Kata Containers gives users freedom to customize at per-pod level, by setting a wide range of Kata specific annotations in the pod specification.
Some annotations may be restricted by the configuration file for security reasons, notably annotations that could lead the runtime to execute programs on the host. Such annotations are marked with (R) in the tables below.
There are several kinds of Kata configurations and they are listed below.
| Key | Value Type | Comments |
|---|---|---|
io.katacontainers.config_path |
string | Kata config file location that overrides the default config paths |
io.katacontainers.pkg.oci.bundle_path |
string | OCI bundle path |
io.katacontainers.pkg.oci.container_type |
string | OCI container type. Only accepts pod_container and pod_sandbox |
| Key | Value Type | Comments |
|---|---|---|
io.katacontainers.config.runtime.experimental |
boolean |
determines if experimental features enabled |
io.katacontainers.config.runtime.disable_guest_seccomp |
boolean |
determines if seccomp should be applied inside guest |
io.katacontainers.config.runtime.disable_new_netns |
boolean |
determines if a new netns is created for the hypervisor process |
io.katacontainers.config.runtime.internetworking_model |
string | determines how the VM should be connected to the container network interface. Valid values are macvtap, tcfilter and none |
io.katacontainers.config.runtime.sandbox_cgroup_only |
boolean |
determines if Kata processes are managed only in sandbox cgroup |
io.katacontainers.config.runtime.enable_pprof |
boolean |
enables Golang pprof for containerd-shim-kata-v2 process |
io.katacontainers.config.runtime.create_container_timeout |
uint64 |
the timeout for create a container in seconds, default is 60 |
| Key | Value Type | Comments |
|---|---|---|
io.katacontainers.config.agent.enable_tracing |
boolean |
enable tracing for the agent |
io.katacontainers.config.agent.container_pipe_size |
uint32 | specify the size of the std(in/out) pipes created for containers |
io.katacontainers.config.agent.kernel_modules |
string | the list of kernel modules and their parameters that will be loaded in the guest kernel. Semicolon separated list of kernel modules and their parameters. These modules will be loaded in the guest kernel using modprobe(8). E.g., e1000e InterruptThrottleRate=3000,3000,3000 EEE=1; i915 enable_ppgtt=0 |
io.katacontainers.config.agent.cdh_api_timeout |
uint32 | timeout in second for Confidential Data Hub (CDH) API service, default is 50 |
| Key | Value Type | Comments |
|---|---|---|
io.katacontainers.config.hypervisor.asset_hash_type |
string | the hash type used for assets verification, default is sha512 |
io.katacontainers.config.hypervisor.block_device_cache_direct |
boolean |
Denotes whether use of O_DIRECT (bypass the host page cache) is enabled |
io.katacontainers.config.hypervisor.block_device_cache_noflush |
boolean |
Denotes whether flush requests for the device are ignored |
io.katacontainers.config.hypervisor.block_device_cache_set |
boolean |
cache-related options will be set to block devices or not |
io.katacontainers.config.hypervisor.block_device_driver |
string | the driver to be used for block device, valid values are virtio-blk, virtio-scsi, nvdimm |
io.katacontainers.config.hypervisor.cpu_features |
string |
Comma-separated list of CPU features to pass to the CPU (QEMU) |
io.katacontainers.config.hypervisor.default_max_vcpus |
uint32 | the maximum number of vCPUs allocated for the VM by the hypervisor |
io.katacontainers.config.hypervisor.default_memory |
uint32 | the memory assigned for a VM by the hypervisor in MiB |
io.katacontainers.config.hypervisor.default_vcpus |
float32 | the default vCPUs assigned for a VM by the hypervisor |
io.katacontainers.config.hypervisor.disable_block_device_use |
boolean |
disallow a block device from being used |
io.katacontainers.config.hypervisor.disable_image_nvdimm |
boolean |
specify if a nvdimm device should be used as rootfs for the guest (QEMU) |
io.katacontainers.config.hypervisor.disable_vhost_net |
boolean |
specify if vhost-net is not available on the host |
io.katacontainers.config.hypervisor.enable_hugepages |
boolean |
if the memory should be pre-allocated from huge pages |
io.katacontainers.config.hypervisor.enable_iommu_platform |
boolean |
enable iommu on CCW devices (QEMU s390x) |
io.katacontainers.config.hypervisor.enable_iommu |
boolean |
enable iommu on Q35 (QEMU x86_64) |
io.katacontainers.config.hypervisor.enable_iothreads |
boolean |
enable IO to be processed in a separate thread. Supported currently for virtio-scsi driver |
io.katacontainers.config.hypervisor.enable_mem_prealloc |
boolean |
the memory space used for nvdimm device by the hypervisor |
io.katacontainers.config.hypervisor.enable_vhost_user_store |
boolean |
enable vhost-user storage device (QEMU) |
