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:
helpor?[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.
qorquit- 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_deldevice- 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).
changedevice settingChange the configuration of a device.
changediskdevice 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 vncdisplay,optionsChange 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: ********
screendumpfilename- Save screen into PPM image filename.
logfilefilename- 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.
logitem1[,...]- Activate logging of the specified items.
savevmtagCreate 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.
loadvmtagSet the whole virtual machine to the snapshot identified by the tag tag.
Since 4.0, loadvm stopped accepting snapshot id as parameter.
delvmtagDelete 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.
corcont- 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 addrPhysical 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,
horwcan be specified with theiformat 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
gpa2hvaaddr- Print the host virtual address at which the guest’s physical address addr is mapped.
gpa2hpaaddr- Print the host physical address at which the guest’s physical address addr is mapped.
gva2gpaaddr- Print the guest physical address at which the guest’s virtual address addr is mapped based on the mapping for the current CPU.
porprint/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.
sendkeykeysSend 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-f1in 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).
sumaddr size- Compute the checksum of a memory region.
device_addconfig- Add device.
device_delid- Remove device id. id may be a short ID or a QOM object path.
cpuindex- Set the default CPU.
mouse_movedx dy [dz]- Move the active mouse to the specified coordinates dx dy with optional scroll axis dz.
mouse_buttonval- Change the active mouse button state val (1=L, 2=M, 4=R).
mouse_setindexSet which mouse device receives events at given index, index can be obtained with:
info mice
wavcapturefilename 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
stopcaptureindexStop capture with a given index, index can be obtained with:
info capture
memsaveaddr size file- save to disk virtual memory dump starting at addr of size size.
pmemsaveaddr size file- save to disk physical memory dump starting at addr of size size.
boot_setbootdevicelistDefine new values for the boot device list. Those values will override the values specified on the command line through the
-bootoption.The values that can be specified here depend on the machine type, but are the same that can be specified in the
-bootcommand line option.nmicpu- Inject an NMI on the default CPU (x86/s390) or all CPUs (ppc64).
ringbuf_writedevice data- Write data to ring buffer character device device. data must be a UTF-8 string.
ringbuf_readdevice- Read and print up to size bytes from ring buffer character
device device.
Certain non-printable characters are printed
\uXXXX, whereXXXXis 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]uriMigrate 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_continuestate- Continue migration from the paused state state
migrate_incominguri- Continue an incoming migration using the uri (that has the same syntax
as the
-incomingoption). migrate_recoveruri- Continue a paused incoming postcopy migration using the uri.
migrate_pause- Pause an ongoing migration. Currently it only supports postcopy.
migrate_set_cache_sizevalue- Set cache size to value (in bytes) for xbzrle migrations.
migrate_set_speedvalue- Set maximum speed to value (in bytes) for migrations.
migrate_set_downtimesecond- Set maximum tolerated downtime (in seconds) for migration.
migrate_set_capabilitycapability state- Enable/Disable the usage of a capability capability for migration.
migrate_set_parameterparameter 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_infoprotocol 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 lengthdump-guest-memory [-z|-l|-s|-w]filenameDump 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-skeysfilename- Save guest storage keys to a file.
migration_modemode- 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.
balloonvalue- Request VM to change its memory allocation to value (in MB).
set_linkname[on|off]- Switch link name on (i.e. up) or off (i.e. down).
watchdog_action- Change watchdog action.
acl_showaclname- 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_policyaclnameallow|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_addaclname matchallow|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.COMto allow all users in theEXAMPLE.COMkerberos 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_removeaclname match- Remove the specified match rule from the access control list.
acl_resetaclname- Remove all matches from the access control list, and set the default
policy back to
deny. nbd_server_starthost:port- Start an NBD server on the given host and/or port. If the
-aoption is included, all of the virtual machine’s block devices that have an inserted media on them are automatically exported; in this case, the-woption makes the devices writable too. nbd_server_adddevice [ name ]- Export a block device through QEMU’s NBD server, which must be started
beforehand with
nbd_server_start. The-woption 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-foption 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.
mcecpu bank status mcgstatus addr misc- Inject an MCE on the given CPU (x86 only).
getfdfdname- 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.
closefdfdname- Close the file descriptor previously assigned to fdname using the
getfdcommand. This is only needed if the file descriptor was never used by another monitor command. block_passwddevice passwordSet the encrypted device device password to password
This command is now obsolete and will always return an error since 2.10
block_set_io_throttledevice 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-timeSpecify 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-addargs- chardev-add accepts the same parameters as the -chardev command line switch.
chardev-changeargs- chardev-change accepts existing chardev id and then the same arguments as the -chardev command line switch (except for “id”).
chardev-removeid- Removes the chardev id.
chardev-send-breakid- Send a break on the chardev id.
qemu-iodevice command- Executes a qemu-io command on the given block device.
cpu-addid- Add CPU with id id. This command is deprecated, please
+use
device_addinstead. For details, refer to ‘docs/cpu-hotplug.rst’. qom-list[path]- Print QOM properties of object at location path
qom-getpath property- Print QOM property property of object at location path
qom-setpath property value- Set QOM property property of object at location path to value value
infosubcommandShow 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 rockername- Show rocker switch.
info rocker-portsname-ports- Show rocker ports.
info rocker-of-dpa-flowsname [tbl_id]- Show rocker OF-DPA flow tables.
info rocker-of-dpa-groupsname [type]- Show rocker OF-DPA groups.
info skeysaddress- Display the value of a storage key (s390 only)
info cmmaaddress- 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 $.