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I am resizing an installed KVM domain

# resize the partitions
virt-resize --expand /dev/vda2 --LV-expand /dev/vg_main/lv_root $VMFILE $VMFILE.tmp

and virt-resize throws an error:

virt-resize: error: You cannot use --expand when there is no surplus space to expand into.  You need to make the target disk larger by at least 224.0K.

What does this mean and how can I avoid it?

I am using resizevm.sh script from CentOS KVM Image Tools and the script produces a dead disk image (domain doesn't boot up).

I am using the latest CentOS 6.5

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1 Answer 1

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Assuming you're using a modern enough version of KVM (CentOS 6+) you'll need to expand the image file prior to running the virt-resize command. Typically it's a 2 step process:

$ sudo truncate -s +2G $VMFILE

Followed by your resize command:

$ sudo virt-resize --expand /dev/vda2 --LV-expand /dev/vg_main/lv_root \
    $VMFILE $VMFILE.tmp

This will have the effect of expanding the .img file by 2GB. Change the argument to truncate to whatever size you'd like to expand the .img file by.

References

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  • 1. So, to expand a file, we should use a command which is named to the opposite of what it does, i.e. truncate? 2. I wonder how it worked previously, without the truncate command. Thanks, will try it! Apr 26, 2014 at 22:16
  • @NickolaiLeschov - yes that step was very counter-intuitive to us as well. I believe the tool needed to be called either reduce or expand and they opted to call it by the shrinking function. You can also do what you want via virt-manager (the GUI).
    – slm
    Apr 26, 2014 at 22:55

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