3 virt-uname - system information for virtual machines
5 virt-dmesg - print kernel messages for virtual machines
7 virt-mem - tool with additional information output
11 virt-uname [-options] [domains...]
13 virt-dmesg [-options] [domains...]
23 These virtualization tools allow you to inspect the status of virtual
24 machines running Linux.
26 These tools are designed to work like familiar Linux/Unix command line
29 These tools all use libvirt so are capable of showing information
30 across a variety of different virtualization systems.
32 The virt-mem tools do not work on domains which are not active
33 (running or paused). eg. They do not work on shut down domains.
34 However they can (usually) be used on domains which are active but
35 hanging or unresponsive. You also have the option of capturing a
36 memory image of a domain for post-mortem analysis, allowing you to
37 quickly reboot a failed domain and analyze it later at your leisure.
41 Each command obeys a common set of options. The general form is:
43 virt-I<program> [-options] [domains...]
45 where I<program> is a subtool such as C<uname>, C<dmesg> or C<ps>, and
46 I<domains> is a list of guest names to act on. If no domains are
47 specified then we act on all active domains by default.
49 A I<domain> may be specified either by its name, by its ID or by its
50 UUID. Use I<virsh list> to get a list of active domain names and IDs.
52 Equivalently you can use the C<virt-mem> meta-tool with subcommands,
55 virt-mem I<program> [...]
57 The C<virt-mem> program offers additional features, such as the
58 ability to capture VM images for post-mortem analysis (see below).
62 =item B<-c uri>, B<--connect uri>
64 Connect to libvirt URI. The default is to connect to the default
65 libvirt URI, normally Xen.
69 Print the results in CSV format, suitable for importing into a
70 spreadsheet or database.
72 This option is only supported if virt-mem was built with CSV support.
76 Emit debugging information on stderr. Please supply this if you
81 Display usage summary.
83 =item B<-t memoryimage>
85 Post-mortem analysis mode.
87 Instead of checking libvirt for domain information, this runs the tool
88 directly on the memory image supplied. You may specify the B<-t>
89 option multiple times. Use the C<virt-mem capture> command to capture
92 See also the section L</"MEMORY IMAGES"> below.
96 Display version and exit.
98 =item B<-E auto|littleendian|bigendian>
100 =item B<-T auto|i386|x86-64|I<address>>
102 =item B<-W auto|32|64>
104 These options force the endianness, text address, and word size for
105 the subsequent domains listed on the command line (or if no domains
106 are listed, then for all domains).
108 These default to I<auto> which tries to do automatic detection (using
109 libvirt, or details from the memory images themselves). You only need
110 to use these options if virt-mem tools get the automatic detection
113 Endianness (I<-E>) sets the memory endianness, for data, pointers and
114 so on. I<-E littleendian> is the endianness used on Intel i386,
115 x86-64 and (usually) IA64. I<-E bigendian> is the endianness used on
116 many RISC chips such as SPARC and PowerPC.
118 Text address (I<-T>) sets the base address of the kernel image. I<-T
119 i386> means to try some common addresses for i386-based kernels. I<-T
120 x86-64> means to try some common addresses for x86-64-based kernels.
121 I<-T I<address>> sets the address specifically (I<0x> prefix is used
122 to specify hex addresses).
124 Word size (I<-W>) sets the word size, 32 or 64 bits.
126 =item B<-A auto|i386|x86-64|...>
128 This option sets the architecture to one of a collection of known
129 architectures. It is equivalent to setting endianness and wordsize in
130 one go, but not text address.
136 This prints the latest kernel messages from the virtual machine, as if
137 you were logged into the machine and used L<dmesg(1)>.
141 This prints the contents of the system C<utsname> structure, similar
142 to what is printed by the L<uname(1)> command.
146 C<virt-mem> is a meta-tool which allows you to run all the commands
147 above, and provides some extra features.
149 Instead of the preceeding commands such as C<virt-dmesg> you can
154 Options and other command line arguments work the same.
156 Additional C<virt-mem> subcommands are listed below.
158 =head2 virt-mem capture -o memoryimage [-options] [domains...]
160 Capture the memory image of a virtual machine for later post-mortem
161 analysis. Use the I<-t memoryimage> option for any other virt-mem
162 tool to analyze the memory image later.
164 The I<-o memoryimage> option is required, and is used to name the
165 output file. If a single guest is captured, then the output is saved
166 in the I<memoryimage> file. However, if multiple guests are captured,
167 then their images are saved in I<memoryimage.ID> where I<ID> is
168 replaced with the domain ID.
