今天发现ohmyzsh更新失败了，我特地找了一下原因，下面是更新失败的日志：

[oh-my-zsh] Would you like to update? [Y/n] Y
Updating Oh My Zsh
fatal: unable to access 'https://github.com/ohmyzsh/ohmyzsh.git/': Failed to connect to github.com port 443: Operation timed out
There was an error updating. Try again later?

后面排查发现，原来是hosts里面配置了github的dns：

52.74.223.119     github.com
52.74.223.119   gist.github.com
54.169.195.247   api.github.com
185.199.111.153   assets-cdn.github.com
199.232.96.133    raw.githubusercontent.com
199.232.96.133    gist.githubusercontent.com
199.232.96.133    cloud.githubusercontent.com
199.232.96.133   camo.githubusercontent.com
199.232.96.133   avatars0.githubusercontent.com
199.232.96.133    avatars1.githubusercontent.com
199.232.96.133   avatars2.githubusercontent.com
199.232.96.133    avatars3.githubusercontent.com
199.232.96.133    avatars4.githubusercontent.com
199.232.96.133    avatars5.githubusercontent.com
199.232.96.133    avatars6.githubusercontent.com
199.232.96.133    avatars7.githubusercontent.com
199.232.96.133    avatars8.githubusercontent.com
199.232.96.133  user-images.githubusercontent.com
185.199.109.154   github.githubassets.com

貌似这些关于github的失效了，于是我把hosts里面关于github的部分全部删除了：

sudo vim /etc/hosts
按dd键可以删除
wq保存推出

然后手动更新：

cd ~/.oh-my-zsh
upgrade_oh_my_zsh

一下子就更新成功了哈：

Note: `upgrade_oh_my_zsh` is deprecated. Use `omz update` instead.
Updating Oh My Zsh
remote: Enumerating objects: 168, done.
remote: Counting objects: 100% (168/168), done.
remote: Compressing objects: 100% (51/51), done.
remote: Total 118 (delta 78), reused 104 (delta 65), pack-reused 0
Receiving objects: 100% (118/118), 32.61 KiB | 184.00 KiB/s, done.
Resolving deltas: 100% (78/78), completed with 39 local objects.
From https://github.com/ohmyzsh/ohmyzsh
 * branch            master     -> FETCH_HEAD
   f21e646..69507c9  master     -> origin/master
   ....

参考文献

oh-my-zsh 更新

ohmyzsh更新失败的解决