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2016-06-08qemu-img bench: Add --flush-intervalKevin Wolf1-1/+7
This options allows to flush the image periodically during write tests. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Denis V. Lunev <den@openvz.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-06-08qemu-img bench: Implement -S (step size)Kevin Wolf1-2/+4
With this new option, qemu-img bench can be told to advance the current offset after each request by a different value than the buffer size. This is useful for controlling the conditions for cluster allocation in image formats (e.g. qcow2 cluster allocation with COW in front of the request, or COW areas that aren't overwritten immediately). Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Denis V. Lunev <den@openvz.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-06-08qemu-img bench: Make start offset configurableKevin Wolf1-2/+3
This patch adds an option the specify the offset of the first request made by qemu-img bench. This allows to benchmark misaligned requests. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Denis V. Lunev <den@openvz.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-06-08qemu-img bench: Sequential writesKevin Wolf1-4/+9
This extends qemu-img bench with an option that makes it use sequential writes instead of reads for the test run. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Denis V. Lunev <den@openvz.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-06-08qemu-img benchKevin Wolf1-0/+10
This adds a qemu-img command that allows doing some simple benchmarks for the block layer without involving guest devices and a real VM. For the start, this implements only a test of sequential reads. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Denis V. Lunev <den@openvz.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-02-22qemu-img: allow specifying image as a set of options argsDaniel P. Berrange1-0/+6
Currently qemu-img allows an image filename to be passed on the command line, but unless using the JSON format, it does not have a way to set any options except the format eg qemu-img info https://127.0.0.1/images/centos7.iso This adds a --image-opts arg that indicates that the positional filename should be interpreted as a full option string, not just a filename. qemu-img info --image-opts driver=https,url=https://127.0.0.1/images,sslverify=off This flag is mutually exclusive with the '-f' / '-F' flags. Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-02-22qemu-img: add support for --object command line argDaniel P. Berrange1-0/+8
Allow creation of user creatable object types with qemu-img via a new --object command line arg. This will be used to supply passwords and/or encryption keys to the various block driver backends via the recently added 'secret' object type. # printf letmein > mypasswd.txt # qemu-img info --object secret,id=sec0,file=mypasswd.txt \ ...other info args... Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-01-26docs: Style the command and its options in the synopsisSitsofe Wheeler1-1/+1
Signed-off-by: Sitsofe Wheeler <sitsofe@yahoo.com> Message-Id: <1452718226-25001-1-git-send-email-sitsofe@yahoo.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-09-11maint: remove / fix many doubled wordsDaniel P. Berrange1-1/+1
Many source files have doubled words (eg "the the", "to to", and so on). Most of these can simply be removed, but a couple were actual mis-spellings (eg "to to" instead of "to do"). There was even one triple word score "to to to" :-) Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2014-11-03qemu-img: Add progress output for amendMax Reitz1-1/+1
Now that bdrv_amend_options() supports a status callback, use it to display a progress report. Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Benoît Canet <benoit.canet@nodalink.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Message-id: 1414404776-4919-3-git-send-email-mreitz@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-11-03qemu-img: Specify backing file for commitMax Reitz1-1/+11
Introduce a new parameter for qemu-img commit which may be used to explicitly specify the backing file into which an image should be committed if the backing chain has more than a single layer. [Applied Eric Blake's qemu-img.texi documentation rewording --Stefan] Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Message-id: 1414159063-25977-12-git-send-email-mreitz@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-11-03qemu-img: Enable progress output for commitMax Reitz1-1/+1
Implement progress output for the commit command by querying the progress of the block job. Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Message-id: 1414159063-25977-11-git-send-email-mreitz@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-11-03qemu-img: Empty image after commitMax Reitz1-1/+5
After the top image has been committed, it should be emptied unless specified otherwise. Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Message-id: 1414159063-25977-10-git-send-email-mreitz@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-09-22block: delete cow block driverStefan Hajnoczi1-2/+2
