KVM Kernel Virtualization Machine on Rocky Linux 9

...below are just rough notes from three different sources, including ChatGPT. They are ordered in each section as below from the following sources;

• https://www.linuxtechi.com/install-kvm-on-rocky-linux-almalinux/
• https://computingforgeeks.com/install-use-kvm-virtualization-on-rocky/
• ChatCPT

Check for VM Support in CPU;

• cat /proc/cpuinfo | egrep "vmx|svm"
• lscpu | grep Virtualization
• No Comment

Install all the Stuff (for the first two sources there were duplicate items on multiple lines that were cleaned up, oops, no proof reading on their part, huh, just a copy and paste);

• dnf install qemu-kvm virt-manager libvirt virt-install virt-viewer libguestfs-tools bridge-utils virt-top
• dnf install qemu-kvm virt-manager libvirt virt-install virt-viewer libguestfs-tools bridge-utils virt-top
• dnf install qemu-kvm libvirt virt-install virt-manager AND apparently installing virt-manager again (just to make sure)

NOTES: And of course there are about a hundred or so other dependencies that are downloaded and installed too.

ISSUES: bridge-utils virt-top might give issues if attempting to install at the same time, so try installing separately.

Check Installation;

• lsmod | grep kvm
• lsmod | grep kvm
• lsmod | grep kvm AND virsh list --all

Start AND Enable Automatic Starting of the "KVM" Services AND see if they're actually running;

• sudo systemctl start libvirtd AND systemctl enable --now libvirtd AND systemctl status libvirtd
• sudo systemctl start libvirtd AND sudo systemctl enable libvirtd AND systemctl status libvirtd
• sudo systemctl start libvirtd AND sudo systemctl enable libvirtd AND No Comment

Permissions and User Related Stuff;

• No Comment
• usermod -aG libvirt $USER AND newgrp libvirt
• usermod -aG libvirt $(whoami)

Network Connectivity, don't forget that;

...and now comes the part where the above noted references show their true colors. IE, the content in the articles on those websites was not created by the people who own those websites. It was aggregated from other websites and put into a format that Google likes. And does it ever show on the Networking aspect of what they document. In short, ignore it. You'll hose your system if you do what is written. Go ahead and try it (no, don't really do that).

The first issue is with the destruction of a perfectly network interface. The second issue is with the creation of a Bridge Interface that was already created as part of the installation process of QEMU / KVM. Keeping in mind this article here was written based on Rocky Linux 9 and the iteration of QEMU / KVM as of late 2023. Earlier versions may have required the creation of a Bridge Interface.

KEEP THIS IN MIND: In the QEMU / KVM world, here's how the networking thing functions:

• After installing QEMU / KVM, it creates a Virtual Bridge Adapter intended to be used with NAT. Leave this one as is if you want to use it. But if you just want a simple bridge to connect to the rest of your network, keep reading. This Virtual Bridge

Here's the assumption (unlike all the other tutorials there);

• There is an existing Ethernet Adapter on the Host Machine for QEMU / KVM that has been configured with an IP Address, Subnet Mask, IE, everything needed to communicate via a Network.
• During the installation for QEMU / KVM, a Virtual Bridge Adapter was automatically configured

OK, here's what to do for creating your own Virtual Bridge Adapter to be used for 'bridging' between your existing network and the Virtual Machine;

• Identify Ethernet Adapter and Virtual Bridge to be used, IE, get their names (eth0, enp1s0of0, virbr0, etc.) using these commands: brctl show AND / OR ip link show
• Disable the existing Ethernet Adapter (through GUI or command line). Don't delete it as most tutorials would have you do (if needed you can always enable it later instead of re-creating it from scratch)
  • nmcli connection modify WhatEverConnectionName connection.autoconnect "no"
  • ifconfig WhatEverConnectionName down OR ip link set dev WhatEverConnectionName down
• nmcli connection add type bridge autoconnect yes con-name virbr1 ifname virbr1
• Other example NMCLI commands;
  • nmcli connection show
  • Modify the /etc/NetworkManager/system-connections File? Nope!
    • nmcli connection modify WhatEverConnectionName ipv4.address "WhatEverIPAddress/SubnetMaskNumber" (192.168.1.1/24)
    • nmcli connection up WhatEverConnectionName (essentially restarts the adapter and adopts new configuration information)
    • Does NOT work as one might think to 'reload' or restart a Network Adapter after configuration changes are made: nmcli connection reload
    • nmcli connection show WhatEverConnectionName (ipv4.address = configured value AND IPV4.ADDRESS = "live / actual value")
  • systemctl restart NetworkManager

