Provided by: xen-utils-common_4.20.0+68-g35cb38b222-1_amd64 
NAME
xl - Xen management tool, based on libxenlight
SYNOPSIS
xl subcommand [args]
DESCRIPTION
The xl program is the new tool 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 xl command is almost always:
xl subcommand [OPTIONS] domain-id
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
start the script /etc/init.d/xencommons at boot time
Most xl operations rely upon xenstored and xenconsoled: make sure you start the script
/etc/init.d/xencommons at boot time to initialize all the daemons needed by xl.
setup a xenbr0 bridge in dom0
In the most common network configuration, you need to setup a bridge in dom0 named xenbr0 in order to
have a working network in the guest domains. Please refer to the documentation of your Linux
distribution to know how to setup the bridge.
autoballoon
If you specify the amount of memory dom0 has, passing dom0_mem to Xen, it is highly recommended to
disable autoballoon. Edit /etc/xen/xl.conf and set it to 0.
run xl as root
Most xl 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.
GLOBAL OPTIONS
Some global options are always available:
-v Verbose.
-N Dry run: do not actually execute the command.
-f Force execution: xl will refuse to run some commands if it detects that xend is also running, this
option will force the execution of those commands, even though it is unsafe.
-t Always use carriage-return-based overwriting for displaying progress messages without scrolling the
screen. Without -t, this is done only if stderr is a tty.
-T Include timestamps and pid of the xl process in output.
DOMAIN SUBCOMMANDS
The following subcommands manipulate domains directly. As stated previously, most commands take domain-
id as the first parameter.
button-press domain-id button
This command is deprecated. Please use "xl trigger" instead.
Indicate an ACPI button press to the domain, where button can be 'power' or 'sleep'. This command is
only available for HVM domains.
create [configfile] [OPTIONS]
The create subcommand takes a config file as its first argument: see xl.cfg(5) for full details of
the file format and possible options. If configfile is missing xl creates the domain assuming the
default values for every option.
configfile has to be an absolute path to a file.
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.
If the -F option is specified, create will start the domain and not return until its death.
OPTIONS
-q, --quiet
No console output.
-f=FILE, --defconfig=FILE
Use the given configuration file.
-p Leave the domain paused after it is created.
-F Run in foreground until death of the domain.
-V, --vncviewer
Attach to domain's VNC server, forking a vncviewer process.
-A, --vncviewer-autopass
Pass the VNC password to vncviewer via stdin.
-c Attach console to the domain as soon as it has started. This is useful for determining issues
with crashing domains and just as a general convenience since you often want to watch the domain
boot.
key=value
It is possible to pass key=value pairs on the command line to provide options as if they were
written in the configuration file; these override whatever is in the configfile.
NB: Many config options require characters such as quotes or brackets which are interpreted by
the shell (and often discarded) before being passed to xl, resulting in xl being unable to parse
the value correctly. A simple work-around is to put all extra options within a single set of
quotes, separated by semicolons. (See below for an example.)
EXAMPLES
with extra parameters
xl create hvm.cfg 'cpus="0-3"; pci=["01:05.1","01:05.2"]'
This creates a domain with the file hvm.cfg, but additionally pins it to cpus 0-3, and passes
through two PCI devices.
config-update domain-id [configfile] [OPTIONS]
Update the saved configuration for a running domain. This has no immediate effect but will be applied
when the guest is next restarted. This command is useful to ensure that runtime modifications made to
the guest will be preserved when the guest is restarted.
Since Xen 4.5 xl has improved capabilities to handle dynamic domain configuration changes and will
preserve any changes made at runtime when necessary. Therefore it should not normally be necessary to
use this command any more.
configfile has to be an absolute path to a file.
OPTIONS
-f=FILE, --defconfig=FILE
Use the given configuration file.
key=value
It is possible to pass key=value pairs on the command line to provide options as if they were
written in the configuration file; these override whatever is in the configfile. Please see the
note under create on handling special characters when passing key=value pairs on the command
line.
console [OPTIONS] domain-id
Attach to the console of a domain specified by domain-id. If you've set up your domains to have a
traditional login console this will look much like a normal text login screen.
Use the escape character key combination (default Ctrl+]) to detach from the domain console.
OPTIONS
-t [pv|serial]
Connect to a PV console or connect to an emulated serial console. PV consoles are the only
consoles available for PV domains while HVM domains can have both. If this option is not
specified it defaults to emulated serial for HVM guests and PV console for PV guests.
-n NUM
Connect to console number NUM. Console numbers start from 0.
-e escapechar
Customize the escape sequence used to detach from the domain console to escapechar. If not
specified, the value "^]" is used.
destroy [OPTIONS] domain-id
Immediately terminate the domain specified by 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.
OPTIONS
-f Allow domain 0 to be destroyed. Because a domain cannot destroy itself, this is only possible
when using a disaggregated toolstack, and is most useful when using a hardware domain separated
from domain 0.
domid domain-name
Converts a domain name to a domain id.
domname domain-id
Converts a domain id to a domain name.
rename domain-id new-name
Change the domain name of a domain specified by domain-id to new-name.
dump-core domain-id [filename]
Dumps the virtual machine's memory for the specified domain to the filename specified, without
pausing the domain. The dump file will be written to a distribution specific directory for dump
files, for example: /var/lib/xen/dump/dump.
help [--long]
Displays the short help message (i.e. common commands) by default.
If the --long option is specified, it displays the complete set of xl subcommands, grouped by
function.
list [OPTIONS] [domain-id ...]
Displays information about one or more domains. If no domains are specified it displays information
about all domains.
OPTIONS
-l, --long
The output for xl list is not the table view shown below, but instead presents the data as a JSON
data structure.