io.katacontainers.config.hypervisor.vhost_user_reconnect_timeout_sec |
string |
the timeout for reconnecting vhost user socket (QEMU) |
io.katacontainers.config.hypervisor.enable_virtio_mem |
boolean |
enable virtio-mem (QEMU) |
io.katacontainers.config.hypervisor.entropy_source (R) |
string | the path to a host source of entropy (/dev/random, /dev/urandom or real hardware RNG device) |
io.katacontainers.config.hypervisor.file_mem_backend (R) |
string | file based memory backend root directory |
io.katacontainers.config.hypervisor.firmware_hash |
string | container firmware SHA-512 hash value |
io.katacontainers.config.hypervisor.firmware |
string | the guest firmware that will run the container VM |
io.katacontainers.config.hypervisor.firmware_volume_hash |
string | container firmware volume SHA-512 hash value |
io.katacontainers.config.hypervisor.firmware_volume |
string | the guest firmware volume that will be passed to the container VM |
io.katacontainers.config.hypervisor.guest_hook_path |
string | the path within the VM that will be used for drop in hooks |
io.katacontainers.config.hypervisor.hotplug_vfio_on_root_bus |
boolean |
indicate if devices need to be hotplugged on the root bus instead of a bridge |
io.katacontainers.config.hypervisor.hypervisor_hash |
string | container hypervisor binary SHA-512 hash value |
io.katacontainers.config.hypervisor.image_hash |
string | container guest image SHA-512 hash value |
io.katacontainers.config.hypervisor.image |
string | the guest image that will run in the container VM |
io.katacontainers.config.hypervisor.initrd_hash |
string | container guest initrd SHA-512 hash value |
io.katacontainers.config.hypervisor.initrd |
string | the guest initrd image that will run in the container VM |
io.katacontainers.config.hypervisor.jailer_hash |
string | container jailer SHA-512 hash value |
io.katacontainers.config.hypervisor.jailer_path (R) |
string | the jailer that will constrain the container VM |
io.katacontainers.config.hypervisor.kernel_hash |
string | container kernel image SHA-512 hash value |
io.katacontainers.config.hypervisor.kernel_params |
string | additional guest kernel parameters |
io.katacontainers.config.hypervisor.kernel |
string | the kernel used to boot the container VM |
io.katacontainers.config.hypervisor.machine_accelerators |
string | machine specific accelerators for the hypervisor |
io.katacontainers.config.hypervisor.machine_type |
string | the type of machine being emulated by the hypervisor |
io.katacontainers.config.hypervisor.memory_offset |
uint64 | the memory space used for nvdimm device by the hypervisor |
io.katacontainers.config.hypervisor.memory_slots |
uint32 | the memory slots assigned to the VM by the hypervisor |
io.katacontainers.config.hypervisor.msize_9p |
uint32 | the msize for 9p shares |
io.katacontainers.config.hypervisor.path |
string | the hypervisor that will run the container VM |
io.katacontainers.config.hypervisor.pcie_root_port |
specify the number of PCIe Root Port devices. The PCIe Root Port device is used to hot-plug a PCIe device (QEMU) | |
io.katacontainers.config.hypervisor.shared_fs |
string | the shared file system type, either virtio-9p or virtio-fs |
io.katacontainers.config.hypervisor.use_vsock |
boolean |
specify use of vsock for agent communication |
io.katacontainers.config.hypervisor.vhost_user_store_path (R) |
string |
specify the directory path where vhost-user devices related folders, sockets and device nodes should be (QEMU) |
io.katacontainers.config.hypervisor.virtio_fs_cache_size |
uint32 | virtio-fs DAX cache size in MiB |
io.katacontainers.config.hypervisor.virtio_fs_cache |
string | the cache mode for virtio-fs, valid values are always, auto and never |
io.katacontainers.config.hypervisor.virtio_fs_daemon |
string | virtio-fs vhost-user daemon path |
io.katacontainers.config.hypervisor.virtio_fs_extra_args |
string | extra options passed to virtiofs daemon |
io.katacontainers.config.hypervisor.enable_guest_swap |
boolean |
enable swap in the guest |
io.katacontainers.config.hypervisor.use_legacy_serial |
boolean |
uses legacy serial device for guest's console (QEMU) |
io.katacontainers.config.hypervisor.default_gpus |
uint32 | the minimum number of GPUs required for the VM. Only used by remote hypervisor to help with instance selection |
io.katacontainers.config.hypervisor.default_gpu_model |
string | the GPU model required for the VM. Only used by remote hypervisor to help with instance selection |
| Key | Value Type | Comments |
|---|---|---|
io.katacontainers.container.resource.swappiness" |
uint64 |
specify the Resources.Memory.Swappiness |
io.katacontainers.container.resource.swap_in_bytes" |
uint64 |
specify the Resources.Memory.Swap |
In case of CRI-O, all annotations specified in the pod spec are passed down to Kata.
