Instance configuration

Instances

Properties

The following are direct instance properties and can’t be part of a profile:

• name

• architecture

Name is the instance name and can only be changed by renaming the instance.

Valid instance names must:

• Be between 1 and 63 characters long

• Be made up exclusively of letters, numbers and dashes from the ASCII table

• Not start with a digit or a dash

• Not end with a dash

This requirement is so that the instance name may properly be used in DNS records, on the filesystem, in various security profiles as well as the hostname of the instance itself.

Key/value configuration

The key/value configuration is namespaced with the following namespaces currently supported:

• boot (boot related options, timing, dependencies, …)

• cloud-init (cloud-init configuration)

• environment (environment variables)

• image (copy of the image properties at time of creation)

• limits (resource limits)

• nvidia (NVIDIA and CUDA configuration)

• raw (raw instance configuration overrides)

• security (security policies)

• user (storage for user properties, searchable)

• volatile (used internally by LXD to store internal data specific to an instance)

The currently supported keys are:

Key	Type	Default	Live update	Condition	Description
agent.nic_config	boolean	false	n/a	virtual-machine	Set the name and MTU of the default network interfaces to be the same as the instance devices (this is automatic for containers).
boot.autostart	boolean	-	n/a	-	Always start the instance when LXD starts (if not set, restore last state)
boot.autostart.delay	integer	0	n/a	-	Number of seconds to wait after the instance started before starting the next one
boot.autostart.priority	integer	0	n/a	-	What order to start the instances in (starting with highest)
boot.host_shutdown_timeout	integer	30	yes	-	Seconds to wait for instance to shutdown before it is force stopped
boot.stop.priority	integer	0	n/a	-	What order to shutdown the instances (starting with highest)
cloud-init.network-config	string	DHCP on eth0	no	-	Cloud-init network-config, content is used as seed value
cloud-init.user-data	string	#cloud-config	no	-	Cloud-init user-data, content is used as seed value
cloud-init.vendor-data	string	#cloud-config	no	-	Cloud-init vendor-data, content is used as seed value
cluster.evacuate	string	auto	n/a	-	What to do when evacuating the instance (auto, migrate, live-migrate, or stop)
environment.*	string	-	yes (exec)	-	key/value environment variables to export to the instance and set on exec
limits.cpu	string	-	yes	-	Number or range of CPUs to expose to the instance (defaults to 1 CPU for VMs)
limits.cpu.allowance	string	100%	yes	container	How much of the CPU can be used. Can be a percentage (e.g. 50%) for a soft limit or hard a chunk of time (25ms/100ms)
limits.cpu.priority	integer	10 (maximum)	yes	container	CPU scheduling priority compared to other instances sharing the same CPUs (overcommit) (integer between 0 and 10)
limits.disk.priority	integer	5 (medium)	yes	-	When under load, how much priority to give to the instance’s I/O requests (integer between 0 and 10)
limits.hugepages.64KB	string	-	yes	container	Fixed value in bytes (various suffixes supported, see Units for storage and network limits) to limit number of 64 KB hugepages (Available hugepage sizes are architecture dependent.)
limits.hugepages.1MB	string	-	yes	container	Fixed value in bytes (various suffixes supported, see Units for storage and network limits) to limit number of 1 MB hugepages (Available hugepage sizes are architecture dependent.)
limits.hugepages.2MB	string	-	yes	container	Fixed value in bytes (various suffixes supported, see Units for storage and network limits) to limit number of 2 MB hugepages (Available hugepage sizes are architecture dependent.)
limits.hugepages.1GB	string	-	yes	container	Fixed value in bytes (various suffixes supported, see Units for storage and network limits) to limit number of 1 GB hugepages (Available hugepage sizes are architecture dependent.)
limits.kernel.*	string	-	no	container	This limits kernel resources per instance (e.g. number of open files)
limits.memory	string	-	yes	-	Percentage of the host’s memory or fixed value in bytes (various suffixes supported, see Units for storage and network limits) (defaults to 1GiB for VMs)
limits.memory.enforce	string	hard	yes	container	If hard, instance can’t exceed its memory limit. If soft, the instance can exceed its memory limit when extra host memory is available
limits.memory.hugepages	boolean	false	no	virtual-machine	Controls whether to back the instance using hugepages rather than regular system memory
limits.memory.swap	boolean	true	yes	container	Controls whether to encourage/discourage swapping less used pages for this instance
limits.memory.swap.priority	integer	10 (maximum)	yes	container	The higher this is set, the least likely the instance is to be swapped to disk (integer between 0 and 10)
limits.network.priority	integer	0 (minimum)	yes	-	When under load, how much priority to give to the instance’s network requests (integer between 0 and 10)
limits.processes	integer	- (max)	yes	container	Maximum number of processes that can run in the instance
linux.kernel_modules	string	-	yes	container	Comma separated list of kernel modules to load before starting the instance
linux.sysctl.*	string	-	no	container	Allow for modify sysctl settings
migration.incremental.memory	boolean	false	yes	container	Incremental memory transfer of the instance’s memory to reduce downtime
migration.incremental.memory.goal	integer	70	yes	container	Percentage of memory to have in sync before stopping the instance
migration.incremental.memory.iterations	integer	10	yes	container	Maximum number of transfer operations to go through before stopping the instance
migration.stateful	boolean	false	no	virtual-machine	Allow for stateful stop/start and snapshots. This will prevent the use of some features that are incompatible with it
nvidia.driver.capabilities	string	compute,utility	no	container	What driver capabilities the instance needs (sets libnvidia-container NVIDIA_DRIVER_CAPABILITIES)
nvidia.runtime	boolean	false	no	container	Pass the host NVIDIA and CUDA runtime libraries into the instance
nvidia.require.cuda	string	-	no	container	Version expression for the required CUDA version (sets libnvidia-container NVIDIA_REQUIRE_CUDA)
nvidia.require.driver	string	-	no	container	Version expression for the required driver version (sets libnvidia-container NVIDIA_REQUIRE_DRIVER)
raw.apparmor	blob	-	yes	-	Apparmor profile entries to be appended to the generated profile
raw.idmap	blob	-	no	unprivileged container	Raw idmap configuration (e.g. “both 1000 1000”)
raw.lxc	blob	-	no	container	Raw LXC configuration to be appended to the generated one
raw.qemu	blob	-	no	virtual-machine	Raw Qemu configuration to be appended to the generated command line
raw.qemu.conf	blob	-	no	virtual-machine	Addition/override to the generated qemu.conf file
raw.seccomp	blob	-	no	container	Raw Seccomp configuration
security.devlxd	boolean	true	no	-	Controls the presence of /dev/lxd in the instance
security.devlxd.images	boolean	false	no	container	Controls the availability of the /1.0/images API over devlxd
security.idmap.base	integer	-	no	unprivileged container	The base host ID to use for the allocation (overrides auto-detection)
security.idmap.isolated	boolean	false	no	unprivileged container	Use an idmap for this instance that is unique among instances with isolated set
security.idmap.size	integer	-	no	unprivileged container	The size of the idmap to use
security.nesting	boolean	false	yes	container	Support running lxd (nested) inside the instance
security.privileged	boolean	false	no	container	Runs the instance in privileged mode
security.protection.delete	boolean	false	yes	-	Prevents the instance from being deleted
security.protection.shift	boolean	false	yes	container	Prevents the instance’s filesystem from being uid/gid shifted on startup
security.agent.metrics	boolean	true	no	virtual-machine	Controls whether the lxd-agent is queried for state information and metrics
security.secureboot	boolean	true	no	virtual-machine	Controls whether UEFI secure boot is enabled with the default Microsoft keys
security.syscalls.allow	string	-	no	container	A ‘\n’ separated list of syscalls to allow (mutually exclusive with security.syscalls.deny*)
security.syscalls.deny	string	-	no	container	A ‘\n’ separated list of syscalls to deny
security.syscalls.deny_compat	boolean	false	no	container	On x86_64 this enables blocking of compat_* syscalls, it is a no-op on other arches
security.syscalls.deny_default	boolean	true	no	container	Enables the default syscall deny
security.syscalls.intercept.bpf	boolean	false	no	container	Handles the bpf system call
security.syscalls.intercept.bpf.devices	boolean	false	no	container	Allows bpf programs for the devices cgroup in the unified hierarchy to be loaded.
security.syscalls.intercept.mknod	boolean	false	no	container	Handles the mknod and mknodat system calls (allows creation of a limited subset of char/block devices)
security.syscalls.intercept.mount	boolean	false	no	container	Handles the mount system call
security.syscalls.intercept.mount.allowed	string	-	yes	container	Specify a comma-separated list of filesystems that are safe to mount for processes inside the instance
security.syscalls.intercept.mount.fuse	string	-	yes	container	Whether to redirect mounts of a given filesystem to their fuse implemenation (e.g. ext4=fuse2fs)
security.syscalls.intercept.mount.shift	boolean	false	yes	container	Whether to mount shiftfs on top of filesystems handled through mount syscall interception
security.syscalls.intercept.sched_setscheduler	boolean	false	no	container	Handles the sched_setscheduler system call (allows increasing process priority)
security.syscalls.intercept.setxattr	boolean	false	no	container	Handles the setxattr system call (allows setting a limited subset of restricted extended attributes)
security.syscalls.intercept.sysinfo	boolean	false	no	container	Handles the sysinfo system call (to get cgroup-based resource usage information)
snapshots.schedule	string	-	no	-	Cron expression (<minute> <hour> <dom> <month> <dow>), or a comma separated list of schedule aliases <@hourly> <@daily> <@midnight> <@weekly> <@monthly> <@annually> <@yearly> <@startup> <@never>
snapshots.schedule.stopped	bool	false	no	-	Controls whether or not stopped instances are to be snapshoted automatically
snapshots.pattern	string	snap%d	no	-	Pongo2 template string which represents the snapshot name (used for scheduled snapshots and unnamed snapshots)
snapshots.expiry	string	-	no	-	Controls when snapshots are to be deleted (expects expression like 1M 2H 3d 4w 5m 6y)
user.*	string	-	n/a	-	Free form user key/value storage (can be used in search)

