This causes the buffer to overflow and corrupt the data it holds. An example of a buffer overflow is sending emails with file names that have characters. Teardrop This type of attack uses larger data packets. The attacker manipulates the packets as they are sent so that they overlap each other.
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- DoS (Denial of Service) Attack Tutorial: Ping of Death, DDOS!
- Windows 95.
This can cause the intended victim to crash as it tries to re-assemble the packets. This type of attack takes advantage of the three-way handshake to establish communication using TCP. This causes the victim machine to allocate memory resources that are never used and deny access to legitimate users.
DoS attack tools The following are some of the tools that can be used to perform DoS attacks. Nemesy — this tool can be used to generate random packets. It works on windows. Due to the nature of the program, if you have an antivirus, it will most likely be detected as a virus. Botnets — these are multitudes of compromised computers on the Internet that can be used to perform a distributed denial of service attack. DoS Protection: Prevent an attack An organization can adopt the following policy to protect itself against Denial of Service attacks. Attacks such as SYN flooding take advantage of bugs in the operating system.
Installing security patches can help reduce the chances of such attacks. Intrusion detection systems can also be used to identify and even stop illegal activities Firewalls can be used to stop simple DoS attacks by blocking all traffic coming from an attacker by identifying his IP. Routers can be configured via the Access Control List to limit access to the network and drop suspected illegal traffic. We will also assume that you have at least two computers that are on the same network. DOS attacks are illegal on networks that you are not authorized to do so. This is why you will need to setup your own network for this exercise.
Open the command prompt on the target computer Enter the command ipconfig. You will get results similar to the ones shown below For this example, we are using Mobile Broadband connection details. Take note of the IP address.
Note: for this example to be more effective, and you must use a LAN network. Switch to the computer that you want to use for the attack and open the command prompt We will ping our victim computer with infinite data packets of Enter the following command ping In order for the attack to be more effective, you should attack the target computer with pings from more than one computer.
The above attack can be used to attacker routers, web servers etc. If you want to see the effects of the attack on the target computer, you can open the task manager and view the network activities. Right click on the taskbar Select start task manager Click on the network tab You will get results similar to the following If the attack is successful, you should be able to see increased network activities. Hacking Activity: Launch a DOS attack In this practical scenario, we are going to use Nemesy to generate data packets and flood the target computer, router or server.
As stated above, Nemesy will be detected as an illegal program by your anti-virus. You will have to disable the anti-virus for this exercise. HERE, 0 as the number of packets means infinity. Normally, if QEMU is compiled with graphical window support, it displays output such as guest graphics, guest console, and the QEMU monitor in a window. With this option, you can totally disable graphical output so that QEMU is a simple command line application.
The emulated serial port is redirected on the console and muxed with the monitor unless redirected elsewhere explicitly. Use C-a h for help on switching between the console and monitor. Nothing is displayed in graphical mode. Note that this also affects the special keys for fullscreen, monitor-mode switching, etc. Use Right-Ctrl to grab mouse instead of Ctrl-Alt. Require that the client use SASL to authenticate with the spice. This ensures a data encryption preventing compromise of authentication credentials.
Force specific channel to be used with or without TLS encryption. The options can be specified multiple times to configure multiple channels. The special name "default" can be used to set the default mode. If not specified, it will pick the first available. Since 2.
Cirrus Logic GD Video card. All Windows versions starting from Windows 95 should recognize and use this graphic card. For optimal performances, use 16 bit color depth in the guest and the host OS. This card was the default before QEMU 2. This card is the default since QEMU 2. QXL paravirtual graphic card. Works best with qxl guest drivers installed though. Recommended choice when using the spice protocol. This is the default framebuffer for sun4m machines and offers both 8-bit and bit colour depths at a fixed resolution of x This is a simple 8-bit framebuffer for sun4m machines available in both x OpenBIOS and x OBP resolutions aimed at people wishing to run older Solaris versions.
