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xm

NAME

xm - Xen management user interface

SYNOPSIS

xm subcommand [args]

DESCRIPTION

The 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 domain-id [OPTIONS]

Where subcommand is one of the subcommands listed below, domain-id is the numeric domain id, or the domain name (which will be internally translated to domain id), and OPTIONS are subcommand specific options. There are a few exceptions to this rule in the cases where the subcommand in question acts on all domains, the entire machine, or directly on the Xen hypervisor. Those exceptions will be clear for each of those subcommands.

NOTES

All xm operations rely upon the Xen control daemon, aka 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 xm commands require root privileges to run due to the communications channels used to talk to the hypervisor. Running as non root will return an error.

Most xm commands act asynchronously, so just because the 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.

DOMAIN SUBCOMMANDS

The following subcommands manipulate domains directly. As stated previously, most commands take domain-id as the first parameter.

console domain-id

Attach to domain domain-id'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 is not advised. Vi tends to get very odd when using it over this interface.

Use the key combination Ctrl+] to detach the domain console.

create configfile [OPTIONS] [vars]..

The create subcommand requires a config file and can optionally take a series of vars that add to or override variables defined in the config file. See xmdomain.cfg for full details of that file format, and possible options used in either the configfile or for vars.

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

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

OPTIONS

--help_config

Print the available configuration variables vars. These variables may be used on the command line or in the configuration file configfile.

-q, --quiet

No console output.

--path

Search path for configuration scripts. The value of PATH is a colon-separated directory list.

-f=FILE, --defconfig=FILE

Use the given Python configuration script. The configuration script is loaded after arguments have been processed. Each command-line option sets a configuration variable named after its long option name, and these variables are placed in the environment of the script before it is loaded. Variables for options that may be repeated have list values. Other variables can be set using name=value on the command line. After the script is loaded, option values that were not set on the command line are replaced by the values set in the script.

-F=FILE, --config=FILE

Use the given SXP formated configuration script. SXP is the underlying configuration format used by Xen. SXP configuration scripts can be hand-written or generated from Python configuration scripts, using the -n (dryrun) option to print the configuration. An SXP formatted configuration file may also be generated for a given domain-id by redirecting the output from the the xm list --long domain-id to a file.

-n, --dryrun

Dry run - prints the resulting configuration in SXP but does not create the domain.

-x, --xmldryrun

XML dry run - prints the resulting configuration in XML but does not create the domain.

-s, --skipdtd

Skip DTD checking - skips checks on XML before creating. Experimental. Can decrease create time.

-p, --paused

Leave the domain paused after it is created.

-c, --console_autoconnect

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

EXAMPLES

with config file

   xm create Fedora4
 
 

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

without config file

   xm create /dev/null ramdisk=initrd.img \
      kernel=/boot/vmlinuz-2.6.12.6-xenU \
      name=ramdisk vif='' 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.)

delete

Remove a domain from Xend domain management. The xm list command shows the domain names.

destroy domain-id

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

domid domain-name

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

domname domain-id

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

dump-core [OPTIONS] domain-id [filename]

Dumps the virtual machine's memory for the specified domain to the filename specified. The dump file will be written to a distribution specific directory for dump files. Such as: /var/lib/xen/dump or /var/xen/dump Defaults to dumping the core without pausing the domain if no OPTIONS are specified.

OPTIONS

-L, --live

Dump core without pausing the domain.

-C, --crash

Crash domain after dumping core.

help [--long]

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

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

list [OPTIONS] [domain-id ...]

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

OPTIONS

-l, --long

The output for xm list is not the table view shown below, but instead presents the data in SXP format.

--label

Security labels are added to the output of xm list and the lines are sorted by the labels (ignoring case). See the ACCESS CONTROL SUBCOMMAND section of this man page for more information about labels.

--state=<state>

Output information for VMs in the specified state.

EXAMPLE
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 numeric domain id. Mem is the desired amount of memory to allocate to the domain (although it may not be the currently allocated amount). VCPUs is the number of virtual CPUs allocated to the domain. State is the run state (see below). Time is the total run time of the domain as accounted for by Xen.

STATES

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

r - running

The domain is currently running on a CPU.

b - blocked

The domain is blocked, and not running or runnable. 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.

p - paused

The domain has been paused, usually occurring through the administrator running 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.

s - shutdown

FIXME: Why would you ever see this state?

