QEMU Monitor

The QEMU monitor is used to give complex commands to the QEMU emulator. You can use it to:

  • Remove or insert removable media images (such as CD-ROM or floppies).
  • Freeze/unfreeze the Virtual Machine (VM) and save or restore its state from a disk file.
  • Inspect the VM state without an external debugger.

Commands

The following commands are available:

help or ? [cmd]
Show the help for all commands or just for command cmd.
commit
Commit changes to the disk images (if -snapshot is used) or backing files. If the backing file is smaller than the snapshot, then the backing file will be resized to be the same size as the snapshot. If the snapshot is smaller than the backing file, the backing file will not be truncated. If you want the backing file to match the size of the smaller snapshot, you can safely truncate it yourself once the commit operation successfully completes.
q or quit
Quit the emulator.
exit_preconfig
This command makes QEMU exit the preconfig state and proceed with VM initialization using configuration data provided on the command line and via the QMP monitor during the preconfig state. The command is only available during the preconfig state (i.e. when the –preconfig command line option was in use).
block_resize
Resize a block image while a guest is running. Usually requires guest action to see the updated size. Resize to a lower size is supported, but should be used with extreme caution. Note that this command only resizes image files, it can not resize block devices like LVM volumes.
block_stream
Copy data from a backing file into a block device.
block_job_set_speed
Set maximum speed for a background block operation.
block_job_cancel
Stop an active background block operation (streaming, mirroring).
block_job_complete
Manually trigger completion of an active background block operation. For mirroring, this will switch the device to the destination path.
block_job_pause
Pause an active block streaming operation.
block_job_resume
Resume a paused block streaming operation.
eject [-f] device
Eject a removable medium (use -f to force it).
drive_del device
Remove host block device. The result is that guest generated IO is no longer submitted against the host device underlying the disk. Once a drive has been deleted, the QEMU Block layer returns -EIO which results in IO errors in the guest for applications that are reading/writing to the device. These errors are always reported to the guest, regardless of the drive’s error actions (drive options rerror, werror).
change device setting

Change the configuration of a device.

change diskdevice filename [format [read-only-mode]]

Change the medium for a removable disk device to point to filename. eg:

(qemu) change ide1-cd0 /path/to/some.iso

format is optional.

read-only-mode may be used to change the read-only status of the device. It accepts the following values:

retain
Retains the current status; this is the default.
read-only
Makes the device read-only.
read-write
Makes the device writable.
change vnc display,options

Change the configuration of the VNC server. The valid syntax for display and options are described at Invocation. eg:

(qemu) change vnc localhost:1

change vnc password [password]

Change the password associated with the VNC server. If the new password is not supplied, the monitor will prompt for it to be entered. VNC passwords are only significant up to 8 letters. eg:

(qemu) change vnc password
Password: ********
screendump filename
Save screen into PPM image filename.
logfile filename
Output logs to filename.
trace-event
changes status of a trace event
trace-file on|off|flush
Open, close, or flush the trace file. If no argument is given, the status of the trace file is displayed.
log item1[,…]
Activate logging of the specified items.
savevm tag

Create a snapshot of the whole virtual machine. If tag is provided, it is used as human readable identifier. If there is already a snapshot with the same tag, it is replaced. More info at VM snapshots.

Since 4.0, savevm stopped allowing the snapshot id to be set, accepting only tag as parameter.

loadvm tag

Set the whole virtual machine to the snapshot identified by the tag tag.

Since 4.0, loadvm stopped accepting snapshot id as parameter.

delvm tag

Delete the snapshot identified by tag.

Since 4.0, delvm stopped deleting snapshots by snapshot id, accepting only tag as parameter.

singlestep [off]
Run the emulation in single step mode. If called with option off, the emulation returns to normal mode.
stop
Stop emulation.
c or cont
Resume emulation.
system_wakeup
Wakeup guest from suspend.
gdbserver [port]
Start gdbserver session (default port=1234)
x/fmt addr
Virtual memory dump starting at addr.
xp /fmt addr

Physical memory dump starting at addr.

fmt is a format which tells the command how to format the data. Its syntax is: /{count}{format}{size}

count
is the number of items to be dumped.
format
can be x (hex), d (signed decimal), u (unsigned decimal), o (octal), c (char) or i (asm instruction).
size
can be b (8 bits), h (16 bits), w (32 bits) or g (64 bits). On x86, h or w can be specified with the i format to respectively select 16 or 32 bit code instruction size.