It is very useful to enable the usb tablet device when using this option option -device usb-tablet. When using the VNC display, you must use the -k parameter to set the keyboard layout if you are not using en-us. Valid syntax for the display is. TCP connections will only be allowed from host on display d.
Optionally, host can be omitted in which case the server will accept connections from any host. Connections will be allowed over UNIX domain sockets where path is the location of a unix socket to listen for connections on. VNC is initialized but not started. The monitor change command can be used to later start the VNC server. Following the display value there may be one or more option flags separated by commas. Valid options are. The client is specified by the display. For reverse network connections host : d , reverse , the d argument is a TCP port number, not a display number.
If host is specified connections will only be allowed from this host. If no TLS credentials are provided, the websocket connection runs in unencrypted mode. If TLS credentials are provided, the websocket connection requires encrypted client connections. They will apply to both the normal VNC server socket and the websocket socket if enabled. The credentials should have been previously created using the -object tls-creds argument.
This object is only resolved at time of use, so can be deleted and recreated on the fly while the VNC server is active. If missing, it will default to denying access. Legacy method for enabling authorization of clients against the x distinguished name and SASL username. It results in the creation of two authz-list objects with IDs of vnc. This option is deprecated and should no longer be used. The new sasl-authz and tls-authz options are a replacement. Enable lossy compression methods gradient, JPEG, If this option is set, VNC client may receive lossy framebuffer updates depending on its encoding settings.
Enabling this option can save a lot of bandwidth at the expense of quality. Disable adaptive encodings. Adaptive encodings are enabled by default. An adaptive encoding will try to detect frequently updated screen regions, and send updates in these regions using a lossy encoding like JPEG. This can be really helpful to save bandwidth when playing videos. Disabling adaptive encodings restores the original static behavior of encodings like Tight. Set display sharing policy. As suggested by the rfb spec this is implemented by dropping other connections.
Connecting multiple clients in parallel requires all clients asking for a shared session vncviewer: -shared switch. This is the default. Set keyboard delay, for key down and key up events, in milliseconds. Default is Keyboards are low-bandwidth devices, so this slowdown can help the device and guest to keep up and not lose events in case events are arriving in bulk. Possible causes for the latter are flaky network connections, or scripts for automated testing. Use it when installing Windows to avoid a disk full bug. After Windows is installed, you no longer need this option this option slows down the IDE transfers.
Disable boot signature checking for floppy disks in BIOS. May be needed to boot from old floppy disks. Add ACPI table with specified header fields and context from specified files. This option is a shortcut for configuring both the on-board default guest NIC hardware and the host network backend in one go. The host backend options are the same as with the corresponding -netdev options below. Indicate that no network devices should be configured.
Configure user mode host network backend which requires no administrator privilege to run. Valid options are:. Specify that either IPv4 or IPv6 must be enabled. If neither is specified both protocols are enabled. Set IP network address the guest will see. Optionally specify the netmask, either in the form a. Specify the guest-visible address of the host. Default is the 2nd IP in the guest network, i.
The network prefix is given in the usual hexadecimal IPv6 address notation. The prefix size is optional, and is given as the number of valid top-most bits default is Specify the guest-visible IPv6 address of the host. Default is the 2nd IPv6 in the guest network, i. If this option is enabled, the guest will be isolated, i. This option does not affect any explicitly set forwarding rules.
Default is the 15th to 31st IP in the guest network, i. Specify the guest-visible address of the virtual nameserver. The address must be different from the host address. Default is the 3rd IP in the guest network, i. Specify the guest-visible address of the IPv6 virtual nameserver. Provides an entry for the domain-search list sent by the built-in DHCP server. More than one domain suffix can be transmitted by specifying this option multiple times. If supported, this will cause the guest to automatically try to append the given domain suffix es in case a domain name can not be resolved.
When using the user mode network stack, activate a built-in TFTP server. The files in dir will be exposed as the root of a TFTP server. This can be used to advise the guest to load boot files or configurations from a different server than the host address.