The following volatile keys are currently internally used by LXD:

Key	Type	Default	Description
volatile.apply_template	string	-	The name of a template hook which should be triggered upon next startup
volatile.apply_nvram	string	-	Whether or not to regenerate VM NVRAM on next start
volatile.base_image	string	-	The hash of the image the instance was created from, if any
volatile.cloud-init.instance-id	string	-	The instance-id (UUID) exposed to cloud-init
volatile.evacuate.origin	string	-	The origin (cluster member) of the evacuated instance
volatile.idmap.base	integer	-	The first id in the instance’s primary idmap range
volatile.idmap.current	string	-	The idmap currently in use by the instance
volatile.idmap.next	string	-	The idmap to use next time the instance starts
volatile.last_state.idmap	string	-	Serialized instance uid/gid map
volatile.last_state.power	string	-	Instance state as of last host shutdown
volatile.vsock_id	string	-	Instance vsock ID used as of last start
volatile.uuid	string	-	Instance UUID (globally unique across all servers and projects)
volatile.<name>.apply_quota	string	-	Disk quota to be applied on next instance start
volatile.<name>.ceph_rbd	string	-	RBD device path for Ceph disk devices
volatile.<name>.host_name	string	-	Network device name on the host
volatile.<name>.hwaddr	string	-	Network device MAC address (when no hwaddr property is set on the device itself)
volatile.<name>.last_state.created	string	-	Whether or not the network device physical device was created (“true” or “false”)
volatile.<name>.last_state.mtu	string	-	Network device original MTU used when moving a physical device into an instance
volatile.<name>.last_state.hwaddr	string	-	Network device original MAC used when moving a physical device into an instance
volatile.<name>.last_state.vf.id	string	-	SR-IOV Virtual function ID used when moving a VF into an instance
volatile.<name>.last_state.vf.hwaddr	string	-	SR-IOV Virtual function original MAC used when moving a VF into an instance
volatile.<name>.last_state.vf.vlan	string	-	SR-IOV Virtual function original VLAN used when moving a VF into an instance
volatile.<name>.last_state.vf.spoofcheck	string	-	SR-IOV Virtual function original spoof check setting used when moving a VF into an instance

Additionally, those user keys have become common with images (support isn’t guaranteed):

Key	Type	Default	Description
user.meta-data	string	-	Cloud-init meta-data, content is appended to seed value

Note that while a type is defined above as a convenience, all values are stored as strings and should be exported over the REST API as strings (which makes it possible to support any extra values without breaking backward compatibility).

Those keys can be set using the lxc tool with:

lxc config set <instance> <key> <value>

Volatile keys can’t be set by the user and can only be set directly against an instance.

The raw keys allow direct interaction with the backend features that LXD itself uses, setting those may very well break LXD in non-obvious ways and should whenever possible be avoided.

CPU limits

The CPU limits are implemented through a mix of the cpuset and cpu CGroup controllers.

limits.cpu results in CPU pinning through the cpuset controller. A set of CPUs (e.g. 1,2,3) or a CPU range (e.g. 0-3) can be specified.

When a number of CPUs is specified instead (e.g. 4), LXD will do dynamic load-balancing of all instances that aren’t pinned to specific CPUs, trying to spread the load on the machine. Instances will then be re-balanced every time an instance starts or stops as well as whenever a CPU is added to the system.

To pin to a single CPU, you have to use the range syntax (e.g. 1-1) to differentiate it from a number of CPUs.

limits.cpu.allowance drives either the CFS scheduler quotas when passed a time constraint, or the generic CPU shares mechanism when passed a percentage value.

The time constraint (e.g. 20ms/50ms) is relative to one CPU worth of time, so to restrict to two CPUs worth of time, something like 100ms/50ms should be used.

When using a percentage value, the limit will only be applied when under load and will be used to calculate the scheduler priority for the instance, relative to any other instance which is using the same CPU(s).

limits.cpu.priority is another knob which is used to compute that scheduler priority score when a number of instances sharing a set of CPUs have the same percentage of CPU assigned to them.

VM CPU topology

LXD virtual machines default to having just one vCPU allocated which shows up as matching the host CPU vendor and type but has a single core and no threads.

When limits.cpu is set to a single integer, this will cause multiple vCPUs to be allocated and exposed to the guest as full cores. Those vCPUs will not be pinned to specific physical cores on the host.

