[yz@test ~]$ sudo yum install tree

[yz@test-2 ~]$ ll da/
-rw-rw-r-- 1 yz yz 3 Jan  9 08:53 f1.txt
-rw-rw-r-- 1 yz yz 3 Jan  9 08:53 f2.txt
[yz@test-2 ~]$ ll db/
-rw-rw-r-- 1 yz yz 3 Jan  9 08:53 f1.txt
-rw-rw-r-- 1 yz yz 3 Jan  9 08:54 f2.txt
-rw-rw-r-- 1 yz yz 3 Jan  9 08:54 f3.txt