy: they don't add up to the total physical storage available. The truth of used and free space is only known by the thin pool, and CLI and GUI programs are unprepared for this. Integration points like rpm free space checks or GNOME disk-space warnings would have to be adapted as well.
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| dm-vdo: is not yet merged, and isn't as straightforward to selectively enable per directory and per file, as is the case on Btrfs using <code>chattr +c</code> on <span style="color: tomato">/var/lib/flatpaks/</span>.
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| Btrfs solves the problems that need solving, with few side effects or pitfalls for users. It has more features we can take advantage of immediately and transparently: compression, integrity, and IO isolation. Many Btrfs features and optimizations can be opted into selectively per directory or file, such as compression and nodatacow, rather than as a layer that's either on or off.
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| ==== What about UI/UX and integration in the desktop? ====
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| If Btrfs isn't the default file system, there's no commitment, nor reason to work on any UI/UX integration. There are ideas to make certain features discoverable: selective compression; systemd-homed may take advantage of either Btrfs online resize, or near-term planned native encryption, which could make it possible to live convert non-encrypted homes to encrypted; and system snapshot and rollbacks.
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| Anaconda already has sophisticated Btrfs integration.
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| ==== What Btrfs features are recommended and supported? ====
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| The primary goal of this feature is to be largely transparent to the user. It does not require or expect users to learn new commands, or to engage in peculiar maintenance rituals.
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| The full set of Btrfs features that is considered stable and enabled by default upstream will be enabled in Fedora. Fedora is a community project. What is supported within Fedora depends on what the community decides to put forward in terms of resources.
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| The upstream [https://btrfs.wiki.kernel.org/index.php/Status Btrfs feature status page].
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| ==== Are subvolumes really mostly like directories? ====
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| Subvolumes behave like directories in terms of navigation in both the GUI and CLI, e.g. <code>cp</code>, <code>mv</code>, <code>du</code>, owner/permissions, and SELinux labels. They also share space, just like a directory.
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| But it is an incomplete answer.
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| A subvolume is an independent file tree, with its own POSIX namespace, and has its own pool of inodes. This means inode numbers repeat themselves on a Btrfs volume. Inodes are only unique within a given subvolume. A subvolume has its own st_dev, so if you use <code>stat FILE</code> it reports a device value referring to the subvolume the file is in. And it also means hard links can't be created between subvolumes. From this perspective, subvolumes start looking more like a separate file system. But subvolumes share most of the other trees, so they're not truly independent file systems. They're also not block devices.
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| == Benefit to Fedora == | | == Benefit to Fedora == |
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| Problems Btrfs helps solve:
| | This is a continuation from the changes outlined in the [[Releases/34|Fedora Linux 34]] Change to [[Changes:UnifyGrubConfig|Unify the Grub configuration files]]. There has been an overwhelming change in the public cloud architectures leading to the widespread support for UEFI boot and add support for other anticipated changes which make it best to modify the boot partitions to include both the classic boot as a fallback and the UEFI. This is going to require a group of modifications to the cloud base, including modifying the partition to support UEFI and a disk label change to GPT. With this change in place, the images will have greater flexibility to support file systems, such as btrfs, for boot across a number of supported providers and environments. |
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| * Users running out of free space on either <span style="color: tomato">/</span> or <span style="color: tomato">/home</span> [https://pagure.io/fedora-workstation/issue/152 Workstation issue #152] | | * To have a consistent configuration across all the architectures |
| ** "one big file system": no hard barriers like partitions or logical volumes | | * Allows the same image to be booted using either EFI or legacy BIOS. |
| ** transparent compression: significantly reduces write amplification, improves lifespan of storage hardware
| | * Allow easier migration from one environment to another where there is potentially a change in boot loader. |
| ** reflinks and snapshots are more efficient for use cases like containers (Podman supports both)
| | * Use the same documentation and commands for the avialable cloud architectures instead of having special cases for different environments. |
| * Storage devices can be flaky, resulting in data corruption
| | * Align with images generated by COSA and OSBuild on how the GRUB configuration files are used. |
| ** Everything is checksummed and verified on every read
| | * Align with other installation methods on how the partitions under <pre>/boot</pre> are defined |
| ** Corrupt data results in EIO (input/output error), instead of resulting in application confusion, and isn't replicated into backups and archives
| | * Align with other distributions, like CentOS and OpenSUSE, on support for GRUB configuration |
| * Poor desktop responsiveness when under pressure [https://pagure.io/fedora-workstation/issue/154 Workstation issue #154]
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| ** Btrfs has been tested in production to have proper IO isolation capability via cgroups2 | |
| ** Completes the resource control picture: memory, cpu, IO isolation
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| * File system resize
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| ** Whether provisioning an additional OS, or possible integration of systemd-homed, shrink capability is desired.