-Z, --context
Also displays the security labels.
-v, --verbose
Also displays the domain UUIDs, the shutdown reason and security labels.
-c, --cpupool
Also displays the cpupool the domain belongs to.
-n, --numa
Also displays the domain NUMA node affinity.
EXAMPLE
An example format for the list is as follows:
Name ID Mem VCPUs State Time(s)
Domain-0 0 750 4 r----- 11794.3
win 1 1019 1 r----- 0.3
linux 2 2048 2 r----- 5624.2
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 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 xl 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
The guest OS has shut down (SCHEDOP_shutdown has been called) but the domain is not dying yet.
c - crashed
The domain has crashed, which is always a violent ending. Usually this state only occurs if the
domain has been configured not to restart on a crash. See xl.cfg(5) for more info.
d - dying
The domain is in the process of dying, but hasn't completely shut down or crashed.
NOTES
The Time column is deceptive. Virtual IO (network and block devices) used by the 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 unreliable, as a high IO workload may show as less utilized than a high CPU
workload. Consider yourself warned.
mem-set domain-id mem
Set the target for the domain's balloon driver.
The default unit is kiB. Add 't' for TiB, 'g' for GiB, 'm' for MiB, 'k' for kiB, and 'b' for bytes
(e.g., `2048m` for 2048 MiB).
This must be less than the initial maxmem parameter in the domain's configuration.
Note that this operation requests the guest operating system's balloon driver to reach the target
amount of memory. The guest may fail to reach that amount of memory for any number of reasons,
including:
• The guest doesn't have a balloon driver installed
• The guest's balloon driver is buggy
• The guest's balloon driver cannot create free guest memory due to guest memory pressure
• The guest's balloon driver cannot allocate memory from Xen because of hypervisor memory pressure
• The guest administrator has disabled the balloon 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.
mem-max domain-id mem
Specify the limit Xen will place on the amount of memory a guest may allocate.
The default unit is kiB. Add 't' for TiB, 'g' for GiB, 'm' for MiB, 'k' for kiB, and 'b' for bytes
(e.g., `2048m` for 2048 MiB).
mem can't be set lower than the current memory target for domain-id. It is allowed to be higher than
the configured maximum memory size of the domain (maxmem parameter in the domain's configuration).
Setting the maximum memory size above the configured maximum memory size will require special guest
support (memory hotplug) in order to be usable by the guest.
The domain will not receive any signal regarding the changed memory limit.
migrate [OPTIONS] domain-id host
Migrate a domain to another host machine. By default xl relies on ssh as a transport mechanism
between the two hosts.
OPTIONS
-s sshcommand
Use <sshcommand> instead of ssh. String will be passed to sh. If empty, run <host> instead of
ssh <host> xl migrate-receive [-d -e].
-e On the new <host>, do not wait in the background for the death of the domain. See the
corresponding option of the create subcommand.
-C config
Send the specified <config> file instead of the file used on creation of the domain.
--debug
Display huge (!) amount of debug information during the migration process.
-p Leave the domain on the receive side paused after migration.
-D Preserve the domain-id in the domain coniguration that is transferred such that it will be
identical on the destination host, unless that configuration is overridden using the -C option.
Note that it is not possible to use this option for a 'localhost' migration.
remus [OPTIONS] domain-id host
Enable Remus HA or COLO HA for domain. By default xl relies on ssh as a transport mechanism between
the two hosts.
NOTES
Remus support in xl is still in experimental (proof-of-concept) phase. Disk replication support
is limited to DRBD disks.
COLO support in xl is still in experimental (proof-of-concept) phase. All options are subject to
change in the future.
COLO disk configuration looks like:
disk = ['...,colo,colo-host=xxx,colo-port=xxx,colo-export=xxx,active-disk=xxx,hidden-disk=xxx...']
The supported options are:
colo-host : Secondary host's ip address.
colo-port : Secondary host's port, we will run a nbd server on the secondary host, and the nbd
server will listen on this port.
colo-export : Nbd server's disk export name of the secondary host.
active-disk : Secondary's guest write will be buffered to this disk, and it's used by the secondary.
hidden-disk : Primary's modified contents will be buffered in this disk, and it's used by the
secondary.
COLO network configuration looks like:
vif = [ '...,forwarddev=xxx,...']
The supported options are:
forwarddev : Forward devices for the primary and the secondary, they are directly connected.
OPTIONS
-i MS
Checkpoint domain memory every MS milliseconds (default 200ms).
-u Disable memory checkpoint compression.
-s sshcommand
Use <sshcommand> instead of ssh. String will be passed to sh. If empty, run <host> instead of
ssh <host> xl migrate-receive -r [-e].
-e On the new <host>, do not wait in the background for the death of the domain. See the
corresponding option of the create subcommand.
-N netbufscript
Use <netbufscript> to setup network buffering instead of the default script
(/etc/xen/scripts/remus-netbuf-setup).
-F Run Remus in unsafe mode. Use this option with caution as failover may not work as intended.
-b Replicate memory checkpoints to /dev/null (blackhole). Generally useful for debugging. Requires
enabling unsafe mode.
-n Disable network output buffering. Requires enabling unsafe mode.
-d Disable disk replication. Requires enabling unsafe mode.
-c Enable COLO HA. This conflicts with -i and -b, and memory checkpoint compression must be
disabled.
-p Use userspace COLO Proxy. This option must be used in conjunction with -c.
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 earlier than
when the domain actually reboots.
For HVM domains this requires PV drivers to be installed in your guest OS. If PV drivers are not
present but you have configured the guest OS to behave appropriately you may be able to use the -F
option to trigger a reset button press.
