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https://github.com/gotoz/runq

run regular Docker images in KVM/Qemu
https://github.com/gotoz/runq

docker kvm oci qemu runtime

Last synced: 6 days ago
JSON representation

run regular Docker images in KVM/Qemu

Host: GitHub
URL: https://github.com/gotoz/runq
Owner: gotoz
License: apache-2.0
Created: 2018-02-27T11:13:31.000Z (over 6 years ago)
Default Branch: master
Last Pushed: 2024-05-19T08:21:51.000Z (6 months ago)
Last Synced: 2024-08-02T02:14:11.806Z (3 months ago)
Topics: docker, kvm, oci, qemu, runtime
Language: Go
Homepage:
Size: 5.13 MB
Stars: 797
Watchers: 29
Forks: 46
Open Issues: 6
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE

Awesome Lists containing this project

awesome-repositories - gotoz/runq - run regular Docker images in KVM/Qemu (Go)

README

# runq

runq is a hypervisor-based Docker runtime based on [runc](https://github.com/opencontainers/runc)
to run regular Docker images as a lightweight KVM/Qemu virtual machine.
The focus is on solving real problems, not on number of features.

Key differences to other hypervisor-based runtimes:

* minimalistic design, small code base
* no modification to existing Docker tools (dockerd, containerd, runc...)
* coexistence of runq containers and regular runc containers
* no extra state outside of Docker (no libvirt, no changes to /var/run/...)
* small init program, no systemd
* no custom guest kernel or custom qemu needed
* runs on x86_64 and s390x (>= z13)

## runc vs. runq

## Installation

runq requires a host kernel >= 4.8 with KVM and VHOST_VSOCK support enabled.
The easiest way to build runq and to put all dependencies together is using Docker.
For fast development cycles a regular build environment might be more
efficient. For this refer to section [Developing runq](#developing-runq).

```sh
# get the runq and runc source code
git clone --recurse-submodules https://github.com/gotoz/runq.git

# compile and create a release tar file in a Docker container
cd runq
make release

# install runq to `/var/lib/runq`
make release-install
```

Register runq as Docker runtime with appropriate defaults. See [daemon.json](test/testdata/daemon.json) for more options.

```json
/etc/docker/daemon.json
{
"runtimes": {
"runq": {
"path": "/var/lib/runq/runq",
"runtimeArgs": [
"--cpu", "1",
"--mem", "256",
"--dns", "8.8.8.8,8.8.4.4",
"--tmpfs", "/tmp"
]
}
}
}
```

reload Docker config

```sh
systemctl reload docker.service
```

### TLS certificates

*runq-exec* creates a secure connection between host and VM guests. Users of *runq-exec* are
authenticated via a client certificate. Access to the client certificate must be limited to
Docker users only.

The CA and server certificates must be installed in `/var/lib/runq/qemu/certs`.
Access must be limited to the root user only.

Examples of server and client TLS certificates can be created with the script:

```sh
/var/lib/runq/qemu/mkcerts.sh
```

Note: On x86 and s390x < z14 the host must provide sufficient entropy to the VM guests via virtio-rng.
If there is not enough entropy available on the host booting of guests can fail with a timeout error.
The entropy that's currently available can be checked with:

```sh
cat /proc/sys/kernel/random/entropy_avail
```

The number returned should always be greater than 1000. On s390x >=z14 random data is provided
by the hardware driven trng device (kernel module s390-trng).

