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2018-07-30qemu-img: Add -C option for convert with copy offloadingFam Zheng1-1/+7
Signed-off-by: Fam Zheng <famz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-07-30Revert "qemu-img: Document copy offloading implications with -S and -c"Fam Zheng1-4/+2
This reverts commit eb461485f4558e362fab905735b50987505bca44. Now that we introduce an explicit option, these implicit rules are not used. Signed-off-by: Fam Zheng <famz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-07-12qemu-img: Document copy offloading implications with -S and -cFam Zheng1-2/+4
Explicitly enabling zero detection or compression suppresses copy offloading during convert. Document it. Suggested-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-06-11qemu-img: Remove deprecated -s snapshot_id_or_name optionThomas Huth1-5/+2
It has been marked as deprecated since QEMU v2.0 already, so it is time now to finally remove it. Signed-off-by: Thomas Huth <thuth@redhat.com> Message-id: 1528288551-31641-1-git-send-email-thuth@redhat.com Reviewed-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-05-20qemu-img: Make documentation between .texi and .hx consistentJohn Snow1-12/+12
These are also different and out of order for whatever reason. I'd like to automate this in the future, but for now let's put on the band-aid. In the case of resize, there were options missing from all three docstrings; the new string is based on the code. Signed-off-by: John Snow <jsnow@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2018-05-20qemu-img.texi: fix command orderingJohn Snow1-28/+30
This should match the summary ordering, which is alphabetical. Signed-off-by: John Snow <jsnow@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2018-02-13qemu-img: Document --force-share / -UFam Zheng1-0/+8
Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-02-13qemu-img.texi: Clean up parameter listFam Zheng1-27/+39
Split options out of the "@table @var" section and create a "@table @option", then use whitespaces and blank lines consistently. Suggested-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-10-26qemu-img.1: Image invalidation on qemu-img commitMax Reitz1-5/+4
qemu-img commit invalidates all images between base and top. This should be mentioned in the man page. Suggested-by: Ping Li <pingl@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-09-26qemu-img: add --shrink flag for resizePavel Butsykin1-1/+5
The flag is additional precaution against data loss. Perhaps in the future the operation shrink without this flag will be blocked for all formats, but for now we need to maintain compatibility with raw. Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: John Snow <jsnow@redhat.com> Message-id: 20170918124230.8152-2-pbutsykin@virtuozzo.com [mreitz: Added a missing space to a warning] Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-09-26qemu-img: Clarify about relative backing file optionsFam Zheng1-0/+9
It's not too surprising when a user specifies the backing file relative to the current working directory instead of the top layer image. This causes error when they differ. Though the error message has enough information to infer the fact about the misunderstanding, it is better if we document this explicitly, so that users don't have to learn from mistakes. Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-07-18qemu-img: Check for backing image if specified during createJohn Snow1-1/+8
Or, rather, force the open of a backing image if one was specified for creation. Using a similar -unsafe option as rebase, allow qemu-img to ignore the backing file validation if possible. It may not always be possible, as in the existing case when a filesize for the new image was not specified. This is accomplished by shifting around the conditionals in bdrv_img_create, such that a backing file is always opened unless we provide BDRV_O_NO_BACKING. qemu-img is adjusted to pass this new flag when -u is provided to create. Sorry for the heinous looking diffstat, but it's mostly whitespace. Inspired by: https://bugzilla.redhat.com/show_bug.cgi?id=1213786 Signed-off-by: John Snow <jsnow@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-07-11qemu-img: Expose PreallocMode for resizingMax Reitz1-1/+6
Add a --preallocation command line option to qemu-img resize which can be used to set the PreallocMode parameter of blk_truncate(). While touching this code, fix the fact that we did not handle errors returned by blk_getlength(). Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 20170613202107.10125-5-mreitz@redhat.com Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-07-11qemu-img: add measure subcommandStefan Hajnoczi1-0/+30
The measure subcommand calculates the size required by a new image file. This can be used by users or management tools that need to allocate space on an LVM volume, SAN LUN, etc before creating or converting an image file. Suggested-by: Maor Lipchuk <mlipchuk@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Message-id: 20170705125738.8777-8-stefanha@redhat.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-07-11qcow: document another weakness of qcow AES encryptionDaniel P. Berrange1-3/+16