Tricks, Tips, and Other Useful Information (all of which applies to Rocky Linux 9, and others based on Red Hat)

• Rocky Linux 9 Network Configuration Files Directory: /etc/Network/Manager/system-connections (NOT /etc/sysconfig/network-scripts)
• Network Configuration for Rocky Linux: nm-connection-editor
• If a Bridged Network Adapter is configured for a Virtual Machine, it will show up in the Host Machine as: vnet1, etc.
• QEMU / KVM Bridges can be configure "within" QEMU / KVM and "externally" using commands like brctl, etc.
• QEMU / KVM Configuration Files: /etc/libvirt/qemu/
  • Heed the warning notes on some of these files as they should not be edited directly. Although a workaround is to edit the files directly, then restart the libvirtd.service (systemctl restart libvirtd.service)
  • virsh net-edit default (it uses the VI editor)
    • VI Editor
      • i = Insert (AKA Edit) Mode
      • ESC = Command Mode
      •  : (Colon) = "Beginning of Command"
      • w = Write (as in :w)
      • x = Exit / Quit and Save (AKA Write) (as in :x)
      • q = Quit (AKA Exit)
• QEMU / KVM Additional Bridge Configuration: /etc/qemu-kvm/
• Documentation from QEMU / KVM on Bridges and Networking: https://libvirt.org/formatnetwork.html
• All, or most of the documentation for Rocky Linux 9 that steers one towards /etc/udev/rules.d is now located in /lib/udev/rules.d
• Network Remapping End Result(s) (IE, if you want to see how the "Predictable Network Interface Naming" decided on how things were to be done: /sys/class/net
  • In short, here's how it goes with Rocky Linux 9 mapping a physical Network Adapter to a configuration file;
    • Physical Network Adapter (represented by files located in /sys/devices and below / down)
    • ⇌
    • Calculations done in the name of "Predictable Network Interface Naming", whose 'scripts' are located in /lib/udev/rules.d/80-net-setu-link.rules and whose result(s) are located in the Symbolic Links located in /sys/class/net (which in turn point to 'device files' in /sys/devices)
    • ⇌
    • Configuration File (in /etc/NetworkManger)
    • ⇌ ⇌ ⇌ ⇌ ⇌ ⇌

ChatGPT to the Rescue

Why is the UUID for the virbr0 Virtual Bridge Adapter displayed in the QEMU / KVM Host using the IP LINK SHOW command different than the UUID setting configured in the /etc/libvirt/qemu/networks/default.xml File, even though the MAC Address is the same in the Host (using IP LINK SHOW) and the default.xml File?

ChatGPT's explanation is below (which is very good considering that Googling an equivalent answer produces nothing but hundreds of stupid forum results that ramble about how something isn't working). There is also some additional information from https://wiki.libvirt.org/Networking.html.

The discrepancy between the UUID in the default.xml file and the one displayed by the ip link show command might be due to the fact that the UUID in the XML configuration file refers to the libvirt network object's UUID, not the actual bridge interface's UUID.

Here's a breakdown:

UUID in default.xml:

The default.xml file typically contains the XML configuration for the default libvirt network (virbr0). The UUID in this file corresponds to the libvirt network's unique identifier. This UUID is associated with the network object managed by libvirt.
UUID displayed by ip link show:

When you use ip link show, you are querying information about the actual bridge interface (virbr0). The UUID displayed here refers to the bridge interface itself, not the libvirt network object.
While the libvirt network and the bridge interface are closely related, they are distinct entities with different UUIDs. The libvirt network configuration includes settings for the bridge interface but also encompasses additional configuration options managed by libvirt.

