path: root/docs/man/xm.pod.1

=head1 NAME

xm - Xen management user interface

=head1 SYNOPSIS

xm <subcommand> [args]

=head1 DESCRIPTION

The B<xm> program is the main interface for managing Xen guest
domains. The program can be used to create, pause, and shutdown
domains. It can also be used to list current domains, enable or pin
VCPUs, and attach or detach virtual block devices.

The basic structure of every xm command is almost always:

  xm <SubCommand> <DomId> [OPTIONS]

Where I<SubCommand> is one of the sub commands listed below, I<DomId>
is the numeric domain id, or the domain name (which will be internally
translated to domain id), and I<OPTIONS> are sub command specific
options.  There are a few exceptions to this rule in the cases where
the sub command in question acts on all domains, the entire machine,
or directly on the xen hypervisor.  Those exceptions will be clear for
each of those sub commands.

=head1 NOTES

All B<xm> opperations rely upon the Xen control daemon, aka B<xend>.
For any xm commands to run xend must also be running.  For this reason
you should start xend as a service when your system first boots using
xen.

Most B<xm> commands require root privledges to run due to the
communications channels used to talk to the hypervisor.  Running as
non root will return an error.

Most B<xm> commands act asynchronously, so just because the B<xm>
command returned, doesn't mean the action is complete.  This is
important, as many operations on domains, like create and shutdown,
can take considerable time (30 seconds or more) to bring the machine
into a fully compliant state.  If you want to know when one of these
actions has finished you must poll through xm list periodically.

=head1 DOMAIN SUBCOMMANDS

The following sub commands manipulate domains directly, as stated
previously most commands take DomId as the first parameter.

=over 4

=item I<console> <DomId>

Attach to domain DomId's console.  If you've set up your Domains to
have a traditional log in console this will look much like a normal
text log in screen.

This uses the back end xenconsole service which currently only
works for para-virtual domains.  

The attached console will perform much like a standard serial console,
so running curses based interfaces over the console B<is not
advised>.  Vi tends to get very odd when using it over this interface.

=item I<create> [-c] <ConfigFile> [Name=Value]..

The create sub command requires a ConfigFile and can optional take a
series of name value pairs that add to or override variables defined
in the config file.  See L<xmdomain.cfg> for full details of that file
format, and possible options used in either the ConfigFile or
Name=Value combinations.

ConfigFile can either be an absolute path to a file, or a relative
path to a file located in /etc/xen.

Create will return B<as soon> as the domain is started.  This B<does
not> mean the guest OS in the domain has actually booted, or is
available for input.

B<OPTIONS>

=over 4 

=item I<-c>

Attache console to the domain as soon as it has started.  This is
useful for determining issues with crashing domains.

=back

B<EXAMPLES>

=over 4

=item I<with config file>

  xm create Fedora4

This creates a domain with the file /etc/xen/Fedora4, and returns as
soon as it is run.

=item I<without config file>
 
  xm create /dev/null ramdisk=initrd.img \
     kernel=/boot/vmlinuz-2.6.12.6-xenU \
     name=ramdisk nics=0 vcpus=1 \
     memory=64 root=/dev/ram0

This creates the domain without using a config file (more specifically
using /dev/null as an empty config file), kernel and ramdisk as
specified, setting the name of the domain to "ramdisk", also disabling
virtual networking.  (This example comes from the xm-test test suite.)

=back

=item I<destroy> <DomId>

Immediately terminate the domain DomId.  This doesn't give the domain
OS any chance to react, and it the equivalent of ripping the power
cord out on a physical machine.  In most cases you will want to use
the B<shutdown> command instead.

=item I<domid> <DomName>

Converts a domain name to a domain id using xend's internal mapping.

=item I<domname> <DomId>

Converts a domain id to a domain name using xend's internal mapping.

=item I<help> [--long]

Displays the short help message (i.e. common commands).

The I<--long> option prints out the complete set of B<xm> subcommands,
grouped by function.

=item I<list> [--long] [DomId, ...]

