安装 bundler 报错：
ERROR: Could not find a valid gem 'bundler' (= 1.17.3), here is why:
Unable to download data from https://rubygems.org/ - Errno::ENETUNREACH: Network is unreachable - connect(2) for "api.rubygems.org" port 443 (https://api.rubygems.org/specs.4.8.gz)
1.添加国内源：
gem sources --add https://gems.ruby-china.com/ --remove https://rubygems.org/
注意：如果之前自己瞎捣鼓已配置过源，建议先清理：
gem sources --remove https://rubygems.org/
gem sources --add https://gems.ruby-china.com/
2.验证当前源：
gem sources -l
应该显示：
*** CURRENT SOURCES ***
https://gems.ruby-china.com/
3.安装 bundler：
gem install bundler -v 1.17.3
或离线安装（下载 .gem 文件）：
gem fetch bundler -v 1.17.3
本地安装：
gem install ./bundler-1.17.3.gem
安装完成后运行：
bundle -v
应输出：
Bundler version 1.17.3
到这里环境已经安装成功！
安装依赖并启动：
cd /home/root/dldl-gm && sh restart-alpha.sh
会报错如下：
Don't run Bundler as root. Bundler can ask for sudo if it is needed, and installing your bundle as root will break this
application for all non-root users on this machine.
Fetching source index from http://rubygems.org/
Retrying fetcher due to error (2/4): Bundler::HTTPError Could not fetch specs from http://rubygems.org/
Retrying fetcher due to error (3/4): Bundler::HTTPError Could not fetch specs from http://rubygems.org/
解决方案一：
全局配置 Bundler 使用 Ruby China 镜像（HTTPS）
bundle config set --global mirror.http://rubygems.org https://gems.ruby-china.com
bundle config set --global mirror.https://rubygems.org https://gems.ruby-china.com
验证配置：
bundle config list
应看到类似：
Settings are listed in order of priority. The top value will be used.
mirror.http://rubygems.org
Set via BUNDLE_MIRROR__HTTP://RUBYGEMS__ORG: "https://gems.ruby-china.com"
mirror.https://rubygems.org
Set via BUNDLE_MIRROR__HTTPS://RUBYGEMS__ORG: "https://gems.ruby-china.com"
这会把所有对 rubygems.org 的请求（无论 HTTP/HTTPS）都重定向到 https://gems.ruby-china.com
解决方案二：
打开：/home/root/dldl-gm/Gemfile和Gemfile.lock
把文件里面的：http://rubygems.org/ 改为 https://gems.ruby-china.com/
重新安装依赖并启动：
cd /home/root/dldl-gm && sh restart-alpha.sh
应看到类似：
Don't run Bundler as root. Bundler can ask for sudo if it is needed, and installing your bundle as root will break this
application for all non-root users on this machine.
Fetching gem metadata from https://gems.ruby-china.com/..........
Fetching rake 12.3.1
Installing rake 12.3.1
Fetching concurrent-ruby 1.0.5
恭喜您，这就是已经在正常安装依赖了！