When limits.cpu is set to a range or comma separate list of CPU IDs (as provided by lxc info --resources), then the vCPUs will be pinned to those physical cores. In this scenario, LXD will check whether the CPU configuration lines up with a realistic hardware topology and if it does, it will replicate that topology in the guest.

This means that if the pinning configuration includes 8 threads, with each pair of thread coming from the same core and an even number of cores spread across two CPUs, LXD will have the guest show two CPUs, each with two cores and each core with two threads. The NUMA layout is similarly replicated and in this scenario, the guest would most likely end up with two NUMA nodes, one for each CPU socket.

In such an environment with multiple NUMA nodes, the memory will similarly be divided across NUMA nodes and be pinned accordingly on the host and then exposed to the guest.

All this allows for very high performance operations in the guest as the guest scheduler can properly reason about sockets, cores and threads as well as consider NUMA topology when sharing memory or moving processes across NUMA nodes.

Devices configuration

LXD will always provide the instance with the basic devices which are required for a standard POSIX system to work. These aren’t visible in instance or profile configuration and may not be overridden.

Those include:

• /dev/null (character device)

• /dev/zero (character device)

• /dev/full (character device)

• /dev/console (character device)

• /dev/tty (character device)

• /dev/random (character device)

• /dev/urandom (character device)

• /dev/net/tun (character device)

• /dev/fuse (character device)

• lo (network interface)

Anything else has to be defined in the instance configuration or in one of its profiles. The default profile will typically contain a network interface to become eth0 in the instance.

To add extra devices to an instance, device entries can be added directly to an instance, or to a profile.

Devices may be added or removed while the instance is running.

Every device entry is identified by a unique name. If the same name is used in a subsequent profile or in the instance’s own configuration, the whole entry is overridden by the new definition.

Device names are limited to a maximum of 64 characters.

Device entries are added to an instance through:

lxc config device add <instance> <name> <type> [key=value]...

or to a profile with:

lxc profile device add <profile> <name> <type> [key=value]...

Device types

LXD supports the following device types:

ID (database)	Name	Condition	Description
0	none	-	Inheritance blocker
1	nic	-	Network interface
2	disk	-	Mountpoint inside the instance
3	unix-char	container	Unix character device
4	unix-block	container	Unix block device
5	usb	-	USB device
6	gpu	-	GPU device
7	infiniband	container	Infiniband device
8	proxy	container	Proxy device
9	unix-hotplug	container	Unix hotplug device
10	tpm	-	TPM device
11	pci	VM	PCI device

Type: none

Supported instance types: container, VM

A none type device doesn’t have any property and doesn’t create anything inside the instance.

It’s only purpose it to stop inheritance of devices coming from profiles.

To do so, just add a none type device with the same name of the one you wish to skip inheriting. It can be added in a profile being applied after the profile it originated from or directly on the instance.

Type: nic

LXD supports several different kinds of network devices (referred to as Network Interface Controller or NIC).

When adding a network device to an instance, there are two ways to specify the type of device you want to add; either by specifying the nictype property or using the network property.

Specifying a NIC using the network property

When specifying the network property, the NIC is linked to an existing managed network and the nictype is automatically detected based on the network’s type.

Some of the NICs properties are inherited from the network rather than being customisable for each NIC.

These are detailed in the “Managed” column in the NIC specific sections below.

NICs Available:

See the NIC’s settings below for details about which properties are available.

The following NICs can be specified using the nictype or network properties:

• bridged: Uses an existing bridge on the host and creates a virtual device pair to connect the host bridge to the instance.

• macvlan: Sets up a new network device based on an existing one but using a different MAC address.

• sriov: Passes a virtual function of an SR-IOV enabled physical network device into the instance.

The following NICs can be specified using only the network property:

• ovn: Uses an existing OVN network and creates a virtual device pair to connect the instance to it.

The following NICs can be specified using only the nictype property:

• physical: Straight physical device passthrough from the host. The targeted device will vanish from the host and appear in the instance.

• ipvlan: Sets up a new network device based on an existing one using the same MAC address but a different IP.

• p2p: Creates a virtual device pair, putting one side in the instance and leaving the other side on the host.

• routed: Creates a virtual device pair to connect the host to the instance and sets up static routes and proxy ARP/NDP entries to allow the instance to join the network of a designated parent interface.

nic: bridged

Supported instance types: container, VM

Selected using: nictype, network

Uses an existing bridge on the host and creates a virtual device pair to connect the host bridge to the instance.

Device configuration properties:

Key	Type	Default	Required	Managed	Description
parent	string	-	yes	yes	The name of the host device
network	string	-	yes	no	The LXD network to link device to (instead of parent)
name	string	kernel assigned	no	no	The name of the interface inside the instance
mtu	integer	parent MTU	no	yes	The MTU of the new interface
hwaddr	string	randomly assigned	no	no	The MAC address of the new interface
host_name	string	randomly assigned	no	no	The name of the interface inside the host
limits.ingress	string	-	no	no	I/O limit in bit/s for incoming traffic (various suffixes supported, see Units for storage and network limits)
limits.egress	string	-	no	no	I/O limit in bit/s for outgoing traffic (various suffixes supported, see Units for storage and network limits)
limits.max	string	-	no	no	Same as modifying both limits.ingress and limits.egress
ipv4.address	string	-	no	no	An IPv4 address to assign to the instance through DHCP (Can be none to restrict all IPv4 traffic when security.ipv4_filtering is set)
ipv6.address	string	-	no	no	An IPv6 address to assign to the instance through DHCP (Can be none to restrict all IPv6 traffic when security.ipv6_filtering is set)
ipv4.routes	string	-	no	no	Comma delimited list of IPv4 static routes to add on host to NIC
ipv6.routes	string	-	no	no	Comma delimited list of IPv6 static routes to add on host to NIC
ipv4.routes.external	string	-	no	no	Comma delimited list of IPv4 static routes to route to the NIC and publish on uplink network (BGP)
ipv6.routes.external	string	-	no	no	Comma delimited list of IPv6 static routes to route to the NIC and publish on uplink network (BGP)
security.mac_filtering	boolean	false	no	no	Prevent the instance from spoofing another’s MAC address
security.ipv4_filtering	boolean	false	no	no	Prevent the instance from spoofing another’s IPv4 address (enables mac_filtering)
security.ipv6_filtering	boolean	false	no	no	Prevent the instance from spoofing another’s IPv6 address (enables mac_filtering)
maas.subnet.ipv4	string	-	no	yes	MAAS IPv4 subnet to register the instance in
maas.subnet.ipv6	string	-	no	yes	MAAS IPv6 subnet to register the instance in
boot.priority	integer	-	no	no	Boot priority for VMs (higher boots first)
vlan	integer	-	no	no	The VLAN ID to use for untagged traffic (Can be none to remove port from default VLAN)
vlan.tagged	integer	-	no	no	Comma delimited list of VLAN IDs or VLAN ranges to join for tagged traffic
security.port_isolation	boolean	false	no	no	Prevent the NIC from communicating with other NICs in the network that have port isolation enabled

nic: macvlan

Supported instance types: container, VM

Selected using: nictype, network

Sets up a new network device based on an existing one but using a different MAC address.