#### Kernel module vhost_vsock

The kernel module `vhost_vsock` must be loaded on the host. This can be achieved by creating
a config file for the systemd-modules-load service: `/etc/modules-load.d/vhost-vsock.conf`:

```sh
# Load vhost_vsock for runq
vhost_vsock
```

## Usage examples

the simplest example

```sh
docker run --runtime runq -ti busybox sh
```

custom VM with 512MiB memory and 2 CPUs

```sh
docker run --runtime runq -e RUNQ_MEM=512 -e RUNQ_CPU=2 -ti busybox sh
```

allow loading of extra kernel modules by adding the SYS_MODULE capability

```sh
docker run --runtime runq --cap-add sys_module -ti busybox sh -c "modprobe brd && lsmod"

```

full example PostgreSQL with custom storage

```sh
dd if=/dev/zero of=data.img bs=1M count=200
mkfs.ext4 -F data.img

docker run \
--runtime runq \
--name pgserver \
-e RUNQ_CPU=2 \
-e RUNQ_MEM=512 \
-e POSTGRES_PASSWORD=mysecret \
-v $PWD/data.img:/dev/runq/0001/none/ext4/var/lib/postgresql \
-d postgres:alpine

sleep 10

docker run \
--runtime runq \
--link pgserver:postgres \
--rm \
-e PGPASSWORD=mysecret \
postgres:alpine psql -h postgres -U postgres -c "select 42 as answer;"

# answer
# --------
# 42
# (1 row)

```

### Container with Systemd

Containers running Systemd should have the environment variable `RUNQ_SYSTEMD` set to `1`.
With `RUNQ_SYSTEMD=1` the behaviour changes as follows:

* The entry-point return code (Systemd exit code) must be treated differently to ensure that
`poweroff` and `reboot` executed inside the container work as expected especially to
support Docker containers created with '--restart on-failure:1'. Therefore
* on **poweroff** and **halt** the Systemd exit code is 2 but the return code as seen by Docker is 0.
* In all other cases the return code as seen by Docker is 1.

* When stopping or restarting a container the signal sent to the docker-entry point is
SIGTERM. Systemd usually ignores SIGTERM. In order to trigger a clean Systemd
shutdown the signal is therefore modified from SIGTERM to SIGRTMIN+4. When Systemd receives SIGRTMIN+4
it starts the poweroff.target unit.

* With `RUNQ_SYSTEMD=1` Linux cgroups are not mounted because this will be done later by Systemd.

See [test/examples/Dockerfile.systemd](test/examples/Dockerfile.systemd)
and [test/examples/systemd.sh](test/examples/systemd.sh) for an example.

### /.runqenv

Runq can write the container environment variables in a file named `/.runqenv` placed in
the root directory of the container. This might be useful for containers running Systemd
as entry point. This feature can be enabled globally by configuring `--runqenv` in
[/etc/docker/daemon.json](test/testdata/daemon.json) or for a single container by setting
the environment variable `RUNQ_RUNQENV` to a true value.

### 9p cache mode

The default 9p cache mode is 'mmap' but can be configured by setting the global
runtime parameter `--9pcache` in [/etc/docker/daemon.json](test/testdata/daemon.json)
or for each container individually by setting the container environment variable RUNQ_9PCACHE.
Valid cache modes are none, loose, fscache and mmap. For details see [9prst.txt](https://www.kernel.org/doc/html/latest/_sources/filesystems/9p.rst.txt).

### Qemu CPU model and flags

The default Qemu CPU model is 'host' with no flags (KVM processor with all supported host features) but can be
configured by setting the global runtime parameter `--cpuargs` in [/etc/docker/daemon.json](test/testdata/daemon.json)
or for each container individually by setting the container environment variable RUNQ_CPUARGS.
E.g. `--env RUNQ_CPUARGS=host,rtm=off`.
See `qemu-system-x86_64 -cpu help` for a list of available CPU models and CPUID flags.

