什麼是ssh
使用 SSH 協議可以連接遠程服務器和服務並向它們驗證。 利用 SSH 密鑰可以連接 GitHub，而無需在每次訪問時提供用戶名或密碼。
查看ssh公鑰是否存在
cat ~/.ssh/id_rsa.pub
如果顯示 cat: /Users/********/.ssh/id_rsa.pub: No such file or directory ，表示沒有創建公鑰，則需要自己創建公鑰。
創建ssh公鑰
（1）用 ssh-keygen 創建公鑰：
xinna@sionas-MacBook-Air ~ % ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/Users/xinna/.ssh/id_rsa):
/Users/xinna/.ssh/id_rsa already exists.
Overwrite (y/n)? y
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /Users/xinna/.ssh/id_rsa.
Your public key has been saved in /Users/xinna/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:UmEi7XKNfPMu1ZkNPtJsGGkCyTrfOjTrF+IQAn7sqwE [email protected]
The key's randomart image is:
+---[RSA 2048]----+
| .o..o |
|. .=o . |
|... + +. . |
| ..o= =.= + . |
|E o. *.oS= B = |
|. .. =.o = X . |
| . .+ = + o . |
| .. = o . |
| .. ..o . |
+----[SHA256]-----+
它先要求你確認保存公鑰的位置（.ssh/id_rsa），然後它會讓你重複一個密碼兩次，如果不想在使用公鑰的時候輸入密碼，可以留空。
（2）使用cat ~/.ssh/id_rsa.pub 查看公鑰：
xinna@sionas-MacBook-Air ~ % cat ~/.ssh/id_rsa.pub
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDkL0lFa+JqVPDiFeE2BvaMwWH496wkc7e+IVOZoJ+UzooK7B6/IBZ7HcBoHs8ckF3DdFpdJonwGkNFlCnpVDs+wxamdUgPqARJq7nEe5DeG5UQ4LCyZSwRA1OUOl/3gpAK+oYm/v11EgdGoajYJDUCTTp5fsSxaCl4s/Ym8uqUWR+Ba4Aoz117ka4i6yX1EiFfkv2ztbES+Lq9wNs57vK/ktoQmBLslGq2HqTt//WrJJkK2C0HlVSV9lkLZgH1qd5K7dxP1rY7IOrdwvhtwVUGE5V3fmBWGqnlZWJ2tkYczlnPWb0uX0FqP1qod8GZGBoJfgVhGShQBFMXdgqY+V9h [email protected]