The behavior of what happens to a domain when it reboots is set by the on_reboot parameter of the
domain configuration file when the domain was created.
OPTIONS
-F If the guest does not support PV reboot control then fallback to sending an ACPI power event
(equivalent to the reset option to trigger).
You should ensure that the guest is configured to behave as expected in response to this event.
restore [OPTIONS] [configfile] checkpointfile
Build a domain from an xl save state file. See save for more info.
OPTIONS
-p Do not unpause the domain after restoring it.
-e Do not wait in the background for the death of the domain on the new host. See the corresponding
option of the create subcommand.
-d Enable debug messages.
-V, --vncviewer
Attach to the domain's VNC server, forking a vncviewer process.
-A, --vncviewer-autopass
Pass the VNC password to vncviewer via stdin.
resume domain-id
Resume a domain, after having been suspended.
save [OPTIONS] domain-id checkpointfile [configfile]
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, unless the -c or -p options are used. xl restore restores from
this checkpoint file. Passing a config file argument allows the user to manually select the VM
config file used to create the domain.
-c Leave the domain running after creating the snapshot.
-p Leave the domain paused after creating the snapshot.
-D Preserve the domain-id in the domain coniguration that is embedded in the state file such that it
will be identical when the domain is restored, unless that configuration is overridden. (See the
restore operation above).
sharing [domain-id]
Display the number of shared pages for a specified domain. If no domain is specified it displays
information about all domains.
shutdown [OPTIONS] -a|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 shut down in the domain.
For HVM domains this requires PV drivers to be installed in your guest OS. If PV drivers are not
present but you have configured the guest OS to behave appropriately you may be able to use the -F
option to trigger a power button press.
The command returns immediately after signaling the domain unless the -w flag is used.
The behavior of what happens to a domain when it reboots is set by the on_shutdown parameter of the
domain configuration file when the domain was created.
OPTIONS
-a, --all
Shutdown all guest domains. Often used when doing a complete shutdown of a Xen system.
-w, --wait
Wait for the domain to complete shutdown before returning. If given once, the wait is for domain
shutdown or domain death. If given multiple times, the wait is for domain death only.
-F If the guest does not support PV shutdown control then fallback to sending an ACPI power event
(equivalent to the power option to trigger).
You should ensure that the guest is configured to behave as expected in response to this event.
suspend domain-id
Suspend a domain. This is a cooperative operation where the domain must respond to the xenstore
trigger. When in a suspended state the domain still consumes allocated resources (such as memory),
but is not eligible for scheduling by the Xen hypervisor. It is in a shutdown state, but not dying.
sysrq domain-id letter
Send a <Magic System Request> to the domain, each type of request is represented by a different
letter. It can be used to send SysRq requests to Linux guests, see sysrq.txt in your Linux Kernel
sources for more information. It requires PV drivers to be installed in your guest OS.
trigger domain-id nmi|reset|init|power|sleep|s3resume [VCPU]
Send a trigger to a domain, where the trigger can be: nmi, reset, init, power or sleep. Optionally a
specific vcpu number can be passed as an argument. This command is only available for HVM domains.
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.
Some guests may need to actually bring the newly added CPU online after vcpu-set, go to SEE ALSO
section for information.
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 [-f|--force] domain-id vcpu cpus hard cpus soft
Set hard and soft affinity for a vcpu of <domain-id>. Normally VCPUs can float between available CPUs
whenever Xen deems a different run state is appropriate.
Hard affinity can be used to restrict this, by ensuring certain VCPUs can only run on certain
physical CPUs. Soft affinity specifies a preferred set of CPUs. Soft affinity needs special support
in the scheduler, which is only provided in credit1.
The keyword all can be used to apply the hard and soft affinity masks to all the VCPUs in the domain.
The symbol '-' can be used to leave either hard or soft affinity alone.
For example:
xl vcpu-pin 0 3 - 6-9
will set soft affinity for vCPU 3 of domain 0 to pCPUs 6,7,8 and 9, leaving its hard affinity
untouched. On the other hand:
xl vcpu-pin 0 3 3,4 6-9
will set both hard and soft affinity, the former to pCPUs 3 and 4, the latter to pCPUs 6,7,8, and 9.
Specifying -f or --force will remove a temporary pinning done by the operating system (normally this
should be done by the operating system). In case a temporary pinning is active for a vcpu the
affinity of this vcpu can't be changed without this option.
vm-list
Prints information about guests. This list excludes information about service or auxiliary domains
such as dom0 and stubdoms.
EXAMPLE
An example format for the list is as follows:
UUID ID name
59e1cf6c-6ab9-4879-90e7-adc8d1c63bf5 2 win
50bc8f75-81d0-4d53-b2e6-95cb44e2682e 3 linux
vncviewer [OPTIONS] domain-id
Attach to the domain's VNC server, forking a vncviewer process.
OPTIONS
--autopass
Pass the VNC password to vncviewer via stdin.
XEN HOST SUBCOMMANDS
debug-keys keys
Send debug keys to Xen. It is the same as pressing the Xen "conswitch" (Ctrl-A by default) three
times and then pressing "keys".
set-parameters params
Set hypervisor parameters as specified in params. This allows for some boot parameters of the
hypervisor to be modified in the running systems.
dmesg [OPTIONS]
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 [OPTIONS]
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. See
https://wiki.xenproject.org/wiki/Reporting_Bugs_against_Xen_Project on how to report Xen bugs.
