For reducing the logical size (what a simple ls -al gives) you need to use virt-spasify or qemu-img (as described in the other answers). Bonus Create a virtual disk qemu-img create -f raw -o size 10G /data/disk.raw-f: Disk format-o: Options, list of format specific options, name1value1, name2value2 etc. However, please note that this can be CPU-intensive for the host (which had to "parse" any guest write searching for repeating zeroes), so it should be only enabled in specific cases.īoth methods will reduce the physical allocated size (what du -hs shows). This can be checked with du -hs on host side (note: ls -al will not show the real allocated size, just the logical one).įor even newer libvirt/qemu instances (ie: RHEL8+), guest file size can be reduced even if the guest OS does not support trim: by enabling both discard='unmap' and discard_zeroes='unmap' (and using the virtio-scsi driver), writing a sequential stream of zero on guest side (ie: via dd if=/dev/zero of=/zero.img bs=1M count=1024) will trigger host-size trimming of the affected LBA ranges.
QEMU IMG FREE
If the virtual machine uses virtio-scsi and the libvirt definition include discard='unmap', a simple fstrim on the guest filesystem will release assigned-but-unused free space on the host. The output image format can be imported to VPS cloud providers like Openstack and other providers like Cloudstack. qemu-img is used to format guest images, add additional storage devices and network storage e.t.c.
QEMU IMG DRIVER
I further advice you to run this command inside a screen or tmux session if it may take very long so you do not loose your job! Close the emulatorĪfter the transfer is complete, you have a ready and converted QCOW2 image on myimage.In addition to the accepted answer (which describe the more common, general method to shrink a qcow2 file), modern version (ie: RHEL7+) of the libvirt/qemu/qcow2 stack supports the virtio-scsi driver which supports the discard='unmap' option. qemu-img is the command line utility that’s used to convert various file systems used by hypervisors like Xen, KVM, VMware, VirtualBox.
QEMU IMG PLUS
I added a plus using pv so you can monitor the progress. You can use any network command, for example ssh and dd to make the magic work: $ dd if=myoriginalimg bs=100M | pv -tebrap -size 500g | ssh myhost dd of=/dev/nbd0 bs=100M If we check these files withqemu-img info. qemu-img is the built-in qemu image manipulation tool convert tells qemu-image that you want to convert one image file, such as. Now you have a /dev/nbd0 device that is a block device just like any block device but any operation done over it will be performed on the QCOW2 image Perform the transfer over the emulated device qemu-img create -f qcow2 vdisk1 40G Formatting vdisk1, fmtqcow2 size42949672960 clustersize65536 lazyrefcountsoff refcountbits16 ls -lh vdisk1 vdisk2 -rw-r-r- 1 ssirohi ssirohi 193K Apr 19 16:30 vdisk1 Above we create 40 GB of file, But this file don’t have meta-data and both have only 193 KB of size. $ qemu-nbd -connect /dev/nbd0 myimage.qcow2 Arch grub menu page is open normally but after that it drop to. Once I try to boot up from this usb stick. the command produce a raw image from qcow2 image and copy it into a usb stick. Code: qemu-img convert -f qcow2 -O raw my-qcow2.img /dev/sdb. This is mostly used to get access to QCOW2 contents, but the device is read-writable so you can treat it as a standard block device: $ modprobe nbd I google around and the best way o found is below command. There is a tool that allows you to emulate a device on top of a QCOW2 image. In destination, create an empty QCOW2 image, for example: $ qemu-img create -f qcow2 myimage.qcow2 500gĬonnect the QCOW2 image using NBD to a device Now perform the 'active block-commit' operation: virsh blockcommit vm1 vda -verbose -pivot -active Block Commit: 100. Use the same procedure discussed earlier to create the disk image chain. So below is what I made: Create an empty QCOW2 image base.raw (live QEMU) Where the base.raw contains the contents of a.qcow2, b.qcow2 and c.qcow2 and the live QEMU is piovoted to point to the base.raw. If your file system supports holes (for example in ext2 or. This can be the fastest file-based format. When a format is specified in any of the qemu-img commands, the following format types may be used: raw - Raw disk image format (default). I had the same problem, but the provided answer from Michael Hampton would not fit for me as the amount of data I had to transfer was too big and the time I had to do the operation would not be enough. A Red Hat training course is available for Red Hat Enterprise Linux. Although this is an old question I think it should be worth to show an interesting alternative.