This patch removes support for the cow file format. Normally we do not break backwards compatibility but in this case there is no impact and it is the most logical option. Extraordinary claims require extraordinary evidence so I will show why removing the cow block driver is the right thing to do. The cow file format is the disk image format for Usermode Linux, a way of running a Linux system in userspace. The performance of UML was never great and it was hacky, but it enjoyed some popularity before hardware virtualization support became mainstream. QEMU's block/cow.c is supposed to read this image file format. Unfortunately the file format was underspecified: 1. Earlier Linux versions used the MAXPATHLEN constant for the backing filename field. The value of MAXPATHLEN can change, so Linux switched to a 4096 literal but QEMU has a 1024 literal. 2. Padding was not used on the header struct (both in the Linux kernel and in QEMU) so the struct layout varied across architectures. In particular, i386 and x86_64 were different due to int64_t alignment differences. Linux now uses __attribute__((packed)), QEMU does not. Therefore: 1. QEMU cow images do not conform to the Linux cow image file format. 2. cow images cannot be shared between different host architectures. This means QEMU cow images are useless and QEMU has not had bug reports from users actually hitting these issues. Let's get rid of this thing, it serves no purpose and no one will be affected. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Message-id: 1410877464-20481-1-git-send-email-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-09-12qcow2: Add falloc and full preallocation optionHu Tao1-3/+5
preallocation=falloc allocates disk space by posix_fallocate(), preallocation=full allocates disk space by writing zeros to disk. Both modes imply preallocation=metadata. Signed-off-by: Hu Tao <hutao@cn.fujitsu.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-09-12raw-posix: Add falloc and full preallocation optionHu Tao1-0/+9
This patch adds a new option preallocation for raw format, and implements falloc and full preallocation. Signed-off-by: Hu Tao <hutao@cn.fujitsu.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-09-08qemu-img: fix rebase src_cache option documentationStefan Hajnoczi1-1/+1
The src_cache option (-T) specifies the cache mode for backing files. It applies both the image's old backing file as well as the new backing file: ret = bdrv_open(&bs_old_backing, backing_name, NULL, NULL, src_flags, old_backing_drv, &local_err); if (ret) { ... } if (out_baseimg[0]) { bs_new_backing = bdrv_new("new_backing", &error_abort); ret = bdrv_open(&bs_new_backing, out_baseimg, NULL, NULL, src_flags, new_backing_drv, &local_err); if (ret) { ... } } The documentation only mentions the new backing file but it really applies to both. Suggested-by: Jeff Nelson <jenelson@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com>
2014-09-08qemu-img: clarify src_cache option documentationStefan Hajnoczi1-2/+3
The source cache option takes the same values as the cache option. The documentation reads a little strange because it starts with "In contrast the src_cache option ...". The fact that this is comparing with the previous documented option (the 'cache' option) is implicit. Readers may be confused, especially if they jump to src_cache without reading cache documentation first. Suggested-by: Jeff Nelson <jenelson@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com>
2014-08-22qemu-img: Allow cache mode specification for amendMax Reitz1-1/+1
qemu-img amend may extensively modify the target image, depending on the options to be amended (e.g. conversion to qcow2 compat level 0.10 from 1.1 for an image with many unallocated zero clusters). Therefore it makes sense to allow the user to specify the cache mode to be used. Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-08-22qemu-img: Allow source cache mode specificationMax Reitz1-4/+10
Many qemu-img subcommands only read the source file(s) once. For these use cases, a full write-back cache is unnecessary and mainly clutters host cache memory. Though this is generally no concern as cache memory is freely available and can be scaled by the host OS, it may become a concern with thin provisioning. For these cases, it makes sense to allow users to freely specify the source cache mode (e.g. use no cache at all). This commit adds a new switch (-T) for the qemu-img subcommands check, compare, convert and rebase to specify the cache to be used for source images (the backing file in case of rebase). Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-07-07Fix nocow typos in manpageChunyan Liu1-2/+2
Signed-off-by: Chunyan Liu <cyliu@suse.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-07-01qemu-img create: add 'nocow' optionChunyan Liu1-0/+16
Add 'nocow' option so that users could have a chance to set NOCOW flag to newly created files. It's useful on btrfs file system to enhance performance. Btrfs has low performance when hosting VM images, even more when the guest in those VM are also using btrfs as file system. One way to mitigate this bad performance is to turn off COW attributes on VM files. Generally, there are two ways to turn off NOCOW on btrfs: a) by mounting fs with nodatacow, then all newly created files will be NOCOW. b) per file. Add the NOCOW file attribute. It could only be done to empty or new files. This patch tries the second way, according to the option, it could add NOCOW per file. For most block drivers, since the create file step is in raw-posix.c, so we can do setting NOCOW flag ioctl in raw-posix.c only. But there are some exceptions, like block/vpc.c and block/vdi.c, they are creating file by calling qemu_open directly. For them, do the same setting NOCOW flag ioctl work in them separately. [Fixed up 082.out due to the new 'nocow' creation option --Stefan] Signed-off-by: Chunyan Liu <cyliu@suse.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-06-04qemu-img: Document check exit codesMax Reitz1-0/+23