Sample output looks as follows:
host : scarlett
release : 3.1.0-rc4+
version : #1001 SMP Wed Oct 19 11:09:54 UTC 2011
machine : x86_64
nr_cpus : 4
nr_nodes : 1
cores_per_socket : 4
threads_per_core : 1
cpu_mhz : 2266
hw_caps : bfebfbff:28100800:00000000:00003b40:009ce3bd:00000000:00000001:00000000
virt_caps : hvm hvm_directio
total_memory : 6141
free_memory : 4274
free_cpus : 0
outstanding_claims : 0
xen_major : 4
xen_minor : 2
xen_extra : -unstable
xen_caps : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler : credit
xen_pagesize : 4096
platform_params : virt_start=0xffff800000000000
xen_changeset : Wed Nov 02 17:09:09 2011 +0000 24066:54a5e994a241
xen_commandline : com1=115200,8n1 guest_loglvl=all dom0_mem=750M console=com1
cc_compiler : gcc version 4.4.5 (Debian 4.4.5-8)
cc_compile_by : sstabellini
cc_compile_domain : uk.xensource.com
cc_compile_date : Tue Nov 8 12:03:05 UTC 2011
xend_config_format : 4
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: they both
derive from the feature bits returned by the cpuid command on x86 platforms.
free_memory
Available memory (in MB) not allocated to Xen, or any other domains, or claimed for domains.
outstanding_claims
When a claim call is done (see xl.conf(5)) a reservation for a specific amount of pages is set
and also a global value is incremented. This global value (outstanding_claims) is then reduced as
the domain's memory is populated and eventually reaches zero. Most of the time the value will be
zero, but if you are launching multiple guests, and claim_mode is enabled, this value can
increase/decrease. Note that the value also affects the free_memory - as it will reflect the free
memory in the hypervisor minus the outstanding pages claimed for guests. See xl info claims
parameter for detailed listing.
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.
OPTIONS
-n, --numa
List host NUMA topology information
top Executes the xentop(1) command, which provides real time monitoring of domains. Xentop has a curses
interface, and is reasonably self explanatory.
uptime
Prints the current uptime of the domains running.
claims
Prints information about outstanding claims by the guests. This provides the outstanding claims and
currently populated memory count for the guests. These values added up reflect the global
outstanding claim value, which is provided via the info argument, outstanding_claims value. The Mem
column has the cumulative value of outstanding claims and the total amount of memory that has been
right now allocated to the guest.
EXAMPLE
An example format for the list is as follows:
Name ID Mem VCPUs State Time(s) Claimed
Domain-0 0 2047 4 r----- 19.7 0
OL5 2 2048 1 --p--- 0.0 847
OL6 3 1024 4 r----- 5.9 0
Windows_XP 4 2047 1 --p--- 0.0 1989
In which it can be seen that the OL5 guest still has 847MB of claimed memory (out of the total 2048MB
where 1191MB has been allocated to the guest).
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.
sched-credit [OPTIONS]
Set or get credit (aka credit1) 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.
OPTIONS
-d DOMAIN, --domain=DOMAIN
Specify domain for which scheduler parameters are to be modified or retrieved. Mandatory for
modifying scheduler parameters.
-w WEIGHT, --weight=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.
-c CAP, --cap=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.
NB: Many systems have features that will scale down the computing power of a cpu that is not 100%
utilized. This can be in the operating system, but can also sometimes be below the operating
system in the BIOS. If you set a cap such that individual cores are running at less than 100%,
this may have an impact on the performance of your workload over and above the impact of the cap.
For example, if your processor runs at 2GHz, and you cap a vm at 50%, the power management system
may also reduce the clock speed to 1GHz; the effect will be that your VM gets 25% of the
available power (50% of 1GHz) rather than 50% (50% of 2GHz). If you are not getting the
performance you expect, look at performance and cpufreq options in your operating system and your
BIOS.
-p CPUPOOL, --cpupool=CPUPOOL
Restrict output to domains in the specified cpupool.
-s, --schedparam
Specify to list or set pool-wide scheduler parameters.
-t TSLICE, --tslice_ms=TSLICE
Timeslice tells the scheduler how long to allow VMs to run before pre-empting. The default is
30ms. Valid ranges are 1ms to 1000ms. The length of the timeslice (in ms) must be higher than
the length of the ratelimit (see below).
-r RLIMIT, --ratelimit_us=RLIMIT
Ratelimit attempts to limit the number of schedules per second. It sets a minimum amount of time
(in microseconds) a VM must run before we will allow a higher-priority VM to pre-empt it. The
default value is 1000 microseconds (1ms). Valid range is 100 to 500000 (500ms). The ratelimit
length must be lower than the timeslice length.
-m DELAY, --migration_delay_us=DELAY
Migration delay specifies for how long a vCPU, after it stopped running should be considered
"cache-hot". Basically, if less than DELAY us passed since when the vCPU was executing on a CPU,
it is likely that most of the vCPU's working set is still in the CPU's cache, and therefore the
vCPU is not migrated.
Default is 0. Maximum is 100 ms. This can be effective at preventing vCPUs to bounce among CPUs
too quickly, but, at the same time, the scheduler stops being fully work-conserving.
COMBINATION
The following is the effect of combining the above options:
<nothing> : List all domain params and sched params from all pools
-d [domid] : List domain params for domain [domid]
-d [domid] [params] : Set domain params for domain [domid]
-p [pool] : list all domains and sched params for [pool]
-s : List sched params for poolid 0
-s [params] : Set sched params for poolid 0
-p [pool] -s : List sched params for [pool]
-p [pool] -s [params] : Set sched params for [pool]
-p [pool] -d... : Illegal
sched-credit2 [OPTIONS]
Set or get credit2 scheduler parameters. The credit2 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.
OPTIONS
-d DOMAIN, --domain=DOMAIN
Specify domain for which scheduler parameters are to be modified or retrieved. Mandatory for
modifying scheduler parameters.
