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 virt-sparsify [--options] --in-place disk
12
14 Using "virt-sparsify" on live virtual machines, or concurrently with
15 other disk editing tools, can be dangerous, potentially causing disk
16 corruption. The virtual machine must be shut down before you use this
17 command, and disk images must not be edited concurrently.
18
20 Virt-sparsify is a tool which can make a virtual machine disk (or any
21 disk image) sparse a.k.a. thin-provisioned. This means that free space
22 within the disk image can be converted back to free space on the host.
23 Virt-sparsify can locate and sparsify free space in most filesystems
25 (eg. ext2/3/4, btrfs, NTFS, etc.), and also in LVM physical volumes.
26 Virt-sparsify can also convert between some disk formats, for example
28 converting a raw disk image to a thin-provisioned qcow2 image.
29 Virt-sparsify can operate on any disk image, not just ones from virtual
31 machines. However if a virtual machine has multiple disks and uses
32 volume management, then virt-sparsify will work but not be very
33 effective (http://bugzilla.redhat.com/887826).
34 IMPORTANT NOTE ABOUT SPARSE OUTPUT IMAGES
36 If the input is raw, then the default output is raw sparse. You must
37 check the output size using a tool that understands sparseness such as
38 "du -sh". It can make a huge difference:
39 $ ls -lh test1.img
41 -rw-rw-r--. 1 rjones rjones 100M Aug 8 08:08 test1.img
42 $ du -sh test1.img
43 3.6M test1.img
44 (Compare the apparent size 100M vs the actual size 3.6M)
46 IMPORTANT LIMITATIONS
48 • The virtual machine must be shut down before using this tool.
49 • Virt-sparsify may require up to 2x the virtual size of the source
51 disk image (1 temporary copy + 1 destination image). This is in
52 the worst case and usually much less space is required.
53 If you are using the --in-place option, then large amounts of
55 temporary space are not required.
56 • Virt-sparsify cannot resize disk images. To do that, use
58 virt-resize(1).
59 • Virt-sparsify cannot handle encrypted disks. Libguestfs supports
61 encrypted disks, but encrypted disks themselves cannot be
62 sparsified.
63 • Virt-sparsify cannot yet sparsify the space between partitions.
65 Note that this space is often used for critical items like
66 bootloaders so it's not really unused.
67 • In copy mode, qcow2 internal snapshots are not copied over to the
69 destination image.
70 You may also want to read the manual pages for the associated tools
72 virt-filesystems(1) and virt-df(1) before starting.
73
75 Typical usage is:
76 virt-sparsify indisk outdisk
78 which copies "indisk" to "outdisk", making the output sparse.
80 "outdisk" is created, or overwritten if it already exists. The format
81 of the input disk is detected (eg. qcow2) and the same format is used
82 for the output disk.
83 To convert between formats, use the --convert option:
85 virt-sparsify disk.raw --convert qcow2 disk.qcow2
87 Virt-sparsify tries to zero and sparsify free space on every filesystem
89 it can find within the source disk image. You can get it to ignore
90 (don't zero free space on) certain filesystems by doing:
91 virt-sparsify --ignore /dev/sda1 indisk outdisk
93 See virt-filesystems(1) to get a list of filesystems within a disk
95 image.
96 Since virt-sparsify ≥ 1.26, you can now sparsify a disk image in place
98 by doing:
99 virt-sparsify --in-place disk.img
101
103 --help
104 Display help.
105 --check-tmpdir ignore
107 --check-tmpdir continue
108 --check-tmpdir warn
109 --check-tmpdir fail
110 Check if "TMPDIR" or --tmp directory has enough space to complete
111 the operation. This is just an estimate.
112 If the check indicates a problem, then you can either:
114 • ignore it,
116 • print a warning and continue,
118 • warn and wait for the user to press the Return key (this is the
120 default), or:
121 • fail and exit.
123 You cannot use this option and --in-place together.
125 --colors
127 --colours
128 Use ANSI colour sequences to colourize messages. This is the
129 default when the output is a tty. If the output of the program is
130 redirected to a file, ANSI colour sequences are disabled unless you
131 use this option.
132 --compress
134 Compress the output file. This only works if the output format is
135 "qcow2".
136 You cannot use this option and --in-place together.
138 --convert raw
140 --convert qcow2
141 --convert [other formats]
142 Use "output-format" as the format for the destination image. If
143 this is not specified, then the input format is used.
144 Supported and known-working output formats are: "raw", "qcow2",
146 "vdi".