Prints information about one or more domains.  If no domains are
specified it prints out information about all domains.

An example format for the list is as follows:

 Name                              ID Mem(MiB) VCPUs State  Time(s)
 Domain-0                           0       98     1 r-----  5068.6
 Fedora3                          164      128     1 r-----     7.6
 Fedora4                          165      128     1 ------     0.6
 Mandrake2006                     166      128     1 -b----     3.6
 Mandrake10.2                     167      128     1 ------     2.5
 Suse9.2                          168      100     1 ------     1.8

Name is the name of the domain.  ID the domain numeric id.  Mem is the
size of the memory allocated to the domain.  VCPUS is the number of
VCPUS allocated to domain.  State is the run state (see below).  Time
is the total run time of the domain as accounted for by Xen.

B<STATES>

=over 4

The State field lists 6 states for a Xen Domain, and which ones the
current Domain is in.

=item I<r - running>

The domain is currently running on a CPU

=item I<b - blocked>

The domain is blocked, and not running or runable.  This can be caused
because the domain is waiting on IO (a traditional wait state) or has
gone to sleep because there was nothing else for it to do.

=item I<p - paused>

The domain has been paused, usually occurring through the administrator
running B<xm pause>.  When in a paused state the domain will still
consume allocated resources like memory, but will not be eligible for
scheduling by the Xen hypervisor.

=item I<s - shutdown>

FIXME: Why would you ever see this state?

=item I<c - crashed>

The domain has crashed, which is always a violent ending.  Usually
this state can only occur if the domain has been configured not to
restart on crash.  See L<xmdomain.cfg> for more info.

=item I<d - dying>

The domain is in process of dying, but hasn't completely shutdown or
crashed.

FIXME: Is this right?

=back

B<LONG OUTPUT>

=over 4

If I<--long> is specified, the output for xm list is not the table
view shown above, but instead is an S-Expression representing all
information known about all domains asked for.  This is mostly only
useful for external programs to parse the data.

B<Note:> there is no stable guarantees on the format of this data.
Use at your own risk.

=back

B<NOTES>

=over 4

The Time column is deceptive.  Virtual IO (network and block devices)
used by Domains requires coordination by Domain0, which means that
Domain0 is actually charged for much of the time that a DomainU is
doing IO.  Use of this time value to determine relative utilizations
by domains is thus very suspect, as a high IO workload may show as
less utilized than a high CPU workload.  Consider yourself warned.

=back

=item I<mem-max> <DomId> <Mem>

Specify the maximum amount of memory the Domain is able to use.  Mem
is specified in megabytes. 

The mem-max value may not correspond to the actual memory used in the
Domain, as it may balloon down it's memory to give more back to the OS.

=item I<mem-set> <DomId> <Mem>

Set the domain's used memory using the balloon driver.  Because this
operation requires cooperation from the domain operating system, there
is no guarantee that it will succeed.

B<Warning:> there is no good way to know in advance how small of a
mem-set will make a domain unstable and cause it to crash.  Be very
careful when using this command on running domains.

=item I<migrate> <DomId> <Host> [Options]

Migrate a domain to another Host machine. B<Xend> must be running on
other host machine, it must be running the same version of xen, it
must have the migration tcp port open and accepting connections from
the source host, and there must be sufficient resources for the domain
to run (memory, disk, etc).

Migration is pretty complicated, and has many security implications,
please read the Xen Users Guide to ensure you understand the
ramifications and limitations on migration before attempting it in
production.

B<OPTIONS>

=over 4

=item I<-l, --live>

Use live migration.  This will migrate the domain between hosts
without shutting down the domain.  See the Xen Users Guide for more
information.

=item I<-r, --resource> Mbs

Set maximum Mbs allowed for migrating the domain.  This ensures that
the network link is not saturated with migration traffic while
attempting to do other useful work.

=back

=item I<pause> <DomId>

Pause a domain.  When in a paused state the domain will still consume
allocated resources such as memory, but will not be eligible for
scheduling by the Xen hypervisor.