-w WEIGHT, --weight=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.
-p CPUPOOL, --cpupool=CPUPOOL
Restrict output to domains in the specified cpupool.
-s, --schedparam
Specify to list or set pool-wide scheduler parameters.
-r RLIMIT, --ratelimit_us=RLIMIT
Attempts to limit the rate of context switching. It is basically the same as --ratelimit_us in
sched-credit
sched-rtds [OPTIONS]
Set or get rtds (Real Time Deferrable Server) scheduler parameters. This rt scheduler applies
Preemptive Global Earliest Deadline First real-time scheduling algorithm to schedule VCPUs in the
system. Each VCPU has a dedicated period, budget and extratime. While scheduled, a VCPU burns its
budget. A VCPU has its budget replenished at the beginning of each period; Unused budget is
discarded at the end of each period. A VCPU with extratime set gets extra time from the unreserved
system resource.
OPTIONS
-d DOMAIN, --domain=DOMAIN
Specify domain for which scheduler parameters are to be modified or retrieved. Mandatory for
modifying scheduler parameters.
-v VCPUID/all, --vcpuid=VCPUID/all
Specify vcpu for which scheduler parameters are to be modified or retrieved.
-p PERIOD, --period=PERIOD
Period of time, in microseconds, over which to replenish the budget.
-b BUDGET, --budget=BUDGET
Amount of time, in microseconds, that the VCPU will be allowed to run every period.
-e Extratime, --extratime=Extratime
Binary flag to decide if the VCPU will be allowed to get extra time from the unreserved system
resource.
-c CPUPOOL, --cpupool=CPUPOOL
Restrict output to domains in the specified cpupool.
EXAMPLE
1) Use -v all to see the budget and period of all the VCPUs of all the domains:
xl sched-rtds -v all
Cpupool Pool-0: sched=RTDS
Name ID VCPU Period Budget Extratime
Domain-0 0 0 10000 4000 yes
vm1 2 0 300 150 yes
vm1 2 1 400 200 yes
vm1 2 2 10000 4000 yes
vm1 2 3 1000 500 yes
vm2 4 0 10000 4000 yes
vm2 4 1 10000 4000 yes
Without any arguments, it will output the default scheduling parameters for each domain:
xl sched-rtds
Cpupool Pool-0: sched=RTDS
Name ID Period Budget Extratime
Domain-0 0 10000 4000 yes
vm1 2 10000 4000 yes
vm2 4 10000 4000 yes
2) Use, for instance, -d vm1, -v all to see the budget and period of all VCPUs of a specific
domain (vm1):
xl sched-rtds -d vm1 -v all
Name ID VCPU Period Budget Extratime
vm1 2 0 300 150 yes
vm1 2 1 400 200 yes
vm1 2 2 10000 4000 yes
vm1 2 3 1000 500 yes
To see the parameters of a subset of the VCPUs of a domain, use:
xl sched-rtds -d vm1 -v 0 -v 3
Name ID VCPU Period Budget Extratime
vm1 2 0 300 150 yes
vm1 2 3 1000 500 yes
If no -v is specified, the default scheduling parameters for the domain are shown:
xl sched-rtds -d vm1
Name ID Period Budget Extratime
vm1 2 10000 4000 yes
3) Users can set the budget and period of multiple VCPUs of a specific domain with only one
command, e.g., "xl sched-rtds -d vm1 -v 0 -p 100 -b 50 -e 1 -v 3 -p 300 -b 150 -e 0".
To change the parameters of all the VCPUs of a domain, use -v all, e.g., "xl sched-rtds -d vm1 -v
all -p 500 -b 250 -e 1".
CPUPOOLS COMMANDS
Xen can group the physical cpus of a server in cpu-pools. Each physical CPU is assigned at most to one
cpu-pool. Domains are each restricted to a single cpu-pool. Scheduling does not cross cpu-pool
boundaries, so each cpu-pool has its own scheduler. Physical cpus and domains can be moved from one cpu-
pool to another only by an explicit command. Cpu-pools can be specified either by name or by id.
cpupool-create [OPTIONS] [configfile] [variable=value ...]
Create a cpu pool based an config from a configfile or command-line parameters. Variable settings
from the configfile may be altered by specifying new or additional assignments on the command line.
See the xlcpupool.cfg(5) manpage for more information.
OPTIONS
-f=FILE, --defconfig=FILE
Use the given configuration file.
cpupool-list [OPTIONS] [cpu-pool]
List CPU pools on the host.
OPTIONS
-c, --cpus
If this option is specified, xl prints a list of CPUs used by cpu-pool.
cpupool-destroy cpu-pool
Deactivates a cpu pool. This is possible only if no domain is active in the cpu-pool.
cpupool-rename cpu-pool <newname>
Renames a cpu-pool to newname.
cpupool-cpu-add cpu-pool cpus|node:nodes
Adds one or more CPUs or NUMA nodes to cpu-pool. CPUs and NUMA nodes can be specified as single
CPU/node IDs or as ranges.
For example:
(a) xl cpupool-cpu-add mypool 4
(b) xl cpupool-cpu-add mypool 1,5,10-16,^13
(c) xl cpupool-cpu-add mypool node:0,nodes:2-3,^10-12,8
means adding CPU 4 to mypool, in (a); adding CPUs 1,5,10,11,12,14,15 and 16, in (b); and adding all
the CPUs of NUMA nodes 0, 2 and 3, plus CPU 8, but keeping out CPUs 10,11,12, in (c).
