/usr/local下一般是你安装软件的目录，这个目录就相当于在windows下的programefiles这个目录(所有文件在一个文件夹) /opt这个目录是一些大型软件的安装目录，或者是一些服务程序的安装目录
- /opt
Here’s where optional stuff is put. Trying out the latest Firefox beta? Install it to /opt where you can delete it without affecting other settings. Programs in here usually live inside a single folder whick contains all of their data, libraries, etc.
安装到/opt目录下的程序，它所有的数据、库文件等等都是放在同个目录下面。删除时可以直接删掉文件夹
- /usr/local
This is where most manually installed(ie. outside of your package manager) software goes.It has the same structure as /usr. It is a good idea to leave /usr to your package manager and put any custom scripts and things into /usr/local, since nothing important normally lives in /usr/local.
这里主要存放那些手动安装的软件
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既然说道安装软件，就说一下 ./configure make make install
./configure 配置 最好带上--prefix选项，制定安装目录，会自动创建目录，不用提前mkdir.
这样删除时，直接删掉此目录即可。而不是安装在分散的地方
eg: /configure --prefix=/usr/local/softdir
make 编译
make install 安装（需要root权限）