Bug 2190226

Summary:	Support defining mount units on the kernel command line
Product:	Red Hat Enterprise Linux 9	Reporter:	Bryn M. Reeves <bmr>
Component:	systemd	Assignee:	David Tardon <dtardon>
Status:	POST ---	QA Contact:	Frantisek Sumsal <fsumsal>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	9.2	CC:	bmader, dtardon, jamacku, pdwyer, systemd-maint-list, vgoyal
Target Milestone:	rc	Keywords:	FutureFeature, Triaged
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:
Clones:	2190228 (view as bug list)		Environment:
Last Closed:		Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	2177839

Description Bryn M. Reeves 2023-04-27 15:31:46 UTC

Description of problem:
We'd like the ability to define mount units on the kernel command line. This allows the system to be booted into a snapshot of the system state (for e.g. using LVM2 CoW or thin provisioned snapshots) and enables rollback for system updates by allowing the administrator to preserve a copy of the prior system state and to optionally roll the system back to that state at a later time using the snapshot merge facility.

This would add new kernel command line syntax something like the following:

  systemd.mount=what:where:fstype:options

The feature has been proposed to upstream systemd and has received some initial positive comments:

  https://github.com/systemd/systemd/issues/27260

The new functionality would be added to the existing systemd-fstab-generator to write out mount units during early boot.

Version-Release number of selected component (if applicable):
systemd-250-12.el9_1

How reproducible:
100%

Steps to Reproduce:
1. man systemd-fstab-generator

Actual results:
No syntax exists for specifying kernel command line mount units.

Expected results:
The ability to specify mount units on the kernel command line

Additional info:
This will be used by Leapp and boom to provide rollback capable upgrades.

Comment 1 Bryn M. Reeves 2023-07-31 15:24:01 UTC

There are two additional pull requests for this feature that were merged for v254:

  fstab-generator: fixes for systemd.mount-extra=
  https://github.com/systemd/systemd/pull/28518

  fstab-generator: enable fsck for block device mounts specified in sys…
  https://github.com/systemd/systemd/pull/28544