2 virt-uname - system information for virtual machines
4 virt-dmesg - print kernel messages for virtual machines
6 virt-mem - tool with additional information output
9 virt-uname [-options] [domains...]
11 virt-dmesg [-options] [domains...]
20 These virtualization tools allow you to inspect the status of virtual
21 machines running Linux.
23 These tools are designed to work like familiar Linux/Unix command line
26 These tools all use libvirt so are capable of showing information across
27 a variety of different virtualization systems.
29 The virt-mem tools do not work on domains which are not active (running
30 or paused). eg. They do not work on shut down domains. However they can
31 (usually) be used on domains which are active but hanging or
32 unresponsive. You also have the option of capturing a memory image of a
33 domain for post-mortem analysis, allowing you to quickly reboot a failed
34 domain and analyze it later at your leisure.
37 Each command obeys a common set of options. The general form is:
39 virt-*program* [-options] [domains...]
41 where *program* is a subtool such as "uname", "dmesg" or "ps", and
42 *domains* is a list of guest names to act on. If no domains are
43 specified then we act on all active domains by default.
45 A *domain* may be specified either by its name, by its ID or by its
46 UUID. Use *virsh list* to get a list of active domain names and IDs.
48 Equivalently you can use the "virt-mem" meta-tool with subcommands, as
51 virt-mem *program* [...]
53 The "virt-mem" program offers additional features, such as the ability
54 to capture VM images for post-mortem analysis (see below).
57 Connect to libvirt URI. The default is to connect to the default
58 libvirt URI, normally Xen.
61 Print the results in CSV format, suitable for importing into a
62 spreadsheet or database.
64 This option is only supported if virt-mem was built with CSV
68 Emit debugging information on stderr. Please supply this if you
72 Display usage summary.
75 Post-mortem analysis mode.
77 Instead of checking libvirt for domain information, this runs the
78 tool directly on the memory image supplied. You may specify the -t
79 option multiple times. Use the "virt-mem capture" command to capture
82 See also the section "MEMORY IMAGES" below.
85 Display version and exit.
87 -E auto|littleendian|bigendian
88 -T auto|i386|x86-64|*address*
90 These options force the endianness, text address, and word size for
91 the subsequent domains listed on the command line (or if no domains
92 are listed, then for all domains).
94 These default to *auto* which tries to do automatic detection (using
95 libvirt, or details from the memory images themselves). You only
96 need to use these options if virt-mem tools get the automatic
99 Endianness (*-E*) sets the memory endianness, for data, pointers and
100 so on. *-E littleendian* is the endianness used on Intel i386,
101 x86-64 and (usually) IA64. *-E bigendian* is the endianness used on
102 many RISC chips such as SPARC and PowerPC.
104 Text address (*-T*) sets the base address of the kernel image. *-T
105 i386* means to try some common addresses for i386-based kernels. *-T
106 x86-64* means to try some common addresses for x86-64-based kernels.
107 *-T *address** sets the address specifically (*0x* prefix is used to
108 specify hex addresses).
110 Word size (*-W*) sets the word size, 32 or 64 bits.
112 -A auto|i386|x86-64|...
113 This option sets the architecture to one of a collection of known
114 architectures. It is equivalent to setting endianness and wordsize
115 in one go, but not text address.
118 This prints the latest kernel messages from the virtual machine, as if
119 you were logged into the machine and used dmesg(1).
122 This prints the contents of the system "utsname" structure, similar to
123 what is printed by the uname(1) command.
126 "virt-mem" is a meta-tool which allows you to run all the commands
127 above, and provides some extra features.
129 Instead of the preceeding commands such as "virt-dmesg" you can write:
133 Options and other command line arguments work the same.
135 Additional "virt-mem" subcommands are listed below.
137 virt-mem capture -o memoryimage [-options] [domains...]
138 Capture the memory image of a virtual machine for later post-mortem
139 analysis. Use the *-t memoryimage* option for any other virt-mem tool to
140 analyze the memory image later.
