====== KVM manual ======

===== General =====

This document shows and describes the most important commands for a KVM environment.

===== Host setup =====

Before you can start with any virtual machine, you have to install the following packages first:

<code bash>
dnf -y install virt-install libvirt-daemon-kvm qemu-kvm libvirt-client qemu libvirt-daemon
</code>

It’s not a bad idea, to check, if your host system is virtualisation capable.

<code bash>
virt-host-validate
  QEMU: Checking for hardware virtualization                                 : PASS
  QEMU: Checking if device /dev/kvm exists                                   : PASS
  QEMU: Checking if device /dev/kvm is accessible                            : PASS
  QEMU: Checking if device /dev/vhost-net exists                             : PASS
  QEMU: Checking if device /dev/net/tun exists                               : PASS
  QEMU: Checking for cgroup 'memory' controller support                      : PASS
  QEMU: Checking for cgroup 'memory' controller mount-point                  : PASS
  QEMU: Checking for cgroup 'cpu' controller support                         : PASS
  QEMU: Checking for cgroup 'cpu' controller mount-point                     : PASS
  QEMU: Checking for cgroup 'cpuacct' controller support                     : PASS
  QEMU: Checking for cgroup 'cpuacct' controller mount-point                 : PASS
  QEMU: Checking for cgroup 'cpuset' controller support                      : PASS
  QEMU: Checking for cgroup 'cpuset' controller mount-point                  : PASS
  QEMU: Checking for cgroup 'devices' controller support                     : PASS
  QEMU: Checking for cgroup 'devices' controller mount-point                 : PASS
  QEMU: Checking for cgroup 'blkio' controller support                       : PASS
  QEMU: Checking for cgroup 'blkio' controller mount-point                   : PASS
  QEMU: Checking for device assignment IOMMU support                         : PASS
  QEMU: Checking if IOMMU is enabled by kernel                               : WARN (IOMMU appears to be disabled in kernel. Add intel_iommu=on to kernel cmdline arguments)
   LXC: Checking for Linux >= 2.6.26                                         : PASS
   LXC: Checking for namespace ipc                                           : PASS
   LXC: Checking for namespace mnt                                           : PASS
   LXC: Checking for namespace pid                                           : PASS
   LXC: Checking for namespace uts                                           : PASS
   LXC: Checking for namespace net                                           : PASS
   LXC: Checking for namespace user                                          : PASS
   LXC: Checking for cgroup 'memory' controller support                      : PASS
   LXC: Checking for cgroup 'memory' controller mount-point                  : PASS
   LXC: Checking for cgroup 'cpu' controller support                         : PASS
   LXC: Checking for cgroup 'cpu' controller mount-point                     : PASS
   LXC: Checking for cgroup 'cpuacct' controller support                     : PASS
   LXC: Checking for cgroup 'cpuacct' controller mount-point                 : PASS
   LXC: Checking for cgroup 'cpuset' controller support                      : PASS
   LXC: Checking for cgroup 'cpuset' controller mount-point                  : PASS
   LXC: Checking for cgroup 'devices' controller support                     : PASS
   LXC: Checking for cgroup 'devices' controller mount-point                 : PASS
   LXC: Checking for cgroup 'blkio' controller support                       : PASS
   LXC: Checking for cgroup 'blkio' controller mount-point                   : PASS
</code>

| **Note:**  | The warning about ''%%IOMMU%%'' can be ignored.  |

==== Test installation tree ====

<code bash>
curl -O http://192.168.122.1/fedora/27/os/
curl -O http://192.168.122.1/centos/7.4/os/
</code>

===== Environment =====

<code bash>
virsh dumpxml <domain name> > <outputfile>.xml
</code>

<code bash>
virsh create <outputfile>.xml
</code>

===== Basic commands =====
  * Completely delete a VM:<code bash>
virsh --connect qemu:///system destroy fedora27
virsh --connect qemu:///system undefine fedora27
</code>| **Note:**  | This does not delete the data on the disk (Logical Volume or image)!  |
  * Unordered List ItemEdit/configure the settings of a virtual machine (domain):<code bash>
virsh edit <domain name>
</code>
  * Unordered List ItemList all (also not started VM's):<code bash>
virsh --connect qemu:///system list --all
 Id    Name                           State
----------------------------------------------------
 4     cc                             running
 9     centos7                        running
 -     fedora27                       shut off
</code>
  * Start a console session for a VM:<code bash>
virsh --connect qemu:///system console centos7
</code>
  * Setup autostart (when booting the KVM server) for a VM:<code bash>
virsh --connect qemu:///system autostart centos7
</code>

| **Note:**  | To remove autostart toggle, just run this command again!  |

===== Installation of VM’s =====

If you want to add a second network interface, you should add it after the ''%%kickstart%%'' installation. If there are two or more interfaces configured, the installer (''%%dracut%%'') does not find the network based installation files. Here two example domains, one is a Fedora server and one is a CentOS server.

