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< body >
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< h1 > libxl hypervisor driver for Xen< / h1 >
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< ul id = "toc" > < / ul >
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< p >
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The libvirt libxl driver provides the ability to manage virtual
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machines on any Xen release from 4.6.0 onwards.
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< / p >
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< h2 > < a id = "project" > Project Links< / a > < / h2 >
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< ul >
< li >
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The < a href = "https://www.xenproject.org" > Xen< / a >
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hypervisor on Linux and Solaris hosts
< / li >
< / ul >
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< h2 > < a id = "prereq" > Deployment pre-requisites< / a > < / h2 >
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< p >
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The libvirt libxl driver uses Xen's libxl API, also known as
libxenlight, to implement libvirt's hypervisor driver
functionality. libxl provides a consolidated interface for
managing a Xen host and its virtual machines, unlike old
versions of Xen where applications often had to communicate
with xend, xenstored, and the hypervisor itself via hypercalls.
With libxl the only pre-requisit is a properly installed Xen
host with the libxl toolstack running in a service domain
(often Domain-0).
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< / p >
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< h2 > < a id = "uri" > Connections to libxl driver< / a > < / h2 >
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< p >
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The libvirt libxl driver is a single-instance privileged driver,
with a driver name of 'xen'. Some example connection URIs for
the libxl driver are:
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< / p >
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< pre >
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xen:///system (local access, direct)
xen+unix:///system (local access, via daemon)
xen://example.com/system (remote access, TLS/x509)
xen+tcp://example.com/system (remote access, SASl/Kerberos)
xen+ssh://root@example.com/system (remote access, SSH tunnelled)
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< / pre >
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< h2 > < a id = "configFiles" > Location of configuration files< / a > < / h2 >
< p >
The libxl driver comes with sane default values. However, during its
initialization it reads a configuration file which offers system
administrator to override some of that default. The file is located
under < code > /etc/libvirt/libxl.conf< / code >
< / p >
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< h2 > < a id = "imex" > Import and export of libvirt domain XML configs< / a > < / h2 >
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< p >
The libxl driver currently supports three native
config formats. The first, known as < code > xen-xm< / code > , is the
original Xen virtual machine config format used by the legacy
xm/xend toolstack. The second, known as < code > xen-sxpr< / code > ,
is also one of the original formats that was used by xend's
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legacy HTTP RPC service (< span class = 'removed' > removed in 5.6.0< / span > )
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< / p >
< p >
The third format is < code > xen-xl< / code > , which is the virtual
machine config format supported by modern Xen. The < code > xen-xl< / code >
format is described in the xl.cfg(5) man page.
< / p >
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< h3 > < a id = "xmlimport" > Converting from XM config files to domain XML< / a > < / h3 >
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< p >
The < code > virsh domxml-from-native< / code > provides a way to convert an
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existing set of xl, xm, or sxpr config files to libvirt Domain XML,
which can then be used by libvirt.
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< / p >
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< pre > $ virsh -c xen:///system domxml-from-native xen-xm rhel5.cfg
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< domain type='xen'>
< name> rhel5pv< /name>
< uuid> 8f07fe28-753f-2729-d76d-bdbd892f949a< /uuid>
< memory> 2560000< /memory>
< currentMemory> 307200< /currentMemory>
< vcpu> 4< /vcpu>
< bootloader> /usr/bin/pygrub< /bootloader>
< os>
< type arch='x86_64' machine='xenpv'> linux< /type>
< /os>
< clock offset='utc'/>
< on_poweroff> destroy< /on_poweroff>
< on_reboot> restart< /on_reboot>
< on_crash> restart< /on_crash>
< devices>
< disk type='file' device='disk'>
< driver name='tap' type='aio'/>
< source file='/var/lib/xen/images/rhel5pv.img'/>
< target dev='xvda' bus='xen'/>
< /disk>
< disk type='file' device='disk'>
< driver name='tap' type='qcow'/>
< source file='/root/qcow1-xen.img'/>
< target dev='xvdd' bus='xen'/>
< /disk>
< interface type='bridge'>
< mac address='00:16:3e:60:36:ba'/>
< source bridge='xenbr0'/>
< /interface>
< console type='pty'>
< target port='0'/>
< /console>
< input type='mouse' bus='xen'/>
< graphics type='vnc' port='-1' autoport='yes' listen='0.0.0.0'/>
< /devices>
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< /domain> < / pre >
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< h3 > < a id = "xmlexport" > Converting from domain XML to XM config files< / a > < / h3 >
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< p >
The < code > virsh domxml-to-native< / code > provides a way to convert a
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guest description using libvirt Domain XML into xl, xm, or sxpr config
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format.