In conjunction with tftp , this can be used to network boot a guest from a local directory. When using the user mode network stack, activate a built-in SMB server so that Windows OSes can access to the host files in dir transparently. By default the 4th IP in the guest network is used, i.
If guestaddr is not specified, its value is x. By specifying hostaddr , the rule can be bound to a specific host interface. If no connection type is set, TCP is used. This option can be given multiple times. To redirect telnet connections from host port to telnet port on the guest, use the following:. Then when you use on the host telnet localhost , you connect to the guest telnet server. Forward guest TCP connections to the IP address server on port port to the character device dev or to a program executed by cmd:command which gets spawned for each connection.
Or you can execute a command on every TCP connection established by the guest, so that QEMU behaves similar to an inetd process for that virtual server:. Use the network script file to configure it and the network script dfile to deconfigure it. If name is not provided, the OS automatically provides one.
Use the network helper helper to configure the TAP interface and attach it to the bridge. If listen is specified, QEMU waits for incoming connections on port host is optional. Configure a L2TPv3 pseudowire host network backend. It is present in routers, firewalls and the Linux kernel from version 3. Cookies are a weak form of security in the l2tpv3 specification. Their function is mostly to prevent misconfiguration. By default they are 32 bit. Work around broken counter handling in peer.
This may also help on networks which have packet reorder. For example, to attach a VM running on host 4. This option is only available if QEMU has been compiled with vde support enabled. Establish a vhost-user netdev, backed by a chardev id. The chardev should be a unix domain socket backed one. The vhost-user uses a specifically defined protocol to pass vhost ioctl replacement messages to an application on the other end of the socket.
On non-MSIX guests, the feature can be forced with vhostforce. Optionally, the MAC address can be changed to mac , the device address set to addr PCI cards only , and a name can be assigned for use in monitor commands.
If no -net option is specified, a single NIC is created. QEMU can emulate several different models of network card. Configure a host network backend with the options corresponding to the same -netdev option and connect it to the emulated hub 0 the default hub. Use name to specify the name of the hub port. Backend is one of: null , socket , udp , msmouse , vc , ringbuf , file , pipe , console , serial , pty , stdio , braille , tty , parallel , parport , spicevmc , spiceport.
The specific backend will determine the applicable options. All devices must have an id, which can be any string up to characters long. It is used to uniquely identify this device in other command line directives. A character device may be used in multiplexing mode by multiple front-ends. A multiplexer is a "1:N" device, and here the "1" end is your specified chardev backend, and the "N" end is the various parts of QEMU that can talk to a chardev.
Up to four different front ends can be connected to a single multiplexed chardev. Without multiplexing enabled, a chardev can only be used by a single front end. For instance you could use this to allow a single stdio chardev to be used by two serial ports and the QEMU monitor:. See Keys in the character backend multiplexer. Note that some other command line options may implicitly create multiplexed character backends; for instance -serial mon:stdio creates a multiplexed stdio backend connected to the serial port and the QEMU monitor, and -nographic also multiplexes the console and the monitor to stdio.
There is currently no support for multiplexing in the other direction where a single QEMU front end takes input and output from multiple chardevs. Every backend supports the logfile option, which supplies the path to a file to record all data transmitted via the backend. The logappend option controls whether the log file will be truncated or appended to when opened. A void device. This device will not emit any data, and will drop any data it receives. The null backend does not take any options. Create a two-way stream socket, which can be either a TCP or a unix socket.
A unix socket will be created if path is specified. Behaviour is undefined if TCP options are specified for a unix socket. Zero disables reconnecting, and is the default. The credentials must be previously created with the -object tls-creds argument. This object is only resolved at time of use, so can be deleted and recreated on the fly while the chardev server is active. For a connecting socket species the remote host to connect to.
If not specified it defaults to 0. For a connecting socket specifies the port on the remote host to connect to. If it is specified, and port cannot be bound, QEMU will attempt to bind to subsequent ports up to and including to until it succeeds. If neither is specified the socket may use either protocol. If not specified it defaults to localhost. If not specified any available local port will be used. If neither is specified the device may use either protocol. Create a ring buffer with fixed size size. This file will be created if it does not already exist, and overwritten if it does.