Device configuration properties:

Key	Type	Default	Required	Managed	Description
parent	string	-	yes	yes	The name of the host device
network	string	-	yes	no	The LXD network to link device to (instead of parent)
name	string	kernel assigned	no	no	The name of the interface inside the instance
mtu	integer	parent MTU	no	yes	The MTU of the new interface
hwaddr	string	randomly assigned	no	no	The MAC address of the new interface
vlan	integer	-	no	no	The VLAN ID to attach to
gvrp	boolean	false	no	no	Register VLAN using GARP VLAN Registration Protocol
maas.subnet.ipv4	string	-	no	yes	MAAS IPv4 subnet to register the instance in
maas.subnet.ipv6	string	-	no	yes	MAAS IPv6 subnet to register the instance in
boot.priority	integer	-	no	no	Boot priority for VMs (higher boots first)

nic: sriov

Supported instance types: container, VM

Selected using: nictype, network

Passes a virtual function of an SR-IOV enabled physical network device into the instance.

Device configuration properties:

Key	Type	Default	Required	Managed	Description
parent	string	-	yes	yes	The name of the host device
network	string	-	yes	no	The LXD network to link device to (instead of parent)
name	string	kernel assigned	no	no	The name of the interface inside the instance
mtu	integer	kernel assigned	no	yes	The MTU of the new interface
hwaddr	string	randomly assigned	no	no	The MAC address of the new interface
security.mac_filtering	boolean	false	no	no	Prevent the instance from spoofing another’s MAC address
vlan	integer	-	no	no	The VLAN ID to attach to
maas.subnet.ipv4	string	-	no	yes	MAAS IPv4 subnet to register the instance in
maas.subnet.ipv6	string	-	no	yes	MAAS IPv6 subnet to register the instance in
boot.priority	integer	-	no	no	Boot priority for VMs (higher boots first)

nic: ovn

Supported instance types: container, VM

Selected using: network

Uses an existing OVN network and creates a virtual device pair to connect the instance to it.

Device configuration properties:

Key	Type	Default	Required	Managed	Description
network	string	-	yes	yes	The LXD network to link device to
acceleration	string	none	no	no	Enable hardware offloading. Either none or sriov (see SR-IOV hardware acceleration below)
name	string	kernel assigned	no	no	The name of the interface inside the instance
host_name	string	randomly assigned	no	no	The name of the interface inside the host
hwaddr	string	randomly assigned	no	no	The MAC address of the new interface
ipv4.address	string	-	no	no	An IPv4 address to assign to the instance through DHCP
ipv6.address	string	-	no	no	An IPv6 address to assign to the instance through DHCP
ipv4.routes	string	-	no	no	Comma delimited list of IPv4 static routes to route to the NIC
ipv6.routes	string	-	no	no	Comma delimited list of IPv6 static routes to route to the NIC
ipv4.routes.external	string	-	no	no	Comma delimited list of IPv4 static routes to route to the NIC and publish on uplink network
ipv6.routes.external	string	-	no	no	Comma delimited list of IPv6 static routes to route to the NIC and publish on uplink network
boot.priority	integer	-	no	no	Boot priority for VMs (higher boots first)
security.acls	string	-	no	no	Comma separated list of Network ACLs to apply
security.acls.default.ingress.action	string	reject	no	no	Action to use for ingress traffic that doesn’t match any ACL rule
security.acls.default.egress.action	string	reject	no	no	Action to use for egress traffic that doesn’t match any ACL rule
security.acls.default.ingress.logged	boolean	false	no	no	Whether to log ingress traffic that doesn’t match any ACL rule
security.acls.default.egress.logged	boolean	false	no	no	Whether to log egress traffic that doesn’t match any ACL rule

SR-IOV hardware acceleration:

In order to use acceleration=sriov you need to have a compatible SR-IOV switchdev capable phyical NIC in your LXD host. LXD assumes that the physical NIC (PF) will be configured in switchdev mode and will be connected to the OVN integration OVS bridge and that it will have one or more virtual functions (VFs) active.

The basic prerequisite setup steps to achieve this are:

PF and VF setup:

Activate some VFs on PF (in this case called enp9s0f0np0 with a PCI address of 0000:09:00.0) and unbind them. Then enable switchdev mode and hw-tc-offload on the the PF. Finally rebind the VFs.

echo 4 > /sys/bus/pci/devices/0000:09:00.0/sriov_numvfs
for i in $(lspci -nnn | grep "Virtual Function" | cut -d' ' -f1); do echo 0000:$i > /sys/bus/pci/drivers/mlx5_core/unbind; done
devlink dev eswitch set pci/0000:09:00.0 mode switchdev
ethtool -K enp9s0f0np0 hw-tc-offload on
for i in $(lspci -nnn | grep "Virtual Function" | cut -d' ' -f1); do echo 0000:$i > /sys/bus/pci/drivers/mlx5_core/bind; done

OVS setup:

Enable hardware offload and add the PF NIC to the integration bridge (normally callled br-int):

ovs-vsctl set open_vswitch . other_config:hw-offload=true
systemctl restart openvswitch-switch
ovs-vsctl add-port br-int enp9s0f0np0
ip link set enp9s0f0np0 up

nic: physical

Supported instance types: container, VM

Selected using: nictype

Straight physical device passthrough from the host. The targeted device will vanish from the host and appear in the instance.

Device configuration properties:

Key	Type	Default	Required	Description
parent	string	-	yes	The name of the host device
name	string	kernel assigned	no	The name of the interface inside the instance
mtu	integer	parent MTU	no	The MTU of the new interface
hwaddr	string	randomly assigned	no	The MAC address of the new interface
vlan	integer	-	no	The VLAN ID to attach to
gvrp	boolean	false	no	Register VLAN using GARP VLAN Registration Protocol
maas.subnet.ipv4	string	-	no	MAAS IPv4 subnet to register the instance in
maas.subnet.ipv6	string	-	no	MAAS IPv6 subnet to register the instance in
boot.priority	integer	-	no	Boot priority for VMs (higher boots first)

nic: ipvlan

Supported instance types: container

Selected using: nictype

Sets up a new network device based on an existing one using the same MAC address but a different IP.

LXD currently supports IPVLAN in L2 and L3S mode.

In this mode, the gateway is automatically set by LXD, however IP addresses must be manually specified using either one or both of ipv4.address and ipv6.address settings before instance is started.

For DNS, the nameservers need to be configured inside the instance, as these will not automatically be set.

It requires the following sysctls to be set:

If using IPv4 addresses:

net.ipv4.conf.<parent>.forwarding=1

If using IPv6 addresses:

net.ipv6.conf.<parent>.forwarding=1
net.ipv6.conf.<parent>.proxy_ndp=1

Device configuration properties:

Key	Type	Default	Required	Description
parent	string	-	yes	The name of the host device
name	string	kernel assigned	no	The name of the interface inside the instance
mtu	integer	parent MTU	no	The MTU of the new interface
mode	string	l3s	no	The IPVLAN mode (either l2 or l3s)
hwaddr	string	randomly assigned	no	The MAC address of the new interface
ipv4.address	string	-	no	Comma delimited list of IPv4 static addresses to add to the instance. In l2 mode these can be specified as CIDR values or singular addresses (if singular a subnet of /24 is used).
ipv4.gateway	string	auto	no	In l3s mode, whether to add an automatic default IPv4 gateway, can be auto or none. In l2 mode specifies the IPv4 address of the gateway.
ipv4.host_table	integer	-	no	The custom policy routing table ID to add IPv4 static routes to (in addition to main routing table).
ipv6.address	string	-	no	Comma delimited list of IPv6 static addresses to add to the instance. In l2 mode these can be specified as CIDR values or singular addresses (if singular a subnet of /64 is used).
ipv6.gateway	string	auto (l3s), - (l2)	no	In l3s mode, whether to add an automatic default IPv6 gateway, can be auto or none. In l2 mode specifies the IPv6 address of the gateway.
ipv6.host_table	integer	-	no	The custom policy routing table ID to add IPv6 static routes to (in addition to main routing table).
vlan	integer	-	no	The VLAN ID to attach to
gvrp	boolean	false	no	Register VLAN using GARP VLAN Registration Protocol

nic: p2p

Supported instance types: container, VM

Selected using: nictype

Creates a virtual device pair, putting one side in the instance and leaving the other side on the host.