< / p >
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< pre > $ virsh -c xen:///system domxml-to-native xen-xm rhel5pv.xml
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name = "rhel5pv"
uuid = "8f07fe28-753f-2729-d76d-bdbd892f949a"
maxmem = 2500
memory = 300
vcpus = 4
bootloader = "/usr/bin/pygrub"
kernel = "/var/lib/xen/boot_kernel.0YK-cS"
ramdisk = "/var/lib/xen/boot_ramdisk.vWgrxK"
extra = "ro root=/dev/VolGroup00/LogVol00 rhgb quiet"
on_poweroff = "destroy"
on_reboot = "restart"
on_crash = "restart"
sdl = 0
vnc = 1
vncunused = 1
vnclisten = "0.0.0.0"
disk = [ "tap:aio:/var/lib/xen/images/rhel5pv.img,xvda,w", "tap:qcow:/root/qcow1-xen.img,xvdd,w" ]
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vif = [ "mac=00:16:3e:60:36:ba,bridge=virbr0,script=vif-bridge,vifname=vif5.0" ]< / pre >
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< h2 > < a id = "xencommand" > Pass-through of arbitrary command-line arguments
to the qemu device model< / a > < / h2 >
< p > < span class = "since" > Since 6.7.0< / span > , the Xen driver supports passing
arbitrary command-line arguments to the qemu device model used by Xen with
the < code > < xen:commandline> < / code > element under < code > domain< / code > .
In order to use command-line pass-through, an XML namespace request must be
issued that pulls in < code > http://libvirt.org/schemas/domain/xen/1.0< / code > .
With the namespace in place, it is then possible to add
< code > < xen:arg> < / code > sub-elements to
< code > < xen:commandline> < / code > describing each argument passed to
the device model when starting the domain.
< / p >
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< p > The following example illustrates passing arguments to the QEMU device
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model that define a floppy drive, which Xen does not support through its
public APIs:
< / p >
< pre >
< domain type="xen" xmlns:xen="http://libvirt.org/schemas/domain/xen/1.0">
...
< xen:commandline>
< xen:arg value='-drive'/>
< xen:arg value='file=/path/to/image,format=raw,if=none,id=drive-fdc0-0-0'/>
< xen:arg value='-global'/>
< xen:arg value='isa-fdc.driveA=drive-fdc0-0-0'/>
< /xen:commandline>
< /domain>
< / pre >
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< h2 > < a id = "xmlconfig" > Example domain XML config< / a > < / h2 >
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< p >
Below are some example XML configurations for Xen guest domains.
For full details of the available options, consult the < a href = "formatdomain.html" > domain XML format< / a >
guide.
< / p >
< h3 > Paravirtualized guest bootloader< / h3 >
< p >
Using a bootloader allows a paravirtualized guest to be booted using
a kernel stored inside its virtual disk image
< / p >
< pre > < domain type='xen' >
< name> fc8< /name>
< bootloader> /usr/bin/pygrub< /bootloader>
< os>
< type> linux< /type>
< /os>
< memory> 131072< /memory>
< vcpu> 1< /vcpu>
< devices>
< disk type='file'>
< source file='/var/lib/xen/images/fc4.img'/>
< target dev='sda1'/>
< /disk>
< interface type='bridge'>
< source bridge='xenbr0'/>
< mac address='aa:00:00:00:00:11'/>
< script path='/etc/xen/scripts/vif-bridge'/>
< /interface>
< console tty='/dev/pts/5'/>
< /devices>
< /domain> < / pre >
< h3 > Paravirtualized guest direct kernel boot< / h3 >
< p >
For installation of paravirtualized guests it is typical to boot the
domain using a kernel and initrd stored in the host OS
< / p >
< pre > < domain type='xen' >
< name> fc8< /name>
< os>
< type> linux< /type>
< kernel> /var/lib/xen/install/vmlinuz-fedora8-x86_64< /kernel>
< initrd> /var/lib/xen/install/initrd-vmlinuz-fedora8-x86_64< /initrd>
< cmdline> kickstart=http://example.com/myguest.ks < /cmdline>
< /os>
< memory> 131072< /memory>
< vcpu> 1< /vcpu>
< devices>
< disk type='file'>
< source file='/var/lib/xen/images/fc4.img'/>
< target dev='sda1'/>
< /disk>
< interface type='bridge'>
< source bridge='xenbr0'/>
< mac address='aa:00:00:00:00:11'/>
< script path='/etc/xen/scripts/vif-bridge'/>
< /interface>
< graphics type='vnc' port='-1'/>
< console tty='/dev/pts/5'/>
< /devices>
< /domain> < / pre >
< h3 > Fullyvirtualized guest BIOS boot< / h3 >
< p >
Fullyvirtualized guests use the emulated BIOS to boot off the primary
harddisk, CDROM or Network PXE ROM.
