Xen shell commands

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susir 2012-05-22 13:33:33

文章标签 xen 文章分类 运维

Xen shell commands

Some more or less commonly used shell commands for managing Xen Virtual Machines (VM, also called Domains). Tested on Xen 3.0, should work also in other versions.

Basic commands

Show the running Virtual Machines: xm list

Start a virtual machine (myhost): xm create myhost

Gracefully shutdown (soft-reset) a virtual machine: xm shutdown myhost

Forced power Off (hard-reset) of a virtual machine: xm destroy myhost

Reboot a VM : xm reboot myhost

Using the console

Start a virtual machine and attach immediately a console: xm create -c myhost

Attach to the console of a VM (sample ID=4 for myhost, as shown in xm list):

xm console myhost or xm console 4

To leave / detach from the xen console press CTRL+5

Resources management and usage

To alter the RAM assigned to a VM (sample 256 Mb): xm mem-set myhost 256

To alter the CPUs assigned to a VM (sample 2 CPUs or cores): xm vcpu-set myhost 2

Shows resource utilization of the running hosts: xm top or xentop

Shows Virtual Machines uptimes: xm uptime

Saving and Restoring

Virtual Machines state can be saved on a file and later restored (sample destination file /var/tmp/myhost.save)

xm save myhost /var/tmp/myhost.save

Note that after this command the VM is no longer active: you can reboot from start it with xm create myhost or restore the saved machine state with xm restore /var/tmp/myhost.save

Note also that the save file ( /var/tmp/myhost.save ) is only the dump on the VM memory, for backups it's of no use if you copy it to another physical host without copying also the VM config file and the file/LVM/partition used for the disk) .

Block Devices management

It's is possible to add block devices (disks) to a running VM:

To add a local file ( /var/tmp/data.disk ) as /dev/xvdc to the myhost paravirtualized VM, in write mode:

xm block-attach myhost file://var/tmp/data.disk /dev/xvdc w

Mode can be: w (read/write), r (read only), w! (shared read/write, when the samer device is attached to two different VMs).

The above file can be created (here 4 Gb) with:

dd if=/dev/zero of=/var/tmp/data.disk bs=1024k count=4096

To add a local physical disk, partition or LVM (for example an USB stick):

xm block-attach myhost phy://dev/sda /dev/xvdc w

Note that I/O performances are much better when using physical devices or LVM instead of plain files as block devices for the VMs.

To list the currently attached block devices to a VM:

xm block-list myhost --long or xm block-list myhost