KVM 虚拟机添加 CDROM 设备并挂载 ISO 引导文件
分类：System 标签：Kvm Virsh Libvirtd
WHAT
根据用户提供的虚拟机导出的 base 镜像:
qemu-img convert -f qcow2 -O qcow2 -c vm.qcow2 imported-vm.qcow2
使用 virt-install ... --import 导入方式安装后，虚拟机无法开机，提示下面报错：
[ 2.772200] XFS (sda4): Internal error XFS_WANT_CORRUPTED_GOTO at line 1627 of file fs/xfs/libxfs/xfs_alloc.c. Caller xfs_free_extent+0xf9/0x130 [xfs]
[ 2.774653] XFS (sda4): Failed to recover EFIs
[ OK ] Started Show Plymouth Boot Screen.
[ OK ] Reached target Paths.
[ OK ] Reached target Basic System.
Mounting Configuration File System...
[ OK ] Mounted Configuration File System.
[ OK ] Found device QEMU_HARDDISK 4.
Starting File System Check on /dev/...7-5271-4030-8808-366e1bc46c0e...
[ OK ] Started dracut initqueue hook.
[ OK ] Reached target Remote File Systems (Pre).
[ OK ] Reached target Remote File Systems.
Starting dracut pre-mount hook...
[ OK ] Started File System Check on /dev/d...627-5271-4030-8808-366e1bc46c0e.
[ OK ] Started dracut pre-mount hook.
Mounting /sysroot...
[ ***] A start job is running for /sysroot (3min 59s / 4min 31s)[ 241.955354] INFO: task mount:533 blocked for more than 120 seconds.
[FAILED] Failed to mount /sysroot.
See 'systemctl status sysroot.mount' for details.
[DEPEND] Dependency failed for Initrd Root File System.
[DEPEND] Depen[ OK ] Reached target Initrd File Systems.
Generating "/run/initramfs/rdsosreport.txt"
Entering emergency mode. Exit the shell to continue.
Type "journalctl" to view system logs.
You might want to save "/run/initramfs/rdsosreport.txt" to a USB stick or /boot
after mounting them and attach it to a bug report.
:/#
VM 开机引导在 Mounting /sysroot... 卡了很久，而且 最上面 也有 XFS 文件系统报错。
应该是 根分区自检 失败了，只能通过挂载 ISO 在系统之外的 LiveOS 里面 xfs_repair 了。
HOW
杯具的是发现 VM 没有 CDROM 设备 - -.：
# virsh domblklist new-vm-imported
Target Source
-------------------------------------------------------------
sda /home/kvm/new-vm-imported.qcow2
尝试使用 attach-device 提示 CDROM 不支持热插拔：
<disk type='file' device='cdrom'>
<driver name='qemu' type='raw'/>
<source index='4'/>
<target dev='sdb' bus='sata'/>
<readonly/>
<alias name='sata0-0-1'/>
<address type='drive' controller='0' bus='0' target='0' unit='1'/>
</disk>
# virsh attach-device new-vm-imported sata-cdrom.xml
error: Failed to attach device from sata-cdrom.xml
error: Operation not supported: cdrom/floppy device hotplug isn't supported
只能使用 virsh edit VM_DOMAIN_NAME 编辑 VM 配置文件了
冷重启 virsh destroy VM_DOMAIN_NAME 后，挂载 ISO 提示 读写权限 有问题：
# virsh attach-disk new-vm-imported /root/CentOS-8.5.2111-x86_64-boot.iso sdb --type cdrom --mode readonly
error: Failed to attach disk
error: Cannot access storage file '/root/CentOS-8.5.2111-x86_64-boot.iso': No such file or directory
将 ISO 移动到 qemu 用户 可读 的目录，即可挂载 ISO 文件：
# namei -l /home/kvm/
f: /home/kvm/
dr-xr-xr-x root root /
drwxr-xr-x root root home
drwxr-xr-x root root kvm
# mv /root/CentOS-8.5.2111-x86_64-boot.iso /home/kvm/
# virsh attach-disk new-vm-imported /home/kvm/CentOS-8.5.2111-x86_64-boot.iso sdb --type cdrom --mode readonly
Disk attached successfully
# virsh domblklist new-vm-imported
Target Source
-------------------------------------------------------------
sda /home/kvm/new-vm-imported.qcow2
sdb /home/kvm/CentOS-8.5.2111-x86_64-boot.iso
也可以 使用 virt-xml 命令添加 CDROM 设备：
# virt-xml new-vm-imported --add-device --disk /home/kvm/CentOS-8.5.2111-x86_64-boot.iso,device=cdrom
Domain 'new-vm-imported' defined successfully.
Changes will take effect after the domain is fully powered off.
# virsh domblklist new-vm-imported
Target Source
-------------------------------------------------------------
sda /home/kvm/new-vm-imported
强制关机 后可以看到新添加的 CDROM 设备：
# virsh destroy new-vm-imported
Domain new-vm-imported destroyed
# virsh domblklist new-vm-imported
Target Source
-------------------------------------------------------------
sda /home/kvm/new-vm-imported
hda /home/kvm/CentOS-8.5.2111-x86_64-boot.iso
然后通过 virsh reset VM_DOMAIN_NAME 命令重启，即可选择 ISO 引导：
Machine UUID new-vm-imported
iPXE (http://ipxe.org) 00:03.0 CB00 PCI2.10 PnP PMM+BFF8F710+BFECF710 CB00
Press ESC for boot menu.
Select boot device:
1. virtio-scsi Drive QEMU QEMU HARDDISK 2.5+
2. Legacy option rom
3. DVD/CD [AHCI/1: QEMU DVD-ROM ATAPI-4 DVD/CD] (CentOS-8-5-2111-x86_64-dvd)
4. iPXE (PCI 00:03.0)
VNC 连接图形界面，使用 Tab 按键修改引导参数，添加 console=ttyS0 inst.text 引导参数：
引导进入 LiveOS 后切换至 shell 页面，使用 xfs_repair -L /dev/sda4 修复一下文件系统：
重启之后，顺利进入系统：
# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 2T 0 disk
├─sda1 8:1 0 1M 0 part
├─sda2 8:2 0 1G 0 part /boot
├─sda3 8:3 0 8G 0 part [SWAP]
└─sda4 8:4 0 2T 0 part /
最后卸载 ISO 即可：
# virsh change-media new-vm-imported sdb --eject
Successfully ejected media.
# virsh domblklist new-vm-imported
Target Source
-------------------------------------------------------------
sda /home/kvm/new-vm-imported.qcow2
sdb -
reference
RHEL8 / Configuring and managing virtualization / Chapter 10. Managing virtual devices