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68396ea @rmustacc Initial commit of d32e8d0b8d9e0ef7cf7ab2e74548982972789dfc from qemu-kvm
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1 @example
2 @c man begin SYNOPSIS
3 usage: qemu-img command [command options]
4 @c man end
5 @end example
6
7 @c man begin OPTIONS
8
9 The following commands are supported:
10
11 @include qemu-img-cmds.texi
12
13 Command parameters:
14 @table @var
15 @item filename
16 is a disk image filename
17 @item fmt
18 is the disk image format. It is guessed automatically in most cases. See below
19 for a description of the supported disk formats.
20
21 @item size
22 is the disk image size in bytes. Optional suffixes @code{k} or @code{K}
23 (kilobyte, 1024) @code{M} (megabyte, 1024k) and @code{G} (gigabyte, 1024M)
24 and T (terabyte, 1024G) are supported. @code{b} is ignored.
25
26 @item output_filename
27 is the destination disk image filename
28
29 @item output_fmt
30 is the destination format
31 @item options
32 is a comma separated list of format specific options in a
33 name=value format. Use @code{-o ?} for an overview of the options supported
34 by the used format or see the format descriptions below for details.
35
36
37 @item -c
38 indicates that target image must be compressed (qcow format only)
39 @item -h
40 with or without a command shows help and lists the supported formats
41 @end table
42
43 Parameters to snapshot subcommand:
44
45 @table @option
46
47 @item snapshot
48 is the name of the snapshot to create, apply or delete
49 @item -a
50 applies a snapshot (revert disk to saved state)
51 @item -c
52 creates a snapshot
53 @item -d
54 deletes a snapshot
55 @item -l
56 lists all snapshots in the given image
57 @end table
58
59 Command description:
60
61 @table @option
62 @item check [-f @var{fmt}] @var{filename}
63
64 Perform a consistency check on the disk image @var{filename}.
65
66 Only the formats @code{qcow2}, @code{qed} and @code{vdi} support
67 consistency checks.
68
69 @item create [-f @var{fmt}] [-o @var{options}] @var{filename} [@var{size}]
70
71 Create the new disk image @var{filename} of size @var{size} and format
72 @var{fmt}. Depending on the file format, you can add one or more @var{options}
73 that enable additional features of this format.
74
75 If the option @var{backing_file} is specified, then the image will record
76 only the differences from @var{backing_file}. No size needs to be specified in
77 this case. @var{backing_file} will never be modified unless you use the
78 @code{commit} monitor command (or qemu-img commit).
79
80 The size can also be specified using the @var{size} option with @code{-o},
81 it doesn't need to be specified separately in this case.
82
83 @item commit [-f @var{fmt}] @var{filename}
84
85 Commit the changes recorded in @var{filename} in its base image.
86
87 @item convert [-c] [-f @var{fmt}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] @var{filename} [@var{filename2} [...]] @var{output_filename}
88
89 Convert the disk image @var{filename} or a snapshot @var{snapshot_name} to disk image @var{output_filename}
90 using format @var{output_fmt}. It can be optionally compressed (@code{-c}
91 option) or use any format specific options like encryption (@code{-o} option).
92
93 Only the formats @code{qcow} and @code{qcow2} support compression. The
94 compression is read-only. It means that if a compressed sector is
95 rewritten, then it is rewritten as uncompressed data.
96
97 Image conversion is also useful to get smaller image when using a
98 growable format such as @code{qcow} or @code{cow}: the empty sectors
99 are detected and suppressed from the destination image.
100
101 You can use the @var{backing_file} option to force the output image to be
102 created as a copy on write image of the specified base image; the
103 @var{backing_file} should have the same content as the input's base image,
104 however the path, image format, etc may differ.
105
106 @item info [-f @var{fmt}] @var{filename}
107
108 Give information about the disk image @var{filename}. Use it in
109 particular to know the size reserved on disk which can be different
110 from the displayed size. If VM snapshots are stored in the disk image,
111 they are displayed too.
112
113 @item snapshot [-l | -a @var{snapshot} | -c @var{snapshot} | -d @var{snapshot} ] @var{filename}
114
115 List, apply, create or delete snapshots in image @var{filename}.
116
117 @item rebase [-f @var{fmt}] [-u] -b @var{backing_file} [-F @var{backing_fmt}] @var{filename}
118
119 Changes the backing file of an image. Only the formats @code{qcow2} and
120 @code{qed} support changing the backing file.
121
122 The backing file is changed to @var{backing_file} and (if the image format of
123 @var{filename} supports this) the backing file format is changed to
124 @var{backing_fmt}.
