If you've used QEMU for much, you've created more shell scripts than you've wanted to in order to manage it all.
These tools provide a simple and reusable framework for a scriptable VM server.
They attempt to be generic enough that you can make some small edits to these example templates and instantly have tools suitable enough to create auto-booting production VMs. At the same time, the simple nature of these scripts doesn't get in the way of all the fancy QEMU developer sauce you don't get with "real" virtual machine managers.
alpine-aarch64- AArch64 softcpu emulator running the Alpine Linux live cdalpine-i386- i386 softcpu emulator running the Alpine Linux live cd (you probably want x86 on x86_64+kvm though)alpine-ppc64- PPC64 softcpu emulator running the Alpine Linux live cdalpine-x86_64- x86_64/x86 (KVM Hypervisor) running the Alpine Linux live cdhugepages- Quick example of using hugetlbfs for optimized guest memorylvmraid_vlanbridge- More involved example showing an optimized LVM setup and the use of VLANFiltering with Linux bridgingwin10- Windows 10 VM with some Hyper-V tuning
Dependencies:
GNU screensocat,libreadline(formonitorcommand)
More involved features might require other tools.
The demo.sh example downloads a Linux installation cd and boots it with basic disk and networking.
Just run the start command like so, it'll format the disk and download the installer automatically:
[sean@kor] $ sudo ./demo.sh start
10240+0 records in
10240+0 records out
41943040 bytes (42 MB, 40 MiB) copied, 0.0400444 s, 1.0 GB/s
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 755M 100 755M 0 0 6988k 0 0:01:50 0:01:50 --:--:-- 10.0M
[sean@kor] $ sudo ./demo.sh status
VM status: running
Just run install.sh.
The installer places [email protected] into /etc/systemd/system and places the example vm.sh files into /etc/qemu.
Now run you can run systemd commands like the following to manage your vms:
systemctl enable --now qemu@demo
[root@vm ~]# systemctl status qemu@demo
● [email protected] - QEMU virtual machine
Loaded: loaded (/etc/systemd/system/[email protected]; enabled; vendor preset: disabled)
Active: active (running) since Sun 2021-05-02 01:48:03 CDT; 5s ago
Process: 35368 ExecStart=/etc/qemu/demo.sh start (code=exited, status=0/SUCCESS)
Main PID: 35221 (qemu-system-x86)
Tasks: 0 (limit: 76892)
Memory: 4.0K
CPU: 64ms
CGroup: /system.slice/system-qemu.slice/[email protected]
‣ 35221 qemu-system-x86_64 -pidfile /run/qemu/demo/demo.pid -name demo -cpu host --enable-kvm -m 2G -nographic ->
May 02 01:48:03 vm systemd[1]: Starting QEMU virtual machine...
May 02 01:48:03 vm demo.sh[35368]: this vm is already running!
May 02 01:48:03 vm systemd[1]: [email protected]: Supervising process 35221 which is not our child. We'll most likely not not>
May 02 01:48:03 vm systemd[1]: Started QEMU virtual machine.
This will create and start the demo VM, and enable it to start on every boot.
To disable it, run systemctl disable -now qemu@demo
To delete the resources from disk, run /etc/qemu/demo.sh delete
This can create disks, download ISO or disk images, or configure any other persistent resources the VM might need.
[root@vm systemd-qemu]# ./demo.sh create
Logical volume "vm.demo.root" created.
Logical volume "vm.demo.root.cache" created.
Logical volume vg0/vm.demo.root is now cached.
Logical volume "vm.demo.swap" created.
With the command option you can send one-liner commands to QEMU like so:
[root@vm ~]# /etc/qemu/demo.sh command info network
virtio-net-pci.0: index=0,type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:56
\ n1: index=0,type=tap,ifname=demo0,script=no,downscript=no
[root@vm ~]# /etc/qemu/demo.sh command info registers
RAX=ffffffff9eadb380 RBX=0000000000000000 RCX=0000000000000001 RDX=000000000005ac02
RSI=0000000000000087 RDI=0000000000000000 RBP=ffffffff9f603e38 RSP=ffffffff9f603e18
R8 =ffff8ba638a1e4a0 R9 =0000000000000200 R10=0000000000000000 R11=0000000000000000
R12=0000000000000000 R13=ffffffff9f613780 R14=0000000000000000 R15=0000000000000000
RIP=ffffffff9eadb76e RFL=00000246 [---Z-P-] CPL=0 II=0 A20=1 SMM=0 HLT=1
...