Device configuration properties:

Key	Type	Default	Required	Description
name	string	kernel assigned	no	The name of the interface inside the instance
mtu	integer	kernel assigned	no	The MTU of the new interface
hwaddr	string	randomly assigned	no	The MAC address of the new interface
host_name	string	randomly assigned	no	The name of the interface inside the host
limits.ingress	string	-	no	I/O limit in bit/s for incoming traffic (various suffixes supported, see Units for storage and network limits)
limits.egress	string	-	no	I/O limit in bit/s for outgoing traffic (various suffixes supported, see Units for storage and network limits)
limits.max	string	-	no	Same as modifying both limits.ingress and limits.egress
ipv4.routes	string	-	no	Comma delimited list of IPv4 static routes to add on host to NIC
ipv6.routes	string	-	no	Comma delimited list of IPv6 static routes to add on host to NIC
boot.priority	integer	-	no	Boot priority for VMs (higher boots first)

nic: routed

Supported instance types: container, VM

Selected using: nictype

This NIC type is similar in operation to IPVLAN, in that it allows an instance to join an external network without needing to configure a bridge and shares the host’s MAC address.

However it differs from IPVLAN because it does not need IPVLAN support in the kernel and the host and instance can communicate with each other.

It will also respect netfilter rules on the host and will use the host’s routing table to route packets which can be useful if the host is connected to multiple networks.

IP addresses must be manually specified using either one or both of ipv4.address and ipv6.address settings before the instance is started.

For containers it uses a veth pair, and for VMs it uses a TAP device. It then configures the following link-local gateway IPs on the host end which are then set as the default gateways in the instance:

169.254.0.1 fe80::1

For containers these are automatically set as default gateways on the instance NIC interface. But for VMs the IP addresses and gateways will need to be configured manually or via a mechanism like cloud-init.

Note also that if your container image is configured to perform DHCP on the interface it will likely remove the automatically added configuration, and will need to be configured manually or via a mechanism like cloud-init.

It then configures static routes on the host pointing to the instance’s veth interface for all of the instance’s IPs.

This nic can operate with and without a parent network interface set.

With the parent network interface set proxy ARP/NDP entries of the instance’s IPs are added to the parent interface allowing the instance to join the parent interface’s network at layer 2.

For DNS, the nameservers need to be configured inside the instance, as these will not automatically be set.

It requires the following sysctls to be set:

If using IPv4 addresses:

net.ipv4.conf.<parent>.forwarding=1

If using IPv6 addresses:

net.ipv6.conf.all.forwarding=1
net.ipv6.conf.<parent>.forwarding=1
net.ipv6.conf.all.proxy_ndp=1
net.ipv6.conf.<parent>.proxy_ndp=1

Each NIC device can have multiple IP addresses added to them. However it may be desirable to utilise multiple routed NIC interfaces. In these cases one should set the ipv4.gateway and ipv6.gateway values to “none” on any subsequent interfaces to avoid default gateway conflicts. It may also be useful to specify a different host-side address for these subsequent interfaces using ipv4.host_address and ipv6.host_address respectively.

Device configuration properties:

Key	Type	Default	Required	Description
parent	string	-	no	The name of the host device to join the instance to
name	string	kernel assigned	no	The name of the interface inside the instance
host_name	string	randomly assigned	no	The name of the interface inside the host
mtu	integer	parent MTU	no	The MTU of the new interface
hwaddr	string	randomly assigned	no	The MAC address of the new interface
limits.ingress	string	-	no	I/O limit in bit/s for incoming traffic (various suffixes supported, see Units for storage and network limits)
limits.egress	string	-	no	I/O limit in bit/s for outgoing traffic (various suffixes supported, see Units for storage and network limits)
limits.max	string	-	no	Same as modifying both limits.ingress and limits.egress
ipv4.address	string	-	no	Comma delimited list of IPv4 static addresses to add to the instance
ipv4.routes	string	-	no	Comma delimited list of IPv4 static routes to add on host to NIC (without L2 ARP/NDP proxy)
ipv4.gateway	string	auto	no	Whether to add an automatic default IPv4 gateway, can be “auto” or “none”
ipv4.host_address	string	169.254.0.1	no	The IPv4 address to add to the host-side veth interface
ipv4.host_table	integer	-	no	The custom policy routing table ID to add IPv4 static routes to (in addition to main routing table)
ipv4.neighbor_probe	boolean	true	no	Whether to probe the parent network for IP address availability.
ipv6.address	string	-	no	Comma delimited list of IPv6 static addresses to add to the instance
ipv6.routes	string	-	no	Comma delimited list of IPv6 static routes to add on host to NIC (without L2 ARP/NDP proxy)
ipv6.gateway	string	auto	no	Whether to add an automatic default IPv6 gateway, can be “auto” or “none”
ipv6.host_address	string	fe80::1	no	The IPv6 address to add to the host-side veth interface
ipv6.host_table	integer	-	no	The custom policy routing table ID to add IPv6 static routes to (in addition to main routing table)
ipv6.neighbor_probe	boolean	true	no	Whether to probe the parent network for IP address availability.
vlan	integer	-	no	The VLAN ID to attach to
gvrp	boolean	false	no	Register VLAN using GARP VLAN Registration Protocol

bridged, macvlan or ipvlan for connection to physical network

The bridged, macvlan and ipvlan interface types can be used to connect to an existing physical network.

macvlan effectively lets you fork your physical NIC, getting a second interface that’s then used by the instance. This saves you from creating a bridge device and veth pairs and usually offers better performance than a bridge.

The downside to this is that macvlan devices while able to communicate between themselves and to the outside, aren’t able to talk to their parent device. This means that you can’t use macvlan if you ever need your instances to talk to the host itself.

In such case, a bridge is preferable. A bridge will also let you use mac filtering and I/O limits which cannot be applied to a macvlan device.

ipvlan is similar to macvlan, with the difference being that the forked device has IPs statically assigned to it and inherits the parent’s MAC address on the network.

SR-IOV

The sriov interface type supports SR-IOV enabled network devices. These devices associate a set of virtual functions (VFs) with the single physical function (PF) of the network device. PFs are standard PCIe functions. VFs on the other hand are very lightweight PCIe functions that are optimized for data movement. They come with a limited set of configuration capabilities to prevent changing properties of the PF. Given that VFs appear as regular PCIe devices to the system they can be passed to instances just like a regular physical device. The sriov interface type expects to be passed the name of an SR-IOV enabled network device on the system via the parent property. LXD will then check for any available VFs on the system. By default LXD will allocate the first free VF it finds. If it detects that either none are enabled or all currently enabled VFs are in use it will bump the number of supported VFs to the maximum value and use the first free VF. If all possible VFs are in use or the kernel or card doesn’t support incrementing the number of VFs LXD will return an error.