Examples:

Dump 10 instructions at the current instruction pointer:

(qemu) x/10i $eip
0x90107063:  ret
0x90107064:  sti
0x90107065:  lea    0x0(%esi,1),%esi
0x90107069:  lea    0x0(%edi,1),%edi
0x90107070:  ret
0x90107071:  jmp    0x90107080
0x90107073:  nop
0x90107074:  nop
0x90107075:  nop
0x90107076:  nop

Dump 80 16 bit values at the start of the video memory:

(qemu) xp/80hx 0xb8000
0x000b8000: 0x0b50 0x0b6c 0x0b65 0x0b78 0x0b38 0x0b36 0x0b2f 0x0b42
0x000b8010: 0x0b6f 0x0b63 0x0b68 0x0b73 0x0b20 0x0b56 0x0b47 0x0b41
0x000b8020: 0x0b42 0x0b69 0x0b6f 0x0b73 0x0b20 0x0b63 0x0b75 0x0b72
0x000b8030: 0x0b72 0x0b65 0x0b6e 0x0b74 0x0b2d 0x0b63 0x0b76 0x0b73
0x000b8040: 0x0b20 0x0b30 0x0b35 0x0b20 0x0b4e 0x0b6f 0x0b76 0x0b20
0x000b8050: 0x0b32 0x0b30 0x0b30 0x0b33 0x0720 0x0720 0x0720 0x0720
0x000b8060: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
0x000b8070: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
0x000b8080: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
0x000b8090: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
gpa2hva addr
Print the host virtual address at which the guest’s physical address addr is mapped.
gpa2hpa addr
Print the host physical address at which the guest’s physical address addr is mapped.
gva2gpa addr
Print the guest physical address at which the guest’s virtual address addr is mapped based on the mapping for the current CPU.
p or print/fmt expr
Print expression value. Only the format part of fmt is used.
i/fmt addr [.index]
Read I/O port.
o/fmt addr val
Write to I/O port.
sendkey keys

Send keys to the guest. keys could be the name of the key or the raw value in hexadecimal format. Use - to press several keys simultaneously. Example:

sendkey ctrl-alt-f1

This command is useful to send keys that your graphical user interface intercepts at low level, such as ctrl-alt-f1 in X Window.

sync-profile [on|off|reset]
Enable, disable or reset synchronization profiling. With no arguments, prints whether profiling is on or off.
system_reset
Reset the system.
system_powerdown
Power down the system (if supported).
sum addr size
Compute the checksum of a memory region.
device_add config
Add device.
device_del id
Remove device id. id may be a short ID or a QOM object path.
cpu index
Set the default CPU.
mouse_move dx dy [dz]
Move the active mouse to the specified coordinates dx dy with optional scroll axis dz.
mouse_button val
Change the active mouse button state val (1=L, 2=M, 4=R).
mouse_set index

Set which mouse device receives events at given index, index can be obtained with:

info mice
wavcapture filename audiodev [frequency [bits [channels]]]

Capture audio into filename from audiodev, using sample rate frequency bits per sample bits and number of channels channels.

Defaults:

  • Sample rate = 44100 Hz - CD quality
  • Bits = 16
  • Number of channels = 2 - Stereo
stopcapture index

Stop capture with a given index, index can be obtained with:

info capture
memsave addr size file
save to disk virtual memory dump starting at addr of size size.
pmemsave addr size file
save to disk physical memory dump starting at addr of size size.
boot_set bootdevicelist

Define new values for the boot device list. Those values will override the values specified on the command line through the -boot option.

The values that can be specified here depend on the machine type, but are the same that can be specified in the -boot command line option.

nmi cpu
Inject an NMI on the default CPU (x86/s390) or all CPUs (ppc64).
ringbuf_write device data
Write data to ring buffer character device device. data must be a UTF-8 string.
ringbuf_read device
Read and print up to size bytes from ring buffer character device device. Certain non-printable characters are printed \uXXXX, where XXXX is the character code in hexadecimal. Character \ is printed \\. Bug: can screw up when the buffer contains invalid UTF-8 sequences, NUL characters, after the ring buffer lost data, and when reading stops because the size limit is reached.
announce_self
Trigger a round of GARP/RARP broadcasts; this is useful for explicitly updating the network infrastructure after a reconfiguration or some forms of migration. The timings of the round are set by the migration announce parameters. An optional comma separated interfaces list restricts the announce to the named set of interfaces. An optional id can be used to start a separate announce timer and to change the parameters of it later.
migrate [-d] [-b] [-i] uri

Migrate to uri (using -d to not wait for completion).