< / p >
< pre > < domain type='xen' id='3'>
< name> fv0< /name>
< uuid> 4dea22b31d52d8f32516782e98ab3fa0< /uuid>
< os>
< type> hvm< /type>
< loader> /usr/lib/xen/boot/hvmloader< /loader>
< boot dev='hd'/>
< /os>
< memory> 524288< /memory>
< vcpu> 1< /vcpu>
< on_poweroff> destroy< /on_poweroff>
< on_reboot> restart< /on_reboot>
< on_crash> restart< /on_crash>
< features>
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< pae/>
< acpi/>
< apic/>
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< /features>
< clock sync="localtime"/>
< devices>
< emulator> /usr/lib/xen/bin/qemu-dm< /emulator>
< interface type='bridge'>
< source bridge='xenbr0'/>
< mac address='00:16:3e:5d:c7:9e'/>
< script path='vif-bridge'/>
< /interface>
< disk type='file'>
< source file='/var/lib/xen/images/fv0'/>
< target dev='hda'/>
< /disk>
< disk type='file' device='cdrom'>
< source file='/var/lib/xen/images/fc5-x86_64-boot.iso'/>
< target dev='hdc'/>
< readonly/>
< /disk>
< disk type='file' device='floppy'>
< source file='/root/fd.img'/>
< target dev='fda'/>
< /disk>
< graphics type='vnc' port='5904'/>
< /devices>
< /domain> < / pre >
< h3 > Fullyvirtualized guest direct kernel boot< / h3 >
< p >
With Xen 3.2.0 or later it is possible to bypass the BIOS and directly
boot a Linux kernel and initrd as a fullyvirtualized domain. This allows
for complete automation of OS installation, for example using the Anaconda
kickstart support.
< / p >
< pre > < domain type='xen' id='3'>
< name> fv0< /name>
< uuid> 4dea22b31d52d8f32516782e98ab3fa0< /uuid>
< os>
< type> hvm< /type>
< loader> /usr/lib/xen/boot/hvmloader< /loader>
< kernel> /var/lib/xen/install/vmlinuz-fedora8-x86_64< /kernel>
< initrd> /var/lib/xen/install/initrd-vmlinuz-fedora8-x86_64< /initrd>
< cmdline> kickstart=http://example.com/myguest.ks < /cmdline>
< /os>
< memory> 524288< /memory>
< vcpu> 1< /vcpu>
< on_poweroff> destroy< /on_poweroff>
< on_reboot> restart< /on_reboot>
< on_crash> restart< /on_crash>
< features>
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< pae/>
< acpi/>
< apic/>
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< /features>
< clock sync="localtime"/>
< devices>
< emulator> /usr/lib/xen/bin/qemu-dm< /emulator>
< interface type='bridge'>
< source bridge='xenbr0'/>
< mac address='00:16:3e:5d:c7:9e'/>
< script path='vif-bridge'/>
< /interface>
< disk type='file'>
< source file='/var/lib/xen/images/fv0'/>
< target dev='hda'/>
< /disk>
< disk type='file' device='cdrom'>
< source file='/var/lib/xen/images/fc5-x86_64-boot.iso'/>
< target dev='hdc'/>
< readonly/>
< /disk>
< disk type='file' device='floppy'>
< source file='/root/fd.img'/>
< target dev='fda'/>
< /disk>
< graphics type='vnc' port='5904'/>
< /devices>
< /domain> < / pre >
< / body >
< / html >
