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--- linux_wiki:kernel-based_virtual_machine_kvm [2015/02/13 21:16]
billdozor
+++ linux_wiki:kernel-based_virtual_machine_kvm [2019/05/25 23:50] (current)
@@ Line 1: / Line 1: @@
 ====== 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.
+**General Information**
-Assumption: Some Red Hat based distro is already installed. (CentOS, Scientific, RHEL, etc)
+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.
--02-13: These are rough notes and in progress as I learn KVM.
+**Checklist**
+  * Distro(s): Enterprise Linux 6
+  * Other: This page was written using CentOS 6.6 with GNOME desktop (headless KVM is on the to do list!)
+  * 2015-02-13: These are rough notes and in progress as I learn KVM.
-===== Installation =====
+----
-  * Install: Virtualization Groups
+====== Installation ======
+==== Install: Required Virtualization Packages (CLI) ====
 <code bash>
-yum groupinstall "Virtualization*"
+yum install qemu-kvm python-virtinst virt-top libvirt libvirt-client
 </code>
-**Group Explanations**
+**CLI Package Explanations**
-This will install the following package groups:
+  * qemu-kvm => The main KVM package.
-  * Virtualization Tools => Tools for offline virtual image management.
+  * python-virtinst => CLI tools and libraries for creating VMs.
-  * Virtualization Platform => Provides an interface for accessing and controlling virtualized guests and containers.
+  * virt-top => CLI VM stats.
-  * Virtualization Client => Clients for installing and managing virtualization instances.
+  * libvirt => Toolkit for libvirtd service.
-  * Virtualization => Provides an environment for hosting virtualized guests.
+  * libvirt-client => Toolkit for VM clients.
-For detailed info and a list of packages that will be installed:
+==== Install: Optional Virtualization Packages (GUI) ====
 <code bash>
-yum groupinfo "Virtualization*"
+yum install virt-manager virt-viewer
 </code>
-  * Install: Additional Useful Packages
+**GUI Package Explanations**
+  * virt-manager => GUI VM administration tool.
+  * virt-viewer => GUI local console connection to VMs.
+==== Install: Optional Useful Packages ====
 <code bash>
 yum install bridge-utils dejavu-lgc-sans-fonts tigervnc xorg-x11-xauth
@@ Line 35: / Line 45: @@
   * 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
+  * tigervnc => VNC to connect remotely to VM's GUI.
   * xorg-x11-xauth => X11 forwarding through ssh. (Remote virt-manager for headless servers)
 ----
-===== Verify Installation and Start Services =====
+====== Verify Installation and Start Services ======
   * Ensure that the KVM kernel module is loaded
 <code bash>
-lsmod | grep kvm
+[root@bash ~]# lsmod | grep kvm
+kvm_intel              55496  0
+kvm                   337900  1 kvm_intel
+</code>
+    * If it is not loaded, attempt to load the module:
+<code bash>
+modprobe -v kvm
 </code>
@@ Line 60: / Line 77: @@
 </code>
-  * Verify libvirtd is running successfully
+  * Verify libvirtd is running successfully (Yes, 3 forward slashes)
 <code bash>
 service libvirtd status
-virsh -c qemu://system list
+virsh -c qemu:///system list
 </code>
 ----
-===== Setup Networking =====
+====== 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.
@@ Line 125: / Line 142: @@
 NETMASK="255.255.255.0"
 GATEWAY="192.168.0.1"
+DNS1="208.67.222.222"
+DNS2="208.67.220.220"
 </code>
+Note: Those DNS entries are for OpenDNS.
 ==== IP Forwarding ====
@@ Line 148: / Line 168: @@
 ----
-===== SELinux =====
+====== SELinux ======
-If SELinux is in Enforcing mode, there is additional configuration if you change the default directory for VM images.
+If SELinux is on and in Enforcing mode, there is additional configuration if you change the default directory for VM images.
+**Check if SELinux is on/enabled**
+<code bash>
+[bash]# sestatus
+SELinux status:                 enabled
+SELinuxfs mount:                /selinux
+Current mode:                   enforcing
+</code>
 **Default VM Image directory:** /var/lib/libvirt/images/
@@ Line 159: / Line 187: @@
 </code>
-  * Install the following package to enable use of the "semanage" utility.
+  * Set the context of the new directory, referencing the default
+<code bash>
+chcon -R --reference /var/lib/libvirt/images /vm-images
+</code>
+  * Verify
 <code bash>
-yum install policycoreutils-python
+ls -Z /vm-images
 </code>
-  * Set security context for the vm-images directory and everything that is created under it.
+  * Create a symlink to the new location to ensure that is survives a SELinux relabel.
+<code bash>
+rmdir /var/lib/libvirt/images
+ln -s /vm-images /var/lib/libvirt/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>
-semanage fcontext -a -t virt_image_t "/vm-images(/.*)?"
+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>
-  * Restore the security context (I don't know why you have to do this yet...but you do)
+=== 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>
-restorecon -R /vm-images
+virt-viewer --connect qemu:///system centos1
 </code>
-  * Verify
+  * **Method 2: Open virt-manager**
+Example open virt-manager and then the VM "centos1"
 <code bash>
-ls -Z /vm-images
+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.
+----
+====== Disabling virbr0 NAT Interface ======
+On some desktop installations, a NAT interface "virbr0" is auto created.
+To disable this interface:
+  * View the interface<code bash>virsh net-list</code>
+  * Turn off the interface<code bash>virsh net-destroy default</code>
+  * Disable auto start on the interface<code bash>virsh net-autostart default –disable</code>
+  * Verify State is "inactive" and Autostart is "no", then ensure virbr0 is not in the interface list<code bash>virsh net-list --all
+ip addr show</code>
+  * Restart the network service
+    * EL6<code bash>service network restart</code>
+    * EL7<code bash>systemctl restart network</code>
+----