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20.12. Retrieving Information about Your Virtual Machine

20.12.1. Displaying Device Block Statistics
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By default, the virsh domblkstat command displays the block statistics for the first block device defined for the domain. To view statistics of other block devices, use the virsh domblklist domain command to list all block devices, and then select a specific block device and display it by specifying either the Target or Source name from the virsh domblklist command output after the domain name. Note that not every hypervisor can display every field. To make sure that the output is presented in its most legible form use the --human argument.

Example 20.21. How to display block statistics for a guest virtual machine

The following example displays the devices that are defined for the guest1 virtual machine, and then lists the block statistics for that device. 
# virsh domblklist guest1

Target     Source
------------------------------------------------
vda        /VirtualMachines/guest1.img
hdc        -

# virsh domblkstat guest1 vda --human
Device: vda
 number of read operations:      174670
 number of bytes read:           3219440128
 number of write operations:     23897
 number of bytes written:        164849664
 number of flush operations:     11577
 total duration of reads (ns):   1005410244506
 total duration of writes (ns):  1085306686457
 total duration of flushes (ns): 340645193294
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20.12.2. Retrieving Network Interface Statistics
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The virsh domifstat domain interface-device command displays the network interface statistics for the specified device running on a given guest virtual machine.
To determine which interface devices are defined for the domain, use the virsh domiflist command and use the output in the Interface column.

Example 20.22. How to display networking statistics for a guest virtual machine

The following example obtains the networking interface defined for the guest1 virtual machine, and then displays the networking statistics on the obtained interface (macvtap0): 
# virsh domiflist guest1
Interface  Type       Source     Model       MAC
-------------------------------------------------------
macvtap0   direct     em1        rtl8139     12:34:00:0f:8a:4a
# virsh domifstat guest1 macvtap0
macvtap0 rx_bytes 51120
macvtap0 rx_packets 440
macvtap0 rx_errs 0
macvtap0 rx_drop 0
macvtap0 tx_bytes 231666
macvtap0 tx_packets 520
macvtap0 tx_errs 0
macvtap0 tx_drop 0
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20.12.5. Setting Network Interface Bandwidth Parameters
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The virsh domiftune domain interface-device command either retrieves or sets the specified domain's interface bandwidth parameters. To determine which interface devices are defined for the domain, use the virsh domiflist command and use either the Interface or MAC column as the interface device option. The following format should be used: 
# virsh domiftune domain interface [--inbound] [--outbound] [--config] [--live] [--current]
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The --config, --live, and --current options are described in Section 20.43, “Setting Schedule Parameters”. If the --inbound or the --outbound option is not specified, virsh domiftune queries the specified network interface and displays the bandwidth settings. By specifying --inbound or --outbound, or both, and the average, peak, and burst values, virsh domiftune sets the bandwidth settings. At minimum the average value is required. In order to clear the bandwidth settings, provide 0 (zero). For a description of the average, peak, and burst values, see Section 20.27.6.2, “Attaching interface devices”.

Example 20.25. How to set the guest virtual machine network interface parameters

The following example sets eth0 parameters for the guest virtual machine named guest1: 
# virsh domiftune guest1 eth0 outbound --live
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20.12.6. Retrieving Memory Statistics
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The virsh dommemstat domain [<period in seconds>] [--config] [--live] [--current] command displays the memory statistics for a running guest virtual machine. Using the optional period switch requires a time period in seconds. Setting this option to a value larger than 0 will allow the balloon driver to return additional statistics which will be displayed by running subsequent dommemstat commands. Setting the period option to 0, stops the balloon driver collection but does not clear the statistics already in the balloon driver. You cannot use the --live, --config, or --current options without also setting the period option. If the --live option is specified, only the guest's running statistics will be collected. If the --config option is used, it will collect the statistics for a persistent guest, but only after the next boot. If the --current option is used, it will collect the current statistics.
Both the --live and --config options may be used but --current is exclusive. If no flag is specified, the guest's state will dictate the behavior of the statistics collection (running or not).