Create a two-way connection to the guest. The behaviour differs slightly between Windows hosts and other hosts:. On other hosts, 2 pipes will be created called path. Data written to path. Data written by the guest can be read from path. QEMU will not create these fifos, and requires them to be present. Create a new pseudo-terminal on the host and connect to it. It is an alias for serial. Connect to a spice port, allowing a Spice client to handle the traffic identified by a name preferably a fqdn.
Defines the function of the corresponding Bluetooth HCI. For example when emulating a machine with only one HCI built into it, only the first -bt hci[ The Transport Layer is decided by the machine type. Currently the machines n and n have one HCI and all other machines have none. Note: This option and the whole bluetooth subsystem is considered as deprecated.
If you still use it, please send a mail to qemu-devel nongnu. Only available on bluez capable systems like Linux. Add a virtual, standard HCI that will participate in the Bluetooth scatternet n default 0. Similarly to -net VLANs, devices inside a bluetooth network n can only communicate with other devices in the same network scatternet. Linux-host only Create a HCI in scatternet n default 0 attached to the host bluetooth stack instead of to the emulated target. This allows the host and target machines to participate in a common scatternet and communicate. Requires the Linux vhci driver installed.
Can be used as following:. Emulate a bluetooth device dev and place it in network n default 0. QEMU can only emulate one type of bluetooth devices currently:. The specific backend type will determine the applicable options. The -tpmdev option creates the TPM backend and requires a -device option that specifies the TPM frontend interface model. The TPM device accessed by the passthrough driver must not be used by any other application on the host.
When using these options, you can use a given Linux or Multiboot kernel without installing it in the disk image. It can be useful for easier testing of various kernels. Use bzImage as kernel image. The kernel can be either a Linux kernel or in multiboot format. To insert contents with embedded NUL characters, you have to use the file parameter. Redirect the virtual serial port to host character device dev. The default device is vc in graphical mode and stdio in non graphical mode. The host serial port parameters are set according to the emulated ones.
If you just want a simple readonly console you can use netcat or nc , by starting QEMU with: -serial udp and nc as: nc -u -l -p Any time QEMU writes something to that port it will appear in the netconsole session. Another approach is to use a patched version of netcat which can listen to a TCP port and send and receive characters via udp.
If you have a patched version of netcat which activates telnet remote echo and single char transfer, then you can use the following options to set up a netcat redirector to allow telnet on port to access the QEMU port. If you use the server option QEMU will wait for a client socket application to connect to the port before continuing, unless the nowait option was specified. The nodelay option disables the Nagle buffering algorithm.
The reconnect option only applies if noserver is set, if the connection goes down it will attempt to reconnect at the given interval. If host is omitted, 0. Only one TCP connection at a time is accepted. You can use telnet to connect to the corresponding character device. The telnet protocol is used instead of raw tcp sockets. The options work the same as if you had specified -serial tcp.
The difference is that the port acts like a telnet server or client using telnet option negotiation. Typically in unix telnet you do it with Control-] and then type "send break" followed by pressing the enter key. The WebSocket protocol is used instead of raw tcp socket. The port acts as a WebSocket server.
Client mode is not supported. A unix domain socket is used instead of a tcp socket. The option works the same as if you had specified -serial tcp except the unix domain socket path is used for connections. This is a special option to allow the monitor to be multiplexed onto another serial port. The monitor is accessed with key sequence of Control-a and then pressing c. An example to multiplex the monitor onto a telnet server listening on port would be:.
Redirect the virtual parallel port to host device dev same devices as the serial port. Redirect the monitor to host device dev same devices as the serial port. Use -monitor none to disable the default monitor. Setup monitor on chardev name. Redirect the debug console to host device dev same devices as the serial port. Pause QEMU for interactive configuration before the machine is created, which allows querying and configuring properties that will affect machine initialization. This option is experimental. Run qemu with realtime features. Run qemu with hints about host resource overcommit.