==== Fedora ====

In this example the new virtual machine or domain (fedora27) will be installed using kickstart. Following features are given:

  * The disk is a logical volume (''%%/dev/mapper/sysvg-fedora27%%'')
  * The VM has two CPU’s and 2GB of RAM
  * The VM has two network interfaces, one for internal guest/host comunication (the default network), and one for external connections via ''%%macvtap%%'' protocol
  * The installation tree lifes on a webserver ( http://dangiga.danlocal.net/fedora/27/os/ )

<code bash>
virt-install --connect qemu:///system --name fedora27 \
    --disk path=/dev/mapper/sysvg-fedora27 --graphics spice \
    --vcpus 2 --ram=2048 --network bridge=virbr0 --os-type=linux \
    --os-variant=fedora26 --accelerate --noautoconsole --hvm \
    --location=http://dangiga.danlocal.net/fedora/27/os/ \
    --extra-args ks=http://dangiga.danlocal.net/ks/def-fedora27.ks console=ttyS0
virsh attach-interface --domain fedora27 --type direct --source enp0s31f6 --model virtio --config
virsh --connect qemu:///system console fedora27
</code>

| **Note:**  | In this example, we install a second network interface for direct connection to physical interface of the KVM host!  |

| **Info:**  | If you want to configure a fix MAC address, use ''%%--mac=52:54:00:f3:30:0f%%'' switch in the ''%%--network%%'' context!  |

==== Centos ====
In this example the new virtual machine or domain (centos7) will be installed using kickstart. Following features are given:

  * The disk is a logical volume (''%%/dev/mapper/sysvg-centos7%%'')
  * The VM has two CPU’s and 2GB of RAM
  * The VM has one network interfaces for internal guest/host comunication (the default network) only
  * The installation tree lifes on a webserver ( http://dangiga.danlocal.net/centos/7.4/os/ )

<code bash>
virt-install --connect qemu:///system --name centos7 \
    --disk path=/dev/mapper/sysvg-centos7 --graphics spice --vcpus 2 \
    --ram=2048 --network bridge=virbr0 --os-type=linux \
    --os-variant=centos7.0 --accelerate --noautoconsole --hvm \
    --location=http://dangiga.danlocal.net/centos/7.4/os/ \
    --extra-args "ks=http://dangiga.danlocal.net/ks/def-centos7.ks console=ttyS0"
virsh --connect qemu:///system console centos7
</code>

===== Networking =====
  * List all networks:<code bash>
virsh net-list --all
</code>
  * Attach a network interface to a virtual machine (domain):<code bash>
virsh attach-interface --domain <vm name> --type bridge --source virbr0 --model virtio --config --live
</code><code bash>
virsh attach-interface --domain <vm name> --type direct --source enp0s31f6 --model virtio --config --live
</code>

| **Note:**  | The ''%%--live%%'' switch only works, if the VM is started!  |

  * Unordered List ItemIf you want to figure out the IP addresss of one or more VM’s, you can use the following command executed on the KVM host:<code bash>
vm=fedora27
for mac in `virsh domiflist $vm |grep -o -E "([0-9a-f]{2}:){5}([0-9a-f]{2})"` ; do
    arp -e |grep $mac  |grep -o -P "^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}"
done
</code>

==== Edit networks ====

  * Unordered List ItemThe ''%%virsh%%'' command also provides a editor for a network configuration. In this example the default network is edited.<code bash>
virsh net-edit default
</code>
  * Show the network configuration of a network (here ''default'' net):<code bash>
virsh net-dumpxml default
</code>Output:<code bash>
<network>
  <name>default</name>
  <uuid>fffdb071-f34b-4672-b8c5-48ee04d7ab4b</uuid>
  <forward mode='nat'>
    <nat>
      <port start='1024' end='65535'/>
    </nat>
  </forward>
  <bridge name='virbr0' stp='on' delay='0'/>
  <mac address='52:54:00:65:80:59'/>
  <ip address='192.168.xxx.1' netmask='255.255.255.0'> (1)
    <dhcp>
      <range start='192.168.122.40' end='192.168.xxx.254'/>
      <host mac='52:54:00:f3:30:0f' ip='192.168.xxx.xx'/> (2)
      <host mac='52:54:00:f3:30:1f' ip='192.168.xxx.xx'/>
      <host mac='52:54:00:f3:30:2f' ip='192.168.xxx.xx'/>
    </dhcp>
  </ip>
</network>
</code>

|**1**|Network IP and netmask                         |
|**2**|Define a fix IP address for a given MAC address|

  * Unordered List ItemAfter changing anything, you must activate the changed configuration, you have to reload the network:<code bash>
virsh net-destroy default && virsh net-start default
</code>
  * Delete a vm (host) in a network (here ''default'' net):<code bash>
virsh net-update default delete ip-dhcp-host "<host mac='52:54:00:f3:30:2f' name='hostname' ip='192.168.xxx.xxx'/>" --live --config
</code>
  * Add a network configuration (host) live:<code bash>
virsh net-update default add ip-dhcp-host "<host mac='52:54:00:43:56:84' name='hostname' ip='192.168.xxx.xxx'/>" --live --config
</code>

===== Harddisks =====

It’s also possible to add a disk to a running VM. The disk can be a disk image or a LVM volume. It’s possible to resize the disk, but, you have to reboot the client or relaod the kernel disk table (''%%partx%%'', only CentOS >=7).

  * Add (persistent) a disk to a VM:<code bash>
virsh attach-disk ds --source /dev/sysvg/ds_test --target vdb --persistent
</code> \\ This adds a new disk to the ''%%ds%%'' VM as ''%%/dev/vdb%%'' persistently.

| **Note:**  | The disk is a logical volume on the KVM host  |

==== Resize (LVM) disk ====

  * First increase size of the LV on KVM host:<code bash>
lvresize -G <size>G /dev/sysvg/<lv name>
</code>
  * Configure the size of that domain and disk using ''virsh'':<code bash>
virsh blockresize <domain> /dev/sysvg/<lv name> --size <size>G
</code> \\ Now, you can resize the disk on the domain (VM).