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docs: add back host network limitation

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Kata Containers doesn't support host network namespace,
it's a common issue for new users. The limitation
is deleted, this commit will add them back.

Also, Docker has support to run containers using
Kata Containers, delete Docker from not support list.

This commit reverts parts of #3710

Fixes: #4794

Signed-off-by: Bin Liu <bin@hyper.sh>
This commit is contained in:
Bin Liu 2022-08-02 15:20:45 +08:00
parent 7503bdab6e
commit 889557ecb1
1 changed files with 47 additions and 2 deletions
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49
docs/Limitations.md
View File

@ -60,17 +60,26 @@ This section lists items that might be possible to fix.
## OCI CLI commands
### Docker and Podman support
Currently Kata Containers does not support Docker or Podman.
Currently Kata Containers does not support Podman.
See issue https://github.com/kata-containers/kata-containers/issues/722 for more information.
Docker supports Kata Containers since 22.06:
```bash
$ sudo docker run --runtime io.containerd.kata.v2
```
Kata Containers works perfectly with containerd, we recommend to use
containerd's Docker-style command line tool [`nerdctl`](https://github.com/containerd/nerdctl).
## Runtime commands
### checkpoint and restore
The runtime does not provide `checkpoint` and `restore` commands. There
are discussions about using VM save and restore to give us a
`[criu](https://github.com/checkpoint-restore/criu)`-like functionality,
[`criu`](https://github.com/checkpoint-restore/criu)-like functionality,
which might provide a solution.
Note that the OCI standard does not specify `checkpoint` and `restore`
@ -93,6 +102,42 @@ All other configurations are supported and are working properly.
## Networking
### Host network
Host network (`nerdctl/docker run --net=host`or [Kubernetes `HostNetwork`](https://kubernetes.io/docs/reference/kubernetes-api/workload-resources/pod-v1/#hosts-namespaces)) is not supported.
It is not possible to directly access the host networking configuration
from within the VM.
The `--net=host` option can still be used with `runc` containers and
inter-mixed with running Kata Containers, thus enabling use of `--net=host`
when necessary.
It should be noted, currently passing the `--net=host` option into a
Kata Container may result in the Kata Container networking setup
modifying, re-configuring and therefore possibly breaking the host
networking setup. Do not use `--net=host` with Kata Containers.
### Support for joining an existing VM network
Docker supports the ability for containers to join another containers
namespace with the `docker run --net=containers` syntax. This allows
multiple containers to share a common network namespace and the network
interfaces placed in the network namespace. Kata Containers does not
support network namespace sharing. If a Kata Container is setup to
share the network namespace of a `runc` container, the runtime
effectively takes over all the network interfaces assigned to the
namespace and binds them to the VM. Consequently, the `runc` container loses
its network connectivity.
### docker run --link
The runtime does not support the `docker run --link` command. This
command is now deprecated by docker and we have no intention of adding support.
Equivalent functionality can be achieved with the newer docker networking commands.
See more documentation at
[docs.docker.com](https://docs.docker.com/network/links/).
## Resource management
Due to the way VMs differ in their CPU and memory allocation, and sharing