The default is to assume that host overcommits all resources. This works when host memory is not overcommitted and reduces the worst-case latency for guest. This is equivalent to realtime. This works best when host CPU is not overcommitted. When used, host estimates of CPU cycle and power utilization will be incorrect, not taking into account guest idle time. The latter is allowing to start QEMU from within gdb and establish the connection via a pipe:. Shorthand for -gdb tcp, i. Filter debug output to that relevant to a range of target addresses.
Will dump output for any code in the 0x sized block starting at 0x and the 0x sized block starting at 0xffffffc and another 0x sized block starting at 0xffffffcf Force the guest to use a deterministic pseudo-random number generator, seeded with number. This does not affect crypto routines within the host. Enable KVM full virtualization support. This option is only available if KVM support is enabled when compiling.
Attach to existing xen domain. Restrict set of available xen operations to specified domain id XEN only. This allows for instance switching to monitor to commit changes to the disk image. Daemonize the QEMU process after initialization. QEMU will not detach from standard IO until it is ready to receive connections on any of its devices. This option is a useful way for external programs to launch QEMU without having to cope with initialization race conditions. Load the contents of file as an option ROM.
This option is useful to load things like EtherBoot. To start at a specific point in time, provide datetime in the format T or The default base is UTC. By default the RTC is driven by the host system time. This allows using of the RTC as accurate reference clock inside the guest, specifically if the host time is smoothly following an accurate external reference clock, e. If you want to isolate the guest time from the host, you can set clock to rt instead, which provides a host monotonic clock if host support it. To even prevent the RTC from progressing during suspension, you can set clock to vm virtual clock.
This option will try to figure out how many timer interrupts were not processed by the Windows guest and will re-inject them. Enable virtual instruction counter. If auto is specified then the virtual cpu speed will be automatically adjusted to keep virtual time within a few seconds of real time. This behavior give deterministic execution times from the guest point of view. Note that while this option can give deterministic behavior, it does not provide cycle accurate emulation. Modern CPUs contain superscalar out of order cores with complex cache hierarchies.
The number of instructions executed often has little or no correlation with actual performance. The goal is to have a guest running at the real frequency imposed by the shift option. Currently this option does not work when shift is auto. Note: The sync algorithm will work for those shift values for which the guest clock runs ahead of the host clock.
Typically this happens when the shift value is high how high depends on the host machine. Replay log is written into filename file in record mode and read from this file in replay mode. Option rrsnapshot is used to create new vm snapshot named snapshot at the start of execution recording. In replay mode this option is used to load the initial VM state.
Create a virtual hardware watchdog device. Once enabled by a guest action , the watchdog must be periodically polled by an agent inside the guest or else the guest will be restarted. Choose a model for which your guest has drivers. The model is the model of hardware watchdog to emulate. Use -watchdog help to list available hardware models.
Only one watchdog can be enabled for a guest. The action controls what QEMU will do when the watchdog timer expires. The default is reset forcefully reset the guest. Other possible actions are: shutdown attempt to gracefully shutdown the guest , poweroff forcefully poweroff the guest , inject-nmi inject a NMI into the guest , pause pause the guest , debug print a debug message and continue , or none do nothing. Note that the shutdown action requires that the guest responds to ACPI signals, which it may not be able to do in the sort of situations where the watchdog would have expired, and thus -watchdog-action shutdown is not recommended for production use.
Change the escape character used for switching to the monitor when using monitor and serial sharing. The default is 0x01 when using the -nographic option. You can select a different character from the ascii control keys where 1 through 26 map to Control-a through Control-z. For instance you could use the either of the following to change the escape character to Control-t.
The -nodefaults option will disable all those default devices. Immediately before starting guest execution, chroot to the specified directory. Especially useful in combination with -runas. This option is not supported for Windows hosts. Immediately before starting guest execution, drop root privileges, switching to the specified user. The default is auto , which means gdb during debug sessions and native otherwise.
