HA: Corrupted config files with null bytes on slave failover

[gsanchietti]

Problem

Recurring issue during HA failover: slave node corruption when rsync syncs from primary.

Config files become corrupted with null bytes, breaking services. Examples:

• /etc/config/firewall → fw4 fails, VRRP reports "Operation not permitted"
• /etc/nginx/mime.types → nginx won't start, shows binary data
• Files in rsync temp dir: /usr/share/keepalived/rsync/etc/nginx/mime.types

Symptoms

• Slave behaves incorrectly: activates interfaces incorrectly
• VRRP can't communicate with master (packets visible in tcpdump, but kernel blocks)
• Secondary filesystem reports improper unmount: "FAT-fs: Volume was not properly unmounted"

Root Cause

Overlayfs/tmpfs corruption during concurrent rsync writes. File system secondary didn't unmount cleanly.

Proposed Fix

• Reduce rsync update frequency from current to 5-10 minute intervals
• Move temporary sync files from disk to tmpfs
• Investigate overlayfs mount state during failover

[github-actions]

Testing image version: 8.8.0-dev.139.20260708122240.fe36b63

Testing image: 8.8.0-dev.246.20260721091943.3cf3652