List Running Virtual Machines
List All Virtual Machines
virsh list --all
Managing Guest State
virsh shutdown $VM_ID_OR_NAME
virsh start $VM_ID_OR_NAME
virsh reboot $VM_ID_OR_NAME
Destroy a Guest
This command is an ungraceful shutdown, much like if you were to pull the power out of a computer. You should use this if a guest becomes unresponsive. It does not delete the guest. The disk image will remain and the guest can be restarted.
virsh destroy $VM_ID_OR_NAME
Suspension is a way to immediately "pause" a guest so that it no longer uses the CPU, disk, or network. However, it will continue to reside in memory. You may want to save/load a session instead, which would mean it no longer takes up memory, but is not instant. such that it no longer takes up memory and can be restored to its exact state (even after a reboot), it is necessary to save and restore the guest.
virsh suspend $VM_ID_OR_NAME
virsh resume $VM_ID_OR_NAME
If you need to determine what state a guest is in, you can run:
virsh domstate $GUEST_ID
This helps with running scripts. E.g. If you wish to make sure the guest has been shut down before running an rsync, you can use:
STATE=$(virsh domstate $GUEST_ID) if [[ "$STATE" =~ "shut off" ]]; then # rsync ... else echo "Cannot backup server that is currently running!" fi
The most useful outputs of domstate are:
Defining a Guest
Defining a guest allows one to start it from its name, rather than having to find it's XML file and running
virsh create $name.xml. This means that guests will also show in
virsh list --all when they are shutdown.
virsh define filename.xml
Undefine a Guest
In order to use a name over again for a new guest, you have to undefine the old one. You need to remove it's storage system as well.
virsh undefine $VM_ID
You can manually edit the guest's xml configuration file with:
virsh edit $VM_ID
List OS Variants
When creating a guest with
virt-install you need to specify the
--os-variant. To get a list of acceptable values (on Ubuntu 16.04), install the
libosinfo-bin package before running the command below:
virsh domrename $OLD_NAME $NEW_NAME
Guest Start on Boot (Autostart)
virsh autostart $VM_ID
To disable Guest Autostart
virsh autostart --disable $VM_ID
Run the following command to bring up the config for the guest.
virsh edit $VM_ID
currentMemory fields to be the size you want in KiB.
Now use virsh to shutdown and startup the container for the changes to take effect.
Resizing Memory With Script
VM_ID="my_vm_id" NEW_AMOUNT="4000" EDITOR='sed -i "s;[0-9]*</currentMemory>;$NEW_AMOUNT</currentMemory>;"' virsh edit $VM_ID EDITOR='sed -i "s;[0-9]*</memory>;$NEW_AMOUNT</memory>;"' virsh edit $VM_ID virsh shutdown $VM_ID virsh start $VM_ID
virsh memtune. See here for more details.
Discover CPU Scheduling Parameters
virsh schedinfo $VM_ID
Permanently Set CPU Shares For Live Running Instance
virsh schedinfo $VM_ID \ --set cpu_shares=[0-262144] \ --live \ --current \ --config
Get the CPU Pinning Settings for a Guest
virsh vcpupin blog.programster.org
VCPU: CPU Affinity ---------------------------------- 0: 0-3 1: 0-3
I got the output above because I gave the guest access to 2 vCPUs but didn't pin anything.
Pin A CPU
If I wanted to set the cores that a guest can use, I could do the following:
virsh vcpupin blog.programster.org 0 2
That will set the first vCPU (the one with ID 0) to only run on core ID 2. Thus the output of
virsh vcpupin blog.programster.org changes to:
VCPU: CPU Affinity ---------------------------------- 0: 2 1: 0-3
Enter Guest's Console
virsh console $VM_ID
Exit Guest's Console
Use the following keyboard shortcut (not a command):
virsh save $VM_ID $FILENAME
Saves the RAM (not including disk) of a running guest to a "state file" at the specified file name/path, so that it can be restored later.
