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@diffficult
Last active June 1, 2024 13:53
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Easy instructions to get virt-manager qemuv/kvm running on Arch

Easy instructions to get QEMU/KVM and virt-manager up and running on Arch

  1. Make sure your cpu support kvm with below command:

     grep -E "(vmx|svm)" --color=always /proc/cpuinfo
    
  2. Make sure BIOS have enable “Virtualization Technology”.

  3. User access to /dev/kvm so add your account into kvm(78) group:

     sudo gpasswd -a $(whoami) kvm
    
  4. Loading kernel modules kvm_intel or kvm_amd depend on your CPU, Add module name in /etc/modules-load.d/kvm.conf:

     kvm_intel
    
  • Load module:

    modprobe kvm_amd
    
  1. Install qemu, virt-manager, dnsmasq and iptables:

     sudo pacman -S --needed qemu virt-manager dnsmasq iptables-nft
    
  2. Run and enable boot up start libvirtd daemon:

     systemctl enable --now libvirtd
    
  3. Use PolicyKit authorization create /etc/polkit-1/rules.d/50-libvirt.rules (before /etc/polkit-1/rules.d/50-org.libvirt.unix.manage.rules) as below context:

/* Allow users in kvm group to manage the libvirt
daemon without authentication */
polkit.addRule(function(action, subject) {
    if (action.id == "org.libvirt.unix.manage" &&
        subject.isInGroup("kvm")) {
            return polkit.Result.YES;
    }
});
  1. You will need to create the libvirt group and add any users you want to have access to libvirt to that group:

     groupadd libvirt
    
     sudo gpasswd -a $(whoami) libvirt
    
  2. Check network interface status:

     sudo virsh net-list --all
    
  • If it is inactive start it using:

     sudo virsh net-start default
    
  1. Now you can use virt-manager manager your virtual machine.

  2. Things to do after installing a Windows VM.

  • Check and install drivers on your guest Windows VM, probably virtio-win is a nice place to start.

What to do if default network interface is not listed

  • If virsh net-list is not listing any network interface just reinitialize it with,

    sudo virsh net-define /usr/share/libvirt/networks/default.xml
    
  • Then just autostart it like so,

    sudo virsh net-autostart default 
    

What to do if you cannot access storage file, and get "Permission denied Error in KVM Libvirt"

  • Step 1: Edit /etc/libvirt/qemu.conf file:

    sudo nano /etc/libvirt/qemu.conf
    
  • Step 2: Find the user and group directives. By default, both are set to "root",

     [...] 
     Some examples of valid values are:
     #
     user = "qemu"   # A user named "qemu"
     user = "+0"     # Super user (uid=0)
     user = "100"    # A user named "100" or a user with uid=100
     #
     #user = "root"
     The group for QEMU processes run by the system instance. It can be
     specified in a similar way to user.
     #group = "root"
     [...]
    

    Uncomment both lines and replace root with your username and group with libvirt as shown below:

     [...] 
     Some examples of valid values are:
     #
     user = "qemu"   # A user named "qemu"
     user = "+0"     # Super user (uid=0)
     user = "100"    # A user named "100" or a user with uid=100
     #
     user = "sk"
     The group for QEMU processes run by the system instance. It can be
     specified in a similar way to user.
     group = "libvirt"
     [...]
    
  • Step 3: Restart libvirtd service:

     sudo systemctl restart libvirtd
    

How to extend / increase a Windows Partition on KVM QEMU VM

We have a Windows 7 VM running on Ubuntu KVM. I needed to give the Windows 7 machine more disk space. This turns out to be really easy (when you know how).

  1. Shutdown the VM

     virsh shutdown hostname
    
  2. Increase the qcow2 image

Find the qcow2 file of the VM and take a backup (just in case).

cp hostname.qcow2 hostname.qcow2.backup
qemu-img resize hostname.qcow2 +100GB
  1. Start the VM

     virsh start hostname
    
  2. Extend the partition in Window

Windows has a really good partition management utility built into it. Search for disk management

Reference:

Original guide - http://wood1978.dyndns.org/~wood/wordpress/2013/07/22/arch-linux-setup-kvm-with-virt-manager-gui/comment-page-1/

KVM @ Arch Wiki - https://wiki.archlinux.org/index.php/KVM

libvirt @ Arch Wiki - https://wiki.archlinux.org/index.php/Libvirt

QEMU @ Arch Wiki - https://wiki.archlinux.org/index.php/QEMU

Network Interface Status - http://ask.xmodulo.com/network-default-is-not-active.html

Network Interface Troubleshooting - https://blog.programster.org/kvm-missing-default-network

Networking libvirt wiki - https://wiki.libvirt.org/page/Networking#NAT_forwarding_.28aka_.22virtual_networks.22.29

Fedora Wiki - Windows Virtio Drivers - https://stg.fedoraproject.org/wiki/Windows_Virtio_Drivers

Extend disk size Windows partition KVM QEMU VM - https://www.randomhacks.co.uk/how-to-extend-increase-a-windows-partition-on-kvm-qemu-vm/

Increasing a KVM machine disk space - https://serverfault.com/questions/324281/how-do-you-increase-a-kvm-guests-disk-space

Fixing Cannot access storage file, Permission denied Error in KVM Libvirt - https://ostechnix.com/solved-cannot-access-storage-file-permission-denied-error-in-kvm-libvirt/

@guigirl42
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Thanks for these edits, @diffficult, now your excellent guide is even more comprehensive.

FYI: Unfortunately, for a few months now, Shared Clipboard [SC] has been broken in ALL my Arch/Arch-based VMs, whereas it continues to work just fine in all my non-Arch VMs [eg, my Fedoras, Mint, PopOS, ZorinLinux VMs all continue happily with good SC]. None of my several attempts to troubleshoot & solve this has been successful. For instance:

In https://wiki.archlinux.org/title/QEMU#Enabling_SPICE_support_on_the_guest [edited on 25 June 2022, at 17:58], it says:

"For Arch Linux guests, for improved support for multiple monitors or _**clipboard sharing**_, the following packages should be installed:

spice-vdagent: Spice agent xorg client that enables copy and paste between client and X-session and more.
xf86-video-qxl: Xorg X11 qxl video driver"

Obviously i've had spice-vdagent installed since 24/1/22, but the other one is new info for me, & was not in either my Arch or Arch-based VMs. I therefore installed it in each relevant Guest, rebooted each Guest, &... it made NO difference, so i uninstalled it again, & have given up.

I've posted this info here for the benefit of other readers -- the original method in this guide [including my 24/1/22 post's update, above] used to work great for ALL my Guests, irrespective of specific distro. A few months ago, implicitly, some Arch package update seems to have broken SC for Arch Guests, but i do not yet know which is the "bad" package.

@skeezmoe
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skeezmoe commented Nov 4, 2022

I just found this and it is great to confirm that Copy / Paste is definitely broken in Virt-Manager. I have been trying to fix this and tried all the solutions for Ubuntu and Arch and none work.

@slash071
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Update required. There is no qemu package anymore, it's divided into three packages: qemu-base, qemu-desktop and qemu-full

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