If you want to inspect the libvirt network configuration and UUID programmatically, you can use the virsh command:

bash
Copy code
virsh net-dumpxml default
This command will display the XML configuration for the default network, including the libvirt network UUID.

If you specifically need the UUID of the bridge interface (virbr0), you can extract it using the nmcli command (assuming NetworkManager is used for managing the bridge):

bash
Copy code
nmcli connection show virbr0 | grep UUID
This will display the UUID associated with the virbr0 connection managed by NetworkManager.

In summary, the libvirt network and the bridge interface have separate UUIDs, and the discrepancy arises from the different contexts in which these UUIDs are used.

The above can be confirmed using the following commands

• virsh net-destroy default (maybe there should be an 'in-between' option like net-stop, but oh well) : "Stops and Destroys" the virbr0 (defined by default.xml, which is not deleted)
• virsh net-start default : Starts the virb0 (defined by the default.xml file)

Rough Notes

<network>

  <name>my-bridge-network</name>

  <forward mode='bridge'/>

  <bridge name='virbr_bridge'/>

</network>

sudo virsh net-define bridge-network.xml

sudo virsh net-start my-bridge-network

sudo virsh net-autostart my-bridge-network

virsh [options]... [<command_string>]
virsh [options]... <command> [args...]

  options:
    -c | --connect=URI      hypervisor connection URI
    -d | --debug=NUM        debug level [0-4]
    -e | --escape <char>    set escape sequence for console
    -h | --help             this help
    -k | --keepalive-interval=NUM
                            keepalive interval in seconds, 0 for disable
    -K | --keepalive-count=NUM
                            number of possible missed keepalive messages
    -l | --log=FILE         output logging to file
    -q | --quiet            quiet mode
    -r | --readonly         connect readonly
    -t | --timing           print timing information
    -v                      short version
    -V                      long version
         --version[=TYPE]   version, TYPE is short or long (default short)
  commands (non interactive mode):

