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--- linux_wiki:kernel-based_virtual_machine_kvm [2015/02/13 21:59]
billdozor
+++ linux_wiki:kernel-based_virtual_machine_kvm [2019/05/25 23:50]
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-====== Kernel-based Virtual Machine (KVM) ======
-Description: KVM is "a full virtualization solution for Linux on x86 hardware containing virtualization extensions." ([[http://www.linux-kvm.org/page/Main_Page|KVM Main Page]]) It can be run on the desktop with GUI managers or on a headless server.
-Assumptions:
-  * Some Red Hat based distro is already installed. (CentOS, Scientific, RHEL, etc)
-  * This page was written using CentOS 6.6
--02-13: These are rough notes and in progress as I learn KVM.
-===== Installation =====
-  * Install: Virtualization Groups
-<code bash>
-yum groupinstall "Virtualization*"
-</code>
-**Group Explanations**
-This will install the following package groups:
-  * Virtualization Tools => Tools for offline virtual image management.
-  * Virtualization Platform => Provides an interface for accessing and controlling virtualized guests and containers.
-  * Virtualization Client => Clients for installing and managing virtualization instances.
-  * Virtualization => Provides an environment for hosting virtualized guests.
-For detailed info and a list of packages that will be installed:
-<code bash>
-yum groupinfo "Virtualization*"
-</code>
-  * Install: Additional Useful Packages
-<code bash>
-yum install bridge-utils dejavu-lgc-sans-fonts tigervnc xorg-x11-xauth
-</code>
-**Packages Descriptions**
-  * bridge-utils => network bridging to allow the VMs to use the host machine's physical interfaces as a bridge.
-  * dejavu-lgc-sans-fonts => Fonts for virt-manager (GUI VM manager)
-  * tigervnc => VNC to connect locally to VM console
-  * xorg-x11-xauth => X11 forwarding through ssh. (Remote virt-manager for headless servers)
-----
-===== Verify Installation and Start Services =====
-  * Ensure that the KVM kernel module is loaded
-<code bash>
-lsmod | grep kvm
-</code>
-  * Start the libvirtd service
-<code bash>
-service libvirtd start
-</code>
-  * Enable libvirtd on system boot
-<code bash>
-chkconfig libvirtd on
-</code>
-  * Verify libvirtd is running successfully
-<code bash>
-service libvirtd status
-virsh -c qemu://system list
-</code>
-----
-===== Setup Networking =====
-By default, VMs will be on a private network with no access to the outside world unless they use a physical host network interface as a bridge.
-==== NetworkManager vs network ====
-  * Turn off NetworkManager, which does not play nice with bridging.
-<code bash>
-chkconfig NetworkManager off
-service NetworkManager stop
-</code>
-  * Ensure the network service is enabled and running.
-<code bash>
-chkconfig network on
-service network start
-</code>
-==== Create a Bridge ====
-  * Create a bridge interface called "br0" that will use the physical interface "eth0" the easy way.
-<code bash>
-virsh iface-bridge eth0 br0
-</code>
-This will create the new file "ifcfg-br0" and modify "ifcfg-eth0" to look as follows:
-**/etc/sysconfig/network-scripts/ifcfg-eth0**
-<code bash>
-DEVICE="eth0"
-HWADDR="00:04:4B:17:3C:FA"
-ONBOOT="yes"
-BRIDGE="br0"
-</code>
-**/etc/sysconfig/network-scripts/ifcfg-br0**
-<code bash>
-DEVICE="br0"
-ONBOOT="yes"
-TYPE="Bridge"
-BOOTPROTO="dhcp"
-STP="on"
-DELAY="0"
-</code>
-br0 will be the interface with an IP address. To make it static, simply edit ifcfg-br0 and change it:
-<code bash>
-DEVICE="br0"
-ONBOOT="yes"
-TYPE="Bridge"
-BOOTPROTO="none"
-STP="on"
-DELAY="0"
-IPADDR="192.168.0.100"
-NETMASK="255.255.255.0"
-GATEWAY="192.168.0.1"
-</code>
-==== IP Forwarding ====
-  * Enable ip forwarding
-**Edit /etc/sysctl.conf**
-<code>
-inet.ipv4.ip_forward = 1
-</code>
-  * Apply settings
-<code bash>
-sysctl -p /etc/sysctl.conf
-</code>
-  * Restart the network service
-<code bash>
-service network restart
-</code>
-----
-===== SELinux =====
-If SELinux is in Enforcing mode, there is additional configuration if you change the default directory for VM images.