The exit code 63 (check not supported by image format) was not even documented in the comment above the check command in the source code; add it, as it does indeed seem useful. Also, document all of check's exit codes in the manpage. Signed-off-by: Max Reitz <mreitz@redhat.com> Reported-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Benoit Canet <benoit@irqsave.net> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-01-31Describe flaws in qcow/qcow2 encryption in the docsDaniel P. Berrange1-3/+20
The qemu-img.texi / qemu-doc.texi files currently describe the qcow2/qcow2 encryption thus "Encryption uses the AES format which is very secure (128 bit keys). Use a long password (16 characters) to get maximum protection." While AES is indeed a strong encryption system, the way that QCow/QCow2 use it results in a poor/weak encryption system. Due to the use of predictable IVs, based on the sector number extended to 128 bits, it is vulnerable to chosen plaintext attacks which can reveal the existence of encrypted data. The direct use of the user passphrase as the encryption key also leads to an inability to change the passphrase of an image. If passphrase is ever compromised the image data will all be vulnerable, since it cannot be re-encrypted. The admin has to clone the image files with a new passphrase and then use a program like shred to secure erase all the old files. Recommend against any use of QCow/QCow2 encryption, directing users to dm-crypt / LUKS which can meet modern cryptography best practices. [Changed "Qcow" to "qcow" for consistency. --Stefan] Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-01-24block: update block commit documentation regarding image truncationJeff Cody1-1/+6
This updates the documentation for commiting snapshot images. Specifically, this highlights what happens when the base image is either smaller or larger than the snapshot image being committed. In the case of the base image being smaller, it is resized to the larger size of the snapshot image. In the case of the base image being larger, it is not resized automatically, but once the commit has completed it is safe for the user to truncate the base image. Signed-off-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-01-24Documentation: qemu-img: Mention SIGUSR1 progress reportKevin Wolf1-1/+3
Document the SIGUSR1 behaviour of qemu-img. Also, added compare to the list of subcommands that support -p. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Benoit Canet <benoit@irqsave.net>
2014-01-22docs: qcow2 compat=1.1 is now the defaultStefan Hajnoczi1-4/+4
Commit 9117b47717ad208b12786ce88eacb013f9b3dd1c ("qcow2: Change default for new images to compat=1.1") changed the default qcow2 image format version but forgot to update qemu-doc.texi and qemu-img.texi. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-12-20docs: updated qemu-img man page and qemu-doc to reflect VHDX support.Jeff Cody1-2/+2
The man page for qemu-img, and the qemu-doc, did not mention VHDX as a supported format. This adds in reference to VHDX in those documents. [Stefan Weil <sw@weilnetz.de> suggested s/Block Size/Block size/ for consistency. I have made this change. --Stefan] Signed-off-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Stefan Weil <sw@weilnetz.de> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-12-04qemu-img: add -l for snapshot in convertWenchao Xia1-4/+8
Now qemu-img convert have similar options as qemu-nbd for internal snapshot. Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-28qemu-img: add support for fully allocated imagesPeter Lieven1-0/+6
Signed-off-by: Peter Lieven <pl@kamp.de> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-12block: Image file option amendmentMax Reitz1-0/+5
This patch adds the "amend" option to qemu-img which allows changing image options on existing image files. It also adds the generic bdrv implementation which is basically just a wrapper for the image format specific function. Signed-off-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-06docs, qapi: document qemu-img mapPaolo Bonzini1-0/+55
Eric Blake also requested including the output in qapi-schema.json, so that it is published through the introspection mechanism. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-06add qemu-img convert -n option (skip target volume creation)Alexandre Derumier1-1/+14
Add a -n option to skip volume creation on qemu-img convert. This is useful for targets such as rbd / ceph, where the target volume may already exist; we cannot always rely on qemu-img convert to create the image, as dependent on the output format, there may be parameters which are not possible to specify through the qemu-img convert command line. Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Alexandre Derumier <aderumier@odiso.com> Signed-off-by: Alex Bligh <alex@alex.org.uk> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-02-22qemu-img: Add compare subcommandMiroslav Rezanina1-0/+53
This patch adds new qemu-img subcommand that compares content of two disk images. Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-02-22qemu-img: Add "Quiet mode" optionMiroslav Rezanina1-0/+3
There can be a need to turn output to stdout off. This patch adds a -q option that enable "Quiet mode". In Quiet mode, only errors are printed out. Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-02-22qemu-img: add json output option to the check commandFederico Simoncelli1-2/+3
