hv_vss_daemon(8)

hv_vss_daemon8

Hyper-v volume shadow copy service daemon

Usage

hv_vss_daemon [-dn]

Overview

The hv_vss_daemon daemon provides the ability to freeze and thaw the file system for FreeBSD guest partitions running on Hyper-V.

Hyper-V allows administrators to backup or restore the FreeBSD guest partition. Administrators can use Windows Powershell scripts to backup or restore the FreeBSD VM.

The hv_vss_daemon accepts file system freeze and thaw requests from the hv_utils(4) driver and performs the actual file-system operation.

The file system freeze and thaw functionality is useful when the Hyper-V host wants to do live backup of FreeBSD guest. Hyper-V host sends file system freezing request to hv_vss_daemon which conducts the real operation. After successfully freezing file system, Hyper-V host takes a snapshot of the VM. In the future, Hyper-V host can restore the FreeBSD VM through that snapshot.

The options are as follows:

-d

Run as regular process instead of a daemon for debugging purpose.

-n

Generate debugging output.

Releases

Unchanged in 25 releases since FreeBSD 10.4-RELEASE.

  1. 10.4–16.0

History

The daemon was introduced in October 2016 and developed by Microsoft Corp.

Authors

FreeBSD support for hv_vss_daemon was first added by Microsoft BSD Integration Services Team ⟨[email protected]⟩.

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.