1virt-resize(1) Virtualization Support virt-resize(1)
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6 virt-resize - Resize a virtual machine disk
7
9 virt-resize [--resize /dev/sdaN=[+/-]<size>[%]]
10 [--expand /dev/sdaN] [--shrink /dev/sdaN]
11 [--ignore /dev/sdaN] [--delete /dev/sdaN] [...] indisk outdisk
12
14 Virt-resize is a tool which can resize a virtual machine disk, making
15 it larger or smaller overall, and resizing or deleting any partitions
16 contained within.
17 Virt-resize cannot resize disk images in-place. Virt-resize should not
19 be used on live virtual machines - for consistent results, shut the
20 virtual machine down before resizing it.
21 If you are not familiar with the associated tools: virt-filesystems(1)
23 and virt-df(1), we recommend you go and read those manual pages first.
24
26 Copy "olddisk" to "newdisk", extending one of the guest's partitions to
27 fill the extra 5GB of space.
28 truncate -r olddisk newdisk; truncate -s +5G newdisk
30 virt-filesystems --long -h --all -a olddisk
31 # Note "/dev/sda2" is a partition inside the "olddisk" file.
32 virt-resize --expand /dev/sda2 olddisk newdisk
33 As above, but make the /boot partition 200MB bigger, while giving the
35 remaining space to /dev/sda2:
36 virt-resize --resize /dev/sda1=+200M --expand /dev/sda2 olddisk newdisk
38 As above, but the output format will be uncompressed qcow2:
40 qemu-img create -f qcow2 newdisk.qcow2 15G
42 virt-resize --expand /dev/sda2 olddisk newdisk.qcow2
43
45 EXPANDING A VIRTUAL MACHINE DISK
46 1. Shut down the virtual machine
47 2. Locate input disk image
48 Locate the input disk image (ie. the file or device on the host
49 containing the guest's disk). If the guest is managed by libvirt,
50 you can use "virsh dumpxml" like this to find the disk image name:
51 # virsh dumpxml guestname | xpath /domain/devices/disk/source
53 Found 1 nodes:
54 -- NODE --
55 <source dev="/dev/vg/lv_guest" />
56 3. Look at current sizing
58 Use virt-filesystems(1) to display the current partitions and
59 sizes:
60 # virt-filesystems --long --parts --blkdevs -h -a /dev/vg/lv_guest
62 Name Type Size Parent
63 /dev/sda1 partition 101M /dev/sda
64 /dev/sda2 partition 7.9G /dev/sda
65 /dev/sda device 8.0G -
66 (This example is a virtual machine with an 8 GB disk which we would
68 like to expand up to 10 GB).
69 4. Create output disk
71 Virt-resize cannot do in-place disk modifications. You have to
72 have space to store the resized output disk.
73 To store the resized disk image in a file, create a file of a
75 suitable size:
76 # rm -f outdisk
78 # truncate -s 10G outdisk
79 Or use lvcreate(1) to create a logical volume:
81 # lvcreate -L 10G -n lv_name vg_name
83 Or use virsh(1) vol-create-as to create a libvirt storage volume:
85 # virsh pool-list
87 # virsh vol-create-as poolname newvol 10G
88 5. Resize
90 virt-resize takes two mandatory parameters, the input disk (eg.
91 device or file) and the output disk. The output disk is the one
92 created in the previous step.
93 # virt-resize indisk outdisk
95 This command just copies disk image "indisk" to disk image
97 "outdisk" without resizing or changing any existing partitions. If
98 "outdisk" is larger, then an extra, empty partition is created at
99 the end of the disk covering the extra space. If "outdisk" is
100 smaller, then it will give an error.
101 More realistically you'd want to expand existing partitions in the
103 disk image by passing extra options (for the full list see the
104 "OPTIONS" section below).
105 "--expand" is the most useful option. It expands the named
107 partition within the disk to fill any extra space:
108 # virt-resize --expand /dev/sda2 indisk outdisk
110 (In this case, an extra partition is not created at the end of the
112 disk, because there will be no unused space).
