在PVE节点上，修改系统→网络配置
修改成功后需要重新启动或点击应用配置才会生效
但是点击应用配置项后，报以下错误
you need ifupdown2 to reload network configuration (500)
这是由于应用配置项时需要ifupdown2包，而当前系统中缺少此包。
解决办法：
点击Shell，输入apt-get install ifupdown2进行安装即可
安装后，重新点击"应用配置"项即可
原文链接：PVE修改网络配置报错需要ifupdown2，转载请注明来源！
apt-get install ifupdown2根本就装不上去
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
root@ming:~# apt-get install ifupdown2
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package ifupdown2 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'ifupdown2' has no installation candidate
配置下国内的源