---
name: "virtio_blk"
section: "4"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/virtio_blk"
---

# virtio\_blk(4)

VirtIO Block driver

## NAME

**virtio\_blk** – VirtIO Block driver

## SYNOPSIS

**device** **virtio\_blk**

In [loader.conf(5)](/loader.conf/5.md): **hw.vtblk.no\_ident** **hw.vtblk.***%d**.no\_ident* **hw.vtblk.writecache\_mode** **hw.vtblk.***%d**.writecache\_mode* **virtio\_blk\_load="YES"**

In [loader.conf(5)](/loader.conf/5.md) or [sysctl.conf(5)](/sysctl.conf/5.md): **dev.vtblk.***%d**.writecache\_mode*

## HARDWARE

The **virtio\_blk** device driver provides support for VirtIO block devices.

## LOADER TUNABLES

Tunables can be set at the [loader(8)](/loader/8.md) prompt before booting the kernel or stored in [loader.conf(5)](/loader.conf/5.md).

- *hw.vtblk.no\_ident*

  - *hw.vtblk.**%d**.no\_ident*

  These tunables disable retrieving the device identification string from the hypervisor either globally or per-device. The default value is 0.

- *hw.vtblk.writecache\_mode*

  - *hw.vtblk.**%d**.writecache\_mode*

  These tunables determine the write cache mode globally or per-device. The mode can changed only if the ConfigWCE feature is negotiated. Set to 0 for writethrough mode, 1 for writeback mode, and -1 to leave it as-is. The default value is to leave as-is.

## SYSCTL VARIABLES

The following variables are available as [sysctl(8)](/sysctl/8.md) variables.

- *dev.vtblk.**%d**.writecache\_mode*

  The write cache mode of the device can be either writethrough (0) or writeback (1). If the ConfigWCE feature is negotiated, the write cache mode can be toggled between writethrough and writeback.

## SEE ALSO

[virtio(4)](/virtio/4.md)

## HISTORY

The **virtio\_blk** driver was written by Bryan Venteicher ⟨*bryanv@FreeBSD.org*⟩. It first appeared in FreeBSD 9.0.