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 xmdomain.cfg for more info.

d - dying

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

FIXME: Is this right?

NOTES

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.

mem-max domain-id 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 its memory to give more back to the OS.

mem-set domain-id 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. This command will definitely not work unless the domain has the required paravirt driver.

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.

migrate domain-id host [OPTIONS]

Migrate a domain to another host machine. 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 User's Guide to ensure you understand the ramifications and limitations on migration before attempting it in production.

OPTIONS

-l, --live

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

-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.

new configfile [OPTIONS] [vars]...

Adds a domain to Xend domain management.

The new subcommand requires a config file and can optionally take a series of vars that add to or override variables defined in the config file. See xmdomain.cfg for full details of that file format, and possible options used in either the configfile or for vars.

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

The new subcommand will return without starting the domain. The domain needs to be started using the xm start command.

OPTIONS

--help_config

Print the available configuration variables vars. These variables may be used on the command line or in the configuration file configfile.

-q, --quiet

No console output.

--path

Search path for configuration scripts. The value of PATH is a colon-separated directory list.

-f=FILE, --defconfig=FILE

Use the given Python configuration script. The configuration script is loaded after arguments have been processed. Each command-line option sets a configuration variable named after its long option name, and these variables are placed in the environment of the script before it is loaded. Variables for options that may be repeated have list values. Other variables can be set using name=value on the command line. After the script is loaded, option values that were not set on the command line are replaced by the values set in the script.

-F=FILE, --config=FILE

Use the given SXP formated configuration script. SXP is the underlying configuration format used by Xen. SXP configuration scripts can be hand-written or generated from Python configuration scripts, using the -n (dryrun) option to print the configuration. An SXP formatted configuration file may also be generated for a given domain-id by redirecting the output from the the xm list --long domain-id to a file.

-n, --dryrun

Dry run - prints the resulting configuration in SXP but does not create the domain.

-x, --xmldryrun

XML dry run - prints the resulting configuration in XML but does not create the domain.

-s, --skipdtd

Skip DTD checking - skips checks on XML before creating. Experimental. Can decrease create time.

-p, --paused

Leave the domain paused after it is created.

-c, --console_autoconnect

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

pause domain-id

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.

reboot [OPTIONS] domain-id

Reboot a domain. This acts just as if the domain had the 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 on_reboot parameter of the xmdomain.cfg file when the domain was created.

OPTIONS

-a, --all

Reboot all domains.

-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.

restore state-file

Build a domain from an xm save state file. See save for more info.

resume domain-name [OPTIONS]

Moves a domain out of the suspended state and back into memory.

OPTIONS

-p, <--paused>

Moves a domain back into memory but leaves the domain in a paused state. The xm unpause subcommand may then be used to bring it out of the paused state.

save domain-id state-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. 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.

shutdown [OPTIONS] domain-id

Gracefully shuts down a domain. This coordinates with the domain OS to perform graceful shutdown, so there is no guarantee 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 -w flag is used.

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

OPTIONS

-a

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

-w

Wait for the domain to complete shutdown before returning.

start domain-name [OPTIONS]

Start a Xend managed domain that was added using the xm new command.

OPTIONS

-p, --paused

Do not unpause domain after starting it.

-c, --console_autoconnect

Connect to the console after the domain is created.

suspend domain-name

Suspend a domain to a state file so that it can be later resumed using the xm resume subcommand. Similar to the xm save subcommand although the state file may not be specified.

sysrq domain-id letter

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

unpause domain-id

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.

vcpu-set domain-id vcpu-count

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

Because this operation requires cooperation from the domain operating system, there is no guarantee that it will succeed. This command will not work with a full virt domain.

vcpu-list [domain-id]

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

vcpu-pin domain-id vcpu cpus

Pins the the VCPU to only run on the specific CPUs. The keyword all can be used to apply the cpus list to all VCPUs in the domain.

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.

XEN HOST SUBCOMMANDS

dmesg [-c]

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.