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| ** Online shrink and grow are fundamental to Btrfs design | |
| * Complex storage setups are... complicated
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| ** Simple and comprehensive command interface. One master command | |
| ** Simpler to boot, all code is in the kernel, no initramfs complexities
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| ** Simple and efficient file system replication, including incremental backups, with <code>btrfs send</code> and <code>btrfs receive</code>
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| == Scope == | | == Scope == |
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| * Proposal owners: | | * Proposal owners: |
| ** Submit PR's for Anaconda to change <code>default_scheme = BTRFS</code> to the proper product files. √ | | ** Submit PRs for Cloud Edition kickstarts to produce hybrid boot. |
| ** Disk image variants of desktops will have their kickstarts adjusted to produce btrfs disk images. √
| | * Release engineering: |
| ** The catch-all "Everything" netinstaller will use Btrfs by default. √
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| ** [https://pagure.io/fedora-qa/issue/634 Test days]: including building a community support network. √ (on-going)
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| ** Aid with documentation (in-progress)
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| ** Make btrfs in kernel built-in instead of a module (<code>CONFIG_BTRFS_FS=m</code> → <code>CONFIG_BTRFS_FS=y</code>) √
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| ** Bugs related to <code>btrfs</code> user-space commands should be filed against the <span style="color: blue">btrfs-progs</span> component. All other bugs should be filed against the <span style="color: blue">kernel</span> component, while also setting the Assignee field to: <span style="color: blue">fedora-kernel-btrfs@fedoraproject.org</span>
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| * Other developers:
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| ** Anaconda, review PRs and merge
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| ** Bootloader team, review PRs and merge
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| ** Recommended optimization <code>chattr +C</code> set on the containing directory for virt-manager and GNOME Boxes, via [https://www.redhat.com/archives/libvir-list/2020-July/msg01382.html libvirt] √
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| * Release engineering: [https://pagure.io/releng/issue/9545 #9545] | |
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| * Policies and guidelines: N/A | | * Policies and guidelines: N/A |
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| * Trademark approval: N/A | | * Trademark approval: N/A |
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| Change will not affect upgrades. | | Change will not affect upgrades. |
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| <s>Documentation will be provided for existing Btrfs users to "retrofit" their setups to that of a default Btrfs installation (base plus any approved options).</s> Layout has not been changed in Fedora 33.
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| == How To Test == | | == How To Test == |
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| '''''Today'''''<br />
| | Once the change lands in Rawhide, spin up the images in AWS, GCP, and |
| Do a custom partitioning installation; change the scheme drop-down menu to Btrfs; click the blue "automatically create partitions"; and install.<br />
| | KVM/OpenStack to test to see systems boot and run. Where possible, |
| Fedora 31, 32, Rawhide, on x86_64 and ARM.
| | test images on cloud virtual machines types where both methods are |
| | support. |
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| '''''Once change lands'''''<br />
| | Verify that the general data partition is properly grown in the case |
| It should be simple enough to test, just do a normal install.
| | that the root volume is larger than the image default. |
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| == User Experience == | | == User Experience == |
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| ==== Pros ====
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| * Mostly transparent. | | * Mostly transparent. |
| * Users won't run out of space in / or /home as a result of competition for free space between them. | | * Consistent recovery experience with other distributions and builds of Fedora Linux. |
| * Space savings and extend hardware life, via compression.