All the specified CPUs that can be added to the cpupool will be added to it. If some CPU can't (e.g.,
because they're already part of another cpupool), an error is reported about each one of them.
cpupool-cpu-remove cpu-pool cpus|node:nodes
Removes one or more CPUs or NUMA nodes from cpu-pool. CPUs and NUMA nodes can be specified as single
CPU/node IDs or as ranges, using the exact same syntax as in cpupool-cpu-add above.
cpupool-migrate domain-id cpu-pool
Moves a domain specified by domain-id or domain-name into a cpu-pool. Domain-0 can't be moved to
another cpu-pool.
cpupool-numa-split
Splits up the machine into one cpu-pool per numa node.
VIRTUAL DEVICE COMMANDS
Most virtual devices can be added and removed while guests are running, assuming that the necessary
support exists in the guest OS. The effect to the guest OS is much the same as any hotplug event.
BLOCK DEVICES
block-attach domain-id disc-spec-component(s) ...
Create a new virtual block device and attach it to the specified domain. A disc specification is in
the same format used for the disk variable in the domain config file. See xl-disk-configuration(5).
This will trigger a hotplug event for the guest.
Note that only PV block devices are supported by block-attach. Requests to attach emulated devices
(eg, vdev=hdc) will result in only the PV view being available to the guest.
block-detach [OPTIONS] domain-id devid
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 xl 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.
OPTIONS
--force
If this parameter is specified the device will be forcefully detached, which may cause IO errors
in the domain and possibly a guest crash
block-list domain-id
List virtual block devices for a domain.
cd-insert domain-id virtualdevice target
Insert a cdrom into a guest domain's existing virtual cd drive. The virtual drive must already exist
but can be empty. How the device should be presented to the guest domain is specified by the
virtualdevice parameter; for example "hdc". Parameter target is the target path in the backend domain
(usually domain 0) to be exported; can be a block device or a file etc. See target in
xl-disk-configuration(5).
Only works with HVM domains.
cd-eject domain-id virtualdevice
Eject a cdrom from a guest domain's virtual cd drive, specified by virtualdevice. Only works with HVM
domains.
NETWORK DEVICES
network-attach domain-id network-device
Creates a new network device in the domain specified by domain-id. network-device describes the
device to attach, using the same format as the vif string in the domain config file. See xl.cfg(5)
and xl-network-configuration(5) for more information.
Note that only attaching PV network interfaces is supported.
network-detach domain-id devid|mac
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). Alternatively, the mac address can be used
to select the virtual interface to detach.
network-list domain-id
List virtual network interfaces for a domain.
CHANNEL DEVICES
channel-list domain-id
List virtual channel interfaces for a domain.
VIRTUAL TRUSTED PLATFORM MODULE (vTPM) DEVICES
vtpm-attach domain-id vtpm-device
Creates a new vtpm (virtual Trusted Platform Module) device in the domain specified by domain-id.
vtpm-device describes the device to attach, using the same format as the vtpm string in the domain
config file. See xl.cfg(5) for more information.
vtpm-detach domain-id devid|uuid
Removes the vtpm device from the domain specified by domain-id. devid is the numeric device id given
to the virtual Trusted Platform Module device. You will need to run xl vtpm-list to determine that
number. Alternatively, the uuid of the vtpm can be used to select the virtual device to detach.
vtpm-list domain-id
List virtual Trusted Platform Modules for a domain.
VDISPL DEVICES
vdispl-attach domain-id vdispl-device
Creates a new vdispl device in the domain specified by domain-id. vdispl-device describes the device
to attach, using the same format as the vdispl string in the domain config file. See xl.cfg(5) for
more information.
NOTES
As in vdispl-device string semicolon is used then put quotes or escaping when using from the
shell.
EXAMPLE
xl vdispl-attach DomU connectors='id0:1920x1080;id1:800x600;id2:640x480'
or
xl vdispl-attach DomU connectors=id0:1920x1080\;id1:800x600\;id2:640x480
vdispl-detach domain-id dev-id
Removes the vdispl device specified by dev-id from the domain specified by domain-id.
vdispl-list domain-id
List virtual displays for a domain.
VSND DEVICES
vsnd-attach domain-id vsnd-item vsnd-item ...
Creates a new vsnd device in the domain specified by domain-id. vsnd-item's describe the vsnd device
to attach, using the same format as the VSND_ITEM_SPEC string in the domain config file. See
xl.cfg(5) for more information.
EXAMPLE
xl vsnd-attach DomU 'CARD, short-name=Main, sample-formats=s16_le;s8;u32_be' 'PCM, name=Main'
'STREAM, id=0, type=p' 'STREAM, id=1, type=c, channels-max=2'
vsnd-detach domain-id dev-id
Removes the vsnd device specified by dev-id from the domain specified by domain-id.
vsnd-list domain-id
List vsnd devices for a domain.
KEYBOARD DEVICES
vkb-attach domain-id vkb-device
Creates a new keyboard device in the domain specified by domain-id. vkb-device describes the device
to attach, using the same format as the VKB_SPEC_STRING string in the domain config file. See
xl.cfg(5) for more information.
vkb-detach domain-id devid
Removes the keyboard device from the domain specified by domain-id. devid is the virtual interface
device number within the domain
vkb-list domain-id
List virtual network interfaces for a domain.
PCI PASS-THROUGH
pci-assignable-list [-n]
List all the BDF of assignable PCI devices. See xl-pci-configuration(5) for more information. If the
-n option is specified then any name supplied when the device was made assignable will also be
displayed.
These are devices in the system which are configured to be available for passthrough and are bound to
a suitable PCI backend driver in domain 0 rather than a real driver.
pci-assignable-add [-n NAME] BDF
Make the device at BDF assignable to guests. See xl-pci-configuration(5) for more information. If the
-n option is supplied then the assignable device entry will the named with the given NAME.
