这个是Apple官方制作指南，支持macOS Sierra、Mac OS X El Capitan、Yosemite 或 Mavericks
请参考 https://support.apple.com/zh-cn/HT201372

流程说明

1、先在Mac App Store里面下载OS X，下载完成后安装器自动打开，请不要安装，直接退出。

2、给U盘/移动硬盘分区，U盘要求8G或以上

3、打开终端，使用createinstallmedia命令制作系统U盘。

给U盘/移动硬盘分区/抹掉，分区名称为:MyVolume (区分大小写)

分区完成后打开终端，输入下面代码

macOS Sierra 10.12.X 的示例:

sudo /Applications/Install macOS Sierra.app/Contents/Resources/createinstallmedia –volume /Volumes/MyVolume –applicationpath /Applications/Install macOS Sierra.app

OS X El Capitan 10.11.X 的示例:

sudo /Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia –volume /Volumes/MyVolume –applicationpath /Applications/Install OS X El Capitan.app

OS X Yosemite 10.10.X 的示例:

sudo /Applications/Install OS X Yosemite.app/Contents/Resources/createinstallmedia –volume /Volumes/MyVolume –applicationpath /Applications/Install OS X Yosemite.app

OS X Mavericks 10.9.X 的示例:

sudo /Applications/Install OS X Mavericks.app/Contents/Resources/createinstallmedia –volume /Volumes/MyVolume –applicationpath /Applications/Install OS X Mavericks.app

Last login: Sun Apr 10 21:35:59 on ttys000
UniexdeMac-mini:~ Uniex$ sudo /Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia –volume /Volumes/MyVolume –applicationpath /Applications/Install OS X El Capitan.app
Password:
Ready to start.
To continue we need to erase the disk at /Volumes/MyVolume.
If you wish to continue type (Y) then press return: y
Erasing Disk: 0%… 10%… 20%… 30%…100%…
Copying installer files to disk…
Copy complete.
Making disk bootable…
Copying boot files…
Copy complete.
Done.
UniexdeMac-mini:~ Uniex$