更新yum 源下载报错

entos7.9 更换yum 源 为阿里云的之后，下载软件包报错 Failed connect to mirrors.aliyuncs.com:80; Connection timed out"

解决办法：
更换yum源后，要清空yum 缓存，并生成新缓存
[root@node01 ~]# yum clean all
Loaded plugins: fastestmirror
Cleaning repos: base docker-ce-stable epel extras updates
Cleaning up list of fastest mirrors
[root@node01 ~]# yum makecache
Loaded plugins: fastestmirror
Determining fastest mirrors
epel/x86_64/metalink | 8.1 kB 00:00:00

• base: mirrors.aliyun.com
• epel: mirror.sjtu.edu.cn
• extras: mirrors.aliyun.com
• updates: mirrors.aliyun.com
  base | 3.6 kB 00:00:00
  docker-ce-stable | 3.5 kB 00:00:00
  epel | 4.7 kB 00:00:00
  extras | 2.9 kB 00:00:00
  updates | 2.9 kB 00:00:00
  (1/20): base/7/x86_64/group_gz | 153 kB 00:00:02
  (2/20): base/7/x86_64/primary_db | 6.1 MB 00:00:03
  (3/20): base/7/x86_64/filelists_db | 7.2 MB 00:00:06
  (4/20): base/7/x86_64/other_db | 2.6 MB 00:00:01
  (5/20): docker-ce-stable/7/x86_64/updateinfo | 55 B 00:00:02
  (6/20): docker-ce-stable/7/x86_64/filelists_db | 31 kB 00:00:02
  (7/20): docker-ce-stable/7/x86_64/other_db | 123 kB 00:00:00
  (8/20): docker-ce-stable/7/x86_64/primary_db | 75 kB 00:00:00
  (9/20): epel/x86_64/group_gz | 96 kB 00:00:02
  (10/20): epel/x86_64/updateinfo | 1.1 MB 00:00:00
  (11/20): epel/x86_64/prestodelta | 5.0 kB 00:00:00
  (12/20): epel/x86_64/primary_db | 7.0 MB 00:00:01
  (13/20): epel/x86_64/other_db | 3.4 MB 00:00:00
  (14/20): extras/7/x86_64/filelists_db | 277 kB 00:00:02
  (15/20): extras/7/x86_64/primary_db | 246 kB 00:00:02
  (16/20): extras/7/x86_64/other_db | 147 kB 00:00:00
  (17/20): epel/x86_64/filelists_db | 12 MB 00:00:09
  (18/20): updates/7/x86_64/filelists_db | 7.8 MB 00:00:06
  (19/20): updates/7/x86_64/other_db | 1.0 MB 00:00:00
  (20/20): updates/7/x86_64/primary_db | 14 MB 00:00:09
  Metadata Cache Created