OPTIONS

-c, --clear

Clears Xen's message buffer.

info

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

Sample output looks as follows (lines wrapped manually to make the man page more readable):

  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
  cores_per_socket       : 1
  threads_per_core       : 1
  cpu_mhz                : 696
  hw_caps                : 0383fbff:00000000:00000000:00000040
  total_memory           : 767
  free_memory            : 37
  xen_major              : 3
  xen_minor              : 0
  xen_extra              : -devel
  xen_caps               : xen-3.0-x86_32
  xen_scheduler          : credit
  xen_pagesize           : 4096
  platform_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
  xend_config_format     : 3
 
 

FIELDS

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

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.

free_memory

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

xen_caps

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

xen_changeset

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

log

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

top

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

uptime

Prints the current uptime of the domains running.

SCHEDULER SUBCOMMANDS

Xen ships with a number of domain schedulers, which can be set at boot time with the sched= parameter on the Xen command line. By default credit is used for scheduling.

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

sched-credit [ -d domain-id [ -w[=WEIGHT] | -c[=CAP] ] ]

Set credit scheduler parameters. The credit scheduler is a proportional fair share CPU scheduler built from the ground up to be work conserving on SMP hosts.

Each domain (including Domain0) is assigned a weight and a cap.

PARAMETERS

WEIGHT

A domain with a weight of 512 will get twice as much CPU as a domain with a weight of 256 on a contended host. Legal weights range from 1 to 65535 and the default is 256.

CAP

The cap optionally fixes the maximum amount of CPU a domain will be able to consume, even if the host system has idle CPU cycles. The cap is expressed in percentage of one physical CPU: 100 is 1 physical CPU, 50 is half a CPU, 400 is 4 CPUs, etc. The default, 0, means there is no upper cap.

sched-sedf period slice latency-hint extratime weight

Set Simple EDF (Earliest Deadline First) scheduler parameters. This scheduler provides weighted CPU sharing in an intuitive way and uses realtime-algorithms to ensure time guarantees. For more information see docs/misc/sedf_scheduler_mini-HOWTO.txt in the Xen distribution.

PARAMETERS

period

The normal EDF scheduling usage in nanoseconds

slice

The normal EDF scheduling usage in nanoseconds

FIXME: these are lame, should explain more.

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.

EXAMPLES
normal EDF (20ms/5ms):

     xm sched-sedf <dom-id> 20000000 5000000 0 0 0
 
 

best-effort domains (i.e. non-realtime):

     xm sched-sedf <dom-id> 20000000 0 0 1 0
 
 

normal EDF (20ms/5ms) + share of extra-time:

     xm sched-sedf <dom-id> 20000000 5000000 0 1 0
 
 

4 domains with weights 2:3:4:2

     xm sched-sedf <d1> 0 0 0 0 2
     xm sched-sedf <d2> 0 0 0 0 3
     xm sched-sedf <d3> 0 0 0 0 4
     xm sched-sedf <d4> 0 0 0 0 2
 
 

1 fully-specified (10ms/3ms) domain, 3 other domains share available rest in 2:7:3 ratio:

     xm sched-sedf <d1> 10000000 3000000 0 0 0
     xm sched-sedf <d2> 0 0 0 0 2
     xm sched-sedf <d3> 0 0 0 0 7
     xm sched-sedf <d4> 0 0 0 0 3
 
 

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.

BLOCK DEVICES

block-attach domain-id be-dev fe-dev mode [bedomain-id]

Create a new virtual block device. This will trigger a hotplug event for the guest.

OPTIONS

domain-id

The domain id of the guest domain that the device will be attached to.

be-dev

The device in the backend domain (usually domain 0) to be exported. This can be specified as a physical partition (phy:sda7) or as a file mounted as loopback (file://path/to/loop.iso).

fe-dev

How the device should be presented to the guest domain. It can be specified as either a symbolic name, such as /dev/hdc, for common devices, or by device id, such as 0x1400 (/dev/hdc device id in hex).

mode

The access mode for the device from the guest domain. Supported modes are w (read/write) or r (read-only).

bedomain-id

The back end domain hosting the device. This defaults to domain 0.

EXAMPLES

Mount an ISO as a Disk

xm block-attach guestdomain file://path/to/dsl-2.0RC2.iso /dev/hdc ro

This will mount the dsl ISO as /dev/hdc in the guestdomain as a read only device. This will probably not be detected as a CD-ROM by the guest, but mounting /dev/hdc manually will work.

block-detach domain-id devid [--force]

Detach a domain's virtual block device. devid may be the symbolic name or the numeric device id given to the device by domain 0. You will need to run xm block-list to determine that number.

