2 virt-uname - system information for virtual machines
4 virt-dmesg - print kernel messages for virtual machines
6 virt-ps - list processes for virtual machines
8 virt-mem - tool with additional information output
11 virt-uname [-options] [domains...]
13 virt-dmesg [-options] [domains...]
15 virt-ps [-options] [domains...]
26 These virtualization tools allow you to inspect the status of virtual
27 machines running Linux.
29 These tools are designed to work like familiar Linux/Unix command line
32 These tools all use libvirt so are capable of showing information across
33 a variety of different virtualization systems.
35 The virt-mem tools do not work on domains which are not active (running
36 or paused). eg. They do not work on shut down domains. However they can
37 (usually) be used on domains which are active but hanging or
38 unresponsive. You also have the option of capturing a memory image of a
39 domain for post-mortem analysis, allowing you to quickly reboot a failed
40 domain and analyze it later at your leisure.
43 Each command obeys a common set of options. The general form is:
45 virt-*program* [-options] [domains...]
47 where *program* is a subtool such as "uname", "dmesg" or "ps", and
48 *domains* is a list of guest names to act on. If no domains are
49 specified then we act on all active domains by default.
51 A *domain* may be specified either by its name, by its ID or by its
52 UUID. Use *virsh list* to get a list of active domain names and IDs.
54 Equivalently you can use the "virt-mem" meta-tool with subcommands, as
57 virt-mem *program* [...]
59 The "virt-mem" program offers additional features, such as the ability
60 to capture VM images for post-mortem analysis (see below).
63 Connect to libvirt URI. The default is to connect to the default
64 libvirt URI, normally Xen.
67 Print the results in CSV format, suitable for importing into a
68 spreadsheet or database.
70 This option is only supported if virt-mem was built with CSV
74 Emit debugging information on stderr. Please supply this if you
78 Display usage summary.
81 Post-mortem analysis mode.
83 Instead of checking libvirt for domain information, this runs the
84 tool directly on the memory image supplied. You may specify the -t
85 option multiple times. Use the "virt-mem capture" command to capture
88 See also the section "MEMORY IMAGES" below.
91 Display version and exit.
93 -E auto|littleendian|bigendian
94 -T auto|i386|x86-64|*address*|*address,min,max*
96 These options force the endianness, text address, and word size for
97 the subsequent domains listed on the command line (or if no domains
98 are listed, then for all domains).
100 These default to *auto* which tries to do automatic detection (using
101 libvirt, or details from the memory images themselves). You only
102 need to use these options if virt-mem tools get the automatic
105 Endianness (*-E*) sets the memory endianness, for data, pointers and
106 so on. *-E littleendian* is the endianness used on Intel i386,
107 x86-64 and (usually) IA64. *-E bigendian* is the endianness used on
108 many RISC chips such as SPARC and PowerPC.
110 Text address (*-T*) sets the base address and optionally min and max
111 addresses of the kernel image. *-T i386* means to try some common
112 addresses for i386-based kernels. *-T x86-64* means to try some
113 common addresses for x86-64-based kernels.
115 *-T address* sets the kernel base address specifically (*0x* prefix
116 is used to specify hex addresses). *-T address,min,max* sets the
117 kernel base address, minimum address and maximum address.
119 Word size (*-W*) sets the word size, 32 or 64 bits.
121 -A auto|i386|x86-64|...
122 This option sets the architecture to one of a collection of known
123 architectures. It is equivalent to setting endianness and wordsize
124 in one go, but not text address.
127 This prints the latest kernel messages from the virtual machine, as if
128 you were logged into the machine and used dmesg(1).
131 This prints the contents of the system "utsname" structure, similar to
132 what is printed by the uname(1) command.
135 "virt-mem" is a meta-tool which allows you to run all the commands
136 above, and provides some extra features.
138 Instead of the preceeding commands such as "virt-dmesg" you can write:
142 Options and other command line arguments work the same.
144 Additional "virt-mem" subcommands are listed below.
146 virt-mem capture -o memoryimage [-options] [domains...]
147 Capture the memory image of a virtual machine for later post-mortem
148 analysis. Use the *-t memoryimage* option for any other virt-mem tool to
149 analyze the memory image later.