## runq Components

```text
docker cli
dockerd engine
docker-containerd-shim
runq container
+--------------------------------------------------------+
| |
docker0 | VM |
`veth <------> veth +--------------------------+ |
| `<--- macvtap ---|-> eth0 | |
| proxy <-----------------> init | |
runq-exec <-----------tls----------------> `vsockd | |
| |+-------------namespace--+| |
overlayfs <-----9pfs-------------------||-> / || |
| || || |
block dev <-----virtio-blk-------------||-> /dev/vdx || |
| || || |
| || || |
| || || |
| || application || |
| || || |
| |+------------------------+| |
| | guest kernel | |
| +--------------------------+ |
| qemu |
+--------------------------------------------------------+

--------------------------------------------------------------------------
host kernel
```

* cmd/runq
* new docker runtime

* cmd/proxy
* new Docker entry point
* first process in container (PID 1)
* configures and starts Qemu (network, disks, ...)
* forwards signals to VM init
* receives application exit code

* cmd/init
* first process in VM (PID 1)
* initializes the VM guest (network, disks, ...)
* starts entry-point in PID and Mount namespace
* sends signals to target application
* forwards application exit code back to proxy

* cmd/runq-exec
* command line utility similar to *docker exec*

* cmd/nsenter
* enters the namespaces of entry-point for runq-exec

* qemu
* creates `/var/lib/runq/qemu`
* read-only volume attached to every container
* contains qemu rootfs (proxy, qemu, kernel and initrd)

* initrd
* prepares the initrd to boot the VM

* pkg
* helper packages

## runq-exec

runq-exec (`/var/lib/runq/runq-exec`) is a command line utility similar to **docker exec**. It allows running
additional commands in existing runq containers executed from the host. It uses
[VirtioVsock](https://wiki.qemu.org/Features/VirtioVsock) for the communication
between host and VMs. TLS is used for encryption and client authorization. Support for
`runq-exec` can be disabled by setting the container environment variable `RUNQ_NOEXEC`
to a true value or by `--noexec` in [/etc/docker/daemon.json](test/testdata/daemon.json).

```text
Usage:
runq-exec [options] command args

Run a command in a running runq container

Options:
-c, --tlscert string TLS certificate file (default "/var/lib/runq/cert.pem")
-k, --tlskey string TLS private key file (default "/var/lib/runq/key.pem")
-e, --env stringArray Set environment variables for command
-h, --help Print this help
-i, --interactive Keep STDIN open even if not attached
-t, --tty Allocate a pseudo-TTY
-v, --version Print version

Environment Variable:
DOCKER_HOST specifies the Docker daemon socket.

Example:
runq-exec -ti a6c3b7c bash
```

## Qemu and guest Kernel

runq runs Qemu and Linux Kernel from the `/var/lib/runq/qemu` directory
on the host. This directory is populated by `make -C qemu`. For simplicity
Qemu and the Linux kernel are taken from the Ubuntu 20.04 LTS Docker base image.
See [qemu/x86_64/Dockerfile](qemu/x86_64/Dockerfile) for details.
This makes runq independent of the Linux distribution on the host.
Qemu does not need to be installed on the host.

The kernel modules directory (`/var/lib/runq/qemu/lib/modules`)
is `bind-mounted` into every container to `/lib/modules`.
This allows the loading of extra kernel modules in any container if needed.
For this SYS_MODULES capability is required (`--cap-add sys_modules`).

## Networking

runq uses Macvtap devices to connect Qemu VirtIO interfaces to Docker
bridges. By default a single Ethernet interface is created.
Multiple networks can be used by connecting a container to the networks
before start. See [test/integration/net.sh](test/integration/net.sh) as an
example.

runq container can also be connected to one or more Docker networks of type Macvlan.
This allows a direct connection between the VM and the physical host network
without bridge and without NAT. See for details.

For custom networks the docker daemon implements an embedded DNS server which provides
built-in service discovery for any container created with a valid container name.
This Docker DNS server (listen address 127.0.0.11:53) is reachable only by runc containers
and not by runq containers.
A work-around is to run one or more DNS proxy container in the custom network with runc and
use the proxy IP address for DNS of runq containers.
See [test/examples/dnsproxy.sh](test/examples/dnsproxy.sh) for details on how to setup a DNS proxy.

