目前在 Ubuntu 18.04.12 上，当我尝试从终端下载某些内容，或推送到 git 或任何类似命令时，它总是无限期地或很长时间地挂在下载上。但是，当我按 Ctrl+C 并重试时，它通常在尝试几次后就会起作用。
我能够进行一些诊断，当 curl 尝试解析服务器的 ipv6 地址而不是 ipv4 时，就会发生挂起。问题是，我没有配置 ipv6 或设置 ipv6 DNS 服务器，所以我真的不明白为什么它会尝试这样做（或者至少为什么它会尝试这么多次而不恢复到 ipv4）。我用 sysctl 禁用了 ipv6，但没有什么区别。
我有点迷茫，因为这似乎没有发生在同一个网络中的其他机器上，但我相信这台机器是唯一一台装有 Ubuntu 18 的机器。
/etc/nsswitch.conf：
# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.
passwd: compat systemd
group: compat systemd
shadow: compat
gshadow: files
hosts: files dns
networks: files
protocols: db files
services: db files
ethers: db files
rpc: db files
netgroup: nis
/etc/resolv.conf：
# This file is managed by man:systemd-resolved(8). Do not edit.
#
# This is a dynamic resolv.conf file for connecting local clients to the
# internal DNS stub resolver of systemd-resolved. This file lists all
# configured search domains.
#
# Run "systemd-resolve --status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs must not access this file directly, but only through the
# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,
# replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.
nameserver 127.0.0.53
options edns0