To create a sriov network device use:

lxc config device add <instance> <device-name> nic nictype=sriov parent=<sriov-enabled-device>

To tell LXD to use a specific unused VF add the host_name property and pass it the name of the enabled VF.

MAAS integration

If you’re using MAAS to manage the physical network under your LXD host and want to attach your instances directly to a MAAS managed network, LXD can be configured to interact with MAAS so that it can track your instances.

At the daemon level, you must configure maas.api.url and maas.api.key, then set the maas.subnet.ipv4 and/or maas.subnet.ipv6 keys on the instance or profile’s nic entry.

This will have LXD register all your instances with MAAS, giving them proper DHCP leases and DNS records.

If you set the ipv4.address or ipv6.address keys on the nic, then those will be registered as static assignments in MAAS too.

Type: infiniband

Supported instance types: container

LXD supports two different kind of network types for infiniband devices:

• physical: Straight physical device passthrough from the host. The targeted device will vanish from the host and appear in the instance.

• sriov: Passes a virtual function of an SR-IOV enabled physical network device into the instance.

Different network interface types have different additional properties, the current list is:

Key	Type	Default	Required	Used by	Description
nictype	string	-	yes	all	The device type, one of “physical”, or “sriov”
name	string	kernel assigned	no	all	The name of the interface inside the instance
hwaddr	string	randomly assigned	no	all	The MAC address of the new interface. Can be either full 20 byte variant or short 8 byte variant (which will only modify the last 8 bytes of the parent device)
mtu	integer	parent MTU	no	all	The MTU of the new interface
parent	string	-	yes	physical, sriov	The name of the host device or bridge

To create a physical infiniband device use:

lxc config device add <instance> <device-name> infiniband nictype=physical parent=<device>

SR-IOV with infiniband devices

Infiniband devices do support SR-IOV but in contrast to other SR-IOV enabled devices infiniband does not support dynamic device creation in SR-IOV mode. This means users need to pre-configure the number of virtual functions by configuring the corresponding kernel module.

To create a sriov infiniband device use:

lxc config device add <instance> <device-name> infiniband nictype=sriov parent=<sriov-enabled-device>

Type: disk

Supported instance types: container, VM

Disk entries are essentially mountpoints inside the instance. They can either be a bind-mount of an existing file or directory on the host, or if the source is a block device, a regular mount.

They can also be created by attaching a storage volume to an instance.

LXD supports the following additional source types:

• Ceph-rbd: Mount from existing Ceph RBD device that is externally managed. LXD can use Ceph to manage an internal file system for the instance, but in the event that a user has a previously existing Ceph RBD that they would like use for this instance, they can use this command. Example command

lxc config device add <instance> ceph-rbd1 disk source=ceph:<my_pool>/<my-volume> ceph.user_name=<username> ceph.cluster_name=<username> path=/ceph

• Ceph-fs: Mount from existing CephFS device that is externally managed. LXD can use Ceph to manage an internal file system for the instance, but in the event that a user has a previously existing Ceph file sys that they would like use for this instancer, they can use this command. Example command.

lxc config device add <instance> ceph-fs1 disk source=cephfs:<my-fs>/<some-path> ceph.user_name=<username> ceph.cluster_name=<username> path=/cephfs

• VM cloud-init: Generate a cloud-init config ISO from the user.vendor-data, user.user-data and user.meta-data config keys and attach to the VM so that cloud-init running inside the VM guest will detect the drive on boot and apply the config. Only applicable to virtual-machine instances. Example command.

lxc config device add <instance> config disk source=cloud-init:config

Currently only the root disk (path=/) and config drive (source=cloud-init:config) are supported with virtual machines.

The following properties exist:

Key	Type	Default	Required	Description
limits.read	string	-	no	I/O limit in byte/s (various suffixes supported, see Units for storage and network limits) or in iops (must be suffixed with “iops”) - see also Configure I/O limits
limits.write	string	-	no	I/O limit in byte/s (various suffixes supported, see Units for storage and network limits) or in iops (must be suffixed with “iops”) - see also Configure I/O limits
limits.max	string	-	no	Same as modifying both limits.read and limits.write
path	string	-	yes	Path inside the instance where the disk will be mounted (only for containers).
source	string	-	yes	Path on the host, either to a file/directory or to a block device
required	boolean	true	no	Controls whether to fail if the source doesn’t exist
readonly	boolean	false	no	Controls whether to make the mount read-only
size	string	-	no	Disk size in bytes (various suffixes supported, see Units for storage and network limits). This is only supported for the rootfs (/)
size.state	string	-	no	Same as size above but applies to the filesystem volume used for saving runtime state in virtual machines.
recursive	boolean	false	no	Whether or not to recursively mount the source path
pool	string	-	no	The storage pool the disk device belongs to. This is only applicable for storage volumes managed by LXD
propagation	string	-	no	Controls how a bind-mount is shared between the instance and the host. (Can be one of private, the default, or shared, slave, unbindable, rshared, rslave, runbindable, rprivate. Please see the Linux Kernel shared subtree documentation for a full explanation)
shift	boolean	false	no	Setup a shifting overlay to translate the source uid/gid to match the instance (only for containers)
raw.mount.options	string	-	no	Filesystem specific mount options
ceph.user_name	string	admin	no	If source is Ceph or CephFS then Ceph user_name must be specified by user for proper mount
ceph.cluster_name	string	ceph	no	If source is Ceph or CephFS then Ceph cluster_name must be specified by user for proper mount
boot.priority	integer	-	no	Boot priority for VMs (higher boots first)

Type: unix-char

Supported instance types: container

Unix character device entries simply make the requested character device appear in the instance’s /dev and allow read/write operations to it.

The following properties exist:

Key	Type	Default	Required	Description
source	string	-	no	Path on the host
path	string	-	no	Path inside the instance (one of “source” and “path” must be set)
major	int	device on host	no	Device major number
minor	int	device on host	no	Device minor number
uid	int	0	no	UID of the device owner in the instance
gid	int	0	no	GID of the device owner in the instance
mode	int	0660	no	Mode of the device in the instance
required	boolean	true	no	Whether or not this device is required to start the instance

Type: unix-block

Supported instance types: container

Unix block device entries simply make the requested block device appear in the instance’s /dev and allow read/write operations to it.

The following properties exist:

Key	Type	Default	Required	Description
source	string	-	no	Path on the host
path	string	-	no	Path inside the instance (one of “source” and “path” must be set)
major	int	device on host	no	Device major number
minor	int	device on host	no	Device minor number
uid	int	0	no	UID of the device owner in the instance
gid	int	0	no	GID of the device owner in the instance
mode	int	0660	no	Mode of the device in the instance
required	boolean	true	no	Whether or not this device is required to start the instance

Type: usb

Supported instance types: container, VM

USB device entries simply make the requested USB device appear in the instance.