Detaching the device requires the cooperation of the domain. If the domain fails to release the device (perhaps because the domain is hung or is still using the device), the detach will fail. The --force parameter will forcefully detach the device, but may cause IO errors in the domain.

block-list [-l|--long] domain-id

List virtual block devices for a domain. The returned output is formatted as a list or as an S-Expression if the --long option was given.

NETWORK DEVICES

network-attach domain-id [script=scriptname] [ip=ipaddr] [mac=macaddr] [bridge=bridge-name] [backend=bedomain-id]

Creates a new network device in the domain specified by domain-id. It takes the following optional options:

OPTIONS

script=scriptname

Use the specified script name to bring up the network. Defaults to the default setting in xend-config.sxp for vif-script.

ip=ipaddr

Passes the specified IP Address to the adapter on creation.

FIXME: this currently appears to be broken. I'm not sure under what circumstances this should actually work.

mac=macaddr

The MAC address that the domain will see on its Ethernet device. If the device is not specified it will be randomly generated with the 00:16:3e vendor id prefix.

bridge=bridge-name

The name of the bridge to attach the vif to, in case you have more than one. This defaults to xenbr0.

backend=bedomain-id

The backend domain id. By default this is domain 0.

network-detach domain-id devid

Removes the network device from the domain specified by domain-id. devid is the virtual interface device number within the domain (i.e. the 3 in vif22.3).

FIXME: this is currently broken. Network devices aren't completely removed from domain 0.

network-list [-l|--long]> domain-id

List virtual network interfaces for a domain. The returned output is formatted as a list or as an S-Expression if the --long option was given.

VIRTUAL TPM DEVICES

vtpm-list [-l|--long] domain-id

Show the virtual TPM device for a domain. The returned output is formatted as a list or as an S-Expression if the --long option was given.

VNET COMMANDS

The Virtual Network interfaces for Xen.

FIXME: This needs a lot more explanation, or it needs to be ripped out entirely.

vnet-list [-l|--long]

List vnets.

vnet-create config

Create a vnet from a config file.

vnet-delete vnetid

Delete a vnet.

ACCESS CONTROL SUBCOMMANDS

Access Control in Xen consists of two components: (i) The Access Control Policy (ACP) defines security labels and access rules based on these labels. (ii) The Access Control Module (ACM) makes access control decisions by interpreting the policy when domains require to communicate or to access resources. The Xen access control has sufficient mechanisms in place to enforce the access decisions even against maliciously acting user domains (mandatory access control).

Access rights for domains in Xen are determined by the domain security label only and not based on the domain Name or ID. The ACP specifies security labels that can then be assigned to domains and resources. Every domain must be assigned exactly one security label, otherwise access control decisions could become indeterministic. ACPs are distinguished by their name, which is a parameter to most of the subcommands described below. Currently, the ACP specifies two ways to interpret labels:

(1) Simple Type Enforcement: Labels are interpreted to decide access of domains to communication means and virtual or physical resources. Communication between domains as well as access to resources are forbidden by default and can only take place if they are explicitly allowed by the security policy. The proper assignment of labels to domains controls the sharing of information (directly through communication or indirectly through shared resources) between domains. This interpretation allows to control the overt (intended) communication channels in Xen.

(2) Chinese Wall: Labels are interpreted to decide which domains can co-exist (be run simultaneously) on the same system. This interpretation allows to prevent direct covert (unintended) channels and mitigates risks caused by imperfect core domain isolation (trade-off between security and other system requirements). For a short introduction to covert channels, please refer to http://www.multicians.org/timing-chn.html.

The following subcommands help you to manage security policies in Xen and to assign security labels to domains. To enable access control security in Xen, you must compile Xen with ACM support enabled as described under ``Configuring Security'' below. There, you will find also examples of each subcommand described here.

setpolicy ACM policy

Makes the given ACM policy available to xend as a xend-managed policy. The policy is compiled and a mapping (.map) as well as a binary (.bin) version of the policy is created. The policy is loaded and the system's bootloader is prepared to boot the system with this policy the next time it is started.

