从 Ubuntu 18.04 版本升级到 20.04（focal）后，缺少 iptables 内核模块：
root@server:~# iptables -L
modprobe: FATAL: Module ip_tables not found in directory /lib/modules/5.4.0-42-generic
iptables v1.8.4 (legacy): can't initialize iptables table `filter': Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.
我尝试了以下操作，但未能解决问题：
sudo apt-get install --reinstall iptables
sudo apt-get install --reinstall linux-headers-$(uname -r)
sudo dpkg-reconfigure iptables
dkms autoinstall
linux-modules-extra 也已安装
的输出ls -R /var/lib/dkms是：
/var/lib/dkms:
dkms_dbversion wireguard
/var/lib/dkms/wireguard:
1.0.20200611 kernel-5.4.0-42-generic-x86_64
/var/lib/dkms/wireguard/1.0.20200611:
5.4.0-42-generic source
/var/lib/dkms/wireguard/1.0.20200611/5.4.0-42-generic:
x86_64
/var/lib/dkms/wireguard/1.0.20200611/5.4.0-42-generic/x86_64:
log module
/var/lib/dkms/wireguard/1.0.20200611/5.4.0-42-generic/x86_64/log:
make.log
/var/lib/dkms/wireguard/1.0.20200611/5.4.0-42-generic/x86_64/module:
wireguard.ko
关于如何重新激活 iptables 有什么想法吗？
答案1
在我的 Ubuntu 20.04 安装中，该文件/lib/modules/5.4.0-40-generic/kernel/net/ipv4/netfilter/ip_tables.ko属于linux-modules软件包，而不是linux-modules-extra。重新安装linux-modules应该可以解决问题：
sudo apt-get install --reinstall linux-modules-5.4.0-42-generic