This option --output=[human|json] makes qemu-img check output a human or JSON representation at the choice of the user. Signed-off-by: Federico Simoncelli <fsimonce@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-11-30Documentation: Update image format informationKevin Wolf1-57/+27
Document new and yet undocumented options and image formats. The qemu-img man page contains information only for raw and qcow2 now and references the HTML documentation for a more detailed description of other formats. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
2012-10-24qemu-img: document 'info --backing-chain'Kashyap Chamarthy1-1/+20
Signed-off-by: Kashyap Chamarthy <kashyap.cv@gmail.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-24qemu-img rebase: use empty string to rebase without backing fileAlex Bligh1-1/+3
This patch allows an empty filename to be passed as the new base image name for qemu-img rebase to mean base the image on no backing file (i.e. independent of any backing file). According to Eric Blake, qemu-img rebase already supports this when '-u' is used; this adds support when -u is not used. Signed-off-by: Alex Bligh <alex@alex.org.uk> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-09-17Merge remote-tracking branch 'kwolf/for-anthony' into stagingAnthony Liguori1-2/+3
* kwolf/for-anthony: block: Don't forget to delete temporary file Don't require encryption password for 'qemu-img info' command qemu-img: Add json output option to the info command. qapi: Add SnapshotInfo and ImageInfo. ahci: properly reset PxCMD on HBA reset block: fix block tray status vdi: Fix warning from clang block/curl: Fix wrong free statement ide: Fix error messages from static code analysis (no real error) ATAPI: STARTSTOPUNIT only eject/load media if powercondition is 0 sheepdog: fix savevm and loadvm
2012-09-14Spelling fixes in comments and documentationStefan Weil1-1/+1
These wrong spellings were detected by codespell: * successully -> successfully * alot -> a lot * wanna -> want to * infomation -> information * occured -> occurred ["also is" -> "is also" and "ressources" -> "resources" suggested by Peter Maydell <peter.maydell@linaro.org>] Signed-off-by: Stefan Weil <sw@weilnetz.de> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2012-09-12qemu-img: Add json output option to the info command.Benoît Canet1-2/+3
This option --output=[human|json] make qemu-img info output on human or JSON representation at the choice of the user. example: { "snapshots": [ { "vm-clock-nsec": 637102488, "name": "vm-20120821145509", "date-sec": 1345553709, "date-nsec": 220289000, "vm-clock-sec": 20, "id": "1", "vm-state-size": 96522745 }, { "vm-clock-nsec": 28210866, "name": "vm-20120821154059", "date-sec": 1345556459, "date-nsec": 171392000, "vm-clock-sec": 46, "id": "2", "vm-state-size": 101208714 } ], "virtual-size": 1073741824, "filename": "snap.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 985587712, "dirty-flag": false } Signed-off-by: Benoit Canet <benoit@irqsave.net> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-08-17Documentation: Warn against qemu-img on active imageKevin Wolf1-0/+10
People have repeatedly expected that you can do things like snapshotting an image with qemu-img while a qemu instance is running. Maybe we need to consider locking the files while they are in use, but having a warning in the qemu-img manpage is doable for 1.2 and can't hurt anyway. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-06-15qemu-img: document qed format on qemu-img man pageStefan Hajnoczi1-0/+23
The qemu-img.1 man page is missing the qed format from its list of supported formats. Document the image creation options for qed. Suggested-by: Michael Tokarev <mjt@tls.msk.ru> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-06-15qemu-img check -r for repairing imagesKevin Wolf1-1/+6
The QED block driver already provides the functionality to not only detect inconsistencies in images, but also fix them. However, this functionality cannot be manually invoked with qemu-img, but the check happens only automatically during bdrv_open(). This adds a -r switch to qemu-img check that allows manual invocation of an image repair. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-05-25qemu-img: Explain how rebase operation can be used to perform a 'diff' ↵Richard W.M. Jones1-0/+18
operation. Signed-off-by: Richard W.M. Jones <rjones@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-12-15Documentation: Add qemu-img -t parameter in man pageKevin Wolf1-3/+7
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2011-08-29qemu-img: Require larger zero areas for sparse handlingKevin Wolf1-1/+6
By default, require 4k of consecutive zero bytes for qemu-img to make the output file sparse by not issuing a write request for the zeroed parts. Add an -S option to allow users to tune this setting. This helps to avoid situations where a lot of zero sectors and data sectors are mixed and qemu-img tended to issue many tiny 512 byte writes. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-07-20Add missing documentation for qemu-img -pJes Sorensen1-2/+4
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-07-05Documentation: Remove outdated host_device noteKevin Wolf1-6/+0
People shouldn't explicitly specify host_device any more. raw is doing the Right Thing. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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