---
name: "ldom.conf"
section: "5"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["openbsd"]
url: "https://new.carta.tech/ldom.conf"
---

# ldom.conf(5)

Logical Domain configuration

## NAME

**ldom.conf** – Logical Domain configuration

## DESCRIPTION

**ldom.conf** is the configuration file to configure logical domains.

Domains are defined in the following format:

- **domain** *name* {...}

  Declare a scope for resources assigned to the specified domain. The scope must be opened and closed with curly braces and contains one or more of the following keywords, each on a separate line. A scope with *name* “primary” configures resources for the primary domain. If no configuration for the primary domain exists, it is assigned all CPU and memory resources not used by any guest domains.

- **vcpu** *number*\[:*stride*\]

  Declare the number of virtual CPUs assigned to a domain. Optionally a stride can be specified to allocate *stride* VCPUs at a time but assign only *number* VCPUs to the domain. This can be used to distribute virtual CPUs over the available CPU cores.

- **memory** *bytes*

  Declare the amount of memory assigned to a domain, in bytes. *bytes* can be specified with a human-readable scale, using the format described in scan\_scaled(3), e.g. 512M.

- **iodevice** *device*

  Assign the specified PCIe device to the guest domain. *device* may be either a device path (*/@400/@2/@0/@8*) or a pseudonym (*/SYS/MB/PCIE0*). This keyword can be used multiple times.

- **variable** *name*=*value*

  Set the specified NVRAM variable for the domain. See [eeprom(8)](/eeprom/8.md) for a list of OpenPROM variables. This keyword can be used multiple times.

- **vdisk** *file* \[*keyword*=*value* *...*\]

  The specified file is used to back a virtual disk of the guest domain. *file* can be a block device node or a disk image file created with the **create-vdisk** command. This keyword can be used multiple times. Unless *boot-device* is set with the **variable** command, the first disk will be the default boot device. Valid options are:

  - **devalias**=*name*

    Alias the virtual disk as *name*.

- **vnet** \[*keyword*=*value* *...*\]

  Assign a [vnet(4)](/vnet/4.md) network interface to the guest domain. This keyword can be used multiple times. Valid options are:

  - **mac-addr**=*address*

    Configure the MAC address of the interface.

  - **mtu**=*number*

    Configure the MTU of the interface.

  - **devalias**=*name*

    Alias the interface as *name*.

## EXAMPLES

Define a domain with 12 virtual cores, 4GB memory, two file based virtual disks and one virtual network interface:

```
domain "puffy" {
	vcpu 12
	memory 4G
	vdisk "/home/puffy/vdisk0"
	vdisk "/home/puffy/vdisk1"
	vnet
}
```

Define another one with slightly less resources:

```
domain "salmah" {
	vcpu 8
	memory 2G
	vdisk "/home/salmah/vdisk0"
	vdisk "/home/salmah/vdisk1"
	vnet
}
```

On a machine with 32 cores and 64GB physical memory, this leaves 12 cores and 58GB memory to the primary domain.

Use a *stride* step size to distribute VCPUs:

```
domain "marlus" {
	vcpu 2:4
	memory 4G
	vdisk "/home/marlus/vdisk0"
}
```

On a machine with eight threads per physical core, this allocates two strides of four VCPUs each for the guest domain but assigns only two VCPUs to it, i.e. makes it occupy an entire physical core while running on two threads only.

## SEE ALSO

[eeprom(8)](/eeprom/8.md), [ldomctl(8)](/ldomctl/8.md), [ldomd(8)](/ldomd/8.md)

## BUGS

The hypervisor requires a machine dependent amount of physical memory that is reserved automatically. Although the Physical Resource Inventory (PRI) seems to account for this by presenting less available memory, using the entire amount via **memory** is not always successful, e.g. the hypervisor would reject the configuration and fallback to “factory-default” upon resetting the machine.

If in doubt, assign **memory** to the “primary” **domain** explicitly, such that enough memory remains unused for the hypervisor to reserve. On T4 based machines, 1024 megabytes has proven to suffice.