2 virt-df - 'df'-like utility for virtualization stats
8 virt-df is a df(1)-like utility for showing the actual disk usage of
9 guests. Many command line options are the same as for ordinary *df*.
11 It uses libvirt so it is capable of showing stats across a variety of
12 different virtualization systems.
14 There are some shortcomings to the whole approach of reading disk state
15 from outside the guest. Please read SHORTCOMINGS section below for more
20 Show all domains. The default is show only running (active) domains.
23 Connect to libvirt URI. The default is to connect to the default
24 libvirt URI, normally Xen.
27 Emit debugging information on stderr. Please supply this if you
31 Display human-readable sizes (eg. 10GiB).
34 Display inode information.
37 Display usage summary.
40 Test mode. Instead of checking libvirt for domain information, this
41 runs virt-df directly on the disk image (or device) supplied. You
42 may specify the -t option multiple times.
45 Display version and exit.
48 virt-df spies on the guest's disk image to try to work out how much disk
49 space it is actually using. There are some shortcomings to this,
52 (1) It does not work over remote connections. The storage API does not
53 support peeking into remote disks, and libvirt has rejected a request to
56 (2) It only understands a limited set of partition types. Assuming that
57 the files and partitions that we get back from libvirt / Xen correspond
58 to block devices in the guests, we can go some way towards manually
59 parsing those partitions to find out what they contain. We can read the
60 MBR, LVM, superblocks and so on. However that's a lot of parsing work,
61 and currently there is no library which understands a wide range of
62 partition schemes and filesystem types (not even libparted which doesn't
63 support LVM yet). The Linux kernel does support that, but there's not
64 really any good way to access that work.
66 The current implementation uses a hand-coded parser which understands
67 some simple formats (MBR, LVM2, ext2/3). In future we should use
68 something like libparted.
70 (3) The statistics you get are delayed. The real state of, for example,
71 an ext2 filesystem is only stored in the memory of the guest's kernel.
72 The ext2 superblock contains some meta-information about blocks used and
73 free, but this superblock is not up to date. In fact the guest kernel
74 may not update it even on a 'sync', not until the filesystem is
75 unmounted. Some operations do appear to write the superblock, for
76 example fsync(2) [that is my reading of the ext2/3 source code at
80 The current code tries hard to be secure against malicious guests, for
81 example guests which set up malicious disk partitions.
84 df(1), virsh(1), xm(1), <http://www.libvirt.org/ocaml/>,
85 <http://www.libvirt.org/>, <http://et.redhat.com/~rjones/>,
86 <http://caml.inria.fr/>
89 Richard W.M. Jones <rjones @ redhat . com>
92 (C) Copyright 2007-2008 Red Hat Inc., Richard W.M. Jones
95 This program is free software; you can redistribute it and/or modify it
96 under the terms of the GNU General Public License as published by the
97 Free Software Foundation; either version 2 of the License, or (at your
98 option) any later version.
100 This program is distributed in the hope that it will be useful, but
101 WITHOUT ANY WARRANTY; without even the implied warranty of
102 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
103 Public License for more details.
105 You should have received a copy of the GNU General Public License along
106 with this program; if not, write to the Free Software Foundation, Inc.,
107 675 Mass Ave, Cambridge, MA 02139, USA.
110 Bugs can be viewed on the Red Hat Bugzilla page:
111 <https://bugzilla.redhat.com/>.
113 If you find a bug in virt-df, please follow these steps to report it:
115 1. Check for existing bug reports
116 Go to <https://bugzilla.redhat.com/> and search for similar bugs.
117 Someone may already have reported the same bug, and they may even
120 2. Capture debug and error messages
123 virt-df --debug > virt-df.log 2>&1
125 and keep *virt-df.log*. It contains error messages which you should
126 submit with your bug report.
128 3. Get version of virt-df and version of libvirt.
133 4. Submit a bug report.
134 Go to <https://bugzilla.redhat.com/> and enter a new bug. Please
135 describe the problem in as much detail as possible.
137 Remember to include the version numbers (step 3) and the debug
138 messages file (step 2).
140 5. Assign the bug to rjones @ redhat.com
141 Assign or reassign the bug to rjones @ redhat.com (without the
142 spaces). You can also send me an email with the bug number if you
143 want a faster response.