由于版本控制问题，安装 virt-manager 时出错

Question

我在 Linux Mint 19.3 上，一天前升级到 20，我现在正在测试我所有的软件以确保它们仍然有效。 Virt-manager 现在不工作（但在 19.3 中可以），我很困惑为什么。 Virsh 似乎工作正常：

kelvin@mint-1:/usr/share$ virsh list --all
 Id   Name            State
--------------------------------
 -    kali            shut off
 -    ubuntu18.04     shut off
 -    ubuntu20.04     shut off
 -    ubuntu20.04.2   shut off
 -    win10           shut off

KVM 似乎也能正常工作：

kelvin@mint-1:/usr/share$ kvm-ok
INFO: /dev/kvm exists
KVM acceleration can be used

Libvirtd 似乎也在工作：

kelvin@mint-1:/usr/share$ service libvirtd status
● libvirtd.service - Virtualization daemon
     Loaded: loaded (/lib/systemd/system/libvirtd.service; enabled; vendor preset: enabled)
     Active: active (running) since Tue 2020-07-07 11:09:16 EDT; 1h 2min ago
TriggeredBy: ● libvirtd-ro.socket
             ● libvirtd-admin.socket
             ● libvirtd.socket
       Docs: man:libvirtd(8)
             https://libvirt.org
   Main PID: 16336 (libvirtd)
      Tasks: 25 (limit: 32768)
     Memory: 48.1M
     CGroup: /system.slice/libvirtd.service
             ├─ 1548 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/wifi1.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
             ├─ 1549 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/wifi1.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
             ├─ 1610 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
             ├─ 1613 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
             ├─ 1716 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/wifi2.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
             ├─ 1717 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/wifi2.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
             ├─ 1801 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/wifi3.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
             ├─ 1803 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/wifi3.conf --leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper
             └─16336 /usr/sbin/libvirtd

Jul 07 11:09:16 mint-1 dnsmasq-dhcp[1548]: read /var/lib/libvirt/dnsmasq/wifi1.hostsfile
Jul 07 11:09:16 mint-1 dnsmasq[1610]: read /var/lib/libvirt/dnsmasq/default.addnhosts - 0 addresses
Jul 07 11:09:16 mint-1 dnsmasq-dhcp[1610]: read /var/lib/libvirt/dnsmasq/default.hostsfile
Jul 07 11:09:16 mint-1 dnsmasq[1801]: read /etc/hosts - 12 addresses
Jul 07 11:09:16 mint-1 dnsmasq[1801]: read /var/lib/libvirt/dnsmasq/wifi3.addnhosts - 0 addresses
Jul 07 11:09:16 mint-1 dnsmasq-dhcp[1801]: read /var/lib/libvirt/dnsmasq/wifi3.hostsfile
Jul 07 11:09:16 mint-1 libvirtd[16336]: libvirt version: 6.0.0, package: 0ubuntu8.1 (Christian Ehrhardt <christian.ehrhardt@canonical.com> Wed, 20 May 2020 06:59:57 +0200)
Jul 07 11:09:16 mint-1 libvirtd[16336]: hostname: mint-1
Jul 07 11:09:16 mint-1 libvirtd[16336]: ignoring dangling symlink '/home/kelvin/.steampath'
Jul 07 11:10:51 mint-1 libvirtd[16336]: End of file while reading data: Input/output error

然后我决定运行 virt-manager:

kelvin@mint-1:/usr/share$ virt-manager
Traceback (most recent call last):
  File "/usr/share/virt-manager/virt-manager", line 19, in <module>
    from virtinst import BuildConfig
  File "/usr/share/virt-manager/virtinst/__init__.py", line 49, in <module>
    from virtinst.domain import *  # pylint: disable=wildcard-import
  File "/usr/share/virt-manager/virtinst/domain/__init__.py", line 5, in <module>
    from .blkiotune import DomainBlkiotune
  File "/usr/share/virt-manager/virtinst/domain/blkiotune.py", line 8, in <module>
    from ..xmlbuilder import XMLBuilder, XMLChildProperty, XMLProperty
  File "/usr/share/virt-manager/virtinst/xmlbuilder.py", line 16, in <module>
    from .xmlapi import XMLAPI
  File "/usr/share/virt-manager/virtinst/xmlapi.py", line 7, in <module>
    import libxml2
ModuleNotFoundError: No module named 'libxml2'
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 153, in apport_excepthook
    with os.fdopen(os.open(pr_filename,
FileNotFoundError: [Errno 2] No such file or directory: '/var/crash/_usr_share_virt-manager_virt-manager.1000.crash'

