QCOW2(QEMU Copy On Write) format disk
1. QCOW2 Creation
1. Create Base Image with 10G size disk
qemu-img create -f qcow2 base.img 10G
2. Create Root Image which using base.img
qemu-img create -b base.img -f qcow2 root.img
qemu-img info shows the chaining information of root.img
sunshout@ubuntu-vm:/storage$ qemu-img info root.img
image: root.img
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 196K
cluster_size: 65536
backing file: base.img
Format specific information:
compat: 1.1
lazy refcounts: false
sunshout@ubuntu-vm:/storage$
2. QCOW2 Rebase image
- Changing base.img to another base image.
- For example, change root file system with new update fetch.
* Create new base image
qemu-img create -f qcow2 new_base.img 10G
* rebase backing image of root.img
qemu-im rebase -f qcow2 -u -F qcow2 -b new_base.img root.img
options:
-f : backing file's format
-F : root disk's file format
-b : new backing file's path
-u : unsafe mode (does not check similarity of base image and new base image)
sunshout@ubuntu-vm:/storage$ qemu-img create -f qcow2 new_base.img 10G
Formatting 'new_base.img', fmt=qcow2 size=10737418240 encryption=off cluster_size=65536 lazy_refcounts=off
sunshout@ubuntu-vm:/storage$ qemu-img rebase -u -f qcow2 -F qcow2 -b new_base.img root.img
sunshout@ubuntu-vm:/storage$ qemu-img info root.img
image: root.img
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 196K
cluster_size: 65536
backing file: new_base.img
backing file format: qcow2
Format specific information:
compat: 1.1
lazy refcounts: false
sunshout@ubuntu-vm:/storage$
- My development git : https://github.com/choonho/qemu-rebase.git
rebase.diff