147 You can also use any format supported by the qemu-img(1) program,
149 eg. "vmdk", but support for other formats is reliant on qemu.
150 Specifying the --convert option is usually a good idea, because
152 then virt-sparsify doesn't need to try to guess the input format.
153 For fine-tuning the output format, see: --compress, -o.
155 You cannot use this option and --in-place together.
157 --echo-keys
159 When prompting for keys and passphrases, virt-sparsify normally
160 turns echoing off so you cannot see what you are typing. If you
161 are not worried about Tempest attacks and there is no one else in
162 the room you can specify this flag to see what you are typing.
163 --format raw
165 --format qcow2
166 Specify the format of the input disk image. If this flag is not
167 given then it is auto-detected from the image itself.
168 If working with untrusted raw-format guest disk images, you should
170 ensure the format is always specified.
171 --ignore filesystem
173 --ignore volgroup
174 Ignore the named filesystem.
175 When not using --in-place: Free space on the filesystem will not be
177 zeroed, but existing blocks of zeroes will still be sparsified.
178 When using --in-place, the filesystem is ignored completely.
180 In the second form, this ignores the named volume group. Use the
182 volume group name without the /dev/ prefix, eg. --ignore vg_foo
183 You can give this option multiple times.
185 --in-place
187 Do in-place sparsification instead of copying sparsification. See
188 "IN-PLACE SPARSIFICATION" below.
189 --key SELECTOR
191 Specify a key for LUKS, to automatically open a LUKS device when
192 using the inspection. "ID" can be either the libguestfs device
193 name, or the UUID of the LUKS device.
194 --key "ID":key:KEY_STRING
196 Use the specified "KEY_STRING" as passphrase.
197 --key "ID":file:FILENAME
199 Read the passphrase from FILENAME.
200 --keys-from-stdin
202 Read key or passphrase parameters from stdin. The default is to
203 try to read passphrases from the user by opening /dev/tty.
204 If there are multiple encrypted devices then you may need to supply
206 multiple keys on stdin, one per line.
207 --machine-readable
209 --machine-readable=format
210 This option is used to make the output more machine friendly when
211 being parsed by other programs. See "MACHINE READABLE OUTPUT"
212 below.
213 -o option[,option,...]
215 Pass -o option(s) to the qemu-img(1) command to fine-tune the
216 output format. Options available depend on the output format (see
217 --convert) and the installed version of the qemu-img program.
218 You should use -o at most once. To pass multiple options, separate
220 them with commas, eg:
221 virt-sparsify --convert qcow2 \
223 -o cluster_size=512,preallocation=metadata ...
224 You cannot use this option and --in-place together.
226 -q
228 --quiet
229 This disables progress bars and other unnecessary output.
230 --tmp block_device
232 --tmp dir
233 In copying mode only, use the named device or directory as the
234 location of the temporary overlay (see also "TMPDIR" below).
235 If the parameter given is a block device, then the block device is
237 written to directly. Note this erases the existing contents of the
238 block device.
239 If the parameter is a directory, then this is the same as setting
241 the "TMPDIR" environment variable.
242 You cannot use this option and --in-place together.
244 --tmp prebuilt:file
246 In copying mode only, the specialized option --tmp prebuilt:file
247 (where "prebuilt:" is a literal string) causes virt-sparsify to use
248 the qcow2 "file" as temporary space.
249 • The file must be freshly formatted as qcow2, with indisk as the
251 backing file.
252 • If you rerun virt-sparsify, you must recreate the file before
254 each run.
255 • Virt-sparsify does not delete the file.
257 This option is used by oVirt which requires a specially formatted
259 temporary file.
260 -v
262 --verbose
263 Enable verbose messages for debugging.
264 -V
266 --version
267 Display version number and exit.
268 --wrap
270 Wrap error, warning, and informative messages. This is the default
271 when the output is a tty. If the output of the program is
272 redirected to a file, wrapping is disabled unless you use this
273 option.
274 -x Enable tracing of libguestfs API calls.
276 --zero partition
278 --zero logvol
279 Zero the contents of the named partition or logical volume in the
280 guest. All data on the device is lost, but sparsification is
281 excellent! You can give this option multiple times.
282
284 Since virt-sparsify ≥ 1.26, the tool is able to do in-place
285 sparsification (instead of copying from an input disk to an output
286 disk). This is more efficient. It is not able to recover quite as
287 much space as copying sparsification.
