Virtualization (virsh)

Notes about using virsh and related commands


Simple installation (using a vnc "display")

virt-install -n myvm \
    --memory 16384 \
    --cpu host \
    --cdrom /path/to/rhel8.4.iso \
    --disk size=50 \
    --graphics vnc,port=5901,listen=,password=myvncpass \
    --network default \
    --vcpus 2 \
    --os-variant rhel8.4

or rebuild from a disk image with all the same settings, by changing:

virt-install -n myvm \
    ... \
    # size=50 becomes...
    --disk /path/to/existing/disk.qcow2 \
    ... \
    # remove --cdrom /path/to/rhel8.4.iso
    --import \

Which is helpful if the qemu XML file gets removed/deleted

once configuration/install is done then console=ttyS0,115200 can be added to the kernel parameters and one can attach to the machine console via virsh console myvm



A block device can be directly attached

virsh attach-disk --domain myvm /dev/sda1 vdb --config --type disk

usb device

Need the code for the usb (e.g. lsusb -v) to place into the following file

vim usbdevice.xml
<hostdev mode='subsystem' type='usb' managed='yes'>
        <vendor id='0x1234'/>
        <product id='0x5678'/>

Which can be attached to a machine

virsh attach-device myvm --file usbdevice.xml --config --persistent

The detach-device command can work to detach the usb device too