1virt-sparsify(1) Virtualization Support virt-sparsify(1)
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6 virt-sparsify - Make a virtual machine disk sparse
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9 virt-sparsify [--options] indisk outdisk
10
12 Virt-sparsify is a tool which can make a virtual machine disk (or any
13 disk image) sparse a.k.a. thin-provisioned. This means that free space
14 within the disk image can be converted back to free space on the host.
15 Virt-sparsify can locate and sparsify free space in most filesystems
17 (eg. ext2/3/4, btrfs, NTFS, etc.), and also in LVM physical volumes.
18 Virt-sparsify can also convert between some disk formats, for example
20 converting a raw disk image to a thin-provisioned qcow2 image.
21 Virt-sparsify can operate on any disk image, not just ones from virtual
23 machines. However if a virtual machine has multiple disks and uses
24 volume management, then virt-sparsify will work but not be very
25 effective (http://bugzilla.redhat.com/887826).
26 IMPORTANT NOTE ABOUT SPARSE OUTPUT IMAGES
28 If the input is raw, then the default output is raw sparse. You must
29 check the output size using a tool that understands sparseness such as
30 "du -sh". It can make a huge difference:
31 $ ls -lh test1.img
33 -rw-rw-r--. 1 rjones rjones 100M Aug 8 08:08 test1.img
34 $ du -sh test1.img
35 3.6M test1.img
36 (Compare the apparent size 100M vs the actual size 3.6M)
38 IMPORTANT LIMITATIONS
40 · Virt-sparsify does not do in-place modifications. It copies from a
41 source image to a destination image, leaving the source unchanged.
42 Check that the sparsification was successful before deleting the
43 source image.
44 · The virtual machine must be shut down before using this tool.
46 · Virt-sparsify may require up to 2x the virtual size of the source
48 disk image (1 temporary copy + 1 destination image). This is in
49 the worst case and usually much less space is required.
50 · Virt-sparsify cannot resize disk images. To do that, use
52 virt-resize(1).
53 · Virt-sparsify cannot handle encrypted disks. Libguestfs supports
55 encrypted disks, but encrypted disks themselves cannot be
56 sparsified.
57 · Virt-sparsify cannot yet sparsify the space between partitions.
59 Note that this space is often used for critical items like
60 bootloaders so it's not really unused.
61 You may also want to read the manual pages for the associated tools
63 virt-filesystems(1) and virt-df(1) before starting.
64
66 Typical usage is:
67 virt-sparsify indisk outdisk
69 which copies "indisk" to "outdisk", making the output sparse.
71 "outdisk" is created, or overwritten if it already exists. The format
72 of the input disk is detected (eg. qcow2) and the same format is used
73 for the output disk.
74 To convert between formats, use the --convert option:
76 virt-sparsify disk.raw --convert qcow2 disk.qcow2
78 Virt-sparsify tries to zero and sparsify free space on every filesystem
80 it can find within the source disk image. You can get it to ignore
81 (don't zero free space on) certain filesystems by doing:
82 virt-sparsify --ignore /dev/sda1 indisk outdisk
84 See virt-filesystems(1) to get a list of filesystems within a disk
86 image.
87
89 --help
90 Display help.
91 --check-tmpdir=ignore
93 --check-tmpdir=continue
94 --check-tmpdir=warn
95 --check-tmpdir=fail
96 Check if "TMPDIR" or --tmp directory has enough space to complete
97 the operation. This is just an estimate.
98 If the check indicates a problem, then you can either:
100 · ignore it,
102 · print a warning and continue,
104 · warn and wait for the user to press the Return key (this is the
106 default), or:
107 · fail and exit.
109 --compress
111 Compress the output file. This only works if the output format is
112 "qcow2".
113 --convert raw
115 --convert qcow2
116 --convert [other formats]
117 Use "output-format" as the format for the destination image. If
118 this is not specified, then the input format is used.
119 Supported and known-working output formats are: "raw", "qcow2",
121 "vdi".
122 You can also use any format supported by the qemu-img(1) program,
124 eg. "vmdk", but support for other formats is reliant on qemu.
125 Specifying the --convert option is usually a good idea, because
127 then virt-sparsify doesn't need to try to guess the input format.
128 For fine-tuning the output format, see: --compress, -o.
130 --debug-gc
132 Debug garbage collection and memory allocation. This is only
133 useful when debugging memory problems in virt-sparsify or the OCaml
134 libguestfs bindings.
135 --format raw
137 --format qcow2
138 Specify the format of the input disk image. If this flag is not
139 given then it is auto-detected from the image itself.
140 If working with untrusted raw-format guest disk images, you should
142 ensure the format is always specified.
143 --ignore filesystem
145 --ignore volgroup
146 Ignore the named filesystem. Free space on the filesystem will not
147 be zeroed, but existing blocks of zeroes will still be sparsified.
148 In the second form, this ignores the named volume group. Use the
150 volume group name without the "/dev/" prefix, eg. --ignore vg_foo
151 You can give this option multiple times.
153 --machine-readable
155 This option is used to make the output more machine friendly when
156 being parsed by other programs. See "MACHINE READABLE OUTPUT"
157 below.
158 -o option[,option,...]
