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86 lines
3.7 KiB
Markdown
86 lines
3.7 KiB
Markdown
# LinuxKit with qemu/kvm
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The `qemu` backend is the most versatile `run` backend for
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`linuxkit`. It can boot both `x86_64` and `arm64` images, runs on
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macOS and Linux (and possibly Windows), and can boot most types of
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output formats. On Linux, `kvm` acceleration is enabled by default if
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available. On macOS, `hvf` acceleration (using the Hypervisor
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framework) is used if your `qemu` version supports it (versions
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released after Jan/Feb 2018 should support it). `s390x` is currently
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only supported in `kvm` mode as the emulated `s390x` architecture (aka
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`tcg` mode) does not seem to support several required platform
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features. Further, on `s390x` platforms you need to set
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`vm.allocate_pgste=1` via `sysctl` (or use `echo 1 >
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/proc/sys/vm/allocate_pgste`).
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## Boot
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By default `linuxkit run qemu` will boot with the host architecture
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(e.g., `aarch64` on `arm64` systems). The architecture can be
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specified with `-arch` and currently accepts `x86_64`, `aarch64`, and
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`s390x` as arguments.
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`linuxkit run qemu` can boot in different types of images:
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- `kernel+initrd`: This is the default mode of `linuxkit run qemu` [`x86_64`, `arm64`, `s390x`]
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- `kernel+squashfs`: `linuxkit run qemu -squashfs <path to directory>`. This expects a kernel and a squashfs image. [`x86_64`, `arm64`, `s390x`]
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- `iso-bios`: `linuxkit run qemu -iso <path to iso>` [`x86_64`]
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- `iso-efi`: `linuxkit run qemu -iso -uefi <path to iso>`. This looks in `/usr/share/ovmf/bios.bin` for the EFI firmware by default. Can be overwritten with `-fw`. [`x86_64`, `arm64`]
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- `qcow-bios`: `linuxkit run qemu disk.qcow2` [`x86_64`]
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- `raw-bios`: `linuxkit run qemu disk.img` [`x86_64`]
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- `aws`: `linuxkit run qemu disk.img` boots a raw AWS disk image. [`x86_64`]
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The formats `qcow-efi` and `raw-efi` may also work, but are currently not tested.
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The default `kernel+initrd` boot uses a RAM disk for the root
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filesystem. If you have RAM constraints or large images we recommend
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using one of the other methods, such as `kernel+squashfs` or booting
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via a ISO image.
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## Console
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With `linuxkit run qemu` the serial console is redirected to stdio,
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providing interactive access to the VM. You can specify `-gui` to get
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a console window.
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## Disks
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The qemu backend supports multiple disks to be attached to the VM
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using the standard `linuxkit` `-disk` syntax. The qemu backend
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supports a number of different disk formats.
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## Networking
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The `qemu` backend supports a number of networking options, depending
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on the platform you are running. The default is the userspace
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networking which provides the VM with a internal DHCP server and
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network connectivity, but does not provide access to the VMs network
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from the outside.
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With user mode networking you can publish selected VM ports on the
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host, using the `-publish` option. It uses the same syntax as the
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`qemu` binary. For example `linuxkit run qemu -publish 8080:80
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linuxkit` exposes port `80` from the VM as port `8080` on the host.
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On Linux, you can attach the VM either to an existing bridge or tap
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interface. These require root privileges and you may want to use the
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[`qemu-bridge-helper`](http://wiki.qemu.org/Features/HelperNetworking). To
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attach to an existing bridge `br0` (e.g., one created with
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`virt-manager`) you can use `linuxkit run qemu -networking
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bridge,br0 linuxkit`.
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## Integration services and Metadata
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The `qemu` backend also allows passing custom userdata into the
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[metadata package](./metadata.md) using either the `-data` or
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`-data-file` command-line option. This attaches a CD device with the
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data on.
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If the `linuxkit/qemu-ga` package is added to the YAML the [Qemu Guest
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Agent](https://wiki.libvirt.org/page/Qemu_guest_agent) will be
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enabled. This provides better integration with `libvirt`.
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