The following properties exist:

Key	Type	Default	Required	Description
vendorid	string	-	no	The vendor id of the USB device
productid	string	-	no	The product id of the USB device
uid	int	0	no	UID of the device owner in the instance
gid	int	0	no	GID of the device owner in the instance
mode	int	0660	no	Mode of the device in the instance
required	boolean	false	no	Whether or not this device is required to start the instance. (The default is false, and all devices are hot-pluggable)

Type: gpu

GPU device entries simply make the requested gpu device appear in the instance.

Note

Container devices may match multiple GPUs at once. However, for virtual machines a device can only match a single GPU.

GPUs Available:

The following GPUs can be specified using the gputype property:

• physical Passes through an entire GPU. This is the default if gputype is unspecified.

• mdev Creates and passes through a virtual GPU into the instance.

• mig Creates and passes through a MIG (Multi-Instance GPU) device into the instance.

• sriov Passes a virtual function of an SR-IOV enabled GPU into the instance.

gpu: physical

Supported instance types: container, VM

Passes through an entire GPU.

The following properties exist:

Key	Type	Default	Required	Description
vendorid	string	-	no	The vendor id of the GPU device
productid	string	-	no	The product id of the GPU device
id	string	-	no	The card id of the GPU device
pci	string	-	no	The pci address of the GPU device
uid	int	0	no	UID of the device owner in the instance (container only)
gid	int	0	no	GID of the device owner in the instance (container only)
mode	int	0660	no	Mode of the device in the instance (container only)

gpu: mdev

Supported instance types: VM

Creates and passes through a virtual GPU into the instance. A list of available mdev profiles can be found by running lxc info --resources.

The following properties exist:

Key	Type	Default	Required	Description
vendorid	string	-	no	The vendor id of the GPU device
productid	string	-	no	The product id of the GPU device
id	string	-	no	The card id of the GPU device
pci	string	-	no	The pci address of the GPU device
mdev	string	-	yes	The mdev profile to use (e.g. i915-GVTg_V5_4)

gpu: mig

Supported instance types: container

Creates and passes through a MIG compute instance. This currently requires NVIDIA MIG instances to be pre-created.

The following properties exist:

Key	Type	Default	Required	Description
vendorid	string	-	no	The vendor id of the GPU device
productid	string	-	no	The product id of the GPU device
id	string	-	no	The card id of the GPU device
pci	string	-	no	The pci address of the GPU device
mig.ci	int	-	no	Existing MIG compute instance ID
mig.gi	int	-	no	Existing MIG GPU instance ID
mig.uuid	string	-	no	Existing MIG device UUID (“MIG-” prefix can be omitted)

Note: Either “mig.uuid” (Nvidia drivers 470+) or both “mig.ci” and “mig.gi” (old Nvidia drivers) must be set.

gpu: sriov

Supported instance types: VM

Passes a virtual function of an SR-IOV enabled GPU into the instance.

The following properties exist:

Key	Type	Default	Required	Description
vendorid	string	-	no	The vendor id of the parent GPU device
productid	string	-	no	The product id of the parent GPU device
id	string	-	no	The card id of the parent GPU device
pci	string	-	no	The pci address of the parent GPU device

Type: proxy

Supported instance types: container (nat and non-nat modes), VM (nat mode only)

Proxy devices allow forwarding network connections between host and instance. This makes it possible to forward traffic hitting one of the host’s addresses to an address inside the instance or to do the reverse and have an address in the instance connect through the host.

The supported connection types are:

• tcp <-> tcp

• udp <-> udp

• unix <-> unix

• tcp <-> unix

• unix <-> tcp

• udp <-> tcp

• tcp <-> udp

• udp <-> unix

• unix <-> udp

The proxy device also supports a nat mode where packets are forwarded using NAT rather than being proxied through a separate connection. This has benefit that the client address is maintained without the need for the target destination to support the PROXY protocol (which is the only way to pass the client address through when using the proxy device in non-nat mode).

When configuring a proxy device with nat=true, you will need to ensure that the target instance has a static IP configured in LXD on its NIC device. E.g.

lxc config device set <instance> <nic> ipv4.address=<ipv4.address> ipv6.address=<ipv6.address>

In order to define a static IPv6 address, the parent managed network needs to have ipv6.dhcp.stateful enabled.

In NAT mode the supported connection types are:

• tcp <-> tcp

• udp <-> udp

When defining IPv6 addresses use square bracket notation, e.g.

connect=tcp:[2001:db8::1]:80

You can specify that the connect address should be the IP of the instance by setting the connect IP to the wildcard address (0.0.0.0 for IPv4 and [::] for IPv6).

The listen address can also use wildcard addresses when using non-NAT mode. However when using nat mode you must specify an IP address on the LXD host.

Key	Type	Default	Required	Description
listen	string	-	yes	The address and port to bind and listen (<type>:<addr>:<port>[-<port>][,<port>])
connect	string	-	yes	The address and port to connect to (<type>:<addr>:<port>[-<port>][,<port>])
bind	string	host	no	Which side to bind on (host/instance)
uid	int	0	no	UID of the owner of the listening Unix socket
gid	int	0	no	GID of the owner of the listening Unix socket
mode	int	0644	no	Mode for the listening Unix socket
nat	bool	false	no	Whether to optimize proxying via NAT (requires instance NIC has static IP address)
proxy_protocol	bool	false	no	Whether to use the HAProxy PROXY protocol to transmit sender information
security.uid	int	0	no	What UID to drop privilege to
security.gid	int	0	no	What GID to drop privilege to

lxc config device add <instance> <device-name> proxy listen=<type>:<addr>:<port>[-<port>][,<port>] connect=<type>:<addr>:<port> bind=<host/instance>

Type: unix-hotplug

Supported instance types: container

Unix hotplug device entries make the requested unix device appear in the instance’s /dev and allow read/write operations to it if the device exists on the host system. Implementation depends on systemd-udev to be run on the host.

The following properties exist:

Key	Type	Default	Required	Description
vendorid	string	-	no	The vendor id of the unix device
productid	string	-	no	The product id of the unix device
uid	int	0	no	UID of the device owner in the instance
gid	int	0	no	GID of the device owner in the instance
mode	int	0660	no	Mode of the device in the instance
required	boolean	false	no	Whether or not this device is required to start the instance. (The default is false, and all devices are hot-pluggable)

Type: tpm

Supported instance types: container, VM

TPM device entries enable access to a TPM emulator.

The following properties exist:

Key	Type	Default	Required	Description
path	string	-	yes	Path inside the instance (only for containers).

Type: pci

Supported instance types: VM

PCI device entries are used to pass raw PCI devices from the host into a virtual machine.

The following properties exist:

Key	Type	Default	Required	Description
address	string	-	yes	PCI address of the device.

Units for storage and network limits

Any value representing bytes or bits can make use of a number of useful suffixes to make it easier to understand what a particular limit is.

Both decimal and binary (kibi) units are supported with the latter mostly making sense for storage limits.

The full list of bit suffixes currently supported is:

• bit (1)

• kbit (1000)

• Mbit (1000^2)

• Gbit (1000^3)

• Tbit (1000^4)

• Pbit (1000^5)

• Ebit (1000^6)

• Kibit (1024)

• Mibit (1024^2)

• Gibit (1024^3)

• Tibit (1024^4)

• Pibit (1024^5)

• Eibit (1024^6)

The full list of byte suffixes currently supported is:

• B or bytes (1)

• kB (1000)

• MB (1000^2)

• GB (1000^3)

• TB (1000^4)

• PB (1000^5)

• EB (1000^6)

• KiB (1024)

• MiB (1024^2)

• GiB (1024^3)

• TiB (1024^4)

• PiB (1024^5)

• EiB (1024^6)

Instance types

LXD supports simple instance types. Those are represented as a string which can be passed at instance creation time.