Allows the user to pass input arguments, and can be used multiple times to build up a list. Enable Seccomp mode 2 system call filter. Read device configuration from file. Write device configuration to file. The file can be either filename to save command line and device configuration into file or dash - character to print the output to stdout.
This can be later used as input file for -readconfig option. The -no-user-config option makes QEMU not load any of the user-provided config files on sysconfdir. Immediately enable events matching pattern either event name or a globbing pattern. This option is only available if QEMU has been compiled with the simple , log or ftrace tracing backend.
To specify multiple events or patterns, specify the -trace option multiple times. Immediately enable events listed in file. The file must contain one event name as listed in the trace-events-all file per line; globbing patterns are accepted too. Log output traces to file. This option is only available if QEMU has been compiled with the simple tracing backend. Create a new object of type typename setting properties in the order they are specified. The id parameter is a unique ID that will be used to reference this memory region when configuring the -numa argument.
The size option provides the size of the memory region, and accepts common suffixes, eg M. The mem-path provides the path to either a shared memory or huge page filesystem mount. The share boolean option determines whether the memory region is marked as private to QEMU, or shared. The latter allows a co-operating external process to access the QEMU memory region. Setting the discard-data boolean option to on indicates that file contents can be destroyed when QEMU exits, to avoid unnecessarily flushing data to the backing file.
Setting the dump boolean option to off excludes the memory from core dumps. The align option specifies the base address alignment when QEMU mmap 2 mem-path , and accepts common suffixes, eg 2M. In such cases, users can specify the required alignment via this option. The pmem option specifies whether the backing file specified by mem-path is in host persistent memory that can be accessed using the SNIA NVM programming model e. Creates a memory backend object, which can be used to back the guest RAM. Memory backend objects offer more control than the -m option that is traditionally used to define guest RAM.
Please refer to memory-backend-file for a description of the options. Creates an anonymous memory file backend object, which allows QEMU to share the memory with an external process e. The memory is allocated with memfd and optional sealing. Linux only. The hugetlb option specify the file to be created resides in the hugetlbfs filesystem since Linux 4.
Used in conjunction with the hugetlb option, the hugetlbsize option specify the hugetlb page size on systems that support multiple hugetlb page sizes it must be a power of 2 value supported by the system. In some versions of Linux, the hugetlb option is incompatible with the seal option requires at least Linux 4. Creates a random number generator backend which obtains entropy from a device on the host. The id parameter is a unique ID that will be used to reference this entropy backend from the virtio-rng device. Creates a random number generator backend which obtains entropy from an external daemon running on the host.
The chardev parameter is the unique ID of a character device backend that provides the connection to the RNG daemon. The id parameter is a unique ID which network backends will use to access the credentials. The endpoint is either server or client depending on whether the QEMU network backend that uses the credentials will be acting as a client or as a server. If verify-peer is enabled the default then once the handshake is completed, the peer credentials will be verified, though this is a no-op for anonymous credentials.
The dir parameter tells QEMU where to find the credential files. For server endpoints, this directory may contain a file dh-params. This is a computationally expensive operation that consumes random pool entropy, so it is recommended that a persistent set of parameters be generated upfront and saved. For clients only, username is the username which will be sent to the server.
The dir parameter tells QEMU where to find the keys file. This file can most easily be created using the GnuTLS psktool program. For server endpoints, dir may also contain a file dh-params. This is a computationally expensive operation that consumes random pool entropy, so it is recommended that a persistent set of parameters be generated up front and saved. If verify-peer is enabled the default then once the handshake is completed, the peer credentials will be verified. With x certificates, this implies that the clients must be provided with valid client certificates too.
For x certificate credentials the directory will contain further files providing the x certificates. The certificates must be stored in PEM format, in filenames ca-cert. For the server-key. This provides the ID of a previously created secret object containing the password for decryption. The priority parameter allows to override the global default priority used by gnutls. This can be useful if the system administrator needs to use a weaker set of crypto priorities for QEMU without potentially forcing the weakness onto all applications.