 Domain Management (help keyword 'domain')
    attach-device                  attach device from an XML file
    attach-disk                    attach disk device
    attach-interface               attach network interface
    autostart                      autostart a domain
    blkdeviotune                   Set or query a block device I/O tuning parameters.
    blkiotune                      Get or set blkio parameters
    blockcommit                    Start a block commit operation.
    blockcopy                      Start a block copy operation.
    blockjob                       Manage active block operations
    blockpull                      Populate a disk from its backing image.
    blockresize                    Resize block device of domain.
    change-media                   Change media of CD or floppy drive
    console                        connect to the guest console
    cpu-stats                      show domain cpu statistics
    create                         create a domain from an XML file
    define                         define (but don't start) a domain from an XML file
    desc                           show or set domain's description or title
    destroy                        destroy (stop) a domain
    detach-device                  detach device from an XML file
    detach-device-alias            detach device from an alias
    detach-disk                    detach disk device
    detach-interface               detach network interface
    domdisplay                     domain display connection URI
    domfsfreeze                    Freeze domain's mounted filesystems.
    domfsthaw                      Thaw domain's mounted filesystems.
    domfsinfo                      Get information of domain's mounted filesystems.
    domfstrim                      Invoke fstrim on domain's mounted filesystems.
    domhostname                    print the domain's hostname
    domid                          convert a domain name or UUID to domain id
    domif-setlink                  set link state of a virtual interface
    domiftune                      get/set parameters of a virtual interface
    domjobabort                    abort active domain job
    domjobinfo                     domain job information
    domlaunchsecinfo               Get domain launch security info
    domsetlaunchsecstate           Set domain launch security state
    domname                        convert a domain id or UUID to domain name
    domrename                      rename a domain
    dompmsuspend                   suspend a domain gracefully using power management functions
    dompmwakeup                    wakeup a domain from pmsuspended state
    domuuid                        convert a domain name or id to domain UUID
    domxml-from-native             Convert native config to domain XML
    domxml-to-native               Convert domain XML to native config
    dump                           dump the core of a domain to a file for analysis
    dumpxml                        domain information in XML
    edit                           edit XML configuration for a domain
    get-user-sshkeys               list authorized SSH keys for given user (via agent)
    inject-nmi                     Inject NMI to the guest
    iothreadinfo                   view domain IOThreads
    iothreadpin                    control domain IOThread affinity
    iothreadadd                    add an IOThread to the guest domain
    iothreadset                    modifies an existing IOThread of the guest domain
    iothreaddel                    delete an IOThread from the guest domain
    send-key                       Send keycodes to the guest
    send-process-signal            Send signals to processes
    lxc-enter-namespace            LXC Guest Enter Namespace
    managedsave                    managed save of a domain state
    managedsave-remove             Remove managed save of a domain
    managedsave-edit               edit XML for a domain's managed save state file
    managedsave-dumpxml            Domain information of managed save state file in XML
    managedsave-define             redefine the XML for a domain's managed save state file
    memtune                        Get or set memory parameters
    perf                           Get or set perf event
    metadata                       show or set domain's custom XML metadata
    migrate                        migrate domain to another host
    migrate-setmaxdowntime         set maximum tolerable downtime
    migrate-getmaxdowntime         get maximum tolerable downtime
    migrate-compcache              get/set compression cache size
    migrate-setspeed               Set the maximum migration bandwidth
    migrate-getspeed               Get the maximum migration bandwidth
    migrate-postcopy               Switch running migration from pre-copy to post-copy
    numatune                       Get or set numa parameters
    qemu-attach                    QEMU Attach
    qemu-monitor-command           QEMU Monitor Command
    qemu-monitor-event             QEMU Monitor Events
    qemu-agent-command             QEMU Guest Agent Command
    guest-agent-timeout            Set the guest agent timeout
    reboot                         reboot a domain
    reset                          reset a domain
    restore                        restore a domain from a saved state in a file
    resume                         resume a domain
    save                           save a domain state to a file
    save-image-define              redefine the XML for a domain's saved state file
    save-image-dumpxml             saved state domain information in XML
    save-image-edit                edit XML for a domain's saved state file
    schedinfo                      show/set scheduler parameters
    screenshot                     take a screenshot of a current domain console and store it into a file
    set-lifecycle-action           change lifecycle actions
    set-user-sshkeys               manipulate authorized SSH keys file for given user (via agent)
    set-user-password              set the user password inside the domain
    setmaxmem                      change maximum memory limit
    setmem                         change memory allocation
    setvcpus                       change number of virtual CPUs
    shutdown                       gracefully shutdown a domain
    start                          start a (previously defined) inactive domain
    suspend                        suspend a domain
    ttyconsole                     tty console
    undefine                       undefine a domain
    update-device                  update device from an XML file
    update-memory-device           update memory device of a domain
    vcpucount                      domain vcpu counts
    vcpuinfo                       detailed domain vcpu information
    vcpupin                        control or query domain vcpu affinity
    emulatorpin                    control or query domain emulator affinity
    vncdisplay                     vnc display
    guestvcpus                     query or modify state of vcpu in the guest (via agent)
    setvcpu                        attach/detach vcpu or groups of threads
    domblkthreshold                set the threshold for block-threshold event for a given block device or it's backing chain element
    guestinfo                      query information about the guest (via agent)
    domdirtyrate-calc              Calculate a vm's memory dirty rate
    dom-fd-associate               associate a FD with a domain

 Domain Monitoring (help keyword 'monitor')
    domblkerror                    Show errors on block devices
    domblkinfo                     domain block device size information
    domblklist                     list all domain blocks
    domblkstat                     get device block stats for a domain
    domcontrol                     domain control interface state
    domif-getlink                  get link state of a virtual interface
    domifaddr                      Get network interfaces' addresses for a running domain
    domiflist                      list all domain virtual interfaces
    domifstat                      get network interface stats for a domain
    dominfo                        domain information
    dommemstat                     get memory statistics for a domain
    domstate                       domain state
    domstats                       get statistics about one or multiple domains
    domtime                        domain time
    list                           list domains

