QEMU常用命令

QEMU常用命令：

1. 创建image，qcow2格式与raw格式的对比

[root@andriy qemu]# qemu-img create -f raw test.img 5G
Formatting 'test.img', fmt=raw size=5368709120 
[root@andriy qemu]# file test.img
test.img: data
[root@andriy qemu]# qemu-img info test.img
image: test.img
file format: raw
virtual size: 5.0G (5368709120 bytes)
disk size: 0
[root@andriy qemu]# qemu-img create -f qcow2 test2.img 10G
Formatting 'test2.img', fmt=qcow2 size=10737418240 encryption=off cluster_size=65536 lazy_refcounts=off 
[root@andriy qemu]# file test2.img
test2.img: QEMU QCOW Image (v3), 10737418240 bytes
[root@andriy qemu]# qemu-img info test2.img
image: test2.img
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 196K
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false
[root@andriy qemu]# ll -h test*
-rw-r--r-- 1 root root 193K Aug 30 14:53 test2.img
-rw-r--r-- 1 root root 5.0G Aug 30 14:53 test.img
[root@andriy qemu]# du -sh test*
196K	test2.img
0	test.img

2. 检查image文件：raw不支持check

[root@andriy qemu]# qemu-img check test.img 
qemu-img: This image format does not support checks
[root@andriy qemu]# qemu-img check test2.img
No errors were found on the image.
Image end offset: 262144

3. 对image文件的可操作性选项

[root@andriy qemu]# qemu-img create -f qcow2 -o ? test2.img
Supported options:
size             Virtual disk size
compat           Compatibility level (0.10 or 1.1)
backing_file     File name of a base image
backing_fmt      Image format of the base image
encryption       Encrypt the image
cluster_size     qcow2 cluster size
preallocation    Preallocation mode (allowed values: off, metadata, falloc, full)
lazy_refcounts   Postpone refcount updates

4. 提交filename文件中的更改到后端支持镜像文件（创建时通过backing_file指定的）中去。

[root@andriy qemu]# qemu-img commit test2.img

5. 转换格式

[root@andriy qemu]# qemu-img convert -f qcow2 -O raw test2.img raw.img      #qcow2格式转换为raw格式
[root@andriy qemu]# qemu-img info raw.img 
image: raw.img
file format: raw
virtual size: 10G (10737418240 bytes)
disk size: 0
[root@andriy qemu]# qemu-img convert -f raw -O qcow2 raw.img qcow2.img      #raw格式转换为qcow2格式
[root@andriy qemu]# qemu-img info qcow2.img 
image: qcow2.img
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 196K
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false

6. 镜像扩容：只支持raw扩容

[root@andriy qemu]# qemu-img resize raw.img -/+1G
[root@andriy qemu]# qemu-img resize raw.img 11G
Image resized.
[root@andriy qemu]# qemu-img info raw.img 
image: raw.img
file format: raw
virtual size: 11G (11811160064 bytes)
disk size: 0
[root@andriy qemu]# qemu-img resize raw.img -1G
Image resized.
[root@andriy qemu]# qemu-img info raw.img 
image: raw.img
file format: raw
virtual size: 10G (10737418240 bytes)
disk size: 0

7. 快照操作

“-l” 选项是查询并列出镜像文件中的所有快照，“-a snapshot”是让镜像文件使用某个快照，“-c snapshot”是创建一个快照，“-d”是删除一个快照。
[root@andriy qemu]# qemu-img snapshot -l qcow2.img 
[root@andriy qemu]# qemu-img snapshot -c snapshot qcow2.img 
[root@andriy qemu]# ls
qcow2.img  raw.img  test2.img  test.img
[root@andriy qemu]# qemu-img snapshot -l qcow2.img 
Snapshot list:
ID        TAG                 VM SIZE                DATE       VM CLOCK
1         snapshot                  0 2017-08-30 15:18:25   00:00:00.000
qemu-img snapshot -a 1 qcow2.img
[root@andriy qemu]# qemu-img snapshot -d snapshot qcow2.img

8. 使用派生镜像

[root@andriy qemu]# qemu-img create -f qcow2 vm.qcow2 -o backing_file=qcow2.img