---
name: "viornd"
section: "4"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["openbsd"]
url: "https://new.carta.tech/viornd"
---

# viornd(4)

VirtIO random number device

## NAME

**viornd** – VirtIO random number device

## SYNOPSIS

**viornd\* at virtio? flags 0x00**

## DESCRIPTION

The **viornd** driver provides a virtual random number generator using a [virtio(4)](/virtio/4.md) entropy device provided by QEMU 1.3 and later, and possibly by other hypervisors.

As there is currently no way for **viornd** to determine how much entropy is needed, the second byte of the flags value can be used to configure how often it should request more entropy from the host. If the second lowest byte of the flags has a value from 1 to 15, **viornd** will ask for 16 bytes of entropy every 15 \* (1 \<\< value) seconds. For example, flags == 0x100 means an interval of 30 seconds, 0x500 means 8 minutes, 0xa00 means 256 minutes, and 0xf00 means about 6 days. For flags == 0, a default value will be used (currently 8 minutes). If the bit 0x1000 is set in the flags, **viornd** will only request entropy from the host once during system boot.

## SEE ALSO

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

## HISTORY

The **viornd** driver first appeared in OpenBSD 5.5.

## AUTHORS

The **viornd** driver was written by Stefan Fritsch ⟨*sf@sfritsch.de*⟩.