 Domain Events (help keyword 'events')
    event                          Domain Events

 Host and Hypervisor (help keyword 'host')
    allocpages                     Manipulate pages pool size
    capabilities                   capabilities
    cpu-baseline                   compute baseline CPU
    cpu-compare                    compare host CPU with a CPU described by an XML file
    cpu-models                     CPU models
    domcapabilities                domain capabilities
    freecell                       NUMA free memory
    freepages                      NUMA free pages
    hostname                       print the hypervisor hostname
    hypervisor-cpu-baseline        compute baseline CPU usable by a specific hypervisor
    hypervisor-cpu-compare         compare a CPU with the CPU created by a hypervisor on the host
    maxvcpus                       connection vcpu maximum
    node-memory-tune               Get or set node memory parameters
    nodecpumap                     node cpu map
    nodecpustats                   Prints cpu stats of the node.
    nodeinfo                       node information
    nodememstats                   Prints memory stats of the node.
    nodesevinfo                    node SEV information
    nodesuspend                    suspend the host node for a given time duration
    sysinfo                        print the hypervisor sysinfo
    uri                            print the hypervisor canonical URI
    version                        show version

 Checkpoint (help keyword 'checkpoint')
    checkpoint-create              Create a checkpoint from XML
    checkpoint-create-as           Create a checkpoint from a set of args
    checkpoint-delete              Delete a domain checkpoint
    checkpoint-dumpxml             Dump XML for a domain checkpoint
    checkpoint-edit                edit XML for a checkpoint
    checkpoint-info                checkpoint information
    checkpoint-list                List checkpoints for a domain
    checkpoint-parent              Get the name of the parent of a checkpoint

 Interface (help keyword 'interface')
    iface-begin                    create a snapshot of current interfaces settings, which can be later committed (iface-commit) or restored (iface-rollback)
    iface-bridge                   create a bridge device and attach an existing network device to it
    iface-commit                   commit changes made since iface-begin and free restore point
    iface-define                   define an inactive persistent physical host interface or modify an existing persistent one from an XML file
    iface-destroy                  destroy a physical host interface (disable it / "if-down")
    iface-dumpxml                  interface information in XML
    iface-edit                     edit XML configuration for a physical host interface
    iface-list                     list physical host interfaces
    iface-mac                      convert an interface name to interface MAC address
    iface-name                     convert an interface MAC address to interface name
    iface-rollback                 rollback to previous saved configuration created via iface-begin
    iface-start                    start a physical host interface (enable it / "if-up")
    iface-unbridge                 undefine a bridge device after detaching its device(s)
    iface-undefine                 undefine a physical host interface (remove it from configuration)

 Network Filter (help keyword 'filter')
    nwfilter-define                define or update a network filter from an XML file
    nwfilter-dumpxml               network filter information in XML
    nwfilter-edit                  edit XML configuration for a network filter
    nwfilter-list                  list network filters
    nwfilter-undefine              undefine a network filter
    nwfilter-binding-create        create a network filter binding from an XML file
    nwfilter-binding-delete        delete a network filter binding
    nwfilter-binding-dumpxml       network filter information in XML
    nwfilter-binding-list          list network filter bindings

 Networking (help keyword 'network')
    net-autostart                  autostart a network
    net-create                     create a network from an XML file
    net-define                     define an inactive persistent virtual network or modify an existing persistent one from an XML file
    net-destroy                    destroy (stop) a network
    net-dhcp-leases                print lease info for a given network
    net-dumpxml                    network information in XML
    net-edit                       edit XML configuration for a network
    net-event                      Network Events
    net-info                       network information
    net-list                       list networks
    net-name                       convert a network UUID to network name
    net-start                      start a (previously defined) inactive network
    net-undefine                   undefine a persistent network
    net-update                     update parts of an existing network's configuration
    net-uuid                       convert a network name to network UUID
    net-port-list                  list network ports
    net-port-create                create a network port from an XML file
    net-port-dumpxml               network port information in XML
    net-port-delete                delete the specified network port