For containerd, annotations specified in the pod spec are passed down to Kata
starting with version 1.3.0 of containerd. Additionally, extra configuration is
needed for containerd, by providing pod_annotations field and
container_annotations field in the containerd config
file. The pod_annotations field and container_annotations field are two lists of
annotations that can be passed down to Kata as OCI annotations. They support golang match
patterns. Since annotations supported by Kata follow the pattern io.katacontainers.*,
the following configuration would work for passing annotations to Kata from containerd:
$ cat /etc/containerd/config
....
[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.kata]
runtime_type = "io.containerd.kata.v2"
pod_annotations = ["io.katacontainers.*"]
container_annotations = ["io.katacontainers.*"]
....
Additional documentation on the above configuration can be found in the containerd docs.
As mentioned above, not all containers need the same modules, therefore using the configuration file for specifying the list of kernel modules per POD can be a pain. Unlike the configuration file, annotations provide a way to specify custom configurations per POD.
The list of kernel modules and parameters can be set using the annotation
io.katacontainers.config.agent.kernel_modules as a semicolon separated
list, where the first word of each element is considered as the module name and
the rest as its parameters.
Also users might want to enable guest seccomp to provide better isolation with a
little performance sacrifice. The annotation
io.katacontainers.config.runtime.disable_guest_seccomp can used for such purpose.
In the following example two PODs are created, but the kernel modules e1000e
and i915 are inserted only in the POD pod1. Also guest seccomp is only enabled
in the POD pod2.
apiVersion: v1
kind: Pod
metadata:
name: pod1
annotations:
io.katacontainers.config.agent.kernel_modules: "e1000e EEE=1; i915"
spec:
runtimeClassName: kata
containers:
- name: c1
image: busybox
command:
- sh
stdin: true
tty: true
---
apiVersion: v1
kind: Pod
metadata:
name: pod2
annotations:
io.katacontainers.config.runtime.disable_guest_seccomp: "false"
spec:
runtimeClassName: kata
containers:
- name: c2
image: busybox
command:
- sh
stdin: true
tty: trueSome annotations are restricted, meaning that the configuration file specifies the acceptable values. Currently, only hypervisor annotations are restricted, for security reason, with the intent to control which binaries the Kata Containers runtime will launch on your behalf.
The configuration file validates the annotation name as well as the annotation value.
The acceptable annotation names are defined by the enable_annotations entry in
the configuration file.
For restricted annotations, an additional configuration entry provides a list of
acceptable values. Since most restricted annotations are intended to control
which binaries the runtime can execute, the valid value is generally provided by
a shell pattern, as defined by glob(3). The table below provides the name of
the configuration entry:
| Key | Config file entry | Comments |
|---|---|---|
entropy_source |
valid_entropy_sources |
Valid entropy sources, e.g. /dev/random |
file_mem_backend |
valid_file_mem_backends |
Valid locations for the file-based memory backend root directory |
jailer_path |
valid_jailer_paths |
Valid paths for the jailer constraining the container VM (Firecracker) |
path |
valid_hypervisor_paths |
Valid hypervisors to run the container VM |
vhost_user_store_path |
valid_vhost_user_store_paths |
Valid paths for vhost-user related files |
virtio_fs_daemon |
valid_virtio_fs_daemon_paths |
Valid paths for the virtiofsd daemon |