Example 20.26. How to collect memory statistics for a running guest virtual machine

The following example shows displaying the memory statistics in the rhel7 domain: 
# virsh dommemstat rhel7
actual 1048576
swap_in 0
swap_out 0
major_fault 2974
minor_fault 1272454
unused 246020
available 1011248
rss 865172
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20.12.7. Displaying Errors on Block Devices
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The virsh domblkerror domain command lists all the block devices in the error state and the error detected on each of them. This command is best used after a virsh domstate command reports that a guest virtual machine is paused due to an I/O error.

Example 20.27. How to display the block device errors for a virtual machine

The following example displays the block device errors for the guest1 virtual machine: 
# virsh domblkerror guest1
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20.12.8. Displaying the Block Device Size
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The virsh domblkinfo domain command lists the capacity, allocation, and physical block sizes for a specific block device in the virtual machine. Use the virsh domblklist command to list all block devices and then choose to display a specific block device by specifying either the Target or Source name from the virsh domblklist output after the domain name.

Example 20.28. How to display the block device size

In this example, you list block devices on the rhel7 virtual machine, and then display the block size for each of the devices. 
# virsh domblklist rhel7
Target     Source
------------------------------------------------
vda        /home/vm-images/rhel7-os
vdb        /home/vm-images/rhel7-data

# virsh domblkinfo rhel7 vda
Capacity:       10737418240
Allocation:     8211980288
Physical:       10737418240

# virsh domblkinfo rhel7 /home/vm-images/rhel7-data
Capacity:       104857600
Allocation:     104857600
Physical:       104857600
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20.12.9. Displaying the Block Devices Associated with a Guest Virtual Machine
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The virsh domblklist domain [--inactive] [--details] command displays a table of all block devices that are associated with the specified guest virtual machine.
If --inactive is specified, the result will show the devices that are to be used at the next boot and will not show those that are currently running in use by the running guest virtual machine. If --details is specified, the disk type and device value will be included in the table. The information displayed in this table can be used with other commands that require a block-device to be provided, such as virsh domblkinfo and virsh snapshot-create. The disk Target or Source contexts can also be used when generating the xmlfile context information for the virsh snapshot-create command.

Example 20.29. How to display the block devices that are associated with a virtual machine

The following example displays details about block devices associated with the rhel7 virtual machine. 
# virsh domblklist rhel7 --details
Type       Device     Target     Source
------------------------------------------------
file       disk       vda        /home/vm-images/rhel7-os
file       disk       vdb        /home/vm-images/rhel7-data
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The virsh domblklist domain command displays a table of all the virtual interfaces that are associated with the specified domain. The virsh domiflist command requires the name of the virtual machine (or domain), and optionally can take the --inactive argument. The latter retrieves the inactive rather than the running configuration, which is retrieved with the default setting. If --inactive is specified, the result shows devices that are to be used at the next boot, and does not show devices that are currently in use by the running guest. Virsh commands that require a MAC address of a virtual interface (such as detach-interface, domif-setlink, domif-getlink, domifstat, and domiftune) accept the output displayed by this command.

Example 20.30. How to display the virtual interfaces associated with a guest virtual machine

The following example displays the virtual interfaces that are associated with the rhel7 virtual machine, and then displays the network interface statistics for the vnet0 device. 
# virsh domiflist rhel7
Interface  Type       Source     Model       MAC
-------------------------------------------------------
vnet0      network    default    virtio      52:54:00:01:1d:d0

# virsh domifstat rhel7 vnet0
vnet0 rx_bytes 55308
vnet0 rx_packets 969
vnet0 rx_errs 0
vnet0 rx_drop 0
vnet0 tx_bytes 14341
vnet0 tx_packets 148
vnet0 tx_errs 0
vnet0 tx_drop 0
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