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| * Utilities for used and free space, CLI and GUI, are expected to behave the same. No special commands are required.
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| * More detailed information can be revealed by <code>btrfs</code> specific commands.
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| * <code>cp</code> command will create reflink copies [https://src.fedoraproject.org/rpms/coreutils/c/5d08d14b/ by default.]
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| ==== Enhancement opportunities ====
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| [https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/I3C5SECAXWNKMJSESZZOE35ZNM6MYL2W/ Nice UX if a MOTD popped up a link to support/recovery docs upon read-only boot.]
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| [https://bugzilla.redhat.com/show_bug.cgi?id=906591 updatedb does not index /home when /home is a bind mount] Also can affected rpm-ostree installations, including Silverblue.
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| [https://gitlab.gnome.org/GNOME/gnome-usage/-/issues/49 GNOME Usage: Incorrect numbers when using multiple btrfs subvolumes] This isn't Btrfs specific, happens with "one big ext4" volume as well.
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| [https://gitlab.gnome.org/GNOME/gnome-boxes/-/issues/88 GNOME Boxes, RFE: create qcow2 with 'nocow' option when on btrfs /home] This is Btrfs specific, and is a recommended optimization for both GNOME Boxes and virt-manager.
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| [https://github.com/containers/libpod/issues/6563 containers/libpod: automatically use btrfs driver if on btrfs]
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| == Dependencies == | | == Dependencies == |
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| None.
| | Grub2 |
| | | GPT |
| == Contingency Plan ==
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| * Contingency mechanism: Owner will revert changes back to LVM+ext4
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| * Contingency deadline: Beta freeze
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| * Blocks release? Yes
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| * Blocks product? Workstation and KDE
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| == Documentation == | | == Documentation == |
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| Strictly speaking no documentation is required reading for users. But there will be some Fedora documentation to help get the ball rolling.
| | No extra documentation is required reading for users. Supporting recovery documentation is already avaialble. |
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| For those who want to know more:
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| [https://btrfs.wiki.kernel.org/index.php/Main_Page btrfs wiki main page and full feature list.]
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| <code>man 5 btrfs</code> contains: mount options, features, swapfile support, checksum algorithms, and more<br />
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| <code>man btrfs</code> contains an overview of the btrfs subcommands<br />
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| <code>man btrfs <nowiki><subcommand></nowiki></code> will show the man page for that subcommand
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| NOTE: The btrfs command will accept an initial part of a subcommand name, as long as it is not ambiguous. These are equivalent commands:<br />
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| <code>btrfs subvolume snapshot</code><br />
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| <code>btrfs sub snap</code><br />
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| <code>btrfs su sn</code>
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| You'll discover your own convention. It might be preferable to write out the full command on forums and lists, but then maybe some folks don't learn about this useful shortcut?
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| For those who want to know a lot more:
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| [https://btrfs.wiki.kernel.org/index.php/Main_Page#Developer_documentation Btrfs developer documentation]<br />
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| [https://github.com/btrfs/btrfs-dev-docs/blob/master/trees.txt Btrfs trees]
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| == Release Notes == | | == Release Notes == |
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| The default file system on the desktop is Btrfs. It specifically excludes Fedora Server, Cloud, IoT, and CoreOS. As a consequence of release engineering complexities, the seldom marketed "Everything" netinstaller will use Btrfs by default. It's advised that headless and PXE installation use cases should use the Fedora Server netinstaller.
| | Fedora cloud images are updated to boot on both UEFI and legacy boot through a hybrid configuration. |
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| All installer images continue to have a custom partitioning option, enabling users to choose their preferred layout and file system.
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