142 The *-o memoryimage* option is required, and is used to name the output
143 file. If a single guest is captured, then the output is saved in the
144 *memoryimage* file. However, if multiple guests are captured, then their
145 images are saved in *memoryimage.ID* where *ID* is replaced with the
148 See also the section "MEMORY IMAGES" below.
152 f9x32kvm: Linux localhost.localdomain 2.6.24-0.155.rc7.git6.fc9 #1
153 SMP Tue Jan 15 17:52:31 EST 2008 i686 (none)
155 # virt-dmesg f9x32kvm | tail
156 <6>Bluetooth: Core ver 2.11
157 <6>NET: Registered protocol family 31
158 <6>Bluetooth: HCI device and connection manager initialized
159 <6>Bluetooth: HCI socket layer initialized
160 <6>Bluetooth: L2CAP ver 2.9
161 <6>Bluetooth: L2CAP socket layer initialized
162 <6>Bluetooth: RFCOMM socket layer initialized
163 <6>Bluetooth: RFCOMM TTY layer initialized
164 <6>Bluetooth: RFCOMM ver 1.8
165 <7>eth0: no IPv6 routers present
168 All the tools can read dumped kernel images, using the common *-t
169 memoryimage* option. In addition you can capture memory images from
170 domains for post-mortem analysis using the "virt-mem capture" command
173 The memory images which are saved by "virt-mem capture" contain a header
174 and some additional information about the kernel image, such as
175 architecture, original text address, and so forth. Thus these images can
176 be reanalysed just using the *-t memoryimage* option.
178 We also support analyzing raw kernel dumps, eg. produced using the
179 qemu(1) monitor's "memsave" command. In this case however you usually
180 need to specify the original architecture, text address and perhaps
181 other details using the *-A*, *-T* and other command line parameters.
184 The virt-mem tools spy on the guest's memory image. There are some
185 shortcomings to this, described here.
187 * Only works on specific, tested releases of Linux kernels. Support
188 for arbitrary Linux kernel versions may be patchy because of changes
189 in the internal structures used. Support for non-Linux kernels is
190 currently non-existent, and probably impossible for Windows because
191 of lack of an acceptable source license.
193 * Heuristics are used which may mean in the worst case that the output
196 * Structures which are frequently modified may cause errors. This
197 could be a problem if, for example, the process table in the guest
198 is being rapidly updated.
200 * We have to scan memory to find kernel symbols, etc., which can be
201 quite slow. Optimizing the memory scanner would help, and caching
202 the base address of the symbol table(s) would make it dramatically
206 The current code tries hard to be secure against malicious guests, for
207 example guests which set up malicious kernel memory.
210 uname(1), dmesg(1), virsh(1), virt-top(1), virt-df(1), xm(1), qemu(1),
211 <http://www.libvirt.org/ocaml/>, <http://www.libvirt.org/>,
212 <http://et.redhat.com/~rjones/>, <http://caml.inria.fr/>
215 Richard W.M. Jones <rjones @ redhat . com>
218 (C) Copyright 2008 Red Hat Inc., Richard W.M. Jones http://libvirt.org/
220 This program is free software; you can redistribute it and/or modify it
221 under the terms of the GNU General Public License as published by the
222 Free Software Foundation; either version 2 of the License, or (at your
223 option) any later version.
225 This program is distributed in the hope that it will be useful, but
226 WITHOUT ANY WARRANTY; without even the implied warranty of
227 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
228 Public License for more details.
230 You should have received a copy of the GNU General Public License along
231 with this program; if not, write to the Free Software Foundation, Inc.,
232 675 Mass Ave, Cambridge, MA 02139, USA.
235 Bugs can be viewed on the Red Hat Bugzilla page:
236 <https://bugzilla.redhat.com/>.
238 If you find a bug in virt-mem, please follow these steps to report it:
240 1. Check for existing bug reports
241 Go to <https://bugzilla.redhat.com/> and search for similar bugs.
242 Someone may already have reported the same bug, and they may even
245 2. Capture debug and error messages
248 virt-*program* --debug > virt-mem.log 2>&1
250 and keep *virt-mem.log*. It contains error messages which you should
251 submit with your bug report.
253 3. Get version of virt-mem and version of libvirt.
256 virt-*program* --version
258 4. Submit a bug report.
259 Go to <https://bugzilla.redhat.com/> and enter a new bug. Please
260 describe the problem in as much detail as possible.
262 Remember to include the version numbers (step 3) and the debug
263 messages file (step 2).
265 5. Assign the bug to rjones @ redhat.com
266 Assign or reassign the bug to rjones @ redhat.com (without the
267 spaces). You can also send me an email with the bug number if you
268 want a faster response.