virt-sparsify(1) Virtualization Support virt-sparsify(1)NAMEvirt-sparsify - Make a virtual machine disk sparse
SYNOPSISvirt-sparsify [--options] indisk outdisk
DESCRIPTION
Virt-sparsify is a tool which can make a virtual machine disk (or any
disk image) sparse a.k.a. thin-provisioned. This means that free space
within the disk image can be converted back to free space on the host.
Virt-sparsify can locate and sparsify free space in most filesystems
(eg. ext2/3/4, btrfs, NTFS, etc.), and also in LVM physical volumes.
Virt-sparsify can also convert between some disk formats, for example
converting a raw disk image to a thin-provisioned qcow2 image.
Virt-sparsify can operate on any disk image, not just ones from virtual
machines. However if a virtual machine has multiple disks and uses
volume management, then virt-sparsify will work but not be very
effective (http://bugzilla.redhat.com/887826).
IMPORTANT NOTE ABOUT SPARSE OUTPUT IMAGES
If the input is raw, then the default output is raw sparse. You must
check the output size using a tool that understands sparseness such as
"du -sh". It can make a huge difference:
$ ls -lh test1.img
-rw-rw-r--. 1 rjones rjones 100M Aug 8 08:08 test1.img
$ du -sh test1.img
3.6M test1.img
(Compare the apparent size 100M vs the actual size 3.6M)
IMPORTANT LIMITATIONS
· Virt-sparsify does not do in-place modifications. It copies from a
source image to a destination image, leaving the source unchanged.
Check that the sparsification was successful before deleting the
source image.
· The virtual machine must be shut down before using this tool.
· Virt-sparsify may require up to 2x the virtual size of the source
disk image (1 temporary copy + 1 destination image). This is in
the worst case and usually much less space is required.
· Virt-sparsify cannot resize disk images. To do that, use
virt-resize(1).
· Virt-sparsify cannot handle encrypted disks. Libguestfs supports
encrypted disks, but encrypted disks themselves cannot be
sparsified.
· Virt-sparsify cannot yet sparsify the space between partitions.
Note that this space is often used for critical items like
bootloaders so it's not really unused.
You may also want to read the manual pages for the associated tools
virt-filesystems(1) and virt-df(1) before starting.
EXAMPLES
Typical usage is:
virt-sparsify indisk outdisk
which copies "indisk" to "outdisk", making the output sparse.
"outdisk" is created, or overwritten if it already exists. The format
of the input disk is detected (eg. qcow2) and the same format is used
for the output disk.
To convert between formats, use the --convert option:
virt-sparsify disk.raw --convert qcow2 disk.qcow2
Virt-sparsify tries to zero and sparsify free space on every filesystem
it can find within the source disk image. You can get it to ignore
(don't zero free space on) certain filesystems by doing:
virt-sparsify--ignore /dev/sda1 indisk outdisk
See virt-filesystems(1) to get a list of filesystems within a disk
image.
OPTIONS--help
Display help.
--compress
Compress the output file. This only works if the output format is
"qcow2".
--convert raw
--convert qcow2
--convert [other formats]
Use "output-format" as the format for the destination image. If
this is not specified, then the input format is used.
Supported and known-working output formats are: "raw", "qcow2",
"vdi".
You can also use any format supported by the qemu-img(1) program,
eg. "vmdk", but support for other formats is reliant on qemu.
Specifying the --convert option is usually a good idea, because
then virt-sparsify doesn't need to try to guess the input format.
For fine-tuning the output format, see: --compress, -o.
--debug-gc
Debug garbage collection and memory allocation. This is only
useful when debugging memory problems in virt-sparsify or the OCaml
libguestfs bindings.
--format raw
--format qcow2
Specify the format of the input disk image. If this flag is not
given then it is auto-detected from the image itself.
If working with untrusted raw-format guest disk images, you should
ensure the format is always specified.
--ignore filesystem
--ignore volgroup
Ignore the named filesystem. Free space on the filesystem will not
be zeroed, but existing blocks of zeroes will still be sparsified.
