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.

quit or q

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 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 or s

Stop emulation.

cont or c

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.

print or p/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_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 specified 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.

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_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 [ -d display ] [ action-if-connected ]

Change spice/vnc password. display can be used with ‘vnc’ to specify which display to set the password on. 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 [ -d display ]

Specify when a password for spice/vnc becomes invalid. display behaves the same as in set_password. 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.

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

replay_break icount

Set replay breakpoint at instruction count icount. Execution stops when the specified instruction is reached. There can be at most one breakpoint. When breakpoint is set, any prior one is removed. The breakpoint may be set only in replay mode and only “in the future”, i.e. at instruction counts greater than the current one. The current instruction count can be observed with info replay.

replay_delete_break

Remove replay breakpoint which was previously set with replay_break. The command is ignored when there are no replay breakpoints.

replay_seek icount

Automatically proceed to the instruction count icount, when replaying the execution. The command automatically loads nearest snapshot and replays the execution to find the desired instruction. When there is no preceding snapshot or the execution is not replayed, then the command fails. icount for the reference may be observed with info replay command.

calc_dirty_rate second

Start a round of dirty rate measurement with the period specified in second. The result of the dirty rate measurement may be observed with info dirty_rate command.

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 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 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 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.

info replay

Display the record/replay information: mode and the current icount.

info dirty_rate

Display the vcpu dirty rate information.

info sgx

Show intel SGX information.

info via

Show guest mos6522 VIA devices.

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 $.