Original exception was:
Traceback (most recent call last):
  File "/usr/share/virt-manager/virt-manager", line 19, in <module>
    from virtinst import BuildConfig
  File "/usr/share/virt-manager/virtinst/__init__.py", line 49, in <module>
    from virtinst.domain import *  # pylint: disable=wildcard-import
  File "/usr/share/virt-manager/virtinst/domain/__init__.py", line 5, in <module>
    from .blkiotune import DomainBlkiotune
  File "/usr/share/virt-manager/virtinst/domain/blkiotune.py", line 8, in <module>
    from ..xmlbuilder import XMLBuilder, XMLChildProperty, XMLProperty
  File "/usr/share/virt-manager/virtinst/xmlbuilder.py", line 16, in <module>
    from .xmlapi import XMLAPI
  File "/usr/share/virt-manager/virtinst/xmlapi.py", line 7, in <module>
    import libxml2
ModuleNotFoundError: No module named 'libxml2'

所以问题显然是缺失的 libxml2 对吧？我到处看，发现 libxml2 是 C library/binary，使用 apt install libxml2 安装，lxml 是 python 绑定到 libxml2，使用 pip3 install lxml 安装。一切都很好。但话又说回来，它仍然输出那个错误。所以我进入文件 /usr/share/virt-manager/virtinst/xmlapi.py 并将 import libxml2 更改为 import lxml as libxml2.

这种方法效果很好，而且 virt-manager 照常启动。但是后来，由于某种原因我无法连接到 QEMU/KVM，所以我决定完全删除连接，并重新创建连接，仍然使用默认的 URL qemu:///system。但是，它无法连接，并转储此日志：

Unable to connect to libvirt qemu:///system.

'virConnect' object has no attribute 'caps'

Libvirt URI is: qemu:///system

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/connection.py", line 1033, in _open_thread
    self._populate_initial_state()
  File "/usr/share/virt-manager/virtManager/connection.py", line 991, in _populate_initial_state
    self.get_uri(), self.caps.get_xml())
  File "/usr/share/virt-manager/virtManager/connection.py", line 314, in <lambda>
    caps = property(lambda self: getattr(self, "_backend").caps)
  File "/usr/share/virt-manager/virtinst/connection.py", line 118, in __getattr__
    return getattr(libvirtconn, attr)
AttributeError: 'virConnect' object has no attribute 'caps'

这是它抛出错误的地方：

def _populate_initial_state(self):
    log.debug("libvirt version=%s",
                  self._backend.local_libvirt_version())
    log.debug("daemon version=%s",
                  self._backend.daemon_version())
    log.debug("conn version=%s", self._backend.conn_version())
    log.debug("%s capabilities:\n%s",
                  self.get_uri(), self.caps.get_xml())

我试图注释掉该部分，但它仍然在另一个位置引发错误。我能看到的唯一定义是：

def invalidate_caps(self):
    return self._backend.invalidate_caps()
caps = property(lambda self: getattr(self, "_backend").caps)

现在，我对此非常深入，以至于如果我真的在更改源代码，我觉得我错过了一些东西。那我哪里错了？

Answer 1

我找到解决办法了！按照说明here（中文的，不过我不是中文，所以chrome自动帮我翻译了），我只需要执行pip3 install libxml2-python3，不用乱将 import libxml2 更改为 import lxml.

由于版本控制问题，安装 virt-manager 时出错

Error while installing virt-manager due to versioning issues

python

qemu

linux-mint

kvm

libvirt