Or conversely if one wants wants a stronger default for QEMU than for all other applications, they can do this through this parameter. Interval is in microseconds. Create a filter-redirector we need to differ outdev id from indev id, id can not be the same. Filter-rewriter is a part of COLO project. It will rewrite tcp packet to secondary from primary to keep secondary tcp connection,and rewrite tcp packet to primary from secondary make tcp packet can be handled by client. Dump the network traffic on netdev dev to the file specified by filename.
At most len bytes 64k by default per packet are stored. The file format is libpcap, so it can be analyzed with tools such as tcpdump or Wireshark. If the packets are same, we will output primary packet to outdev chardevid , else we will notify colo-frame do checkpoint and send primary packet to outdev chardevid. In order to improve efficiency, we need to put the task of comparison in another thread. The id parameter is a unique ID that will be used to reference this cryptodev backend from the virtio-crypto device.
The queues parameter is optional, which specify the queue number of cryptodev backend, the default of queues is 1. Creates a vhost-user cryptodev backend, backed by a chardev chardevid. The queues parameter is optional, which specify the queue number of cryptodev backend for multiqueue vhost-user, the default of queues is 1. Defines a secret to store a password, encryption key, or some other sensitive data. The sensitive data can either be passed directly via the data parameter, or indirectly via the file parameter. Using the data parameter is insecure unless the sensitive data is encrypted.
The sensitive data can be provided in raw format the default , or base QEMU will convert from which ever format is provided to the format it needs internally. Use of encryption is indicated by providing the keyid and iv parameters. The keyid parameter provides the ID of a previously defined secret that contains the AES decryption key. This key should be bytes long and be base64 encoded. The iv parameter provides the random initialization vector used for encryption of this particular secret and should be a base64 encrypted string of the byte IV.
To illustrate usage, consider the openssl command line tool which can encrypt the data. Each secret to be encrypted needs to have a random initialization vector generated. These do not need to be kept secret. When launching QEMU, create a master secret pointing to key. Pass the contents of iv. When memory encryption is enabled, one of the physical address bit aka the C-bit is utilized to mark if a memory page is protected.
The cbitpos is used to provide the C-bit position. The C-bit position is Host family dependent hence user must provide this value. On EPYC, the value should be When memory encryption is enabled, we loose certain bits in physical address space. The reduced-phys-bits is used to provide the number of bits we loose in physical address space. Similar to C-bit, the value is Host family dependent. On EPYC, the value should be 5. The policy provides the guest policy to be enforced by the SEV firmware and restrict what configuration and operational commands can be performed on this guest by the hypervisor.
The policy should be provided by the guest owner and is bound to the guest and cannot be changed throughout the lifetime of the guest. The default is 0. If guest policy allows sharing the key with another SEV guest then handle can be use to provide handle of the guest from which to share the key.
The PDH and session parameters are used for establishing a cryptographic session with the guest owner to negotiate keys used for attestation. The file must be encoded in base The identity parameter is identifies the user and its format depends on the network service that authorization object is associated with. For authorizing based on TLS x certificates, the identity must be the x distinguished name. Note that care must be taken to escape any commas in the distinguished name. The filename parameter is the fully qualified path to a file containing the access control list rules in JSON format.
When checking access the object will iterate over all the rules and the first rule to match will have its policy value returned as the result. If no rules match, then the default policy value is returned. The rules can either be an exact string match, or they can use the simple UNIX glob pattern matching to allow wildcards to be used. If refresh is set to true the file will be monitored and automatically reloaded whenever its content changes.
As with the authz-simple object, the format of the identity strings being matched depends on the network service, but is usually a TLS x distinguished name, or a SASL username. The service parameter provides the name of a PAM service to use for authorization. These are specified using a special URL syntax. Both disk and cdrom images are supported. Since version Qemu 2. The timeout is specified in seconds. The default is 0 which means no timeout. Libiscsi 1. Currently authentication must be done using ssh-agent. Other authentication methods may be supported in future.