288 To use this mode, specify a disk image which will be modified in place:
290 virt-sparsify --in-place disk.img
292 Some options are not compatible with this mode: --convert, --compress
294 and -o because they require wholesale disk format changes;
295 --check-tmpdir because large amounts of temporary space are not
296 required.
297 In-place sparsification works using discard (a.k.a trim or unmap)
299 support.
300
302 The --machine-readable option can be used to make the output more
303 machine friendly, which is useful when calling virt-sparsify from other
304 programs, GUIs etc.
305 There are two ways to use this option.
307 Firstly use the option on its own to query the capabilities of the
309 virt-sparsify binary. Typical output looks like this:
310 $ virt-sparsify --machine-readable
312 virt-sparsify
313 ntfs
314 btrfs
315 A list of features is printed, one per line, and the program exits with
317 status 0.
318 Secondly use the option in conjunction with other options to make the
320 regular program output more machine friendly.
321 At the moment this means:
323 1. Progress bar messages can be parsed from stdout by looking for this
325 regular expression:
326 ^[0-9]+/[0-9]+$
328 2. The calling program should treat messages sent to stdout (except
330 for progress bar messages) as status messages. They can be logged
331 and/or displayed to the user.
332 3. The calling program should treat messages sent to stderr as error
334 messages. In addition, virt-sparsify exits with a non-zero status
335 code if there was a fatal error.
336 All versions of virt-sparsify have supported the --machine-readable
338 option.
339 It is possible to specify a format string for controlling the output;
341 see "ADVANCED MACHINE READABLE OUTPUT" in guestfs(3).
342
344 Windows 8 "fast startup" can prevent virt-sparsify from working. See
345 "WINDOWS HIBERNATION AND WINDOWS 8 FAST STARTUP" in guestfs(3).
346
348 TMPDIR
349 Location of the temporary directory used for the potentially large
350 temporary overlay file.
351 In virt-sparsify ≥ 1.28, you can override this environment variable
353 using the --tmp option.
354 You should ensure there is enough free space in the worst case for
356 a full copy of the source disk (virtual size), or else set $TMPDIR
357 to point to another directory that has enough space.
358 This defaults to /tmp.
360 Note that if $TMPDIR is a tmpfs (eg. if /tmp is on tmpfs, or if you
362 use "TMPDIR=/dev/shm"), tmpfs defaults to a maximum size of half of
363 physical RAM. If virt-sparsify exceeds this, it will hang. The
364 solution is either to use a real disk, or to increase the maximum
365 size of the tmpfs mountpoint, eg:
366 mount -o remount,size=10G /tmp
368 If you are using the --in-place option, then large amounts of
370 temporary space are not required.
371 For other environment variables, see "ENVIRONMENT VARIABLES" in
373 guestfs(3).
374
376 This program returns 0 if the operation completed without errors.
377 (This doesn't necessarily mean that space could be freed up.)
378 A non-zero exit code indicates an error.
380 If the exit code is 3 and the --in-place option was used, that
382 indicates that discard support is not available in libguestfs, so
383 copying mode must be used instead.
384
386 virt-df(1), virt-filesystems(1), virt-resize(1), virt-rescue(1),
387 guestfs(3), guestfish(1), truncate(1), fallocate(1), qemu-img(1),
388 http://libguestfs.org/.
389
391 Richard W.M. Jones http://people.redhat.com/~rjones/
392
394 Copyright (C) 2011-2020 Red Hat Inc.
395
397 This program is free software; you can redistribute it and/or modify it
398 under the terms of the GNU General Public License as published by the
399 Free Software Foundation; either version 2 of the License, or (at your
400 option) any later version.
401 This program is distributed in the hope that it will be useful, but
403 WITHOUT ANY WARRANTY; without even the implied warranty of
404 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
405 General Public License for more details.
406 You should have received a copy of the GNU General Public License along
408 with this program; if not, write to the Free Software Foundation, Inc.,
409 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
410
412 To get a list of bugs against libguestfs, use this link:
413 https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
414 To report a new bug against libguestfs, use this link:
416 https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
417 When reporting a bug, please supply:
419 • The version of libguestfs.
421 • Where you got libguestfs (eg. which Linux distro, compiled from
423 source, etc)
424 • Describe the bug accurately and give a way to reproduce it.
426 • Run libguestfs-test-tool(1) and paste the complete, unedited output
428 into the bug report.
429guestfs-tools-1.48.2 2022-05-26 virt-sparsify(1)