误删tree命令如何恢复
考察rpm,yum的用法

一、删除tree命令，tree命令不可用
[root@centos7 ~]# which tree
/usr/bin/tree
[root@centos7 ~]# rm -f /usr/bin/tree
[root@centos7 ~]# tree .
bash: tree: command not found...
二、直接yum或rpm安装将提示tree已经安装
[root@centos7 ~]# yum install tree
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile

• base: mirror.bit.edu.cn
• extras: mirrors.tuna.tsinghua.edu.cn
• updates: mirrors.tuna.tsinghua.edu.cn
  base | 3.6 kB 00:00:00
  extras | 3.4 kB 00:00:00
  nginx | 2.9 kB 00:00:00
  updates | 3.4 kB 00:00:00
  Package tree-1.6.0-10.el7.x86_64 already installed and latest version
  Nothing to do
  [root@centos7 ~]# rpm -ivh /misc/cd/Packages/tree-1.6.0-10.el7.x86_64.rpm
  Preparing... ################################# [100%]
  package tree-1.6.0-10.el7.x86_64 is already installed
  三、解决办法：强制覆盖安装
  [root@centos7 ~]# rpm --help
  --replacepkgs reinstall if the package is already present
  [root@centos7 ~]# rpm -ivh /misc/cd/Packages/tree-1.6.0-10.el7.x86_64.rpm --replacepkgs
  Preparing... ################################# [100%]
  Updating / installing...
  1:tree-1.6.0-10.el7 ################################# [100%]
  四、此时的tree已经可以使用
  [root@centos7 ~]# tree . -d
  .
  ├── Desktop
  ├── Documents
  ├── Downloads
  ├── Music
  ├── Pictures
  ├── Public
  ├── scripts
  ├── Templates
  └── Videos

9 directories
五、yum的话可以重新安装
[root@centos7 ~]# yum --help
reinstall reinstall a package
[root@centos7 ~]# rm -f /usr/bin/tree
[root@centos7 ~]# tree -d .
-bash: /usr/bin/tree: No such file or directory
[root@centos7 ~]# yum reinstall tree -y
[root@centos7 ~]# tree -d .
.
├── Desktop
├── Documents
├── Downloads
├── Music
├── Pictures
├── Public
├── scripts
├── Templates
└── Videos

9 directories
六、当然还可以找到tree的rpm包，使用rpm2cpio和cpio -id解压包，并将tree命令移回到原来的位置