学习Linux安装tree命令，发现红帽默认无法使用yum。查询资料了解到修改yum源的方法如下：

  1. 在/mnt目录下增加一个cdrom目录进行挂载；
  2. 编辑/etc/yum.repos.d 下的repo文件。
  3. 具体步骤如下：
  1. 默认安装yum报错，如下
[root@localhost ~]# yum install tree
Loaded plugins: langpacks, product-id, search-disabled-repos, subscription-manager
This system is not registered with an entitlement server. You can use subscription-manager to register.
There are no enabled repos.
 Run "yum repolist all" to see the repos you have.
 To enable Red Hat Subscription Management repositories:
     subscription-manager repos --enable <repo>
 To enable custom repositories:
     yum-config-manager --enable <repo>

[root@localhost ~]# mkdir /mnt/cdrom [root@localhost ~]# mount /dev/cdrom /mnt/cdrom/ [root@localhost ~]# ll /mnt/cdrom/ total 962 dr-xr-xr-x. 4 root root 2048 Oct 10 2018 addons dr-xr-xr-x. 3 root root 2048 Oct 10 2018 EFI -r--r--r--. 1 root root 8266 Apr 4 2014 EULA -r--r--r--. 1 root root 1455 Oct 10 2018 extra_files.json -r--r--r--. 1 root root 18092 Mar 6 2012 GPL dr-xr-xr-x. 3 root root 2048 Oct 10 2018 images dr-xr-xr-x. 2 root root 2048 Oct 10 2018 isolinux dr-xr-xr-x. 2 root root 2048 Oct 10 2018 LiveOS -r--r--r--. 1 root root 114 Oct 10 2018 media.repo dr-xr-xr-x. 2 root root 931840 Oct 10 2018 Packages dr-xr-xr-x. 2 root root 4096 Oct 10 2018 repodata -r--r--r--. 1 root root 3375 Sep 21 2018 RPM-GPG-KEY-redhat-beta -r--r--r--. 1 root root 3211 Sep 21 2018 RPM-GPG-KEY-redhat-release -r--r--r--. 1 root root 1796 Oct 10 2018 TRANS.TBL

3.进入repos目录，创建repo文件，增加cdrom源 [root@localhost ~]# cd /etc/yum.repos.d/ [root@localhost yum.repos.d]# ls redhat.repo [root@localhost yum.repos.d]# mv redhat.repo redhat.repo.bak [root@localhost yum.repos.d]# vi iso.repo [root@localhost yum.repos.d]# cat iso.repo [base] name=centos baseurl=file:///mnt/cdrom enable=1 gpgcheck=0 gpgkey=file:///mnt/cdrom/RPM-GPG-KEY-redhat-release 4.清理yum：yum clean all 5.安装tree命令 [root@localhost yum.repos.d]# yum -y install tree Loaded plugins: langpacks, product-id, search-disabled-repos, subscription-manager This system is not registered with an entitlement server. You can use subscription-manager to register. base | 4.3 kB 00:00:00 (1/2): base/group_gz | 146 kB 00:00:00 (2/2): base/primary_db | 4.2 MB 00:00:00 Resolving Dependencies --> Running transaction check ---> Package tree.x86_64 0:1.6.0-10.el7 will be installed --> Finished Dependency Resolution

Dependencies Resolved

========================================================================================= Package Arch Version Repository Size

Installing: tree x86_64 1.6.0-10.el7 base 46 k

Transaction Summary

Install 1 Package

Total download size: 46 k Installed size: 87 k Downloading packages: Running transaction check Running transaction test Transaction test succeeded Running transaction Installing : tree-1.6.0-10.el7.x86_64 1/1 base/productid | 1.6 kB 00:00:00 Verifying : tree-1.6.0-10.el7.x86_64 1/1

Installed: tree.x86_64 0:1.6.0-10.el7

Complete! 6.至此修改yum源为本地完成。