KVM : Create Virtual Machine2022/01/20

	Install GuestOS and Create a Virtual Machine. This example shows to create VM with installing CentOS Stream 9.
[1]	On this example, Download an ISO file of CentOS Stream 9 on a directory first and Install GuestOS from the ISO on the text mode. It's OK on the console or remote connection via SSH and so on. Furthermore, Virtual Machine's images are placed at [/var/lib/libvirt/images] by default as a Storage Pool, however, this example shows to create and use a new Storage Pool. (OK to use any place you like)

# create a Storage Pool directory

[root@dlp ~]#

mkdir -p /var/kvm/images

[root@dlp ~]#

virt-install \

--name centos-st9 \
--ram 4096 \
--disk path=/var/kvm/images/centos-st9.img,size=20 \
--vcpus 2 \
--os-variant centos-stream9 \
--network bridge=br0 \
--graphics none \
--console pty,target_type=serial \
--location /home/CentOS-Stream-9-latest-x86_64-dvd1.iso \
--extra-args 'console=ttyS0,115200n8'

Starting install...

# installation starts

The example of options above means like follows. There are many options for others, make sure with [man virt-install].

--name	specify the name of Virtual Machine
--ram	specify the amount of memory of Virtual Machine
--disk path=xxx,size=xxx	[path=xxx] : specify the location of disks of Virtual Machine (default is [/var/lib/libvirt/images]) [size=xxx] : specify the amount of disk of Virtual Machine
--vcpus	specify the virtual CPUs
--os-variant	specify the kind of GuestOS possible to show the list of available OS with the command below [# osinfo-query os]
--network	specify network type of Virtual Machine
--graphics	specify the kind of graphics possible to specify spice, vnc, none and so on
--console	specify the console type
--location	specify the location of installation source where from
--extra-args	specify parameters that are set in Kernel

[2]	For installing on text mode, it's the same with common installation procedure. After finishing installation, restart computer and then login prompt is shown like follows.

CentOS Stream 9
Kernel 5.14.0-34.el9.x86_64 on an x86_64

Activate the web console with: systemctl enable --now cockpit.socket

localhost login:

[3]	Move to GuestOS to HostOS with Ctrl + ] key. Move to HostOS to GuestOS with a command [virsh console (name of virtual machine)].

[root@localhost ~]#        # Ctrl + ] key
[root@dlp ~]#              # Host's console

[root@dlp ~]# virsh console centos-st9    # switch to Guest's console
Connected to domain centos-st9

Escape character is ^]     # Enter key

[root@localhost ~]#        # Guest's console

[4]	It's easy to replicate a copy VM from current VM with a command below.

[root@dlp ~]#

virt-clone --original centos-st9 --name template --file /var/kvm/images/template.img

Allocating 'template.img'                                   |  20 GB  00:02

Clone 'template' created successfully.

# disk image

[root@dlp ~]#

ll /var/kvm/images/template.img

-rw-------. 1 root root 2092433408 Jan 19 13:58 /var/kvm/images/template.img

# configuration file

[root@dlp ~]#

ll /etc/libvirt/qemu/template.xml

-rw-------. 1 root root 4962 Jan 19 13:58 /etc/libvirt/qemu/template.xml

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