 Node Device (help keyword 'nodedev')
    nodedev-create                 create a device defined by an XML file on the node
    nodedev-destroy                destroy (stop) a device on the node
    nodedev-detach                 detach node device from its device driver
    nodedev-dumpxml                node device details in XML
    nodedev-list                   enumerate devices on this host
    nodedev-reattach               reattach node device to its device driver
    nodedev-reset                  reset node device
    nodedev-event                  Node Device Events
    nodedev-define                 Define a device by an xml file on a node
    nodedev-undefine               Undefine an inactive node device
    nodedev-start                  Start an inactive node device
    nodedev-autostart              autostart a defined node device
    nodedev-info                   node device information

 Secret (help keyword 'secret')
    secret-define                  define or modify a secret from an XML file
    secret-dumpxml                 secret attributes in XML
    secret-event                   Secret Events
    secret-get-value               Output a secret value
    secret-list                    list secrets
    secret-set-value               set a secret value
    secret-undefine                undefine a secret

 Snapshot (help keyword 'snapshot')
    snapshot-create                Create a snapshot from XML
    snapshot-create-as             Create a snapshot from a set of args
    snapshot-current               Get or set the current snapshot
    snapshot-delete                Delete a domain snapshot
    snapshot-dumpxml               Dump XML for a domain snapshot
    snapshot-edit                  edit XML for a snapshot
    snapshot-info                  snapshot information
    snapshot-list                  List snapshots for a domain
    snapshot-parent                Get the name of the parent of a snapshot
    snapshot-revert                Revert a domain to a snapshot

 Backup (help keyword 'backup')
    backup-begin                   Start a disk backup of a live domain
    backup-dumpxml                 Dump XML for an ongoing domain block backup job

 Storage Pool (help keyword 'pool')
    find-storage-pool-sources-as   find potential storage pool sources
    find-storage-pool-sources      discover potential storage pool sources
    pool-autostart                 autostart a pool
    pool-build                     build a pool
    pool-create-as                 create a pool from a set of args
    pool-create                    create a pool from an XML file
    pool-define-as                 define a pool from a set of args
    pool-define                    define an inactive persistent storage pool or modify an existing persistent one from an XML file
    pool-delete                    delete a pool
    pool-destroy                   destroy (stop) a pool
    pool-dumpxml                   pool information in XML
    pool-edit                      edit XML configuration for a storage pool
    pool-info                      storage pool information
    pool-list                      list pools
    pool-name                      convert a pool UUID to pool name
    pool-refresh                   refresh a pool
    pool-start                     start a (previously defined) inactive pool
    pool-undefine                  undefine an inactive pool
    pool-uuid                      convert a pool name to pool UUID
    pool-event                     Storage Pool Events
    pool-capabilities              storage pool capabilities

 Storage Volume (help keyword 'volume')
    vol-clone                      clone a volume.
    vol-create-as                  create a volume from a set of args
    vol-create                     create a vol from an XML file
    vol-create-from                create a vol, using another volume as input
    vol-delete                     delete a vol
    vol-download                   download volume contents to a file
    vol-dumpxml                    vol information in XML
    vol-info                       storage vol information
    vol-key                        returns the volume key for a given volume name or path
    vol-list                       list vols
    vol-name                       returns the volume name for a given volume key or path
    vol-path                       returns the volume path for a given volume name or key
    vol-pool                       returns the storage pool for a given volume key or path
    vol-resize                     resize a vol
    vol-upload                     upload file contents to a volume
    vol-wipe                       wipe a vol

 Virsh itself (help keyword 'virsh')
    cd                             change the current directory
    echo                           echo arguments. Used for internal testing.
    exit                           quit this interactive terminal
    help                           print help
    pwd                            print the current directory
    quit                           quit this interactive terminal
    connect                        (re)connect to hypervisor


  (specify help <group> for details about the commands in the group)

  (specify help <command> for details about the command)