policy is a dot-separated list of names. The last part is the file name pre-fix for the policy XML file. The preceding name parts are translated into the local path pointing to the policy XML file relative to the global policy root directory (/etc/xen/acm-security/policies). For example, example.chwall_ste.client_v1 denotes the policy file example/chwall_ste/client_v1-security_policy.xml relative to the global policy root directory.

resetpolicy

Reset the system's policy to the default state where the DEFAULT policy is loaded and enforced. This operation may fail if for example guest VMs are running and and one of them uses a different label than what Domain-0 does. It is best to make sure that no guests are running before issuing this command.

getpolicy [--dumpxml]

Displays information about the current xend-managed policy, such as name and type of the policy, the uuid xend has assigned to it on the local system, the version of the XML representation and the status of the policy, such as whether it is currently loaded into Xen or whether the policy is automatically loaded during system boot. With the --dumpxml option, the XML representation of the policy is displayed.

dumppolicy

Prints the current security policy state information of Xen.

labels [policy] [type=dom|res|any]

Lists all labels of a type (domain, resource, or both) that are defined in the policy. Unless specified, the default policy is the currently enforced access control policy. The default for type is 'dom'. The labels are arranged in alphabetical order.

addlabel label dom configfile [policy]

addlabel label mgt domain name [policy type:policy]

addlabel label res resource [policy]

addlabel label vif-idx domain name [policy type:policy]

Adds the security label with name label to a domain configfile (dom), a Xend-managed domain (mgt), to the global resource label file for the given resource (res), or to a managed domain's virtual network interface (vif) that is specified by its index. Unless specified, the default policy is the currently enforced access control policy. This subcommand also verifies that the policy definition supports the specified label name.

The only policy type that is currently supported is ACM.

rmlabel dom configfile

rmlabel mgt domain name

rmlabel res resource

rmlabel vif-idx domain name

Works the same as the addlabel command (above), except that this command will remove the label from the domain configfile (dom), a Xend-managed domain (mgt), the global resource label file (res), or a managed domain's network interface (vif).

getlabel dom configfile

getlabel mgt domain name

getlabel res resource

getlabel vif-idx domain name

Shows the label for a domain's configuration in the given configfile, a xend-managed domain (mgt), a resource, or a managed domain's network interface (vif).

resources

Lists all resources in the global resource label file. Each resource is listed with its associated label and policy name.

dry-run configfile

Determines if the specified configfile describes a domain with a valid security configuration for type enforcement. The test shows the policy decision made for each resource label against the domain label as well as the overall decision.

CONFIGURING SECURITY

In xen_source_dir/Config.mk set the following parameter:

     XSM_ENABLE ?= y
     ACM_SECURITY ?= y
 
 

Then recompile and install xen and the security tools and then reboot:

     cd xen_source_dir; make clean; make install
     reboot into Xen
 
 

RESETTING THE SYSTEM'S SECURITY

To set the system's security policy enforcement into its default state, the follow command can be issued. Make sure that no guests are running while doing this.

     xm resetpolicy
 
 

After this command has successfully completed, the system's DEFAULT policy is enforced.

SETTING A SECURITY POLICY

This step sets the system's policy and automatically loads it into Xen for enforcement.

     xm setpolicy ACM example.client_v1
 
 

LISTING SECURITY LABELS

This subcommand shows all labels that are defined and which can be attached to domains.

     xm labels example.client_v1 type=dom
 
 

will print for our example policy:

         dom_BoincClient
         dom_Fun
         dom_HomeBanking
         dom_NetworkDomain
         dom_StorageDomain
         dom_SystemManagement
 
 

ATTACHING A SECURITY LABEL TO A DOMAIN

The addlabel subcommand can attach a security label to a domain configuration file, here a HomeBanking label. The example policy ensures that this domain does not share information with other non-homebanking user domains (i.e., domains labeled as dom_Fun or dom_Boinc) and that it will not run simultaneously with domains labeled as dom_Fun.
We assume that the specified myconfig.xm configuration file actually instantiates a domain that runs workloads related to home-banking, probably just a browser environment for online-banking.

     xm addlabel dom_HomeBanking dom myconfig.xm
 
 

The very simple configuration file might now look as printed below. The addlabel subcommand added the access_control entry at the end of the file, consisting of a label name and the policy that specifies this label name:

     kernel = "/boot/vmlinuz-2.6.16-xen"
     ramdisk="/boot/U1_home_banking_ramdisk.img"
     memory = 164
     name = "homebanking"
     vif = [ '' ]
     dhcp = "dhcp"
     access_control = ['policy=example.chwall_ste.client_v1,
                        label=dom_HomeBanking']
 
 

Security labels must be assigned to domain configurations because these labels are essential for making access control decisions as early as during the configuration phase of a newly instantiated domain. Consequently, a security-enabled Xen hypervisor will only start domains that have a security label configured and whose security label is consistent with the currently enforced policy. Otherwise, starting the domain will fail with the error condition ``operation not permitted''.