113 "--resize" is the other commonly used option. The following would
115 increase the size of /dev/sda1 by 200M, and expand /dev/sda2 to
116 fill the rest of the available space:
117 # virt-resize --resize /dev/sda1=+200M --expand /dev/sda2 \
119 indisk outdisk
120 If the expanded partition in the image contains a filesystem or LVM
122 PV, then if virt-resize knows how, it will resize the contents, the
123 equivalent of calling a command such as pvresize(8), resize2fs(8)
124 or ntfsresize(8). However virt-resize does not know how to resize
125 some filesystems, so you would have to online resize them after
126 booting the guest.
127 Other options are covered below.
129 6. Test
131 Thoroughly test the new disk image before discarding the old one.
132 If you are using libvirt, edit the XML to point at the new disk:
134 # virsh edit guestname
136 Change <source ...>, see
138 <http://libvirt.org/formatdomain.html#elementsDisks>
139 Then start up the domain with the new, resized disk:
141 # virsh start guestname
143 and check that it still works. See also the "NOTES" section below
145 for additional information.
146 7. Resize LVs etc inside the guest
148 (This can also be done offline using guestfish(1))
149 Once the guest has booted you should see the new space available,
151 at least for filesystems that virt-resize knows how to resize, and
152 for PVs. The user may need to resize LVs inside PVs, and also
153 resize filesystem types that virt-resize does not know how to
154 expand.
155 SHRINKING A VIRTUAL MACHINE DISK
157 Shrinking is somewhat more complex than expanding, and only an overview
158 is given here.
159 Firstly virt-resize will not attempt to shrink any partition content
161 (PVs, filesystems). The user has to shrink content before passing the
162 disk image to virt-resize, and virt-resize will check that the content
163 has been shrunk properly.
164 (Shrinking can also be done offline using guestfish(1))
166 After shrinking PVs and filesystems, shut down the guest, and proceed
168 with steps 3 and 4 above to allocate a new disk image.
169 Then run virt-resize with any of the "--shrink" and/or "--resize"
171 options.
172 IGNORING OR DELETING PARTITIONS
174 virt-resize also gives a convenient way to ignore or delete partitions
175 when copying from the input disk to the output disk. Ignoring a
176 partition speeds up the copy where you don't care about the existing
177 contents of a partition. Deleting a partition removes it completely,
178 but note that it also renumbers any partitions after the one which is
179 deleted, which can leave some guests unbootable.
180 QCOW2 AND NON-SPARSE RAW FORMATS
182 If the input disk is in qcow2 format, then you may prefer that the
183 output is in qcow2 format as well. Alternately, virt-resize can
184 convert the format on the fly. The output format is simply determined
185 by the format of the empty output container that you provide. Thus to
186 create qcow2 output, use:
187 qemu-img create [-c] -f qcow2 outdisk [size]
189 instead of the truncate command (use "-c" for a compressed disk).
191 Similarly, to get non-sparse raw output use:
193 fallocate -l size outdisk
195 (on older systems that don't have the fallocate(1) command use "dd
197 if=/dev/zero of=outdisk bs=1M count=..")
198
200 --help
201 Display help.
202 --version
204 Display version number and exit.
205 --resize part=size
207 Resize the named partition (expanding or shrinking it) so that it
208 has the given size.
209 "size" can be expressed as an absolute number followed by
211 b/K/M/G/T/P/E to mean bytes, Kilobytes, Megabytes, Gigabytes,
212 Terabytes, Petabytes or Exabytes; or as a percentage of the current
213 size; or as a relative number or percentage. For example:
214 --resize /dev/sda2=10G
216 --resize /dev/sda4=90%
218 --resize /dev/sda2=+1G
220 --resize /dev/sda2=-200M
222 --resize /dev/sda1=+128K
224 --resize /dev/sda1=+10%
226 --resize /dev/sda1=-10%
228 You can increase the size of any partition. Virt-resize will
230 expand the direct content of the partition if it knows how (see
231 "--expand" below).
232 You can only decrease the size of partitions that contain
234 filesystems or PVs which have already been shrunk. Virt-resize
235 will check this has been done before proceeding, or else will print
236 an error (see also "--resize-force").
237 You can give this option multiple times.
239 --resize-force part=size
241 This is the same as "--resize" except that it will let you decrease
242 the size of any partition. Generally this means you will lose any
243 data which was at the end of the partition you shrink, but you may
244 not care about that (eg. if shrinking an unused partition, or if
245 you can easily recreate it such as a swap partition).
246 See also the "--ignore" option.
248 --expand part
250 Expand the named partition so it uses up all extra space (space
251 left over after any other resize changes that you request have been
252 done).
