Virsh Command Line Interface

Command-line tool for managing KVM/QEMU virtual machines through the libvirt API, covering VM lifecycle, snapshots, networking, and automation.

Table of Contents#

1. Overview
2. Installation
3. Basic Virsh Commands
4. Creating a Virtual Machine
5. Advanced Usage
6. Troubleshooting
7. See Also
8. Sources

1. Overview#

Virsh is the primary command-line interface for managing virtual machines through the libvirt library. It provides full control over VM lifecycle, configuration, snapshots, networking, and storage without requiring a graphical interface.

Virsh supports a wide variety of hypervisors, including QEMU, KVM, Xen, and more. It operates by connecting to the libvirt daemon (libvirtd) and can manage both local and remote hypervisors.

2. Installation#

To use virsh, install libvirt and its dependencies:

# Debian/Ubuntu
sudo apt install libvirt-daemon-system libvirt-clients qemu-kvm

# CentOS/RHEL/Fedora
sudo dnf install libvirt libvirt-client libguestfs-tools virt-install qemu-kvm

# Arch Linux
sudo pacman -S libvirt qemu-full virt-install

Enable and start the libvirt daemon:

sudo systemctl enable --now libvirtd

3. Basic Virsh Commands#

VM Lifecycle#

Snapshots#

4. Creating a Virtual Machine#

4.1 Preparing the Virtual Machine Image#

Download an OS image. For example, Arch Linux:

wget https://geo.mirror.pkgbuild.com/iso/latest/archlinux-x86_64.iso

4.2 Creating a Qcow2 Disk for the VM#

Create a qcow2 disk image for the virtual machine:

qemu-img create -f qcow2 /var/lib/libvirt/images/<vm-name>.qcow2 20G

This creates a 20 GB thin-provisioned disk (actual size grows as data is written).

4.3 Defining the Virtual Machine#

Use virt-install to create and define a VM:

virt-install \
    --name=<vm-name> \
    --memory=2048 \
    --disk path=/var/lib/libvirt/images/<vm-name>.qcow2,size=20,bus=virtio,format=qcow2 \
    --vcpus=2 \
    --os-variant=archlinux \
    --network bridge=virbr0 \
    --graphics none \
    --console pty,target_type=serial \
    --cdrom=/path/to/<iso-file>.iso

Note: Use osinfo-query os to list available --os-variant values for your system.

4.4 Starting the Virtual Machine#

After defining the VM, start it and connect to its console:

virsh start <vm-name>
virsh console <vm-name>

5. Advanced Usage#

5.1 Managing Network Interfaces#

# List all virtual networks
virsh net-list --all

# Start a network
virsh net-start <network-name>

# Set a network to autostart
virsh net-autostart <network-name>

# Show network details
virsh net-info <network-name>

5.2 Configuring Virtual Machine Settings#

Modify VM settings by editing its XML configuration:

# Dump current configuration to a file
virsh dumpxml <vm-name> > vm-config.xml

# Edit inline (opens in $EDITOR)
virsh edit <vm-name>

# Redefine from a modified XML file
virsh define vm-config.xml

5.3 Automating Tasks with Virsh#

Virsh integrates well into shell scripts. Example to start a list of VMs from a file:

while read -r vm; do
    virsh start "$vm"
done < vm-list.txt

Example to snapshot all running VMs:

virsh list --name | while read -r vm; do
    [ -n "$vm" ] && virsh snapshot-create-as "$vm" "auto-$(date +%Y%m%d)"
done

Troubleshooting#

See Also#

• KVM Tuning
• Single-GPU Passthrough on Linux
• Linux Containers (LXC)

Sources#

• https://libvirt.org/manpages/virsh.html
• https://libvirt.org/formatdomain.html
• https://wiki.archlinux.org/title/Libvirt