ATTACHING A SECURITY LABEL TO A XEND-MANAGED DOMAIN

The addlabel subcommand supports labeling of domains that are managed by xend. This includes domains that are currently running, such as for example Domain-0, or those that are in a dormant state. Depending on the state of the system, it is possible that the new label is rejected. An example for a reason for the rejection of the relabeling of a domain would be if a domain is currently allowed to access its labeled resources but due to the new label would be prevented from accessing one or more of them.

     xm addlabel dom_Fun mgt Domain-0
 
 

This changes the label of Domain-0 to dom_Fun under the condition that this new label of Domain-0 would not prevent any other domain from accessing its resources that are provided through Domain-0, such as for example network or block device access.

ATTACHING A SECURITY LABEL TO A RESOURCE

The addlabel subcommand can also be used to attach a security label to a resource. Following the home banking example from above, we can label a disk resource (e.g., a physical partition or a file) to make it accessible to the home banking domain. The example policy provides a resource label, res_LogicalDiskPartition1(hda1), that is compatible with the HomeBanking domain label.

     xm addlabel "res_LogicalDiskPartition1(hda1)" res phy:hda6
 
 

After labeling this disk resource, it can be attached to the domain by adding a line to the domain configuration file. The line below attaches this disk to the domain at boot time.

     disk = [ 'phy:hda6,sda2,w' ]
 
 

Alternatively, the resource can be attached after booting the domain by using the block-attach subcommand.

     xm block-attach homebanking phy:hda6 sda2 w
 
 

Note that labeled resources cannot be used when security is turned off. Any attempt to use labeled resources with security turned off will result in a failure with a corresponding error message. The solution is to enable security or, if security is no longer desired, to remove the resource label using the rmlabel subcommand.

STARTING AND LISTING LABELED DOMAINS

     xm create myconfig.xm
 
     xm list --label
 
       Name         ID ...  Time(s)  Label
       homebanking  23 ...      4.4  dom_HomeBanking
       Domain-0      0 ...   2658.8  dom_SystemManagement
 
 

LISTING LABELED RESOURCES

     xm resources
 
       phy:hda6
             type: ACM
           policy: example.chwall_ste.client_v1
           label:  res_LogicalDiskPartition1(hda1)
       file:/xen/disk_image/disk.img
             type: ACM
           policy: example.chwall_ste.client_v1
           label:  res_LogicalDiskPartition2(hda2)
 
 

POLICY REPRESENTATIONS

We distinguish three representations of the Xen access control policy: the source XML version, its binary counterpart, and a mapping representation that enables the tools to deterministically translate back and forth between label names of the XML policy and label identifiers of the binary policy. All three versions must be kept consistent to achieve predictable security guarantees.
The XML version is the version that users are supposed to create or change, either by manually editing the XML file or by using the Xen policy generation tool (xensec_gen). After changing the XML file, run the setpolicy subcommand to ensure that the new policy is available to xend. Use, for example, the subcommand activatepolicy to activate the changes during the next system reboot.
The binary version of the policy is derived from the XML policy by tokenizing the specified labels and is used inside Xen only. It is created with the setpolicy subcommand. Essentially, the binary version is much more compact than the XML version and is easier to evaluate during access control decisions.
The mapping version of the policy is created during the XML-to-binary policy translation (setpolicy) and is used by xend and the management tools to translate between label names used as input to the tools and their binary identifiers (ssidrefs) used inside Xen.

SEE ALSO

xmdomain.cfg(5), xentop(1)

AUTHOR

   Sean Dague <sean at dague dot net>
   Daniel Stekloff <dsteklof at us dot ibm dot com>
   Reiner Sailer <sailer at us dot ibm dot com>
   Stefan Berger <stefanb at us dot ibm dot com>
 
 

BUGS