125
126 There are two different modes in which @code{rebase} can operate:
127 @table @option
128 @item Safe mode
129 This is the default mode and performs a real rebase operation. The new backing
130 file may differ from the old one and qemu-img rebase will take care of keeping
131 the guest-visible content of @var{filename} unchanged.
132
133 In order to achieve this, any clusters that differ between @var{backing_file}
134 and the old backing file of @var{filename} are merged into @var{filename}
135 before actually changing the backing file.
136
137 Note that the safe mode is an expensive operation, comparable to converting
138 an image. It only works if the old backing file still exists.
139
140 @item Unsafe mode
141 qemu-img uses the unsafe mode if @code{-u} is specified. In this mode, only the
142 backing file name and format of @var{filename} is changed without any checks
143 on the file contents. The user must take care of specifying the correct new
144 backing file, or the guest-visible content of the image will be corrupted.
145
146 This mode is useful for renaming or moving the backing file to somewhere else.
147 It can be used without an accessible old backing file, i.e. you can use it to
148 fix an image whose backing file has already been moved/renamed.
149 @end table
150
151 @item resize @var{filename} [+ | -]@var{size}
152
153 Change the disk image as if it had been created with @var{size}.
154
155 Before using this command to shrink a disk image, you MUST use file system and
156 partitioning tools inside the VM to reduce allocated file systems and partition
157 sizes accordingly. Failure to do so will result in data loss!
158
159 After using this command to grow a disk image, you must use file system and
160 partitioning tools inside the VM to actually begin using the new space on the
161 device.
162 @end table
163
164 Supported image file formats:
165
166 @table @option
167 @item raw
168
169 Raw disk image format (default). This format has the advantage of
170 being simple and easily exportable to all other emulators. If your
171 file system supports @emph{holes} (for example in ext2 or ext3 on
172 Linux or NTFS on Windows), then only the written sectors will reserve
173 space. Use @code{qemu-img info} to know the real size used by the
174 image or @code{ls -ls} on Unix/Linux.
175
176 @item host_device
177
178 Host device format. This format should be used instead of raw when
179 converting to block devices or other devices where "holes" are not
180 supported.
181
182 @item qcow2
183 QEMU image format, the most versatile format. Use it to have smaller
184 images (useful if your filesystem does not supports holes, for example
185 on Windows), optional AES encryption, zlib based compression and
186 support of multiple VM snapshots.
187
188 Supported options:
189 @table @code
190 @item backing_file
191 File name of a base image (see @option{create} subcommand)
192 @item backing_fmt
193 Image format of the base image
194 @item encryption
195 If this option is set to @code{on}, the image is encrypted.
196
197 Encryption uses the AES format which is very secure (128 bit keys). Use
198 a long password (16 characters) to get maximum protection.
199
200 @item cluster_size
201 Changes the qcow2 cluster size (must be between 512 and 2M). Smaller cluster
202 sizes can improve the image file size whereas larger cluster sizes generally
203 provide better performance.
204
205 @item preallocation
206 Preallocation mode (allowed values: off, metadata). An image with preallocated
207 metadata is initially larger but can improve performance when the image needs
208 to grow.
209
210 @end table
211
212
213 @item qcow
214 Old QEMU image format. Left for compatibility.
215
216 Supported options:
217 @table @code
218 @item backing_file
219 File name of a base image (see @option{create} subcommand)
220 @item encryption
221 If this option is set to @code{on}, the image is encrypted.
222 @end table
223
224 @item cow
225 User Mode Linux Copy On Write image format. Used to be the only growable
226 image format in QEMU. It is supported only for compatibility with
227 previous versions. It does not work on win32.
228 @item vdi
229 VirtualBox 1.1 compatible image format.
230 @item vmdk
231 VMware 3 and 4 compatible image format.
232
233 Supported options:
234 @table @code
235 @item backing_fmt
236 Image format of the base image
237 @item compat6
238 Create a VMDK version 6 image (instead of version 4)
239 @end table
240
241 @item vpc
242 VirtualPC compatible image format (VHD).
243
244 @item cloop
245 Linux Compressed Loop image, useful only to reuse directly compressed
246 CD-ROM images present for example in the Knoppix CD-ROMs.
247 @end table
248
249
250 @c man end
251
252 @ignore
253
254 @setfilename qemu-img
255 @settitle QEMU disk image utility
256
257 @c man begin SEEALSO
258 The HTML documentation of QEMU for more precise information and Linux
259 user mode emulator invocation.
260 @c man end
261
262 @c man begin AUTHOR
263 Fabrice Bellard
264 @c man end
265
266 @end ignore
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