|
|
@@ -0,0 +1,107 @@
|
|
|
+---
|
|
|
+title: libvirt & KVM
|
|
|
+breadcrumbs:
|
|
|
+- title: Configuration
|
|
|
+- title: Virtualization & Containerization
|
|
|
+---
|
|
|
+{% include header.md %}
|
|
|
+
|
|
|
+libvirt is a tool for managing platform virtualization like KVM and QEMU (among others).
|
|
|
+I'll only focus on using it with KVM (and QEMU) here.
|
|
|
+
|
|
|
+Using **Debian**.
|
|
|
+
|
|
|
+## General
|
|
|
+
|
|
|
+- Requires Intel VT or AMD-V to be enabled to function optimally.
|
|
|
+- Note that running commands as non-root or not in the libvirt group will generally work but will not show all VMs. etc.
|
|
|
+
|
|
|
+## Installation
|
|
|
+
|
|
|
+1. Install without extra stuff (like GUIs): `apt-get install --no-install-recommends iptables bridge-utils qemu-system qemu-utils libvirt-clients libvirt-daemon-system virtinst libosinfo-bin`
|
|
|
+1. (Optional) Install `dnsmasq-base` for accessing guests using their hostnames.
|
|
|
+1. (Optional) Add users to the `libvirt` group to allow them to manage libvirt without sudo.
|
|
|
+
|
|
|
+## Usage
|
|
|
+
|
|
|
+### Manage VMs
|
|
|
+
|
|
|
+- Show VMs: `virsh list --all`
|
|
|
+- Start/shutdown/reboot/kill VM: `virsh {start | shutdown | reboot | kill} <vm>`
|
|
|
+- Suspend/resume VM: `virsh {suspend | resume} <vm>`
|
|
|
+- Enter/exit console for VM:
|
|
|
+ - Enter: `virsh console <vm>`
|
|
|
+ - Exit: `Ctrl+¨` (Norwegian) or `Ctrl+]` (US)
|
|
|
+- Create VM:
|
|
|
+ - Example: `virt-install --name=example-vm --network=network=default,model=virtio --os-variant=debian10 --ram=$((1*1024)) --vcpus=1 --disk=path=/var/lib/libvirt/images/example-vm.qcow2,bus=virtio,size=5 --graphics=none --check=all=off --extra-args="console=ttyS0" --location=debian-10.7.0-amd64-netinst.iso`
|
|
|
+ - The disk path should match a storage pool path.
|
|
|
+ - Show available OS variants: `osinfo-query os`
|
|
|
+ - This will automatically open a console for the VM. Specify `--noautoconsole` to avoid that.
|
|
|
+ - If it "can't find the kernel" when using `--location`, use `--cdrom` instead. This disallows using arguments like `--extra-args`, so you'll need to find another console.
|
|
|
+ - Make sure the ISO is readable by the QEMU user.
|
|
|
+ - To install using a VNC screen instead of console (e.g. if you need richer graphics or when using `--cdrom` and no console is allocated), replace `--graphics=none` with `--noautoconsole --graphics=vnc,password=<password>`. It only binds to localhost by default, so use something like SSH port forwarding (`ssh -L 5900:127.0.0.1:5900 <user>@<addr>`) to access it remotely.
|
|
|
+- Clone VM:
|
|
|
+ 1. Create a source/template VM and make sure it's not running.
|
|
|
+ 1. Clone it: `virt-clone --original=<source-vm> --name=<vm> -f <vm>.qcow2`
|
|
|
+- Remove VM: `virsh undefine <vm>`
|
|
|
+- Set VM to automatically start (or disable it): `virsh autostart [--disable] <vm>`
|
|
|
+- Edit VM config: `virsh edit <vm>`
|
|
|
+- Show VM config: `virsh dumpxml <vm>`
|
|
|
+- Show VM graphics URI: `virsh domdisplay <vm>`
|
|
|
+ - For VNC, the shown port is offset from port 5900.
|
|
|
+- Run QEMU monitor command: `qemu-monitor-command <vm> --hmp <command>`
|
|
|
+
|
|
|
+### Networking
|
|
|
+
|
|
|
+- Set up networking on host:
|
|
|
+ 1. Enable IP forwarding on the system (IPv4 and IPv6).
|
|
|
+ 1. Create bridges to connect VMs to networks.
|
|
|
+ 1. Add firewall rules to allow traffic.
|
|
|
+- Show networks: `virsh net-list`
|
|
|
+- Show network config: `virsh net-dumpxml <network>`
|
|
|
+- Edit network config (without applying it): `virsh net-edit <network>`
|
|
|
+- Apply changed network config: Restart libvirt or reboot the system.
|
|
|
+- The default network interface is `virbr0`, called `default` in libvirt.
|
|
|
+- Enable the default network: `virsh net-start default && virsh net-autostart default`
|
|
|
+
|
|
|
+### Storage
|
|
|
+
|
|
|
+- Effectively, the pool is a directory while the files in it (typically disk images) are the volumes.
|
|
|
+- Pool basics:
|
|
|
+ - Show pools: `virsh pool-list [--all] [--details]`
|
|
|
+- Volume basics:
|
|
|
+ - Show volumes: `virsh list-vol <pool> [--details]`
|
|
|
+ - Show volume info: `virsh vol-info <file>`
|
|
|
+- Create default storage pool:
|
|
|
+ 1. Create it: `virsh pool-define-as default --type=dir --target=/var/lib/libvirt/images`
|
|
|
+ 1. Start it: `virsh pool-start default`
|
|
|
+ 1. Autostart it: `virsh pool-autostart default`
|
|
|
+- Resize disk: `qemu-img resize <file> <size-change>` (e.g. +1G)
|
|
|
+- Cold backup of VM:
|
|
|
+ - Make sure the VM is stopped so that the disk image is consistent.
|
|
|
+ - Backup the image in `/var/lib/libvirt/images/`.
|
|
|
+ - Backup the config in `/etc/libvirt/qemu/`.
|
|
|
+
|
|
|
+### Snapshots
|
|
|
+
|
|
|
+- The current snapshot means the last one.
|
|
|
+- List snapshots for a VM: `virsh snapshot-list <vm>`
|
|
|
+- Show snapshot info: `virsh snapshot-info --domain=<vm> [--current]`
|
|
|
+- Create snapshot: `virsh snapshot-create-as --domain=<vm> --name=<snapshot> --description=<description>`
|
|
|
+- Revert a snapshot:
|
|
|
+ 1. Stop the VM.
|
|
|
+ 1. Revert a named or the current snapshot: `virsh snapshot-revert {--domain=<vm> | --current} --snapshotname=<snapshot> [--running]`
|
|
|
+
|
|
|
+### Tuning
|
|
|
+
|
|
|
+Assign more CPU cores. When adding many, attempt to assign every hyperthreaded twin to the same VM.
|
|
|
+TODO Cache mode write-through and write-back.
|
|
|
+Consider enabling huge pages.
|
|
|
+Consider using memory ballooning to save memory on the host when the VM doesn't need it.
|
|
|
+
|
|
|
+### Miscellanea
|
|
|
+
|
|
|
+- Use `LIBVIRT_DEFAULT_URI=qemu:///system` to use the system URI.
|
|
|
+- To repair a corrupted QEMU disk, try using `guestfish`.
|
|
|
+
|
|
|
+{% include footer.md %}
|
Håvard O. Nordstrand