CentOS 7 KVM 总结(二） KVM管理

1. 常用kvm命令
2. 调整虚拟机硬盘
3. 热修改虚拟机配置
- 3.1. 修改内存
- 3.2. 修改CPU
4. 删除虚拟机
5. 快照
6. 问题整理

1. 常用kvm命令

列出所有虚拟机

  $ virsh list --all
   Id    Name                           State
  ----------------------------------------------------
   54    ubuntu_16_04                   running
   55    ubuntu_14_04                   running
   73    k8s_m1                         running
   74    k8s_m3                         running
   76    k8s_m2                         running

显示虚拟机信息

  $ virsh dominfo k8s_m1 
  Id:             73
  Name:           k8s_m1
  UUID:           2470dd0c-7956-44df-9b68-b1db5c30d502
  OS Type:        hvm
  State:          running
  CPU(s):         4
  CPU time:       231.5s
  Max memory:     4194304 KiB
  Used memory:    2097152 KiB
  Persistent:     yes
  Autostart:      enable
  Managed save:   no
  Security model: none
  Security DOI:   0

显示虚拟机内存和cpu使用情况,类似top

  More help in virt-top(1) man page. Press any key to return.
  virt-top 12:51:57 - x86_64 8/8CPU 800MHz 16266MB
  11 domains, 5 active, 5 running, 0 sleeping, 0 paused, 6 inactive D:0 O:0 X:0
  CPU: 0.3%  Mem: 10240 MB (10240 MB by guests)
	
     ID S RDRQ WRRQ RXBY TXBY %CPU %MEM    TIME   NAME                                                                                                   
     76 R    0    0  180    0  0.1 12.0   3:38.32 k8s_m2
     74 R    0    0  180    0  0.1 12.0   3:51.02 k8s_m3
     55 R    0    0  180    0  0.1 12.0   1:53.30 ubuntu_14_04
     73 R    0    0  180    0  0.1 12.0   3:57.13 k8s_m1
     54 R    0    0  180    0  0.0 12.0   2:06.37 ubuntu_16_04

显示分区信息

  $ virt-df k8s_m1
  Filesystem                           1K-blocks       Used  Available  Use%
  k8s_m1:/dev/sda1                       1038336     115276     923060   12%
  k8s_m1:/dev/centos/root               36936068    1188372   35747696    4%

或

  $ virsh domblklist k8s_m1
  Target     Source
  ------------------------------------------------
  vda        /data/kvmdiskk8s_m1.img

关闭虚拟机
```
  $ virsh shutdown k8s_m1
```
启动虚拟机
```
  $ virsh start k8s_m1
```
设置虚拟机开机启动
```
  $ virsh autostart k8s_m1
```
关闭虚拟及自启
```
  $ virsh undefine kvm-1
```
删除虚拟机
```
  $ virsh undefine k8s_m1
```
通过控制窗口登录虚拟机
```
  $ virsh console kvm-1
```

2. 调整虚拟机硬盘

查看虚拟机磁盘情况

  $ virt-df k8s_m1
  Filesystem                           1K-blocks       Used  Available  Use%
  k8s_m1:/dev/sda1                       1038336     115276     923060   12%
  k8s_m1:/dev/centos/root               36936068    1188372   35747696    4%

使用qemu-img 创建格式为qcow2的磁盘

  $ qemu-img create -f qcow2 k8s_m1_data.img 10g

添加到虚拟机

  $ virsh attach-disk k8s_m1 /data/kvmdisk/k8s_m1_data.img vdb --cache writeback --subdriver qcow2 

进入虚拟机
```
  $ virsh console k8s_m1
```

挂载磁盘

  $ mkfs.ext4 /dev/vdb

  $ mount /dev/vdb /data/

查看虚拟机磁盘情况,发现已经多出一块新建的磁盘

  $ virt-df k8s_m1
  Filesystem                           1K-blocks       Used  Available  Use%
  k8s_m1:/dev/sdb                       10190100      36888    9612540    1%
  k8s_m1:/dev/sda1                       1038336     115276     923060   12%
  k8s_m1:/dev/centos/root      

3. 热修改虚拟机配置

3.1. 修改内存

查看当前内存

 $ virsh dominfo k8s_m1 |grep memory
 Max memory:     4194304 KiB
 Used memory:    2097152 KiB

修改配置
```
 $ virsh setmem k8s_m1 4194304
```

查看修改后内存

 $ virsh dominfo k8s_m1 |grep memory
 Max memory:     4194304 KiB
 Used memory:    4194304 KiB

3.2. 修改CPU

查看当前CPU

 $ virsh dominfo k8s_m1|grep CPU
 CPU(s):         4
 CPU time:       242.7s

修改CPU
```
 $ virsh setvcpus k8s_m1 6
```

查看修改后的CPU

 $ virsh dominfo k8s_m1|grep CPU
 CPU(s):         6
 CPU time:       251.1s

4. 删除虚拟机

vm_name="k8s_m1"
#第一步，停掉虚拟机
virsh shutdown $vm_name
#第二步
virsh destroy $vm_name
#第三步
virsh undefine $vm_name
#第四部
rm /data/${vm_name}.img  # 不建议删除硬盘

5. 快照

5.1. 创建快照

$ virsh snapshot-create-as kvm-1 kvm-1-original

5.2. 查看快照

$ virsh snapshot-list kvm-1
 Name                 Creation Time             State
------------------------------------------------------------
 kvm-1-original      2018-03-19 22:41:08 -0400 running

5.3. 进入虚拟机，安装mysql

# 进入虚拟机
$ virsh console kvm-1

# 在虚拟机中yum安装mysql

$ yum -y install http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm
$ yum -y install mysql-community-server
# 启动服务
$ systemctl start  mysqld.service
# 获取初始密码
$ mysql_pass=$(awk '/temporary password/ {print $NF}' /var/log/mysqld.log)
# 登录
$ mysql -uroot -p${mysql_pass}
# 修改默认密码
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'Nu@2KLTpeap9..@GeRRa';
Query OK, 0 rows affected (0.00 sec)

5.4. 退出虚拟机，恢复快照

$ virsh snapshot-revert kvm-1 kvm-1-original

# 重启虚拟机

$ virsh shutdown kvm-1
$ virsh start kvm-1

再次登录发现mysql已经不存在了

6. 问题整理

raw格式无法创建快照

 $ virsh snapshot-create CentOs6.8
 error: unsupported configuration: internal snapshot for disk vda unsupported for storage type raw

解决方法：

转换 raw 为 qcow2

  qemu-img convert -f raw -O qcow2 /data/kvm/CentOs6.8.img /data/kvm/centos6.8.qcow2

修改虚拟机配置文件

  virsh edit vm_name
  # 此命令编辑的文件实际上是/etc/libvirt/qemu/目录下和虚拟机同名并且以xml结尾的文件
  virsh edit CentOs6.8 

  #将type和source file修改为指定格式。
		
  <disk type='file' device='disk'>
		
        <driver name='qemu' type='qcow2' cache='none'/>
		
        <source file='/data/kvm/centos6.8.qcow2'/>
		
        <target dev='vda' bus='virtio'/>
		
        <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
		
      </disk>

创建快照

  virsh snapshot-create CentOs6.8
  Domain snapshot 1457182425 created

Larry