=item I<reboot> [Options] <DomId>

Reboot a domain.  This acts just as if the domain had the B<reboot>
command run from the console.  The command returns as soon as it has
executed the reboot action, which may be significantly before the
domain actually reboots.

The behavior of what happens to a domain when it reboots is set by the
B<on_reboot> parameter of the xmdomain.cfg file when the domain was
created.

B<OPTIONS>

=over 4

=item I<-a, --all>

Reboot all domains

=item I<-w, --wait>

Wait for reboot to complete before returning.  This may take a while,
as all services in the domain will have to be shut down cleanly.

=back

=item I<restore> <File>

Build a domain from an B<xm save> state file.  See I<save> for more info.

=item I<save> <DomId> <File>

Saves a running domain to a state file 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.  B<xm restore> restores from this state file.

This is roughly equivalent to doing a hibernate on a running computer,
with all the same limitations.  Open network connections may be
severed upon restore, as TCP timeouts may have expired.

=item I<shutdown> [Options] <DomId>

Gracefully shuts down a domain.  This coordinates with the domain OS
to perform graceful shutdown, so there is no guaruntee that it will
succeed, and may take a variable length of time depending on what
services must be shutdown in the domain.  The command returns
immediately after signally the domain unless that I<-w> flag is used.

The behavior of what happens to a domain when it reboots is set by the
B<on_shutdown> parameter of the xmdomain.cfg file when the domain was
created.

B<OPTIONS>

=over 4

=item I<-a> 

Shutdown B<all> domains.  Often used when doing a complete shutdown of
a Xen system.

=item I<-w>

Wait for the domain to complete shutdown before returning.

=back

=item I<sysrq> <DomId> <letter>

Send a I<Magic System Request> signal to the domain.  For more
information on available magic sys req operations, see sysrq.txt in
your Linux Kernel sources.

=item I<unpause> <DomId>

Moves a domain out of the paused state.  This will allow a previously
paused domain to now be eligible for scheduling by the Xen hypervisor.

=item I<set-vcpus> <DomId> <VCPUCount>

Enables the I<VCPUcount> virtual CPUs for the domain in question.
Like mem-set, this command can only allocate up to the maximum virtual
CPU count configured at boot for the domain.

If the VCPUcount is smaller than the current number of active VCPUs,
the highest number VCPUs will be hotplug removed.  This may be
important for pinning purposes.

Attempting to set-vcpus to a number larger than the initially
configured VCPU count is an error.  Trying to set-vcpus to < 1 will be
quietly ignored.

=item I<vpcu-list> [DomID]

Lists VCPU information for a specific domain.  If no domain is
specified, VCPU information for all domains will be provided.

=item I<vcpu-pin> <DomId> <VCPU> <CPUs>

Pins the the VCPU to only run on the specific CPUs.  

Normally VCPUs can float between available CPUs whenever Xen deems a
different run state is appropriate.  Pinning can be used to restrict
this, by ensuring certain VCPUs can only run on certain physical
CPUs.

=back

=head1 XEN HOST SUBCOMMANDS

=over 4

=item I<dmesg> [OPTION]

Reads the Xen message buffer, similar to dmesg on a Linux system.  The
buffer contains informational, warning, and error messages created
during Xen's boot process.  If you are having problems with Xen, this
is one of the first places to look as part of problem determination.

B<OPTIONS>

=over 4

=item I<-c, --clear>

Clears Xen's message buffer.

=back

=item I<info>

Print information about the Xen host in I<name : value> format.  When
reporting a Xen bug, please provide this information as part of the
bug report.

