16.7.2. Running virt-df
To display file system usage for all file systems found in a disk image, enter the following:
# virt-df /dev/vg_guests/RHEL6 Filesystem 1K-blocks Used Available Use% RHEL6:/dev/sda1 101086 10233 85634 11% RHEL6:/dev/VolGroup00/LogVol00 7127864 2272744 4493036 32%
(Where
/dev/vg_guests/RHEL6 is a Red Hat Enterprise Linux 6 guest virtual machine disk image. The path in this case is the host physical machine logical volume where this disk image is located.)
You can also use
virt-df on its own to list information about all of your guest virtual machines (ie. those known to libvirt). The virt-df command recognizes some of the same options as the standard df such as -h (human-readable) and -i (show inodes instead of blocks).
virt-df also works on Windows guest virtual machines:
# virt-df -h
Filesystem Size Used Available Use%
F14x64:/dev/sda1 484.2M 66.3M 392.9M 14%
F14x64:/dev/vg_f14x64/lv_root 7.4G 3.0G 4.4G 41%
RHEL6brewx64:/dev/sda1 484.2M 52.6M 406.6M 11%
RHEL6brewx64:/dev/vg_rhel6brewx64/lv_root
13.3G 3.4G 9.2G 26%
Win7x32:/dev/sda1 100.0M 24.1M 75.9M 25%
Win7x32:/dev/sda2 19.9G 7.4G 12.5G 38%
Note
You can use
virt-df safely on live guest virtual machines, since it only needs read-only access. However, you should not expect the numbers to be precisely the same as those from a df command running inside the guest virtual machine. This is because what is on disk will be slightly out of synch with the state of the live guest virtual machine. Nevertheless it should be a good enough approximation for analysis and monitoring purposes.
virt-df is designed to allow you to integrate the statistics into monitoring tools, databases and so on. This allows system administrators to generate reports on trends in disk usage, and alerts if a guest virtual machine is about to run out of disk space. To do this you should use the
--csv option to generate machine-readable Comma-Separated-Values (CSV) output. CSV output is readable by most databases, spreadsheet software and a variety of other tools and programming languages. The raw CSV looks like the following:
# virt-df --csv WindowsGuest Virtual Machine,Filesystem,1K-blocks,Used,Available,Use% Win7x32,/dev/sda1,102396,24712,77684,24.1% Win7x32,/dev/sda2,20866940,7786652,13080288,37.3%
For resources and ideas on how to process this output to produce trends and alerts, refer to the following URL: http://libguestfs.org/virt-df.1.html.