Or, you can use the monitor option to run commands interactively within a readline shell.
Swapping the cdrom:
[root@vm ~]# /etc/qemu/demo.sh monitor
QEMU 5.2.0 monitor - type 'help' for more information
(qemu) eject -f ide1-cd0
eject -f ide1-cd0
(qemu) change ide1-cd0 /isos/ubuntu-20.04.iso
change ide1-cd0 /isos/ubuntu-20.04.iso
Enable VNC access:
[root@vm ~]# /etc/qemu/demo.sh monitor
QEMU 5.2.0 monitor - type 'help' for more information
(qemu) change vnc 127.0.0.1:0
change vnc 127.0.0.1:0
(qemu) change vnc password
change vnc password
Password: hunter2
Also, by default, QEMU runs inside its own screen session. If you want access to the serial console of your vm, just run screen -DR demo. Here you can see the bios, and if your OS has a serial console enabled, you can interact with that too.
Usage: vmname.sh (start | run | wait | status | create | command | monitor | shutdown | reboot | delete)
Management util for creating/launching/monitoring a QEMU virtual machine
Commands:
start: run this virtual machine and return
run: run this virtual machine and wait until it powers off
wait: wait until the VM powers off and then cleanup
status: show the VMs current run status
create: create new virtual disks and anyh other one-time setup
command: run a monitor command (like 'info vnc' or 'device add ...')
monitor: start a monitor shell (^D to exit, 'quit' will terminate the VM)
shutdown: shutdown the VM gracefully (like short-pressing the power button)
reboot: reset the VM
delete: delete the disks and any other persistent resources
There are 3 main ways to go about customizing a VM script.
- Adding/removing setup macros in the VM script
- Defining "hook" functions
- Implementing "site" libraries
The first line in any VM script should include the main qemuonrails.sh library like so:
. $(dirname $0)/lib/qemuonrails.shSimilarly, the last line in the vmscript should always be:
command_handler "$@"Most scripts will want to include some common functionality:
include platforms
include disk
include networkThe plaforms library contains a collection of common settings for various hardware and software combinations. These will usually pre-define which CPU and Machine type to use, if KVM should be enabled, SMP, common peripherals, etc.
It also exposes a few helper functions to override the defaults, like so:
memory 4G
processors 2The disk library will auto-provision new disk images for you when your VM is created and clean them up when it is deleted. It has support for flat file images, qcow2 images, and it can also download and cache images from a given URL.
Examples:
disk raw -name "rootfs" -size 10G -if virtio
disk qcow -name "c-drive" -size 64G -if virtio
cdrom -url "https://dl-cdn.alpinelinux.org/alpine/v3.13/releases/x86_64/alpine-standard-3.13.5-x86_64.iso"
cdrom -path "/home/sean/Windows10.iso"At present, the only one default networking mode is supported: usermode networking. This is because the most common other modes require pre-existing system configuration, like bridging to be up and ready. There is an example "site" library for dealing with this, but it is always going to be rather specific to the individual host.
network virtio_userTo further customize the virtual machine environment, you can define one of a few main shell functions that allow you to inject arguments at various points in the vm creation and startup process.
data_create: this function is called when the vm data is created for the first time.data_delete: called when deleting all persistent vm resourcesnetwork_create: called when turning on the vm to provision network resourcesnetwork_delete: called after the vm has stopped runningqemu_launch: called just before QEMU lauches, giving a last chance to alter the QEMU arguments
These libraries allow you to create new macros specific to your local setup. The examples included add new disk types that support LVM raid and cacheing features as well as new networking types that support bridged tap adapters with hidden vlan tagging.