Sample xen domain info looks as follows:

 system                 : Linux
 host                   : talon
 release                : 2.6.12.6-xen0
 version                : #1 Mon Nov 14 14:26:26 EST 2005
 machine                : i686
 nr_cpus                : 2
 nr_nodes               : 1
 sockets_per_node       : 2
 cores_per_socket       : 1
 threads_per_core       : 1
 cpu_mhz                : 696
 hw_caps                : 0383fbff:00000000:00000000:00000040
 memory                 : 767
 free_memory            : 37
 xen_major              : 3
 xen_minor              : 0
 xen_extra              : -devel
 xen_caps               : xen-3.0-x86_32
 xen_params             : virt_start=0xfc000000
 xen_changeset          : Mon Nov 14 18:13:38 2005 +0100 7793:090e44133d40
 cc_compiler            : gcc version 3.4.3 (Mandrakelinux 10.2 3.4.3-7mdk)
 cc_compile_by          : sdague
 cc_compile_domain      : (none)
 cc_compile_date        : Mon Nov 14 14:16:48 EST 2005

B<FIELDS>

=over 4

Not all fields will be explained here, but some of the less obvious
ones deserve explanation:

=item I<hw_caps>

A vector showing what hardware capabilities are supported by your
processor.  This is equivalent to, though more cryptic, the flags
field in /proc/cpuinfo on a normal Linux machine.

=item I<free_memory>

Available memory (in MB) not allocated to Xen, or any other Domains.

=item I<xen_caps>

The xen version, architecture.  Architecture values can be one of:
x86_32, x86_32p (i.e. PAE enabled), x86_64, ia64.

=item I<xen_changeset>

The xen mercurial changeset id.  Very useful for determining exactly
what version of code your Xen system was built from.

=back

=item I<log>

Print out the B<xend> log.  This log file can be found in
/var/log/xend.log.

=item I<top>

Executes the xentop command, which provides real time monitoring of
domains.  Xentop is a curses interface, and reasonably self
explainitory.

=back

=head1 SCHEDULER SUBCOMMANDS

FIXME: we really need a scheduler expert to write up this section.

=over 4

=item I<sched-bvt> <Parameters>

Set Borrowed Virtual Time (BVT) scheduler parameters. There are five
parameters, which are given in order below.

=over 4

Parameters:

    mcuadv - Minimum Charging Unit (MCU) advance.
    warpback - Warp back time allowed.
    warpvalue - Warp value.
    warpl - Warp maximum limit.
    warpu - Unwarped minimum limit.

=back 

=item I<sched-bvt-ctxallow> <Allow>

Sets the BVT scheduler's context switch allowance. Allow is the
minimum time slice allowed to run before being pre-empted.

=item I<sched-sedf> <Parameters>

Set simple sEDF scheduler parameters. Use the following parametersin
order.

=over 4

Parameters:

    period - in nanoseconds
    slice - in nanoseconds
    latency-hint - scaled period if domain is doing heavy I/O
    extratime - flag for allowing domain to run in extra time.
    weight - another way of setting cpu slice.

=back

=back

=head1 VIRTUAL DEVICE COMMANDS

Most virtual devices can be added and removed while guests are
running.  The effect to the guest OS is much the same as any hotplug
event.

=over 4

=item I<block-attach <DomId> <BackDev> <FrontDev> <Mode> [BackDomId]

Create a new virtual block device

=item I<block-detach> <DomId> <DevId>

Destroy a domain's virtual block device. DevId may either be a device
ID or the device name as mounted in the guest.

=item I<block-list> <DomId>

List virtual block devices for a domain.

=item I<network-limit> <DomId> <Vif> <Credit> <Period>

Limit the transmission rate of a virtual network interface.

=item I<network-list> <DomId>

List virtual network interfaces for a domain.

=back

=head1 VNET COMMANDS

The Virtual Network interfaces for Xen 

=over 4

=item I<vnet-list> [-l|--long]

List vnets.

=item I<vnet-create> <config>

Create a vnet from a config file.

=item I<vnet-delete> <vnetid>

Delete a vnet.

=back

=head1 EXAMPLES

=head1 SEE ALSO

B<xmdomain.cfg>(5)

=head1 AUTHOR

  Sean Dague <sean at dague dot net>
  Daniel Stekloff <dsteklof at us dot ibm dot com>

=head1 BUGS