LVM A B Daemon

Warning from Arvor Wiki : This tool was developed for Arvor Linux and is no longer in use. Any information provided here is outdated.

LVMABD (Logical Volume Manager A/B Daemon) was a system utility designed to manage automated A/B system recovery using Logical Volume Manager (LVM) snapshots. It was originally developed as the A/B implementation for Arvor Linux, prior to its removal in version 7. Unlike typical A/B update schemes that rely on immutable file systems, LVMABD was implemented in Arvor Linux despite the operating system being a mutable (non-immutable) distribution.

Mechanism of Operation The daemon operates by creating automated LVM snapshots to serve as seamless fallback points. Its operational workflow is structured as follows:

Snapshot Creation: During the boot process, the daemon automatically generates a snapshot of the root volume. This snapshot is designated with a _b suffix corresponding to the root volume (for instance, creating root_b in Arvor Linux). Failure Detection: After the snapshot is successfully created, the system proceeds to boot. If a critical failure—such as a kernel panic—occurs during this phase, the daemon registers the primary environment as unbootable. Automatic Fallback: Upon the next reboot, LVMABD automatically intervenes, merging the system state into the previously created snapshot (root_b) to restore functionality. Iterative Recovery: In the event that the primary fallback snapshot (root_b) also fails to boot successfully, the daemon initiates an extended recovery protocol, iterating through other available LVM snapshots until a stable system state is found. Historical Context LVMABD served as the core redundancy mechanism for Arvor Linux in earlier iterations. However, the feature was deprecated and subsequently removed from the operating system starting with Arvor Linux 7.