Document that use of guest virtual sector numbers as the basis for the initialization vectors is a potential weakness, when combined with internal snapshots or multiple images using the same passphrase. This fixes the formatting of the itemized list too. Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170623162419.26068-4-berrange@redhat.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-05-29qemu-img: introduce --target-image-opts for 'convert' commandDaniel P. Berrange1-2/+10
The '--image-opts' flag indicates whether the source filename includes options. The target filename has to remain in the plain filename format though, since it needs to be passed to bdrv_create(). When using --skip-create though, it would be possible to use image-opts syntax. This adds --target-image-opts to indicate that the target filename includes options. Currently this mandates use of the --skip-create flag too. Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170515164712.6643-4-berrange@redhat.com Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-04-28progress: Show current progress on SIGINFOMax Reitz1-1/+2
Currently we only print progress information on retrieval of SIGUSR1. Some systems have a dedicated SIGINFO for this, however, so it should be handled appropriately if it is available. Buglink: https://bugs.launchpad.net/qemu/+bug/1662468 Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 20170207235757.2026-1-mreitz@redhat.com Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-04-27qemu-img: Document backing optionsMax Reitz1-2/+2
The create and convert subcommands have shorthands to set the backing_file and, in the case of create, the backing_fmt options for the new image. However, they have not been documented so far, which is remedied by this patch. Reported-by: Eric Blake <eblake@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-02-28qemu-img: make convert asyncPeter Lieven1-1/+15
the convert process is currently completely implemented with sync operations. That means it reads one buffer and then writes it. No parallelism and each sync request takes as long as it takes until it is completed. This can be a big performance hit when the convert process reads and writes to devices which do not benefit from kernel readahead or pagecache. In our environment we heavily have the following two use cases when using qemu-img convert. a) reading from NFS and writing to iSCSI for deploying templates b) reading from iSCSI and writing to NFS for backups In both processes we use libiscsi and libnfs so we have no kernel cache. This patch changes the convert process to work with parallel running coroutines which can significantly improve performance for network storage devices: qemu-img (master) nfs -> iscsi 22.8 secs nfs -> ram 11.7 secs ram -> iscsi 12.3 secs qemu-img-async (8 coroutines, in-order write disabled) nfs -> iscsi 11.0 secs nfs -> ram 10.4 secs ram -> iscsi 9.0 secs This patches introduces 2 new cmdline parameters. The -m parameter to specify the number of coroutines running in parallel (defaults to 8). And the -W parameter to allow qemu-img to write to the target out of order rather than sequential. This improves performance as the writes do not have to wait for each other to complete. Signed-off-by: Peter Lieven <pl@kamp.de> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-09-20qemu-img: add skip option to ddReda Sallahi1-1/+3
This adds the skip option which allows qemu-img dd to skip a number of blocks before copying the input. A test case was added to test the skip option. Signed-off-by: Reda Sallahi <fullmanet@gmail.com> Message-id: 20160810141609.32727-1-fullmanet@gmail.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2016-09-20qemu-img: add the 'dd' subcommandReda Sallahi1-0/+25
This patch adds a basic dd subcommand analogous to dd(1) to qemu-img. For the start, this implements the bs, if, of and count options and requires both if and of to be specified (no stdin/stdout if not specified) and doesn't support tty, pipes, etc. The image format must be specified with -O for the output if the raw format is not the intended one. Two tests are added to test qemu-img dd. Signed-off-by: Reda Sallahi <fullmanet@gmail.com> Message-id: 20160810024312.14544-1-fullmanet@gmail.com Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> [mreitz: Moved test 158 to 170] Signed-off-by: Max Reitz <mreitz@redhat.com>
2016-06-28trace: enable tracing in qemu-imgDenis V. Lunev1-0/+3
The command will work this way: qemu-img --trace "qcow2*" create -f qcow2 1.img 64G [Quote "qcow2*" to protect against shell globbing as suggested by Eric Blake <eblake@redhat.com>. --Stefan] Signed-off-by: Denis V. Lunev <den@openvz.org> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 1466174654-30130-8-git-send-email-den@openvz.org Suggested by: Daniel P. Berrange <berrange@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> CC: Paolo Bonzini <pbonzini@redhat.com> CC: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-06-28qemu-img: move common options parsing before commands processingDenis V. Lunev1-1/+9
This is necessary to enable creation of common qemu-img options which will be specified before command. The patch also enables '-V' alias to '--version' (exactly like in other block utilities) and documents this change. Signed-off-by: Denis V. Lunev <den@openvz.org> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 1466174654-30130-7-git-send-email-den@openvz.org CC: Paolo Bonzini <pbonzini@redhat.com> CC: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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>
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