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= Put /var on its own Btrfs subvolume by default, on Silverblue and Kinoite
Summary
Silverblue and Kinoite: For new clean automatic installs, create a "var" subvolume to be mounted at /var.
Owner
- Name: Chris Murphy
- Email: bugzilla@colorremedies.com
Current status
- Targeted release: Fedora Linux 36
- Last updated: 2022-01-18
- FESCo issue: <will be assigned by the Wrangler>
- Tracker bug: <will be assigned by the Wrangler>
- Release notes tracker: <will be assigned by the Wrangler>
Detailed Description
Currently, Silverblue and Kinoite mimic other Fedora desktops. There is a "root" subvolume mounted at / and a "home" subvolume mounted at /home. This proposal will add a "var" subvolume to be mounted at /var. It will be located at the top-level of the Btrfs file system, along-side the "root" and "home" subvolumes, with an entry in /etc/fstab to mount it into the proper position during startup.
Feedback
Benefit to Fedora
Users who opt into Btrfs features like snapshots and rollbacks.
- By moving /var into its own subvolume, it will be excluded from snapshots and rollbacks of the "root" subvolume, which contains
/etcand/usr. - Users will find it straightforward to rollback "root" while not rolling back "var": including logs, VMs, databases, and so on.
- The ability to snapshot only "var" and use Btrfs send/receive to replicate only "var" permits for an efficient way of backing up the variable system data.
- A clean install can restore the "root", therefore it doesn't strictly need to be backed up. Meanwhile "var" and "home" can be restored using snapshot replication via send/receive.
Scope
- Proposal owners:
- changes to lorax and anaconda as needed so that Silverblue and Kinoite variants have their own installation kickstart, such that automatic/guided installation automatically creates "var".
- possible liability, determine whether the the addition of /var mount point for Btrfs scheme results in /var mount point for other schemes (and inhibit)
- changes to lorax and anaconda as needed so that Silverblue and Kinoite variants have their own installation kickstart, such that automatic/guided installation automatically creates "var".
- Other developers:
- Release engineering: #Releng issue number
- Policies and guidelines: N/A (not needed for this Change)
- Trademark approval: N/A (not needed for this Change)
- Alignment with Objectives:
Upgrade/compatibility impact
Change will not be applied to upgrades. But we can document steps to apply the change to existing installations.
How To Test
- Do a clean installation and check
dfand/etc/fstabfor an explicitly listed/varmount point.
User Experience
- The change won't generally be noticeable to users
- Users will see an additional
/varmount point in /etc/fstab, anddf - Some utilities, notably backup programs like borg backup, and rsync with -x option, will treat Btrfs subvolumes as separate file systems and may not descend (recursively) into them.
Dependencies
- Anaconda/blivet, lorax, and possibly kickstarts
Contingency Plan
- Contingency mechanism: (What to do? Who will do it?) N/A (not a System Wide Change)
- Contingency deadline: beta freeze (not a System Wide Change)
- Blocks release? No
Documentation
No significant documentation is planned other than this change proposal.
N/A (not a System Wide Change)