First, I have a feeling this might be a question I could ask on a qemu
list. Is there a way for me to tell which questions should go where?
Is it OK to ask here?
As I install software onto a system I want to preserve its state--just
the disk state---at various points so I can go back. What is the best
way to do this?
First, I think I could just make a copy of the virtual disk, although I
haven't seen this suggested anywhere. I assume this will work if the VM
is off; are there other circumstances in which it is safe? Since my
original virtual disk file isn't really occupying its nominal space, I
assume this will be true of the copy too.
Second, kvm-img could create a copy on write image. There are several
things I don't understand about this. Suppose I go
kvm-img -b A.img B.img
If I then go on and use A.img as I did before, changing what is on disk,
have I screwed up B.img?
Do A.img or B.img have to be qcow2 format? I created a raw image for
portability.
Suppose I work for awhile installing new stuff on B.img, and then want
to preserve the state. Is
kvm-img -b B.img C.img
sensible, or is this kind of recursive operation (B.img is already the
copy on write version of A.img) not OK?
Does ʽcommit [-f fmt] filenameʼ, documented as
Commit the changes recorded in filename in its base image.
mean commit the recorded changes TO its base image?
Here are some other things I think I don't want to do. Please let me
know if I'm mistaken.
-snapshot on the kvm command line: nothing persistent comes of this
(maybe if you commit you update the original image, but you don't get
2).
snapshot in the monitor: this snapshots the non-disk state of the VM;
further, that state is not guaranteed to work if you later change what
is on the disk. I think kvm-img snapshot also accesses these
facilities.
Yours in confusion :)
Ross
P.S. Please cc me.
--
Ross Boylan wk: (415) 514-8146
185 Berry St #5700 ross@xxxxxxxxxxxxxxxx
Dept of Epidemiology and Biostatistics fax: (415) 514-8150
University of California, San Francisco
San Francisco, CA 94107-1739 hm: (415) 550-1062
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