This will bind the device to the pciback driver and assign it to the "quarantine domain". If it is
already bound to a driver, it will first be unbound, and the original driver stored so that it can be
re-bound to the same driver later if desired. If the device is already bound, it will assign it to
the quarantine domain and return success.
CAUTION: This will make the device unusable by Domain 0 until it is returned with pci-assignable-
remove. Care should therefore be taken not to do this on a device critical to domain 0's operation,
such as storage controllers, network interfaces, or GPUs that are currently being used.
pci-assignable-remove [-r] BDF|NAME
Make a device non-assignable to guests. The device may be identified either by its BDF or the NAME
supplied when the device was made assignable. See xl-pci-configuration(5) for more information.
This will at least unbind the device from pciback, and re-assign it from the "quarantine domain" back
to domain 0. If the -r option is specified, it will also attempt to re-bind the device to its
original driver, making it usable by Domain 0 again. If the device is not bound to pciback, it will
return success.
Note that this functionality will work even for devices which were not made assignable by pci-
assignable-add. This can be used to allow dom0 to access devices which were automatically
quarantined by Xen after domain destruction as a result of Xen's iommu=quarantine command-line
default.
As always, this should only be done if you trust the guest, or are confident that the particular
device you're re-assigning to dom0 will cancel all in-flight DMA on FLR.
pci-attach domain-id PCI_SPEC_STRING
Hot-plug a new pass-through pci device to the specified domain. See xl-pci-configuration(5) for more
information.
pci-detach [OPTIONS] domain-id PCI_SPEC_STRING
Hot-unplug a pci device that was previously passed through to a domain. See xl-pci-configuration(5)
for more information.
OPTIONS
-f If this parameter is specified, xl is going to forcefully remove the device even without guest
domain's collaboration.
pci-list domain-id
List the BDF of pci devices passed through to a domain.
USB PASS-THROUGH
usbctrl-attach domain-id usbctrl-device
Create a new USB controller in the domain specified by domain-id, usbctrl-device describes the device
to attach, using form "KEY=VALUE KEY=VALUE ..." where KEY=VALUE has the same meaning as the usbctrl
description in the domain config file. See xl.cfg(5) for more information.
usbctrl-detach domain-id devid
Destroy a USB controller from the specified domain. devid is devid of the USB controller.
usbdev-attach domain-id usbdev-device
Hot-plug a new pass-through USB device to the domain specified by domain-id, usbdev-device describes
the device to attach, using form "KEY=VALUE KEY=VALUE ..." where KEY=VALUE has the same meaning as
the usbdev description in the domain config file. See xl.cfg(5) for more information.
usbdev-detach domain-id controller=devid port=number
Hot-unplug a previously assigned USB device from a domain. controller=devid and port=number is USB
controller:port in the guest domain the USB device is attached to.
usb-list domain-id
List pass-through usb devices for a domain.
DEVICE-MODEL CONTROL
qemu-monitor-command domain-id command
Issue a monitor command to the device model of the domain specified by domain-id. command can be any
valid command qemu understands. This can be e.g. used to add non-standard devices or devices with
non-standard parameters to a domain. The output of the command is printed to stdout.
Warning: This qemu monitor access is provided for convenience when debugging, troubleshooting, and
experimenting. Its use is not supported by the Xen Project.
Specifically, not all information displayed by the qemu monitor will necessarily be accurate or
complete, because in a Xen system qemu does not have a complete view of the guest.
Furthermore, modifying the guest's setup via the qemu monitor may conflict with the Xen toolstack's
assumptions. Resulting problems may include, but are not limited to: guest crashes; toolstack error
messages; inability to migrate the guest; and security vulnerabilities which are not covered by the
Xen Project security response policy.
EXAMPLE
Obtain information of USB devices connected as such via the device model (only!) to a domain:
xl qemu-monitor-command vm1 'info usb'
Device 0.2, Port 5, Speed 480 Mb/s, Product Mass Storage
FLASK
FLASK is a security framework that defines a mandatory access control policy providing fine-grained
controls over Xen domains, allowing the policy writer to define what interactions between domains,
devices, and the hypervisor are permitted. Some example of what you can do using XSM/FLASK:
- Prevent two domains from communicating via event channels or grants
- Control which domains can use device passthrough (and which devices)
- Restrict or audit operations performed by privileged domains
- Prevent a privileged domain from arbitrarily mapping pages from other
domains.
You can find more details on how to use FLASK and an example security policy here:
<https://xenbits.xenproject.org/docs/unstable/misc/xsm-flask.txt>
getenforce
Determine if the FLASK security module is loaded and enforcing its policy.
setenforce 1|0|Enforcing|Permissive
Enable or disable enforcing of the FLASK access controls. The default is permissive, but this can be
changed to enforcing by specifying "flask=enforcing" or "flask=late" on the hypervisor's command
line.
loadpolicy policy-file
Load FLASK policy from the given policy file. The initial policy is provided to the hypervisor as a
multiboot module; this command allows runtime updates to the policy. Loading new security policy will
reset runtime changes to device labels.
PLATFORM SHARED RESOURCE MONITORING/CONTROL
Intel Haswell and later server platforms offer shared resource monitoring and control technologies. The
availability of these technologies and the hardware capabilities can be shown with psr-hwinfo.
See <https://xenbits.xenproject.org/docs/unstable/misc/xl-psr.html> for more information.
psr-hwinfo [OPTIONS]
Show Platform Shared Resource (PSR) hardware information.
OPTIONS
-m, --cmt
Show Cache Monitoring Technology (CMT) hardware information.
-a, --cat
Show Cache Allocation Technology (CAT) hardware information.