Once saved, the domain will no longer be running on the system, thus the memory allocated for the domain will be free for other domains to use.
virsh restore (in "Load Guest" below) restores from this state file.
- --xml $FILEPATH - Usually omitted, but can be used to supply an alternative XML file for use on the restored guest with changes only in the host-specific portions of the domain XML . For example, it can be used to account for file naming differences that are planned to be made via disk snapshots of underlying storage after the guest is saved.
If you forgot to provide this, you can make use of
save-image-definelater to achieve the same effect. You may also wish to refer to
- --bypass-cache - the save will avoid the file system cache, although this may slow down the operation.
- --running | --paused - Normally, restoring a saved image will decide between running or paused based on the state the domain was in when the save was done; passing either the --running or --paused flag will allow overriding which state the restore should use.
Progress may be monitored using
domjobinfo virsh command and canceled with
domjobabort (or just Ctrl-C).
Load Guest (restore)
virsh restore $FILENAME
Below is a simple example of cloning a guest.
virt-clone \ --original $VM_TO_CLONE \ --auto-clone \ --name $NEW_VM_NAME
List Running Network Configs
List All Network Configs
virsh net-list --all
Edit Network Config
virsh net-list $NETWORK_NAME
Create Temporary Network Config
virsh net-create --file $ABSOLUTE_FILE_PATH
Create Permanent Network Config
virsh net-define --file $ABSOLUTE_FILE_PATH
Example Bridge Network Config File
<network> <name>examplebridge</name> <forward mode='route'/> <bridge name='kvmbr0' stp='on' delay='0'/> <ip address='192.168.1.1' netmask='255.255.255.0' /> </network>
Start Network Config
virsh net-start $NETWORK_ID
Enable Network Autostart
net-autostart --network $NETWORK_ID
Disable Network Autostart
net-autostart \ --network $NETWORK_ID \ --disable
Example Manual Network Config With Bridge
This is an example
/etc/network/interfaces file for Ubuntu users.
bridge-utils package beforehand.
# The loopback network interface auto lo iface lo inet loopback # The primary network interface auto p17p1 iface p17p1 inet manual auto kvmbr0 iface kvmbr0 inet static address 192.168.1.19 netmask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255 gateway 192.168.1.254 bridge_ports p17p1 bridge_stp off bridge_fd 0 bridge_maxwait 0
Here is a netplan version:
# This file describes the network interfaces available on your system # For more information, see netplan(5). network: version: 2 renderer: networkd ethernets: enp39s0: dhcp4: no bridges: kvmbr0: addresses: [ 192.168.1.186/24 ] gateway4: 192.168.1.1 nameservers: addresses: - 18.104.22.168 - 22.214.171.124 interfaces: - enp39s0
Example Netplan DHCP Config
The following config will set up a bridge where your host is using DHCP.
network: version: 2 renderer: networkd ethernets: enp3s0: dhcp4: no dhcp6: no bridges: kvmbr0: dhcp4: yes dhcp6: no nameservers: addresses: - 126.96.36.199 - 188.8.131.52 interfaces: - enp3s0
Configure VM To Use Manual Bridge
If you manually set the bridge up with the section above rather than through using the virsh net commands, this is how to configure deployed guests make use of it:
virsh edit $VM_ID
Find the following section
<interface type='network'> <mac address='52:54:00:4d:3a:bd'/> <source network=''/> <model type='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> </interface>
Change it to be like so:
<interface type='bridge'> <mac address='52:54:00:4d:3a:bd'/> <source bridge='[bridge name here]'/> <model type='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> </interface>
Now run the following two commands since reboots wont work.
virsh shutdown $VM_ID virsh start $VM_ID
Add Network Interface to VM
I used the command below to add a NIC to my guest that uses my host's bridge interface called kvmbr1.
virsh attach-interface \ --domain guest1 \ --type bridge \ --source kvmbr1 \ --model virtio \ --config
--mac but without it, one will be generated randomly.
