1virt-sparsify(1)            Virtualization Support            virt-sparsify(1)
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3
4

NAME

6       virt-sparsify - Make a virtual machine disk sparse
7

SYNOPSIS

9        virt-sparsify [--options] indisk outdisk
10
11        virt-sparsify [--options] --in-place disk
12

WARNING

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

DESCRIPTION

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
24       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
27       Virt-sparsify can also convert between some disk formats, for example
28       converting a raw disk image to a thin-provisioned qcow2 image.
29
30       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
35   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
40        $ 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
45       (Compare the apparent size 100M vs the actual size 3.6M)
46
47   IMPORTANT LIMITATIONS
48       ·   The virtual machine must be shut down before using this tool.
49
50       ·   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
54           If you are using the --in-place option, then large amounts of
55           temporary space are not required.
56
57       ·   Virt-sparsify cannot resize disk images.  To do that, use
58           virt-resize(1).
59
60       ·   Virt-sparsify cannot handle encrypted disks.  Libguestfs supports
61           encrypted disks, but encrypted disks themselves cannot be
62           sparsified.
63
64       ·   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
68       ·   In copy mode, qcow2 internal snapshots are not copied over to the
69           destination image.
70
71       You may also want to read the manual pages for the associated tools
72       virt-filesystems(1) and virt-df(1) before starting.
73

EXAMPLES

75       Typical usage is:
76
77        virt-sparsify indisk outdisk
78
79       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
84       To convert between formats, use the --convert option:
85
86        virt-sparsify disk.raw --convert qcow2 disk.qcow2
87
88       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
92        virt-sparsify --ignore /dev/sda1 indisk outdisk
93
94       See virt-filesystems(1) to get a list of filesystems within a disk
95       image.
96
97       Since virt-sparsify ≥ 1.26, you can now sparsify a disk image in place
98       by doing:
99
100        virt-sparsify --in-place disk.img
101

OPTIONS

103       --help
104           Display help.
105
106       --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
113           If the check indicates a problem, then you can either:
114
115           ·   ignore it,
116
117           ·   print a warning and continue,
118
119           ·   warn and wait for the user to press the Return key (this is the
120               default), or:
121
122           ·   fail and exit.
123
124           You cannot use this option and --in-place together.
125
126       --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
133       --compress
134           Compress the output file.  This only works if the output format is
135           "qcow2".
136
137           You cannot use this option and --in-place together.
138
139       --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
145           Supported and known-working output formats are: "raw", "qcow2",
146           "vdi".
147
148           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
151           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
154           For fine-tuning the output format, see: --compress, -o.
155
156           You cannot use this option and --in-place together.
157
158       --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
164       --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
169           If working with untrusted raw-format guest disk images, you should
170           ensure the format is always specified.
171
172       --ignore filesystem
173       --ignore volgroup
174           Ignore the named filesystem.
175
176           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
179           When using --in-place, the filesystem is ignored completely.
180
181           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
184           You can give this option multiple times.
185
186       --in-place
187           Do in-place sparsification instead of copying sparsification.  See
188           "IN-PLACE SPARSIFICATION" below.
189
190       --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
195           --key "ID":key:KEY_STRING
196               Use the specified "KEY_STRING" as passphrase.
197
198           --key "ID":file:FILENAME
199               Read the passphrase from FILENAME.
200
201       --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
205           If there are multiple encrypted devices then you may need to supply
206           multiple keys on stdin, one per line.
207
208       --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
214       -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
219           You should use -o at most once.  To pass multiple options, separate
220           them with commas, eg:
221
222            virt-sparsify --convert qcow2 \
223              -o cluster_size=512,preallocation=metadata ...
224
225           You cannot use this option and --in-place together.
226
227       -q
228       --quiet
229           This disables progress bars and other unnecessary output.
230
231       --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
236           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
240           If the parameter is a directory, then this is the same as setting
241           the "TMPDIR" environment variable.
242
243           You cannot use this option and --in-place together.
244
245       --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
250           ·   The file must be freshly formatted as qcow2, with indisk as the
251               backing file.
252
253           ·   If you rerun virt-sparsify, you must recreate the file before
254               each run.
255
256           ·   Virt-sparsify does not delete the file.
257
258           This option is used by oVirt which requires a specially formatted
259           temporary file.
260
261       -v
262       --verbose
263           Enable verbose messages for debugging.
264
265       -V
266       --version
267           Display version number and exit.
268
269       -x  Enable tracing of libguestfs API calls.
270
271       --zero partition
272       --zero logvol
273           Zero the contents of the named partition or logical volume in the
274           guest.  All data on the device is lost, but sparsification is
275           excellent!  You can give this option multiple times.
276

