scripts/pct-shrink-rootfs runs as root on the Proxmox node and keeps
the VMID. Without --yes it only measures and prints the plan.
It adds a temporary mp9 of the new size (Proxmox allocates and formats
it), rsyncs the root disk into it, and swaps it into rootfs under
Proxmox's config flock. The config is written like
file_set_contents does on pmxcfs (tmp file, then rename), after
checking that rootfs and mp9 did not change during the copy. The old
volume is kept as the first free unusedK and the exact delete command
is printed; pct rescan is not used, so other orphans of the VMID are
not pulled in.
It refuses snapshots and pending sections, a lock, template,
protection, HA, replication, any mount point, and sizes the data does
not fit (10 % headroom on top of the ext4 reserve and metadata, and an
inode check). On an rsync failure the new volume is freed by its volid.
Tests run the real script against stub pct, df, rsync, flock,
ha-manager, pvesr and id. README documents both shrink routes.
Design: docs/plans/lxc-shrink.md (section B).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
