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virt-df - Display free space on virtual filesystems

 virt-df [--options]

 virt-df [--options] -d domname

 virt-df [--options] -a disk.img [-a disk.img ...]

Old style:

 virt-df [--options] domname

 virt-df [--options] disk.img [disk.img ...]

virt-df is a command line tool to display free space on virtual machine filesystems. Unlike other tools, it doesn't just display the size of disk allocated to a virtual machine, but can look inside disk images to see how much space is really being used.

If used without any -a or -d arguments, virt-df checks with libvirt to get a list of all active and inactive guests, and performs a df-type operation on each one in turn, printing out the results.

If any -a or -d arguments are specified, virt-df performs a df-type operation on either the single named libvirt domain, or on the disk image(s) listed on the command line (which must all belong to a single VM). In this mode (with arguments), virt-df will only work for a single guest. If you want to run on multiple guests, then you have to invoke virt-df multiple times.

Use the --csv option to get a format which can be easily parsed by other programs. Other options are similar to the standard df(1) command.

Show disk usage for a single libvirt guest called F14x64. Make the output human-readable:

 # virt-df -d F14x64 -h
 Filesystem                       Size     Used  Available  Use%
 F14x64:/dev/sda1                 484M      66M       393M   14%
 F14x64:/dev/vg_f13x64/lv_root    7.4G     3.4G       4.0G   46%

Show disk usage for a disk image file called test.img:

 $ virt-df -a test1.img
 Filesystem                  1K-blocks     Used  Available  Use%
 test1.img:/dev/sda1             99099     1551      92432    2%

Display brief help.

Add file which should be a disk image from a virtual machine. If the virtual machine has multiple block devices, you must supply all of them with separate -a options.

The format of the disk image is auto-detected. To override this and force a particular format use the --format=.. option.

If using libvirt, connect to the given URI. If omitted, then we connect to the default libvirt hypervisor.

If you specify guest block devices directly (-a), then libvirt is not used at all.

Write out the results in CSV format (comma-separated values). This format can be imported easily into databases and spreadsheets, but read "NOTE ABOUT CSV FORMAT" below.

Add all the disks from the named libvirt guest. Domain UUIDs can be used instead of names.

The default for the -a option is to auto-detect the format of the disk image. Using this forces the disk format for -a options which follow on the command line. Using --format with no argument switches back to auto-detection for subsequent -a options.

For example:

 virt-df --format=raw -a disk.img

forces raw format (no auto-detection) for disk.img.

 virt-df --format=raw -a disk.img --format -a another.img

forces raw format (no auto-detection) for disk.img and reverts to auto-detection for another.img.

If you have untrusted raw-format guest disk images, you should use this option to specify the disk format. This avoids a possible security problem with malicious guests (CVE-2010-3851).

Print sizes in human-readable format.

You are not allowed to use -h and --csv at the same time.

Print inodes instead of blocks.

Run one libguestfs appliance per guest. Normally virt-df will add the disks from several guests to a single libguestfs appliance.

You might use this option in the following circumstances:

  • If you think an untrusted guest might actively try to exploit the libguestfs appliance kernel, then this prevents one guest from interfering with the stats printed for another guest.
  • If the kernel has a bug which stops it from accessing a filesystem in one guest (see for example RHBZ#635373) then this allows libguestfs to continue and report stats for further guests.

Print UUIDs instead of names. This is useful for following a guest even when the guest is migrated or renamed, or when two guests happen to have the same name.

Note that only domains that we fetch from libvirt come with UUIDs. For disk images, we still print the disk image name even when this option is specified.

Enable verbose messages for debugging.

Display version number and exit.

Enable tracing of libguestfs API calls.

virt-df (and df(1)) get information by issuing a statvfs(3) system call. You can get the same information directly, either from the host (using libguestfs) or inside the guest:

Run this command:

 guestfish --ro -d GuestName -i statvfs /

(change / to see stats for other filesystems).

Run this command:

 python -c 'import os; s = os.statvfs ("/"); print s'

(change / to see stats for other filesystems).

Comma-separated values (CSV) is a deceptive format. It seems like it should be easy to parse, but it is definitely not easy to parse.

Myth: Just split fields at commas. Reality: This does not work reliably. This example has two columns:

 "foo,bar",baz

Myth: Read the file one line at a time. Reality: This does not work reliably. This example has one row:

 "foo
 bar",baz

For shell scripts, use csvtool (http://merjis.com/developers/csv also packaged in major Linux distributions).

For other languages, use a CSV processing library (eg. Text::CSV for Perl or Python's built-in csv library).

Most spreadsheets and databases can import CSV directly.

Libvirt guest names can contain arbitrary characters, some of which have meaning to the shell such as # and space. You may need to quote or escape these characters on the command line. See the shell manual page sh(1) for details.

This program returns 0 if successful, or non-zero if there was an error.

df(1), guestfs(3), guestfish(1), virt-filesystems(1), http://libguestfs.org/.

Richard W.M. Jones http://people.redhat.com/~rjones/

Copyright (C) 2009-2012 Red Hat Inc.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

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