Proxmox VE and Corosync: Quorum Loss and pmxcfs Write Access

Proxmox VE utilizes the Corosync cluster engine to manage membership and maintain quorum. A critical dependency exists between the cluster's quorum state and the Proxmox Cluster File System (pmxcfs), which handles configuration files in /etc/pve.

In a multi-node environment, the system is designed to prevent split-brain scenarios by restricting write access to the cluster filesystem when a node no longer possesses a majority of votes. This ensures data consistency across the remaining healthy nodes.

When managing recovery in a degraded cluster, there is a need to understand the precise transition of the filesystem state and the implications of manual vote overrides.

• What is the exact mechanism that triggers the transition of /etc/pve to read-only mode upon quorum loss?
• How does the pvecm expected command interact with the pmxcfs lock to restore write capabilities?