In the second form, this ignores the named volume group. Use the
volume group name without the "/dev/" prefix, eg. --ignore vg_foo
You can give this option multiple times.
--machine-readable
This option is used to make the output more machine friendly when
being parsed by other programs. See "MACHINE READABLE OUTPUT"
below.
-o option[,option,...]
Pass -ooption(s) to the qemu-img(1) command to fine-tune the
output format. Options available depend on the output format (see
--convert) and the installed version of the qemu-img program.
You should use -o at most once. To pass multiple options, separate
them with commas, eg:
virt-sparsify--convert qcow2 \
-o cluster_size=512,preallocation=metadata ...
-q
--quiet
This disables progress bars and other unnecessary output.
-v
--verbose
Enable verbose messages for debugging.
-V
--version
Display version number and exit.
-x Enable tracing of libguestfs API calls.
--zero partition
--zero logvol
Zero the contents of the named partition or logical volume in the
guest. All data on the device is lost, but sparsification is
excellent! You can give this option multiple times.
MACHINE READABLE OUTPUT
The --machine-readable option can be used to make the output more
machine friendly, which is useful when calling virt-sparsify from other
programs, GUIs etc.
There are two ways to use this option.
Firstly use the option on its own to query the capabilities of the
virt-sparsify binary. Typical output looks like this:
$ virt-sparsify--machine-readable
virt-sparsify
ntfs
btrfs
A list of features is printed, one per line, and the program exits with
status 0.
Secondly use the option in conjunction with other options to make the
regular program output more machine friendly.
At the moment this means:
1. Progress bar messages can be parsed from stdout by looking for this
regular expression:
^[0-9]+/[0-9]+$
2. The calling program should treat messages sent to stdout (except
for progress bar messages) as status messages. They can be logged
and/or displayed to the user.
3. The calling program should treat messages sent to stderr as error
messages. In addition, virt-sparsify exits with a non-zero status
code if there was a fatal error.
All versions of virt-sparsify have supported the --machine-readable
option.
WINDOWS 8
Windows 8 "fast startup" can prevent virt-sparsify from working. See
"WINDOWS HIBERNATION AND WINDOWS 8 FAST STARTUP" in guestfs(3).
EXIT STATUS
This program returns 0 if successful, or non-zero if there was an
error.
ENVIRONMENT VARIABLES
TMPDIR
Location of the temporary directory used for the potentially large
temporary overlay file.
You should ensure there is enough free space in the worst case for
a full copy of the source disk (virtual size), or else set $TMPDIR
to point to another directory that has enough space.
This defaults to "/tmp".
Note that if $TMPDIR is a tmpfs (eg. if "/tmp" is on tmpfs, or if
you use "TMPDIR=/dev/shm"), tmpfs defaults to a maximum size of
half of physical RAM. If virt-sparsify exceeds this, it will hang.
The solution is either to use a real disk, or to increase the
maximum size of the tmpfs mountpoint, eg:
mount -o remount,size=10G /tmp
For other environment variables, see "ENVIRONMENT VARIABLES" in
guestfs(3).
SEE ALSOvirt-filesystems(1), virt-df(1), virt-resize(1), virt-rescue(1),
guestfs(3), guestfish(1), truncate(1), fallocate(1), qemu-img(1),
http://libguestfs.org/.
AUTHOR
Richard W.M. Jones http://people.redhat.com/~rjones/
COPYRIGHT
Copyright (C) 2011-2012 Red Hat Inc.
LICENSE
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
BUGS
To get a list of bugs against libguestfs, use this link:
https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
To report a new bug against libguestfs, use this link:
https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
When reporting a bug, please supply:
· The version of libguestfs.
· Where you got libguestfs (eg. which Linux distro, compiled from
source, etc)
· Describe the bug accurately and give a way to reproduce it.
· Run libguestfs-test-tool(1) and paste the complete, unedited output
into the bug report.
libguestfs-1.20.4 2013-03-12 virt-sparsify(1)
