mount， 目录mount到另外一个目录

Since Linux 2.4.0 it is possible to remount part of the file hierarchy somewhere else. The call is

mount --bind olddir newdir

       After this call the same contents is accessible in two places.  One can also remount a single file (on a singlefile).

比如：

# mkdir dir1 dir2

# mount --bind  ./dir1 ./dir2

# mount

/usr/local/app/dir1 on /usr/local/app/dir2 type none (rw,bind)

# touch dir1/test.txt

ls dir1 dir2

发现两个目录都有test.txt了。   这个功能就好似于硬链接/软链接。 应用的场景， 我估计是有一些web服务器或者ftp服务器， 不支持读入到软/硬链接里面去。