Add README

readme.md

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+# qemu-docker
+
+This repository contains a Docker container for running x86\_64 virtual
+machines using QEMU. It uses high-performance QEMU options
+(KVM, and TAP network driver).
+
+Docker Hub: [jkz0/qemu](https://hub.docker.com/r/jkz0/qemu)
+
+## Using the container
+
+Via `docker run`:
+
+```bash
+$ docker run --rm -it \
+    --device=/dev/kvm:/dev/kvm --device=/dev/net/tun:/dev/net/tun \
+    --cap-add NET_ADMIN -v $VM_IMAGE_FILE:/image \
+    jkz0/qemu:latest
+```
+
+Via `docker-compose.yml`:
+
+```yaml
+version: "3"
+services:
+    vm:
+        image: jkz0/qemu:latest
+        cap_add:
+            - NET_ADMIN
+        devices:
+            - /dev/net/tun
+            - /dev/kvm
+        volumes:
+            - ${VM_IMAGE:?VM image must be supplied}:/image
+        restart: always
+```
+
+## Tips 
+
+* VM networking is configured via DHCP, make sure to enable DHCP in your
+  VM image. VMs will use the IP address of the container.
+* You can quit the VM (when attached to the container) by entering the special
+  key sequence `C-a x`. Killing the docker container will also shut down the
+  VM.
+
+## Caveat Emptor
+
+* Only x86\_64 supported new. PRs to support other architectures welcome,
+  though I imagine 99% of use-cases will be x86\_64.
+* VMs will not be able to resolve container-names on user-defined bridges.
+  This is due to the way Docker's "Embedded DNS" server works. VMs can still
+  connect to other containers on the same bridge using IP addresses.