DNS configuration without proxy can be done globally via runtime options specified in
'/etc/docker/daemon.json' (see example above) or via environment variables for each
container at container start.
The environment variables are `RUNQ_DNS`, `RUNQ_DNS_OPT` and `RUNQ_DNS_SEARCH`.
Environment variables have priority over global options.

Setting the environment variable RUNQ_DNS_PRESERVE to "1" completely disables generation of
/etc/resolv.conf by runq.

## Storage

Extra storage can be added in the form of Qcow2 images, raw file images or
regular block devices. Storage devices will be mounted automatically if
a filesystem and a mount point has been specified.
Supported filesystems are ext2, ext3, ext4, xfs and btrfs.
Cache type must be writeback, writethrough, none or unsafe.
Cache type "none" is recommended for filesystems that support `O_DIRECT`.
See man qemu(1) for details about different cache types.

Syntax:

```sh
--volume :/dev/runq//[/]
--device :/dev/runq//[/]
```

`` is used to create symbolic links inside the VM guest that point to the Qemu Virtio device
files. The `id` can be any character string that matches the regex pattern `"^[a-zA-Z0-9-_]{1,36}$"`
but it must be unique within a container.

```sh
/dev/disk/by-runq-id/0001 -> ../../vda
```

### Storage examples

Mount the existing Qcow image `/data.qcow2` with xfs filesystem to `/mnt/data`:

```sh
docker run -v /data.qcow2:/dev/runq/0001/none/xfs/mnt/data ...
```

Attach the host device `/dev/sdb1` formatted with ext4 to `/mnt/data2`:

```sh
docker run --device /dev/sdb1:/dev/runq/0002/writethrough/ext4/mnt/data2 ...
```

Attach the host device `/dev/sdb2` without mounting:

```sh
docker run --device /dev/sdb2:/dev/runq/0003/writethrough ...
```

### Rootdisk

A block device or a raw file with an EXT2 or EXT4 filesystem can be used as rootdisk
of the VM. On first boot of the container the content of the Docker image is copied into the rootdisk.
The block device or raw file will then be used as root filesystem via virtio-blk instead of 9pfs. But be aware that changes to the root filesystem will not be reflected in the source docker container filesystem. (`docker cp` will no longer work as expected)

```sh
# existing block device with empty ext4 filesystem
docker run --runtime runq --device /dev/sdb1:/dev/runq/0001/none/ext4 -e RUNQ_ROOTDISK=0001 -ti alpine sh

# new raw file
fallocate -l 1G disk.raw
mkfs.ext4 disk.raw
docker run --runtime runq --volume $PWD/disk.raw:/dev/runq/0001/none/ext4 -e RUNQ_ROOTDISK=0001 -ti alpine sh
```

Directories can be excluded from being copied with the RUNQ_ROOTDISK_EXCLUDE environment
variable. E.g. `-e RUNQ_ROOTDISK_EXCLUDE="/foo,/bar"`

See [Dockerfile.rootdisk](test/examples/Dockerfile.rootdisk) and [rootdisk.sh](test/examples/rootdisk.sh) as a further example.

## Capabilities

By default runq drops all capabilities except those needed (same as regular Docker does).
The white list of the remaining capabilities is provided by the Docker engine.

`AUDIT_WRITE CHOWN DAC_OVERRIDE FOWNER FSETID KILL MKNOD NET_BIND_SERVICE
NET_RAW SETFCAP SETGID SETPCAP SETUID SYS_CHROOT`

See `man capabilities` for a list of all available capabilities.
Additional Capabilities can be added to the white list at container start:

```sh
docker run --cap-add SYS_TIME --cap-add SYS_MODULE ...`
```

## Seccomp

runq supports the [default Docker seccomp profile](https://github.com/docker/docker-ce/blob/master/components/engine/profiles/seccomp/default.json) as well as custom profiles.

```sh
docker run --security-opt seccomp= ...
```

The default profile is defined by the Docker daemon and gets applied automatically.
Note: Only the runq init binary is statically linked against libseccomp.
Therefore libseccomp is needed only at compile time.