-b
for migration with full copy of disk
-i
for migration with incremental copy of disk (base image is shared)
migrate_cancel
Cancel the current VM migration.
migrate_continue state
Continue migration from the paused state state
migrate_incoming uri
Continue an incoming migration using the uri (that has the same syntax as the -incoming option).
migrate_recover uri
Continue a paused incoming postcopy migration using the uri.
migrate_pause
Pause an ongoing migration. Currently it only supports postcopy.
migrate_set_cache_size value
Set cache size to value (in bytes) for xbzrle migrations.
migrate_set_speed value
Set maximum speed to value (in bytes) for migrations.
migrate_set_downtime second
Set maximum tolerated downtime (in seconds) for migration.
migrate_set_capability capability state
Enable/Disable the usage of a capability capability for migration.
migrate_set_parameter parameter value
Set the parameter parameter for migration.
migrate_start_postcopy
Switch in-progress migration to postcopy mode. Ignored after the end of migration (or once already in postcopy).
x_colo_lost_heartbeat
Tell COLO that heartbeat is lost, a failover or takeover is needed.
client_migrate_info protocol hostname port tls-port cert-subject
Set migration information for remote display. This makes the server ask the client to automatically reconnect using the new parameters once migration finished successfully. Only implemented for SPICE.
dump-guest-memory [-p] filename begin length
dump-guest-memory [-z|-l|-s|-w] filename

Dump guest memory to protocol. The file can be processed with crash or gdb. Without -z|-l|-s|-w, the dump format is ELF.

-p
do paging to get guest’s memory mapping.
-z
dump in kdump-compressed format, with zlib compression.
-l
dump in kdump-compressed format, with lzo compression.
-s
dump in kdump-compressed format, with snappy compression.
-w
dump in Windows crashdump format (can be used instead of ELF-dump converting), for Windows x64 guests with vmcoreinfo driver only
filename
dump file name.
begin
the starting physical address. It’s optional, and should be specified together with length.
length
the memory size, in bytes. It’s optional, and should be specified together with begin.
dump-skeys filename
Save guest storage keys to a file.
migration_mode mode
Enables or disables migration mode.
snapshot_blkdev
Snapshot device, using snapshot file as target if provided
snapshot_blkdev_internal
Take an internal snapshot on device if it support
snapshot_delete_blkdev_internal
Delete an internal snapshot on device if it support
drive_mirror
Start mirroring a block device’s writes to a new destination, using the specified target.
drive_backup
Start a point-in-time copy of a block device to a specificed target.
drive_add
Add drive to PCI storage controller.
pcie_aer_inject_error
Inject PCIe AER error
netdev_add
Add host network device.
netdev_del
Remove host network device.
object_add
Create QOM object.
object_del
Destroy QOM object.
hostfwd_add
Redirect TCP or UDP connections from host to guest (requires -net user).
hostfwd_remove
Remove host-to-guest TCP or UDP redirection.
balloon value
Request VM to change its memory allocation to value (in MB).
set_link name [on|off]
Switch link name on (i.e. up) or off (i.e. down).
watchdog_action
Change watchdog action.
acl_show aclname
List all the matching rules in the access control list, and the default policy. There are currently two named access control lists, vnc.x509dname and vnc.username matching on the x509 client certificate distinguished name, and SASL username respectively.
acl_policy aclname allow|deny
Set the default access control list policy, used in the event that none of the explicit rules match. The default policy at startup is always deny.
acl_add aclname match allow|deny [index]
Add a match rule to the access control list, allowing or denying access. The match will normally be an exact username or x509 distinguished name, but can optionally include wildcard globs. eg *@EXAMPLE.COM to allow all users in the EXAMPLE.COM kerberos realm. The match will normally be appended to the end of the ACL, but can be inserted earlier in the list if the optional index parameter is supplied.
acl_remove aclname match
Remove the specified match rule from the access control list.
acl_reset aclname
Remove all matches from the access control list, and set the default policy back to deny.
nbd_server_start host:port
Start an NBD server on the given host and/or port. If the -a option is included, all of the virtual machine’s block devices that have an inserted media on them are automatically exported; in this case, the -w option makes the devices writable too.
nbd_server_add device [ name ]
Export a block device through QEMU’s NBD server, which must be started beforehand with nbd_server_start. The -w option makes the exported device writable too. The export name is controlled by name, defaulting to device.
nbd_server_remove [-f] name
Stop exporting a block device through QEMU’s NBD server, which was previously started with nbd_server_add. The -f option forces the server to drop the export immediately even if clients are connected; otherwise the command fails unless there are no clients.
nbd_server_stop
Stop the QEMU embedded NBD server.
mce cpu bank status mcgstatus addr misc
Inject an MCE on the given CPU (x86 only).
getfd fdname
If a file descriptor is passed alongside this command using the SCM_RIGHTS mechanism on unix sockets, it is stored using the name fdname for later use by other monitor commands.
closefd fdname
Close the file descriptor previously assigned to fdname using the getfd command. This is only needed if the file descriptor was never used by another monitor command.
block_passwd device password