Sheepdog is a distributed storage system for QEMU. QEMU supports using either local sheepdog devices or remote networked devices.
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GlusterFS is a user space distributed file system. The amount of data to read ahead with each range request to the remote server. If it does not have a suffix, it will be assumed to be in bytes. The value must be a multiple of bytes. It defaults to k. Only supported when using protocols such as HTTP which support cookies, otherwise ignored. Set the timeout in seconds of the CURL connection. This timeout is the time that CURL waits for a response from the remote server to get the size of the image to be downloaded. If not set, the default timeout of 5 seconds is used.
Example: boot from a remote Fedora 20 cloud image using a local overlay for writes, copy-on-read, and a readahead of 64k. Example: boot from an image stored on a VMware vSphere server with a self-signed certificate using a local overlay for writes, a readahead of 64k and a timeout of 10 seconds. During the graphical emulation, you can use special key combinations to change modes.
The default key mappings are shown below, but if you use -alt-grab then the modifier is Ctrl-Alt-Shift instead of Ctrl-Alt and if you use -ctrl-grab then the modifier is the right Ctrl key instead of Ctrl-Alt :. During emulation, if you are using a character backend multiplexer which is the default if you are using -nographic then several commands are available via an escape sequence.
These key sequences all start with an escape character, which is Ctrl-a by default, but can be changed with -echr. Rotate between the frontends connected to the multiplexer usually this switches between the monitor and the console. 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. 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. 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. Manually trigger completion of an active background block operation. For mirroring, this will switch the device to the destination path. Remove host block device. The result is that guest generated IO is no longer submitted against the host device underlying the disk. It accepts the following values:. Change the configuration of the VNC server.
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. Open, close, or flush the trace file. If no argument is given, the status of the trace file is displayed.
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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. Run the emulation in single step mode. If called with option off, the emulation returns to normal mode. On x86, h or w can be specified with the i format to respectively select 16 or 32 bit code instruction size.
Send keys to the guest.
Use - to press several keys simultaneously. This command is useful to send keys that your graphical user interface intercepts at low level, such as ctrl-alt-f1 in X Window. Enable, disable or reset synchronization profiling. With no arguments, prints whether profiling is on or off.
Move the active mouse to the specified coordinates dx dy with optional scroll axis dz. Capture audio into filename. Using sample rate frequency bits per sample bits and number of channels channels. 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.
Write data to ring buffer character device device. Read and print up to size bytes from ring buffer character device device. 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. 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 to uri using -d to not wait for completion. Continue an incoming migration using the uri that has the same syntax as the -incoming option.
Switch in-progress migration to postcopy mode. Ignored after the end of migration or once already in postcopy. Set migration information for remote display. This makes the server ask the client to automatically reconnect using the new parameters once migration finished successfully. Dump guest memory to protocol. The file can be processed with crash or gdb. Without -z -l -s -w, the dump format is ELF. List all the matching rules in the access control list, and the default policy. There are currently two named access control lists, vnc.
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. Add a match rule to the access control list, allowing or denying access. The match will normally be an exact username or x distinguished name, but can optionally include wildcard globs. 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.
Remove all matches from the access control list, and set the default policy back to deny. The -w option makes the exported device writable too. The export name is controlled by name , defaulting to device. 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.
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. Use zero to make the password stay valid forever. Password is invalidated at the given time. Add CPU with id id. Set QOM property property of object at location path to value value. Show synchronization profiling info, up to max entries default: 10 , sorted by total wait time.
The monitor understands integers expressions for every integer argument.
Increase number of visible lines in cmd
This passes the host CPU model features, model, stepping, exactly to the guest. This is the recommended CPU to use, provided live migration is not required. These allow the guest VMs to have a degree of isolation from the host CPU, allowing greater flexibility in live migrating between hosts with differing hardware.
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