There are three allowed syntaxes:

• <instance type>

• <cloud>:<instance type>

• c<CPU>-m<RAM in GB>

For example, those 3 are equivalent:

• t2.micro

• aws:t2.micro

• c1-m1

On the command line, this is passed like this:

lxc launch ubuntu:22.04 my-instance -t t2.micro

The list of supported clouds and instance types can be found here:

https://github.com/dustinkirkland/instance-type

Hugepage limits via limits.hugepages.[size]

LXD allows to limit the number of hugepages available to a container through the limits.hugepage.[size] key. Limiting hugepages is done through the hugetlb cgroup controller. This means the host system needs to expose the hugetlb controller in the legacy or unified cgroup hierarchy for these limits to apply. Note that architectures often expose multiple hugepage sizes. In addition, architectures may expose different hugepage sizes than other architectures.

Limiting hugepages is especially useful when LXD is configured to intercept the mount syscall for the hugetlbfs filesystem in unprivileged containers. When LXD intercepts a hugetlbfs mount syscall, it will mount the hugetlbfs filesystem for a container with correct uid and gid values as mount options. This makes it possible to use hugepages from unprivileged containers. However, it is recommended to limit the number of hugepages available to the container through limits.hugepages.[size] to stop the container from being able to exhaust the hugepages available to the host.

Resource limits via limits.kernel.[limit name]

LXD exposes a generic namespaced key limits.kernel.* which can be used to set resource limits for a given instance. It is generic in the sense that LXD will not perform any validation on the resource that is specified following the limits.kernel.* prefix. LXD cannot know about all the possible resources that a given kernel supports. Instead, LXD will simply pass down the corresponding resource key after the limits.kernel.* prefix and its value to the kernel. The kernel will do the appropriate validation. This allows users to specify any supported limit on their system. Some common limits are:

Key	Resource	Description
limits.kernel.as	RLIMIT_AS	Maximum size of the process’s virtual memory
limits.kernel.core	RLIMIT_CORE	Maximum size of the process’s coredump file
limits.kernel.cpu	RLIMIT_CPU	Limit in seconds on the amount of cpu time the process can consume
limits.kernel.data	RLIMIT_DATA	Maximum size of the process’s data segment
limits.kernel.fsize	RLIMIT_FSIZE	Maximum size of files the process may create
limits.kernel.locks	RLIMIT_LOCKS	Limit on the number of file locks that this process may establish
limits.kernel.memlock	RLIMIT_MEMLOCK	Limit on the number of bytes of memory that the process may lock in RAM
limits.kernel.nice	RLIMIT_NICE	Maximum value to which the process’s nice value can be raised
limits.kernel.nofile	RLIMIT_NOFILE	Maximum number of open files for the process
limits.kernel.nproc	RLIMIT_NPROC	Maximum number of processes that can be created for the user of the calling process
limits.kernel.rtprio	RLIMIT_RTPRIO	Maximum value on the real-time-priority that maybe set for this process
limits.kernel.sigpending	RLIMIT_SIGPENDING	Maximum number of signals that maybe queued for the user of the calling process

A full list of all available limits can be found in the manpages for the getrlimit(2)/setrlimit(2) system calls. To specify a limit within the limits.kernel.* namespace use the resource name in lowercase without the RLIMIT_ prefix, e.g. RLIMIT_NOFILE should be specified as nofile. A limit is specified as two colon separated values which are either numeric or the word unlimited (e.g. limits.kernel.nofile=1000:2000). A single value can be used as a shortcut to set both soft and hard limit (e.g. limits.kernel.nofile=3000) to the same value. A resource with no explicitly configured limitation will be inherited from the process starting up the instance. Note that this inheritance is not enforced by LXD but by the kernel.

Snapshot scheduling and configuration

LXD supports scheduled snapshots which can be created at most once every minute. There are three configuration options:

• snapshots.schedule takes a shortened cron expression: <minute> <hour> <day-of-month> <month> <day-of-week>. If this is empty (default), no snapshots will be created.

• snapshots.schedule.stopped controls whether or not stopped instance are to be automatically snapshotted. It defaults to false.

• snapshots.pattern takes a pongo2 template string to format the snapshot name. To name snapshots with time stamps, the pongo2 context variable creation_date can be used. Be aware that you should format the date (e.g. use {{ creation_date|date:"2006-01-02_15-04-05" }}) in your template string to avoid forbidden characters in the snapshot name. Another way to avoid name collisions is to use the placeholder %d. If a snapshot with the same name (excluding the placeholder) already exists, all existing snapshot names will be taken into account to find the highest number at the placeholders position. This number will be incremented by one for the new name. The starting number if no snapshot exists will be 0. The default behavior of snapshots.pattern is equivalent to a format string of snap%d.

Example of using pongo2 syntax to format snapshot names with timestamps:

lxc config set INSTANCE snapshots.pattern "{{ creation_date|date:'2006-01-02_15-04-05' }}"

This results in snapshots named {date/time of creation} down to the precision of a second.

Overriding qemu configuration

For VM instances, LXD configures qemu via a somewhat undocumented configuration file format passed to qemu with the -readconfig command-line option, with each instance having a configuration file generated before boot. The generated configuration file can be found at /var/log/lxd/[instance-name]/qemu.conf.

The default configuration works fine for LXD most common use case: Modern UEFI guests with virtio devices. In some situations however, it can be desirable to override the generated configuration:

• Running an old guest OS that doesn’t support UEFI.

• Specify custom virtual devices when virtio is not supported by the guest OS .

• Add devices not supported by LXD before the machines boots.

• Remove devices that conflict with the guest OS.

This level of customization can be achieved through the raw.qemu.conf config option, which supports a format similar to qemu.conf with some additions. Here’s how to override the default “virtio-gpu-pci” GPU driver:

raw.qemu.conf: |-
    [device "qemu_gpu"]
    driver = "qxl-vga"

The above would replace the corresponding section/key in the generated config file. Since raw.qemu.conf is a multi-line config option, multiple sections/keys can be modified.

It is also possible to entirely remove sections/keys by specifying a section without any keys:

raw.qemu.conf: |-
    [device "qemu_gpu"]

To remove a key, specify an empty string as the value:

raw.qemu.conf: |-
    [device "qemu_gpu"]
    driver = ""

The configuration file format used by qemu allows multiple sections with the same name. Here’s a piece of the config generated by LXD:

[global]
driver = "ICH9-LPC"
property = "disable_s3"
value = "1"

[global]
driver = "ICH9-LPC"
property = "disable_s4"
value = "1"

To specify which section will be overridden, an index can be specified like this:

raw.qemu.conf: |-
    [global][1]
    value = "0"

Section indexes start at 0 (which is the default value when not specified), so the raw.qemu.conf above example would generate this:

[global]
driver = "ICH9-LPC"
property = "disable_s3"
value = "1"

[global]
driver = "ICH9-LPC"
property = "disable_s4"
value = "0"

To add new sections, simply specify section names that are not present in the config file.