IN-PLACE SPARSIFICATION

278       Since virt-sparsify ≥ 1.26, the tool is able to do in-place
279       sparsification (instead of copying from an input disk to an output
280       disk).  This is more efficient.  It is not able to recover quite as
281       much space as copying sparsification.
282
283       To use this mode, specify a disk image which will be modified in place:
284
285        virt-sparsify --in-place disk.img
286
287       Some options are not compatible with this mode: --convert, --compress
288       and -o because they require wholesale disk format changes;
289       --check-tmpdir because large amounts of temporary space are not
290       required.
291
292       In-place sparsification works using discard (a.k.a trim or unmap)
293       support.
294

MACHINE READABLE OUTPUT

296       The --machine-readable option can be used to make the output more
297       machine friendly, which is useful when calling virt-sparsify from other
298       programs, GUIs etc.
299
300       There are two ways to use this option.
301
302       Firstly use the option on its own to query the capabilities of the
303       virt-sparsify binary.  Typical output looks like this:
304
305        $ virt-sparsify --machine-readable
306        virt-sparsify
307        ntfs
308        btrfs
309
310       A list of features is printed, one per line, and the program exits with
311       status 0.
312
313       Secondly use the option in conjunction with other options to make the
314       regular program output more machine friendly.
315
316       At the moment this means:
317
318       1.  Progress bar messages can be parsed from stdout by looking for this
319           regular expression:
320
321            ^[0-9]+/[0-9]+$
322
323       2.  The calling program should treat messages sent to stdout (except
324           for progress bar messages) as status messages.  They can be logged
325           and/or displayed to the user.
326
327       3.  The calling program should treat messages sent to stderr as error
328           messages.  In addition, virt-sparsify exits with a non-zero status
329           code if there was a fatal error.
330
331       All versions of virt-sparsify have supported the --machine-readable
332       option.
333
334       It is possible to specify a format string for controlling the output;
335       see "ADVANCED MACHINE READABLE OUTPUT" in guestfs(3).
336

WINDOWS 8

338       Windows 8 "fast startup" can prevent virt-sparsify from working.  See
339       "WINDOWS HIBERNATION AND WINDOWS 8 FAST STARTUP" in guestfs(3).
340

ENVIRONMENT VARIABLES

342       TMPDIR
343           Location of the temporary directory used for the potentially large
344           temporary overlay file.
345
346           In virt-sparsify ≥ 1.28, you can override this environment variable
347           using the --tmp option.
348
349           You should ensure there is enough free space in the worst case for
350           a full copy of the source disk (virtual size), or else set $TMPDIR
351           to point to another directory that has enough space.
352
353           This defaults to /tmp.
354
355           Note that if $TMPDIR is a tmpfs (eg. if /tmp is on tmpfs, or if you
356           use "TMPDIR=/dev/shm"), tmpfs defaults to a maximum size of half of
357           physical RAM.  If virt-sparsify exceeds this, it will hang.  The
358           solution is either to use a real disk, or to increase the maximum
359           size of the tmpfs mountpoint, eg:
360
361            mount -o remount,size=10G /tmp
362
363           If you are using the --in-place option, then large amounts of
364           temporary space are not required.
365
366       For other environment variables, see "ENVIRONMENT VARIABLES" in
367       guestfs(3).
368

EXIT STATUS

370       This program returns 0 if the operation completed without errors.
371       (This doesn't necessarily mean that space could be freed up.)
372
373       A non-zero exit code indicates an error.
374
375       If the exit code is 3 and the --in-place option was used, that
376       indicates that discard support is not available in libguestfs, so
377       copying mode must be used instead.
378

SEE ALSO

380       virt-df(1), virt-filesystems(1), virt-resize(1), virt-rescue(1),
381       guestfs(3), guestfish(1), truncate(1), fallocate(1), qemu-img(1),
382       http://libguestfs.org/.
383

AUTHOR

385       Richard W.M. Jones http://people.redhat.com/~rjones/
386
388       Copyright (C) 2011-2020 Red Hat Inc.
389

LICENSE

391       This program is free software; you can redistribute it and/or modify it
392       under the terms of the GNU General Public License as published by the
393       Free Software Foundation; either version 2 of the License, or (at your
394       option) any later version.
395
396       This program is distributed in the hope that it will be useful, but
397       WITHOUT ANY WARRANTY; without even the implied warranty of
398       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
399       General Public License for more details.
400
401       You should have received a copy of the GNU General Public License along
402       with this program; if not, write to the Free Software Foundation, Inc.,
403       51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
404

BUGS

406       To get a list of bugs against libguestfs, use this link:
407       https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
408
409       To report a new bug against libguestfs, use this link:
410       https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
411
412       When reporting a bug, please supply:
413
414       ·   The version of libguestfs.
415
416       ·   Where you got libguestfs (eg. which Linux distro, compiled from
417           source, etc)
418
419       ·   Describe the bug accurately and give a way to reproduce it.
420
421       ·   Run libguestfs-test-tool(1) and paste the complete, unedited output
422           into the bug report.
423
424
425
426libguestfs-1.44.0                 2021-01-05                  virt-sparsify(1)
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