-**Default VM Image directory:** /var/lib/libvirt/images/
-==== Changing the Default VM Image Path ====
-  * Create the directory
-<code bash>
-mkdir /vm-images
-</code>
-  * Install the following package to enable use of the "semanage" utility.
-<code bash>
-yum install policycoreutils-python
-</code>
-  * Set security context for the vm-images directory and everything that is created under it.
-<code bash>
-semanage fcontext -a -t virt_image_t "/vm-images(/.*)?"
-</code>
-  * Restore the security context (I don't know why you have to do this yet...but you do)
-<code bash>
-restorecon -R /vm-images
-</code>
-  * Verify
-<code bash>
-ls -Z /vm-images
-</code>
-----
-===== Creating VMs =====
-VMs can be installed via a command line tool (virt-install) or a GUI (virt-manager).
-==== CLI: virt-install ====
-virt-install has many options, see them with "virt-install --help".
-Common options:
-<code bash>
-General Options
---name=NAME  (Name of the guest)
---ram=MEMORY  (Memory in megabytes)
---vcpus=VCPUS  (Number of vcpus)
-Installation Method
---cdrom=CDROM  (CD-ROM installation media, can be ISO or physical cd-rom drive)
---location=LOCATION  (Installation source via http, ftp, or nfs.)
---pxe  (Boot from network using PXE)
---extra-args "ks=http://myserver/mykickstartfile.ks"  (Path to kickstart file for automated installs)
-Storage Configuration
---disk=DISKOPTS  (Storage with different options)
-  --disk path=/my/existing/disk
-  --disk path=/my/new/disk,size=10 (in GB)
-Network
---network bridge=br0  (Guest network interface)
-Graphics
---graphics=GRAPHICS  (Guest display settings)
-  --graphics vnc  (Default if DISPLAY environment variable is set)
-  --graphics none  (Default if DISPLAY environment variable is not set)
-</code>
-=== Example: Interactive Install with VNC ===
-Install a VM called "centos1", create a 20GB hard drive, 1 CPU, 1GB ram, point it to the iso, have it use the network interface "br0"
-<code bash>
-virt-install \
---name=centos1 \
---disk path=/vm-images/centos1.img,size=20 \
---vcpus=1 --ram=1024 \
---cdrom=/vm-images/CentOS-6.6-x86_64-netinstall.iso \
---network bridge=br0
-</code>
-=== Connect to Guest for Installation ===
-After the VM is created, if you are using the "--graphics vnc" option (either by default or explicitly), a console is opened up for interactive install.
-If you close it, this is how you can connect back to the guest:
-  * **Method 1: Connect directly to the guest console**
-Example connect to the guest named "centos1" (Yes, that is 3 slashes)
-<code bash>
-virt-viewer --connect qemu:///system centos1
-</code>
-  * **Method 2: Open virt-manager**
-Example open virt-manager and then the VM "centos1"
-<code bash>
-virt-manager
-</code>
-    * Select the VM
-    * Click "Open"
-Proceed with installation as normal.
-----
-==== GUI: virt-manager ====
-Installing locally via a GUI.
-  * Open a terminal and type:
-<code bash>
-virt-manager
-</code>
-  * The virt-manager GUI will open.
-  * Select the name of the host (probably "localhost (QEMU)")
-  * Click the "Create a New Virtual Machine" button (the monitor with a play button on it)
-    * Step 1 =>
-      * Name: Name the virtual machine
-      * Choose how to install: Select the install method
-    * Step 2 =>
-      * Browse for the media
-      * OS Type/Version: Optionally, select the OS type and version
-    * Step 3 =>
-      * Memory/CPU: Select memory and CPU.
-    * Step 4 =>
-      * Storage: Create or use existing storage
-    * Step 5 =>
-      * Ready to install: Confirm settings, set advanced options such as Host network device.