Create Internal Snapshot
virsh snapshot-create $VM_ID
Create Internal Snapshot With Name
virsh snapshot-create-as $VM_ID $SNAPSHOT_NAME
Create Internal Snapshot With Name and Description
virsh snapshot-create-as $VM_ID $SNAPSHOT_NAME $DESCRIPTION
Create Internal Snapshot With Name and Description Using File
If you just love writing xml, then you can create a file like so:
<domainsnapshot> <name>Name for the snapshot</name> <description>Description for the snapshot</description> </domainsnapshot>
... then pass it to virsh snapshot-create to create the snapshot
virsh snapshot-create $VM_ID $FILEPATH
Create External Snapshot
virsh snapshot-list $VM_ID
virsh snapshot-revert $VM_ID $SNAPSHOT_NAME
virsh snapshot-delete $VM_ID $SNAPSHOT_NAME
If you use virsh with internal qcow2 snapshots and you decide to move the file to another location, you will not be able to restore those snapshots. This is easily fixed by editing the snapshots and updating the filepath.
virsh snapshot-edit $VM_ID_OR_NAME $NAME_OF_SNAPSHOT
Use blockcommit to merge a qcow2 file down into its backing file.
- Use blockpull to flatten a disk/image chain by moving data up the chain.
- The principal here is to "flatten" a chain, so it is impossible to target the removal of a single node in the chain except if your chain happens to be small enough.
- The original files will be kept unless you provide the
- Be careful about providing
--deleteas you might have other guests using disk images that reference them if you use thin-provisioning.
- Be careful about providing
- Full list of options can be found here.
This example will pull all the images up into the current active/head image, for disk
virsh blockpull $GUEST_ID vda --wait
--waitcauses the command to block until the operation completes.
The following example will flatten a chain by merging all images above the specified
base, so that the base will be referenced by the current top/active disk image.
E.g. your chain will only contain the active, the base, and any images the base references.
virsh blockpull \ $GUEST_ID \ vda \ --base /path/to/disk-image.qcow2 \ --verbose \ --wait
If you are trying to use external snapshots, you may find it easier to disable apparmor. Do this by editing your qemu configuration:
sudo vim /etc/libvirt/qemu.conf
... and adding the following line for the
security_driver = "none"
Then restart libvirt for the changes to take effect.
sudo service libvirtd restart
To share a clipboard between your host and guest, you just need to install the
spice-vdagent package in the guest.
sudo apt install spice-vdagent
KVM XML Config File Location
If your server dies, and you need to somehow retrieve the XML configurations for your virtual machines from the disk drives, it's good to know that you can find them in the folder at:
- Managing KVM on RHEL 6 using the virsh Command-line Tool
- Red Hat Docs - Chapter 20. Managing guests with virsh
- Libvirt Docs - net-create
- Libvirt Docs - net-define
- Ubuntu Docs - KVM/Managing
- virt-clone(1) - Linux man page
- IBM - Working with libvirt cgroups
- Libvirt - memtune
- Using CGroups with libvirt and LXC/KVM guests in Fedora 12
- KVM - Changing Memory of Guests Live
- Stack Overflow - Changing the dhcp IP range in Virbr0's XML file using virsh in bash script
- Nixcraft - KVM: Start a Virtual Machine / Guest At Boot Time
- Nixcraft - How to rename KVM virtual machine (VM) domain with virsh command
- Redhat Docs - 8.3 LIBVIRT NUMA TUNING
- Unix & Linux - libvirt: error : unable to set AppArmor profile
- Unix & Linux - How to configure AppArmor so that KVM can start guest that has a backing file chain
- Red Hat Docs - 20.13. Working with Snapshots
- Ask Ubuntu - How can I copy&paste from the host to a KVM guest?
First published: 16th August 2018