Tech Tutorial: 351.2 Xen (weight: 3) #

Introduction #

Xen is a powerful, open-source virtualization technology that allows multiple operating systems to run on the same physical hardware concurrently. It is widely used for server virtualization, infrastructure as a service (IaaS) platforms, and for testing and development purposes. In this tutorial, we will explore key aspects of managing and using Xen, focusing on commands and utilities involved in configuring and maintaining Xen virtual machines.

Key Knowledge Areas: #

Xen configuration files
Xen tools
Managing Xen with xm/xl
Networking for Xen domains
Troubleshooting Xen installations

Utilities: #

xm
xl
xenstore
xen-create-image
xentop

Step-by-Step Guide #

1. Installation #

Before diving into the commands and utilities, ensure Xen is installed on your system. Xen typically runs on Linux distributions such as CentOS and Debian. Here’s a quick guide to install Xen on a CentOS system:

sudo yum install centos-release-xen
sudo yum install xen
sudo systemctl enable xen-qemu-dom0-disk-backend.service
sudo systemctl enable xen-init-dom0.service
sudo systemctl enable xenconsoled.service
sudo systemctl start xen-qemu-dom0-disk-backend.service
sudo systemctl start xen-init-dom0.service
sudo systemctl start xenconsoled.service

2. Creating Virtual Machines with xen-create-image #

xen-create-image is a tool for creating Xen domainU images. Here’s how you can create a new virtual machine:

sudo xen-create-image --hostname=myvm1 --size=10Gb --swap=512Mb --memory=1024Mb --arch=amd64 --dist=buster --network=dhcp

This command will create a new virtual machine named myvm1 with 10GB of disk, 512MB of swap, 1GB of memory, using the Debian Buster distribution, and configured to obtain an IP via DHCP.

3. Managing Domains with xl #

The xl tool is the successor to the older xm and is used to manage Xen domains:

List all running domains:
```
sudo xl list
```
Create a domain:
```
sudo xl create /etc/xen/myvm1.cfg
```
Pause a domain:
```
sudo xl pause myvm1
```
Unpause a domain:
```
sudo xl unpause myvm1
```
Shutdown a domain:
```
sudo xl shutdown myvm1
```
Destroy a domain (force shutdown):
```
sudo xl destroy myvm1
```

4. Monitoring with xentop #

xentop displays real-time information about the Xen system and domains. Simply enter:

sudo xentop

This tool will show CPU usage, memory usage, and other important metrics for all running domains.

5. Using xenstore #

xenstore is used for accessing the XenStore, a database shared between domains:

List all keys:
```
sudo xenstore-ls
```
Read a key:
```
sudo xenstore-read vm/myvm1/name
```

Write a key:

sudo xenstore-write vm/myvm1/name "New VM Name"

Conclusion #

In this tutorial, we’ve covered basic yet essential commands and utilities to manage Xen virtual environments. From installing Xen, creating virtual machines, managing them using xl, monitoring with xentop, and using xenstore for XenStore interactions, these operations form the backbone of effective Xen administration. Mastery of these tools will allow you to efficiently manage and troubleshoot Xen virtual machines, ensuring robust virtualization environments.