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virt-df

NAME

virt-df - 'df'-like utility for virtualization stats

SUMMARY

virt-df [-options]

DESCRIPTION

virt-df is a df(1)-like utility for showing the actual disk usage of guests. Many command line options are the same as for ordinary df.

It uses libvirt so it is capable of showing stats across a variety of different virtualization systems.

OPTIONS

-a, --all

Show all domains. The default is show only running (active) domains.

-c uri, --connect uri

Connect to libvirt URI. The default is to connect to the default libvirt URI, normally Xen.

--csv

Print the results in CSV format, suitable for importing into a spreadsheet or database.

This option is only supported if virt-df was built with CSV support.

--debug

Emit debugging information on stderr. Please supply this if you report a bug.

-h, --human-readable

Display human-readable sizes (eg. ``10GiB'' instead of large numbers).

-i, --inodes

Display inode information.

This option only works for Unix-like filesystems.

--help

Display usage summary.

-t diskimage

Test mode. Instead of checking libvirt for domain information, this runs virt-df directly on the disk image (or device) supplied. You may specify the -t option multiple times.

--version

Display version and exit.

EXAMPLE

  # virt-df 
  Filesystem                1K-blocks    Used Available Type
  f9x32kvm:hda1                190740   24817    165923 Linux ext2/3
  f9x32kvm:VolGroup/LogVol00  6568348 3401656   3166692 Linux ext2/3
  f9x32kvm:VolGroup/LogVol01  1015808                   Linux swap
 
 

SHORTCOMINGS

virt-df spies on the guest's disk image to try to work out how much disk space it is actually using. There are some shortcomings to this, described here.

(1) It only understands a limited set of partition types. Assuming that the files and partitions that we get back from libvirt / Xen correspond to block devices in the guests, we can go some way towards manually parsing those partitions to find out what they contain. We can read the MBR, LVM, superblocks and so on. However that's a lot of parsing work, and currently there is no library which understands a wide range of partition schemes and filesystem types (not even libparted which doesn't support LVM yet). The Linux kernel does support that, but there's not really any good way to access that work.

The current implementation uses a hand-coded parser which understands some formats (MBR, LVM2, ext2/3, DOS FAT, Windows NTFS, Linux swap and Linux suspend partitions).

(2) The statistics you get are delayed. The real state of, for example, an ext2 filesystem is only stored in the memory of the guest's kernel. The ext2 superblock contains some meta-information about blocks used and free, but this superblock is not up to date. In fact the guest kernel may not update it even on a 'sync', not until the filesystem is unmounted. Some operations do appear to write the superblock, for example fsync(2) [that is my reading of the ext2/3 source code at least].

SECURITY

The current code tries hard to be secure against malicious guests, for example guests which set up malicious disk partitions.

SEE ALSO

df(1), virsh(1), xm(1), <http://www.libvirt.org/ocaml/>, <http://www.libvirt.org/>, <http://et.redhat.com/~rjones/>, <http://caml.inria.fr/>

AUTHORS

Richard W.M. Jones <rjones @ redhat . com>

COPYRIGHT

(C) Copyright 2007-2008 Red Hat Inc., Richard W.M. Jones http://libvirt.org/

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., 675 Mass Ave, Cambridge, MA 02139, USA.

REPORTING BUGS

Bugs can be viewed on the Red Hat Bugzilla page: <https://bugzilla.redhat.com/>.

If you find a bug in virt-df, please follow these steps to report it:

1. Check for existing bug reports

Go to <https://bugzilla.redhat.com/> and search for similar bugs. Someone may already have reported the same bug, and they may even have fixed it.

2. Capture debug and error messages

Run

  virt-df --debug > virt-df.log 2>&1
 
 

and keep virt-df.log. It contains error messages which you should submit with your bug report.

3. Get version of virt-df and version of libvirt.

Run

  virt-df --version
 
 

4. Submit a bug report.

Go to <https://bugzilla.redhat.com/> and enter a new bug. Please describe the problem in as much detail as possible.

Remember to include the version numbers (step 3) and the debug messages file (step 2).

5. Assign the bug to rjones @ redhat.com

Assign or reassign the bug to rjones @ redhat.com (without the spaces). You can also send me an email with the bug number if you want a faster response.