151 The *-o memoryimage* option is required, and is used to name the output
152 file. If a single guest is captured, then the output is saved in the
153 *memoryimage* file. However, if multiple guests are captured, then their
154 images are saved in *memoryimage.ID* where *ID* is replaced with the
157 See also the section "MEMORY IMAGES" below.
161 f9x32kvm: Linux localhost.localdomain 2.6.24-0.155.rc7.git6.fc9 #1
162 SMP Tue Jan 15 17:52:31 EST 2008 i686 (none)
164 # virt-dmesg f9x32kvm | tail
165 <6>Bluetooth: Core ver 2.11
166 <6>NET: Registered protocol family 31
167 <6>Bluetooth: HCI device and connection manager initialized
168 <6>Bluetooth: HCI socket layer initialized
169 <6>Bluetooth: L2CAP ver 2.9
170 <6>Bluetooth: L2CAP socket layer initialized
171 <6>Bluetooth: RFCOMM socket layer initialized
172 <6>Bluetooth: RFCOMM TTY layer initialized
173 <6>Bluetooth: RFCOMM ver 1.8
174 <7>eth0: no IPv6 routers present
177 All the tools can read dumped kernel images, using the common *-t
178 memoryimage* option. In addition you can capture memory images from
179 domains for post-mortem analysis using the "virt-mem capture" command
182 The memory images which are saved by "virt-mem capture" contain a header
183 and some additional information about the kernel image, such as
184 architecture, original text address, and so forth. Thus these images can
185 be reanalysed just using the *-t memoryimage* option.
187 We also support analyzing raw kernel dumps, eg. produced using the
188 qemu(1) monitor's "memsave" command. In this case however you usually
189 need to specify the original architecture, text address and perhaps
190 other details using the *-A*, *-T* and other command line parameters.
193 The virt-mem tools spy on the guest's memory image. There are some
194 shortcomings to this, described here.
196 * Only works on specific, tested releases of Linux kernels. Support
197 for arbitrary Linux kernel versions may be patchy because of changes
198 in the internal structures used. Support for non-Linux kernels is
199 currently non-existent, and probably impossible for Windows because
200 of lack of an acceptable source license.
202 * Heuristics are used which may mean in the worst case that the output
205 * Structures which are frequently modified may cause errors. This
206 could be a problem if, for example, the process table in the guest
207 is being rapidly updated.
209 * We have to scan memory to find kernel symbols, etc., which can be
210 quite slow. Optimizing the memory scanner would help, and caching
211 the base address of the symbol table(s) would make it dramatically
215 The current code tries hard to be secure against malicious guests, for
216 example guests which set up malicious kernel memory.
219 uname(1), dmesg(1), virsh(1), virt-top(1), virt-df(1), xm(1), qemu(1),
220 <http://www.libvirt.org/ocaml/>, <http://www.libvirt.org/>,
221 <http://et.redhat.com/~rjones/>, <http://caml.inria.fr/>
224 Richard W.M. Jones <rjones @ redhat . com>
227 (C) Copyright 2008 Red Hat Inc., Richard W.M. Jones http://libvirt.org/
229 This program is free software; you can redistribute it and/or modify it
230 under the terms of the GNU General Public License as published by the
231 Free Software Foundation; either version 2 of the License, or (at your
232 option) any later version.
234 This program is distributed in the hope that it will be useful, but
235 WITHOUT ANY WARRANTY; without even the implied warranty of
236 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
237 Public License for more details.
239 You should have received a copy of the GNU General Public License along
240 with this program; if not, write to the Free Software Foundation, Inc.,
241 675 Mass Ave, Cambridge, MA 02139, USA.
244 Bugs can be viewed on the Red Hat Bugzilla page:
245 <https://bugzilla.redhat.com/>.
247 If you find a bug in virt-mem, please follow these steps to report it:
249 1. Check for existing bug reports
250 Go to <https://bugzilla.redhat.com/> and search for similar bugs.
251 Someone may already have reported the same bug, and they may even
254 2. Capture debug and error messages
257 virt-*program* --debug > virt-mem.log 2>&1
259 and keep *virt-mem.log*. It contains error messages which you should
260 submit with your bug report.
262 3. Get version of virt-mem and version of libvirt.
265 virt-*program* --version
267 4. Submit a bug report.
268 Go to <https://bugzilla.redhat.com/> and enter a new bug. Please
269 describe the problem in as much detail as possible.
271 Remember to include the version numbers (step 3) and the debug
272 messages file (step 2).
274 5. Assign the bug to rjones @ redhat.com
275 Assign or reassign the bug to rjones @ redhat.com (without the
276 spaces). You can also send me an email with the bug number if you
277 want a faster response.