253 If virt-resize knows how, it will expand the direct content of the
255 partition. For example, if the partition is an LVM PV, it will
256 expand the PV to fit (like calling pvresize(8)). Virt-resize
257 leaves any other content it doesn't know about alone.
258 Currently virt-resize can resize:
260 · ext2, ext3 and ext4 filesystems when they are contained
262 directly inside a partition.
263 · NTFS filesystems contained directly in a partition, if
265 libguestfs was compiled with support for NTFS.
266 The filesystem must have been shut down consistently last time
268 it was used. Additionally, ntfsresize(8) marks the resized
269 filesystem as requiring a consistency check, so at the first
270 boot after resizing Windows will check the disk.
271 · LVM PVs (physical volumes). virt-resize does not usually
273 resize anything inside the PV, but see the "--LV-expand"
274 option. The user could also resize LVs as desired after boot.
275 Note that you cannot use "--expand" and "--shrink" together.
277 --shrink part
279 Shrink the named partition until the overall disk image fits in the
280 destination. The named partition must contain a filesystem or PV
281 which has already been shrunk using another tool (eg. guestfish(1)
282 or other online tools). Virt-resize will check this and give an
283 error if it has not been done.
284 The amount by which the overall disk must be shrunk (after carrying
286 out all other operations requested by the user) is called the
287 "deficit". For example, a straight copy (assume no other
288 operations) from a 5GB disk image to a 4GB disk image results in a
289 1GB deficit. In this case, virt-resize would give an error unless
290 the user specified a partition to shrink and that partition had
291 more than a gigabyte of free space.
292 Note that you cannot use "--expand" and "--shrink" together.
294 --ignore part
296 Ignore the named partition. Effectively this means the partition
297 is allocated on the destination disk, but the content is not copied
298 across from the source disk. The content of the partition will be
299 blank (all zero bytes).
300 You can give this option multiple times.
302 --delete part
304 Delete the named partition. It would be more accurate to describe
305 this as "don't copy it over", since virt-resize doesn't do in-place
306 changes and the original disk image is left intact.
307 Note that when you delete a partition, then anything contained in
309 the partition is also deleted. Furthermore, this causes any
310 partitions that come after to be renumbered, which can easily make
311 your guest unbootable.
312 You can give this option multiple times.
314 --LV-expand logvol
316 This takes the logical volume and, as a final step, expands it to
317 fill all the space available in its volume group. A typical usage,
318 assuming a Linux guest with a single PV "/dev/sda2" and a root
319 device called "/dev/vg_guest/lv_root" would be:
320 virt-resize indisk outdisk \
322 --expand /dev/sda2 --LV-expand /dev/vg_guest/lv_root
323 This would first expand the partition (and PV), and then expand the
325 root device to fill the extra space in the PV.
326 The contents of the LV are also resized if virt-resize knows how to
328 do that. You can stop virt-resize from trying to expand the
329 content by using the option "--no-expand-content".
330 Use virt-filesystems(1) to list the filesystems in the guest.
332 You can give this option multiple times, but it doesn't make sense
334 to do this unless the logical volumes you specify are all in
335 different volume groups.
336 --no-copy-boot-loader
338 By default, virt-resize copies over some sectors at the start of
339 the disk (up to the beginning of the first partition). Commonly
340 these sectors contain the Master Boot Record (MBR) and the boot
341 loader, and are required in order for the guest to boot correctly.
342 If you specify this flag, then this initial copy is not done. You
344 may need to reinstall the boot loader in this case.
345 --no-extra-partition
347 By default, virt-resize creates an extra partition if there is any
348 extra, unused space after all resizing has happened. Use this
349 option to prevent the extra partition from being created. If you
350 do this then the extra space will be inaccessible until you run
351 fdisk, parted, or some other partitioning tool in the guest.
352 Note that if the surplus space is smaller than 10 MB, no extra
354 partition will be created.
355 --no-expand-content
357 By default, virt-resize will try to expand the direct contents of
358 partitions, if it knows how (see "--expand" option above).
359 If you give the "--no-expand-content" option then virt-resize will
361 not attempt this.