160 Pass -o option(s) to the qemu-img(1) command to fine-tune the
161 output format. Options available depend on the output format (see
162 --convert) and the installed version of the qemu-img program.
163 You should use -o at most once. To pass multiple options, separate
165 them with commas, eg:
166 virt-sparsify --convert qcow2 \
168 -o cluster_size=512,preallocation=metadata ...
169 -q
171 --quiet
172 This disables progress bars and other unnecessary output.
173 --tmp block_device
175 --tmp dir
176 In copying mode only, use the named device or directory as the
177 location of the temporary overlay (see also "TMPDIR" below).
178 If the parameter given is a block device, then the block device is
180 written to directly. Note this erases the existing contents of the
181 block device.
182 If the parameter is a directory, then this is the same as setting
184 the "TMPDIR" environment variable.
185 --tmp prebuilt:file
187 In copying mode only, the specialized option --tmp prebuilt:file
188 (where "prebuilt:" is a literal string) causes virt-sparsify to use
189 the qcow2 "file" as temporary space.
190 · The file must be freshly formatted as qcow2, with indisk as the
192 backing file.
193 · If you rerun virt-sparsify, you must recreate the file before
195 each run.
196 · Virt-sparsify does not delete the file.
198 This option is used by oVirt which requires a specially formatted
200 temporary file.
201 -v
203 --verbose
204 Enable verbose messages for debugging.
205 -V
207 --version
208 Display version number and exit.
209 -x Enable tracing of libguestfs API calls.
211 --zero partition
213 --zero logvol
214 Zero the contents of the named partition or logical volume in the
215 guest. All data on the device is lost, but sparsification is
216 excellent! You can give this option multiple times.
217
219 The --machine-readable option can be used to make the output more
220 machine friendly, which is useful when calling virt-sparsify from other
221 programs, GUIs etc.
222 There are two ways to use this option.
224 Firstly use the option on its own to query the capabilities of the
226 virt-sparsify binary. Typical output looks like this:
227 $ virt-sparsify --machine-readable
229 virt-sparsify
230 ntfs
231 btrfs
232 A list of features is printed, one per line, and the program exits with
234 status 0.
235 Secondly use the option in conjunction with other options to make the
237 regular program output more machine friendly.
238 At the moment this means:
240 1. Progress bar messages can be parsed from stdout by looking for this
242 regular expression:
243 ^[0-9]+/[0-9]+$
245 2. The calling program should treat messages sent to stdout (except
247 for progress bar messages) as status messages. They can be logged
248 and/or displayed to the user.
249 3. The calling program should treat messages sent to stderr as error
251 messages. In addition, virt-sparsify exits with a non-zero status
252 code if there was a fatal error.
253 All versions of virt-sparsify have supported the --machine-readable
255 option.
256
258 Windows 8 "fast startup" can prevent virt-sparsify from working. See
259 "WINDOWS HIBERNATION AND WINDOWS 8 FAST STARTUP" in guestfs(3).
260
262 This program returns 0 if successful, or non-zero if there was an
263 error.
264
266 TMPDIR
267 Location of the temporary directory used for the potentially large
268 temporary overlay file.
269 You can override this environment variable using the --tmp option.
271 You should ensure there is enough free space in the worst case for
273 a full copy of the source disk (virtual size), or else set $TMPDIR
274 to point to another directory that has enough space.
275 This defaults to "/tmp".
277 Note that if $TMPDIR is a tmpfs (eg. if "/tmp" is on tmpfs, or if
279 you use "TMPDIR=/dev/shm"), tmpfs defaults to a maximum size of
280 half of physical RAM. If virt-sparsify exceeds this, it will hang.
281 The solution is either to use a real disk, or to increase the
282 maximum size of the tmpfs mountpoint, eg:
283 mount -o remount,size=10G /tmp
285 For other environment variables, see "ENVIRONMENT VARIABLES" in
287 guestfs(3).
288
290 virt-filesystems(1), virt-df(1), virt-resize(1), virt-rescue(1),
291 guestfs(3), guestfish(1), truncate(1), fallocate(1), qemu-img(1),
292 http://libguestfs.org/.
293
295 Richard W.M. Jones http://people.redhat.com/~rjones/
296
298 Copyright (C) 2011-2012 Red Hat Inc.
299
301 This program is free software; you can redistribute it and/or modify it
302 under the terms of the GNU General Public License as published by the
303 Free Software Foundation; either version 2 of the License, or (at your
304 option) any later version.
305 This program is distributed in the hope that it will be useful, but
307 WITHOUT ANY WARRANTY; without even the implied warranty of
308 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
309 General Public License for more details.
310 You should have received a copy of the GNU General Public License along
312 with this program; if not, write to the Free Software Foundation, Inc.,
313 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
314
316 To get a list of bugs against libguestfs, use this link:
317 https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
318 To report a new bug against libguestfs, use this link:
320 https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
321 When reporting a bug, please supply:
323 · The version of libguestfs.
325 · Where you got libguestfs (eg. which Linux distro, compiled from
327 source, etc)
328 · Describe the bug accurately and give a way to reproduce it.
330 · Run libguestfs-test-tool(1) and paste the complete, unedited output
332 into the bug report.
333libguestfs-1.20.11 2013-08-27 virt-sparsify(1)