Set the encrypted device device password to password

This command is now obsolete and will always return an error since 2.10

block_set_io_throttle device bps bps_rd bps_wr iops iops_rd iops_wr
Change I/O throttle limits for a block drive to bps bps_rd bps_wr iops iops_rd iops_wr. device can be a block device name, a qdev ID or a QOM path.
set_password [ vnc | spice ] password [ action-if-connected ]
Change spice/vnc password. Use zero to make the password stay valid forever. action-if-connected specifies what should happen in case a connection is established: fail makes the password change fail. disconnect changes the password and disconnects the client. keep changes the password and keeps the connection up. keep is the default.
expire_password [ vnc | spice ] expire-time

Specify when a password for spice/vnc becomes invalid. expire-time accepts:

now
Invalidate password instantly.
never
Password stays valid forever.
+nsec
Password stays valid for nsec seconds starting now.
nsec
Password is invalidated at the given time. nsec are the seconds passed since 1970, i.e. unix epoch.
chardev-add args
chardev-add accepts the same parameters as the -chardev command line switch.
chardev-change args
chardev-change accepts existing chardev id and then the same arguments as the -chardev command line switch (except for “id”).
chardev-remove id
Removes the chardev id.
chardev-send-break id
Send a break on the chardev id.
qemu-io device command
Executes a qemu-io command on the given block device.
cpu-add id
Add CPU with id id. This command is deprecated, please +use device_add instead. For details, refer to ‘docs/cpu-hotplug.rst’.
qom-list [path]
Print QOM properties of object at location path
qom-get path property
Print QOM property property of object at location path
qom-set path property value
Set QOM property property of object at location path to value value
info subcommand

Show various information about the system state.

info version
Show the version of QEMU.
info network
Show the network state.
info chardev
Show the character devices.
info block
Show info of one block device or all block devices.
info blockstats
Show block device statistics.
info block-jobs
Show progress of ongoing block device operations.
info registers
Show the cpu registers.
info lapic
Show local APIC state
info ioapic
Show io APIC state
info cpus
Show infos for each CPU.
info history
Show the command line history.
info irq
Show the interrupts statistics (if available).
info pic
Show PIC state.
info rdma
Show RDMA state.
info pci
Show PCI information.
info tlb
Show virtual to physical memory mappings.
info mem
Show the active virtual memory mappings.
info mtree
Show memory tree.
info jit
Show dynamic compiler info.
info opcount
Show dynamic compiler opcode counters
info sync-profile [-m|-n] [max]

Show synchronization profiling info, up to max entries (default: 10), sorted by total wait time.

-m
sort by mean wait time
-n
do not coalesce objects with the same call site

When different objects that share the same call site are coalesced, the “Object” field shows—enclosed in brackets—the number of objects being coalesced.

info kvm
Show KVM information.
info numa
Show NUMA information.
info usb
Show guest USB devices.
info usbhost
Show host USB devices.
info profile
Show profiling information.
info capture
Show capture information.
info snapshots
Show the currently saved VM snapshots.
info status
Show the current VM status (running|paused).
info mice
Show which guest mouse is receiving events.
info vnc
Show the vnc server status.
info spice
Show the spice server status.
info name
Show the current VM name.
info uuid
Show the current VM UUID.
info cpustats
Show CPU statistics.
info usernet
Show user network stack connection states.
info migrate
Show migration status.
info migrate_capabilities
Show current migration capabilities.
info migrate_parameters
Show current migration parameters.
info migrate_cache_size
Show current migration xbzrle cache size.
info balloon
Show balloon information.
info qtree
Show device tree.
info qdm
Show qdev device model list.
info qom-tree
Show QOM composition tree.
info roms
Show roms.
info trace-events
Show available trace-events & their state.
info tpm
Show the TPM device.
info memdev
Show memory backends
info memory-devices
Show memory devices.
info iothreads
Show iothread’s identifiers.
info rocker name
Show rocker switch.
info rocker-ports name-ports
Show rocker ports.
info rocker-of-dpa-flows name [tbl_id]
Show rocker OF-DPA flow tables.
info rocker-of-dpa-groups name [type]
Show rocker OF-DPA groups.
info skeys address
Display the value of a storage key (s390 only)
info cmma address
Display the values of the CMMA storage attributes for a range of pages (s390 only)
info dump
Display the latest dump status.
info ramblock
Dump all the ramblocks of the system.
info hotpluggable-cpus
Show information about hotpluggable CPUs
info vm-generation-id
Show Virtual Machine Generation ID
info memory_size_summary
Display the amount of initially allocated and present hotpluggable (if enabled) memory in bytes.
info sev
Show SEV information.

Integer expressions

The monitor understands integers expressions for every integer argument. You can use register names to get the value of specifics CPU registers by prefixing them with $.