为何仅rbenv+ruby-build可在无权限Ubuntu集群安装Ruby？

问题背景 #

我在无管理员权限的Ubuntu集群中尝试常规方法安装Ruby均失败，仅通过以下结合rbenv和ruby-build的脚本成功安装了Ruby 3.1.2：

#!/usr/bin/env bash
# -- this really is the only solution that worked for me on snap :/

ruby -v
if ! command -v ruby &> /dev/null
then
    echo "Going to try to install ruby (ideally 3.1.2)"
    # - install rbenv (following ruby-build really is needed eventhough it doesn't look like it)
    mkdir -p ~/.rbenv
    cd ~/.rbenv
    git clone https://github.com/rbenv/rbenv.git .
    # if $HOME/.rbenv/bin not in path append it, otherwise don't change it
    echo $PATH | tr ':' '
' | awk '{print "  " $0}';
    if [[ ":$PATH:" != *":$HOME/.rbenv/bin:"* ]]; then
      echo "might want to put $HOME/.rbenv/bin in your path"
      export PATH="$HOME/.rbenv/bin:$PATH"
#      echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc.lfs
    fi
    eval "$(rbenv init -)"
    rbenv -v

    # - install ruby-build, odd, this really is needed for ruby to install despite it not looking like ruby build is need at the bottom
    mkdir -p ~/.ruby-build
    cd ~/.ruby-build
    git clone https://github.com/rbenv/ruby-build.git .
    # if $HOME/.ruby-build/bin not in path append it, otherwise don't change it
    echo $PATH | tr ':' '
' | awk '{print "  " $0}';
    if [[ $PATH != *"$HOME/.ruby-build/bin"* ]]; then
      echo "might want to put $HOME/.ruby-build/bin in your path"
      export PATH="$HOME/.ruby-build/bin:$PATH"
#      echo 'export PATH="$HOME/.ruby-build/bin:$PATH"' >> ~/.bashrc.lfs
    fi
    ruby-build --version

    # - install ruby without sudo -- using rbenv
    mkdir -p ~/.local
    #    ruby-build 3.1.2 ~/.local/
    rbenv install 3.1.2
    rbenv global 3.1.2
fi
ruby -v

# - Original Prover doesn't work on SNAP
# Proverbot's way to install ruby
#    # First, install Ruby, as that is for some reason required to build the "system" project
#    git clone https://github.com/rbenv/ruby-build.git ~/ruby-build
#    mkdir -p ~/.local
#    PREFIX=~/.local ./ruby-build/install.sh
#    ~/.local/ruby-build 3.1.2 ~/.local/
# ref: https://superuser.com/questions/340490/how-to-install-and-use-different-versions-of-ruby/1756372#1756372

为什么常规方法失败，而rbenv+ruby-build可行？ #

• 常规系统级安装工具（如apt）需要管理员权限，无sudo权限无法执行；且Ubuntu默认仓库中的Ruby版本通常不是目标的3.1.2版本。
• 直接源码编译Ruby需要手动处理编译依赖、配置安装路径（必须指向用户可读写目录，如~/.local），过程繁琐，容易因依赖缺失、路径配置错误导致失败。
• rbenv是用户级Ruby版本管理器，所有操作均在用户主目录内完成，无需管理员权限；ruby-build作为rbenv的核心插件，会自动处理Ruby源码的下载、编译、安装全流程，帮你规避手动编译的各种细节问题，比如依赖检查、路径适配等。

更简单的官方推荐安装方法（针对Ruby 3.1.2） #

rbenv+ruby-build本身就是Ruby官方认可的用户级安装方式，可简化如下步骤：

方法一：用官方脚本一键安装rbenv+ruby-build #

1. 确保集群已预装基础工具（git、curl、编译依赖如build-essential等，无权限安装依赖可跳过，ruby-build会尝试自动适配）
2. 执行官方安装脚本：

curl -fsSL https://github.com/rbenv/rbenv-installer/raw/main/bin/rbenv-installer | bash

3. 配置shell环境（仅需执行一次，后续登录自动生效）：

echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(rbenv init -)"' >> ~/.bashrc
source ~/.bashrc

4. 安装并设置Ruby 3.1.2为全局版本：

rbenv install 3.1.2
rbenv global 3.1.2

5. 验证安装结果：

ruby -v

方法二：直接用ruby-build安装单一版本（无需rbenv） #

若仅需安装Ruby 3.1.2，可跳过rbenv，直接用ruby-build安装到用户目录：

git clone https://github.com/rbenv/ruby-build.git
PREFIX=~/.local ./ruby-build/install.sh
~/.local/bin/ruby-build 3.1.2 ~/.local
echo 'export PATH="$HOME/.local/bin:$PATH"' >> ~/.bashrc
source ~/.bashrc

补充说明 #

• 若集群有Snap环境限制，rbenv的用户级安装不会触发权限问题，因为所有文件均存储在用户主目录内，不属于系统级修改。
• 手动克隆仓库的方式与官方脚本本质一致，但官方脚本更高效，还能自动处理后续的版本更新。

内容的提问来源于stack exchange，提问作者Charlie Parker