170 See also the section L</"MEMORY IMAGES"> below.
175 f9x32kvm: Linux localhost.localdomain 2.6.24-0.155.rc7.git6.fc9 #1
176 SMP Tue Jan 15 17:52:31 EST 2008 i686 (none)
178 # virt-dmesg f9x32kvm | tail
179 <6>Bluetooth: Core ver 2.11
180 <6>NET: Registered protocol family 31
181 <6>Bluetooth: HCI device and connection manager initialized
182 <6>Bluetooth: HCI socket layer initialized
183 <6>Bluetooth: L2CAP ver 2.9
184 <6>Bluetooth: L2CAP socket layer initialized
185 <6>Bluetooth: RFCOMM socket layer initialized
186 <6>Bluetooth: RFCOMM TTY layer initialized
187 <6>Bluetooth: RFCOMM ver 1.8
188 <7>eth0: no IPv6 routers present
192 All the tools can read dumped kernel images, using the common
193 I<-t memoryimage> option. In addition you can capture memory
194 images from domains for post-mortem analysis using the
195 C<virt-mem capture> command (see above).
197 The memory images which are saved by C<virt-mem capture> contain a
198 header and some additional information about the kernel image, such as
199 architecture, original text address, and so forth. Thus these images
200 can be reanalysed just using the I<-t memoryimage> option.
202 We also support analyzing raw kernel dumps, eg. produced using the
203 L<qemu(1)> monitor's C<memsave> command. In this case however you
204 usually need to specify the original architecture, text address and
205 perhaps other details using the I<-A>, I<-T> and other command line
210 The virt-mem tools spy on the guest's memory image. There are some
211 shortcomings to this, described here.
217 Only works on specific, tested releases of Linux kernels. Support
218 for arbitrary Linux kernel versions may be patchy because of changes
219 in the internal structures used. Support for non-Linux kernels is
220 currently non-existent, and probably impossible for Windows because of
221 lack of an acceptable source license.
225 Heuristics are used which may mean in the worst case that the
230 Structures which are frequently modified may cause errors. This
231 could be a problem if, for example, the process table in the guest is
232 being rapidly updated.
236 We have to scan memory to find kernel symbols, etc., which can be
237 quite slow. Optimizing the memory scanner would help, and caching the
238 base address of the symbol table(s) would make it dramatically faster.
244 The current code tries hard to be secure against malicious guests, for
245 example guests which set up malicious kernel memory.
256 L<http://www.libvirt.org/ocaml/>,
257 L<http://www.libvirt.org/>,
258 L<http://et.redhat.com/~rjones/>,
259 L<http://caml.inria.fr/>
263 Richard W.M. Jones <rjones @ redhat . com>
267 (C) Copyright 2008 Red Hat Inc., Richard W.M. Jones
270 This program is free software; you can redistribute it and/or modify
271 it under the terms of the GNU General Public License as published by
272 the Free Software Foundation; either version 2 of the License, or
273 (at your option) any later version.
275 This program is distributed in the hope that it will be useful,
276 but WITHOUT ANY WARRANTY; without even the implied warranty of
277 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
278 GNU General Public License for more details.
280 You should have received a copy of the GNU General Public License
281 along with this program; if not, write to the Free Software
282 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
284 =head1 REPORTING BUGS
286 Bugs can be viewed on the Red Hat Bugzilla page:
287 L<https://bugzilla.redhat.com/>.
289 If you find a bug in virt-mem, please follow these steps to report it:
293 =item 1. Check for existing bug reports
295 Go to L<https://bugzilla.redhat.com/> and search for similar bugs.
296 Someone may already have reported the same bug, and they may even
299 =item 2. Capture debug and error messages
303 virt-I<program> --debug > virt-mem.log 2>&1
305 and keep I<virt-mem.log>. It contains error messages which you should
306 submit with your bug report.
308 =item 3. Get version of virt-mem and version of libvirt.
312 virt-I<program> --version
314 =item 4. Submit a bug report.
316 Go to L<https://bugzilla.redhat.com/> and enter a new bug.
317 Please describe the problem in as much detail as possible.
319 Remember to include the version numbers (step 3) and the debug
320 messages file (step 2).
322 =item 5. Assign the bug to rjones @ redhat.com
324 Assign or reassign the bug to B<rjones @ redhat.com> (without the
325 spaces). You can also send me an email with the bug number if you
326 want a faster response.