CACHE MONITORING TECHNOLOGY
Intel Haswell and later server platforms offer monitoring capability in each logical processor to measure
specific platform shared resource metric, for example, L3 cache occupancy. In the Xen implementation, the
monitoring granularity is domain level. To monitor a specific domain, just attach the domain id with the
monitoring service. When the domain doesn't need to be monitored any more, detach the domain id from the
monitoring service.
Intel Broadwell and later server platforms also offer total/local memory bandwidth monitoring. Xen
supports per-domain monitoring for these two additional monitoring types. Both memory bandwidth
monitoring and L3 cache occupancy monitoring share the same set of underlying monitoring service. Once a
domain is attached to the monitoring service, monitoring data can be shown for any of these monitoring
types.
There is no cache monitoring and memory bandwidth monitoring on L2 cache so far.
psr-cmt-attach domain-id
attach: Attach the platform shared resource monitoring service to a domain.
psr-cmt-detach domain-id
detach: Detach the platform shared resource monitoring service from a domain.
psr-cmt-show psr-monitor-type [domain-id]
Show monitoring data for a certain domain or all domains. Current supported monitor types are:
- "cache-occupancy": showing the L3 cache occupancy(KB).
- "total-mem-bandwidth": showing the total memory bandwidth(KB/s).
- "local-mem-bandwidth": showing the local memory bandwidth(KB/s).
CACHE ALLOCATION TECHNOLOGY
Intel Broadwell and later server platforms offer capabilities to configure and make use of the Cache
Allocation Technology (CAT) mechanisms, which enable more cache resources (i.e. L3/L2 cache) to be made
available for high priority applications. In the Xen implementation, CAT is used to control cache
allocation on VM basis. To enforce cache on a specific domain, just set capacity bitmasks (CBM) for the
domain.
Intel Broadwell and later server platforms also offer Code/Data Prioritization (CDP) for cache
allocations, which support specifying code or data cache for applications. CDP is used on a per VM basis
in the Xen implementation. To specify code or data CBM for the domain, CDP feature must be enabled and
CBM type options need to be specified when setting CBM, and the type options (code and data) are mutually
exclusive. There is no CDP support on L2 so far.
psr-cat-set [OPTIONS] domain-id cbm
Set cache capacity bitmasks(CBM) for a domain. For how to specify cbm please refer to
<https://xenbits.xenproject.org/docs/unstable/misc/xl-psr.html>.
OPTIONS
-s SOCKET, --socket=SOCKET
Specify the socket to process, otherwise all sockets are processed.
-l LEVEL, --level=LEVEL
Specify the cache level to process, otherwise the last level cache (L3) is processed.
-c, --code
Set code CBM when CDP is enabled.
-d, --data
Set data CBM when CDP is enabled.
psr-cat-show [OPTIONS] [domain-id]
Show CAT settings for a certain domain or all domains.
OPTIONS
-l LEVEL, --level=LEVEL
Specify the cache level to process, otherwise the last level cache (L3) is processed.
Memory Bandwidth Allocation
Intel Skylake and later server platforms offer capabilities to configure and make use of the Memory
Bandwidth Allocation (MBA) mechanisms, which provides OS/VMMs the ability to slow misbehaving apps/VMs by
using a credit-based throttling mechanism. In the Xen implementation, MBA is used to control memory
bandwidth on VM basis. To enforce bandwidth on a specific domain, just set throttling value (THRTL) for
the domain.
psr-mba-set [OPTIONS] domain-id thrtl
Set throttling value (THRTL) for a domain. For how to specify thrtl please refer to
<https://xenbits.xenproject.org/docs/unstable/misc/xl-psr.html>.
OPTIONS
-s SOCKET, --socket=SOCKET
Specify the socket to process, otherwise all sockets are processed.
psr-mba-show [domain-id]
Show MBA settings for a certain domain or all domains. For linear mode, it shows the decimal value.
For non-linear mode, it shows hexadecimal value.
IGNORED FOR COMPATIBILITY WITH XM
xl is mostly command-line compatible with the old xm utility used with the old Python xend. For
compatibility, the following options are ignored:
xl migrate --live
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of xl:
LIBXL_BOOTLOADER_RESTRICT
Equivalent to xl.cfg(5) bootloader_restrict option. Provided for compatibility reasons. Having this
variable set is equivalent to enabling the option, even if the value is 0.
If set takes precedence over xl.cfg(5) and xl.conf(5) bootloader_restrict options.
LIBXL_BOOTLOADER_USER
Equivalent to xl.cfg(5) bootloader_user option. Provided for compatibility reasons.
If set takes precedence over xl.cfg(5) bootloader_user option.
LIBXL_BOOTLOADER_TIMEOUT
Timeout in seconds for bootloader execution when running in restricted mode. Otherwise the build
time default in LIBXL_BOOTLOADER_TIMEOUT will be used.
If defined the value must be an unsigned integer between 0 and INT_MAX, otherwise behavior is
undefined. Setting to 0 disables the timeout.
SEE ALSO
The following man pages:
xl.cfg(5), xlcpupool.cfg(5), xentop(1), xl-disk-configuration(5) xl-network-configuration(5)
And the following documents on the xenproject.org website:
<https://xenbits.xenproject.org/docs/unstable/misc/xsm-flask.txt>
<https://xenbits.xenproject.org/docs/unstable/misc/xl-psr.html>
For systems that don't automatically bring the CPU online:
<https://wiki.xenproject.org/wiki/Paravirt_Linux_CPU_Hotplug>
BUGS
Send bugs to xen-devel@lists.xenproject.org, see
https://wiki.xenproject.org/wiki/Reporting_Bugs_against_Xen_Project on how to send bug reports.
4.20.1-pre 2025-05-05 xl(1)