362 -d | --debug
364 Enable debugging messages.
365 -n | --dryrun
367 Print a summary of what would be done, but don't do anything.
368 -q | --quiet
370 Don't print the summary.
371 --format raw
373 Specify the format of the input disk image. If this flag is not
374 given then it is auto-detected from the image itself.
375 If working with untrusted raw-format guest disk images, you should
377 ensure the format is always specified.
378 Note that this option does not affect the output format. See
380 "QCOW2 AND NON-SPARSE RAW FORMATS".
381 --output-format raw
383 Specify the format of the output disk image. If this flag is not
384 given then it is auto-detected from the image itself.
385 If working with untrusted raw-format guest disk images, you should
387 ensure the format is always specified.
388 Note that you still need to create the output disk with the right
390 format. See "QCOW2 AND NON-SPARSE RAW FORMATS".
391
393 "Partition 1 does not end on cylinder boundary."
394 Virt-resize aligns partitions to multiples of 64 sectors. Usually this
395 means the partitions will not be aligned to the ancient CHS geometry.
396 However CHS geometry is meaningless for disks manufactured since the
397 early 1990s, and doubly so for virtual hard drives. Alignment of
398 partitions to cylinders is not required by any modern operating system.
399 RESIZING WINDOWS VIRTUAL MACHINES
401 In Windows Vista and later versions, Microsoft switched to using a
402 separate boot partition. In these VMs, typically "/dev/sda1" is the
403 boot partition and "/dev/sda2" is the main (C:) drive. We have not had
404 any luck resizing the boot partition. Doing so seems to break the
405 guest completely. However expanding the second partition (ie. C:
406 drive) should work.
407 Windows may initiate a lengthy "chkdsk" on first boot after a resize,
409 if NTFS partitions have been expanded. This is just a safety check and
410 (unless it find errors) is nothing to worry about.
411 GUEST BOOT STUCK AT "GRUB"
413 If a Linux guest does not boot after resizing, and the boot is stuck
414 after printing "GRUB" on the console, try reinstalling grub. This
415 sometimes happens on older (RHEL 5-era) guests, for reasons we don't
416 fully understand, although we think is to do with partition alignment.
417 guestfish -i -a newdisk
419 ><fs> cat /boot/grub/device.map
420 # check the contents of this file are sensible or
421 # edit the file if necessary
422 ><fs> grub-install / /dev/vda
423 ><fs> exit
424 For more flexible guest reconfiguration, including if you need to
426 specify other parameters to grub-install, use virt-rescue(1).
427
429 There are several proprietary tools for resizing partitions. We won't
430 mention any here.
431 parted(8) and its graphical shell gparted can do some types of resizing
433 operations on disk images. They can resize and move partitions, but I
434 don't think they can do anything with the contents, and they certainly
435 don't understand LVM.
436 guestfish(1) can do everything that virt-resize can do and a lot more,
438 but at a much lower level. You will probably end up hand-calculating
439 sector offsets, which is something that virt-resize was designed to
440 avoid. If you want to see the guestfish-equivalent commands that virt-
441 resize runs, use the "--debug" flag.
442
444 Libvirt guest names can contain arbitrary characters, some of which
445 have meaning to the shell such as "#" and space. You may need to quote
446 or escape these characters on the command line. See the shell manual
447 page sh(1) for details.
448
450 virt-filesystems(1), virt-df(1), guestfs(3), guestfish(1), lvm(8),
451 pvresize(8), lvresize(8), resize2fs(8), ntfsresize(8), virsh(1),
452 parted(8), truncate(1), fallocate(1), grub(8), grub-install(8),
453 virt-rescue(1), Sys::Guestfs(3), <http://libguestfs.org/>.
454
456 Richard W.M. Jones <http://people.redhat.com/~rjones/>
457
459 Copyright (C) 2010 Red Hat Inc.
460 This program is free software; you can redistribute it and/or modify it
462 under the terms of the GNU General Public License as published by the
463 Free Software Foundation; either version 2 of the License, or (at your
464 option) any later version.
465 This program is distributed in the hope that it will be useful, but
467 WITHOUT ANY WARRANTY; without even the implied warranty of
468 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
469 General Public License for more details.
470 You should have received a copy of the GNU General Public License along
472 with this program; if not, write to the Free Software Foundation, Inc.,
473 675 Mass Ave, Cambridge, MA 02139, USA.
474libguestfs-1.8.15 2011-11-10 virt-resize(1)