If the host operating system where runq is being built does not provide static libseccomp
libraries one can also simply build and install [libseccomp](https://github.com/seccomp/libseccomp/)
from the sources.

Seccomp can be disabled at container start:

```sh
docker run --security-opt seccomp=unconfined ...
```

Note: Some Docker daemon don't support custom Seccomp profiles. Run `docker info` to verify
that Seccomp is supported by your daemon. If it is supported the output of `docker info` looks like this:

```text
Security Options:
seccomp
Profile: default
```

## AP adapter passthrough (s390x only)

AP devices provide cryptographic functions to all CPUs assigned to a Linux system running in
an IBM Z system LPAR. AP devices can be made available to a runq container by passing a VFIO mediated
device from the host through Qemu into the runq VM guest. VFIO mediated devices are enabled by the
`vfio_ap` kernel module and allow for partitioning of AP devices and domains. The environment variable RUNQ_APUUID specifies the VFIO mediated device UUID. runq automatically loads the required zcrypt kernel modules inside the VM. E.g.:

```sh
docker run --runtime runq -e RUNQ_APUUID=b34543ee-496b-4769-8312-83707033e1de ...
```

For details on how to setup mediated devices on the host see

## Limitations

Most docker commands and options work as expected. However, due to
the fact that the target application runs inside a Qemu VM which itself runs
inside a Docker container and because of the minimalistic design principle of runq
some docker commands and options don't work. E.g:

* adding / removing networks and storage dynamically
* docker exec (see runq-exec)
* docker swarm
* privileged mode
* apparmor, selinux, ambient
* docker HEALTHCHECK

The following common options of `docker run` are supported:

```text
--attach --name
--cap-add --network
--cap-drop --publish
--cpus --restart
--cpuset-cpus --rm
--detach --runtime
--entrypoint --sysctl
--env --security-opt seccomp=unconfined
--env-file --security-opt no-new-privileges
--expose --security-opt seccomp=
--group-add --tmpfs
--help --tty
--hostname --ulimit
--init --user
--interactive --volume
--ip --volumes-from
--link --workdir
--mount
```

### Nested VM

A nested VM is a virtual machine that runs inside of a virtual machine. In plain KVM this feature is
considered working but not meant for production use. Running KVM guests inside guests of other
hypervisors such as VMware might not work as expected or might not work at all.
However to try out runq in a VM guest the (experimental) runq runtime configuration parameter
`--nestedvm` can be used. It modifies the parameters of the Qemu process.

## Developing runq

For fast development cycles runq can be build on the host as follows:

1. Prerequisites:

* Docker >= 19.03.x-ce
* Go >= 1.20
* `/var/lib/runq` must be writable by the current user
* [Libseccomp](https://github.com/seccomp/libseccomp/) static library.
E.g. `libseccomp-dev` for Ubuntu or `libseccomp-static` for Fedora

1. Download runq and runc source code

```sh
git clone --recurse-submodules https://github.com/gotoz/runq.git
```

1. Install Qemu and guest kernel to `/var/lib/runq/qemu`.
All files are taken from the Ubuntu 20.04 LTS Docker base image. (`/var/lib/runq` must be writeable by the current user.)

```sh
cd runq
make -C qemu all install
```

1. Compile and install runq components to `/var/lib/runq`

```sh
make install
```

1. Create TLS certificates

```sh
/var/lib/runq/qemu/mkcerts.sh
```

1. Adjust file and directory permissions

```sh
sudo chown -R root:root /var/lib/runq
```

1. Register runq as Docker runtime with appropriate defaults as shown in section *Installation* above.

## Contributing

See [CONTRIBUTING](CONTRIBUTING.md) for details.

## License

The code is licensed under the Apache License 2.0.

See [LICENSE](LICENSE) for further details.