ssh免密登录
免密登录，用到的就是一个公钥。如果之前在机器上用过github的ssh模式，那你一定还记得，秘钥生成到哪一个文件夹下了。
用到的指令就一个 ssh-keygen,几乎可以不用加任何参数，直接生成一对key文件: id_rsa.pub和id_rsa
bash
ssh-keygen --help
usage: ssh-keygen [-q] [-b bits] [-C comment] [-f output_keyfile] [-m format]
[-N new_passphrase] [-t dsa | ecdsa | ed25519 | rsa]
ssh-keygen -p [-f keyfile] [-m format] [-N new_passphrase]
[-P old_passphrase]
ssh-keygen -i [-f input_keyfile] [-m key_format]
ssh-keygen -e [-f input_keyfile] [-m key_format]
ssh-keygen -y [-f input_keyfile]
ssh-keygen -c [-C comment] [-f keyfile] [-P passphrase]
ssh-keygen -l [-v] [-E fingerprint_hash] [-f input_keyfile]
ssh-keygen -B [-f input_keyfile]
ssh-keygen -D pkcs11
ssh-keygen -F hostname [-lv] [-f known_hosts_file]
ssh-keygen -H [-f known_hosts_file]
ssh-keygen -R hostname [-f known_hosts_file]
ssh-keygen -r hostname [-g] [-f input_keyfile]
ssh-keygen -G output_file [-v] [-b bits] [-M memory] [-S start_point]
ssh-keygen -f input_file -T output_file [-v] [-a rounds] [-J num_lines]
[-j start_line] [-K checkpt] [-W generator]
ssh-keygen -I certificate_identity -s ca_key [-hU] [-D pkcs11_provider]
[-n principals] [-O option] [-V validity_interval]
[-z serial_number] file ...
ssh-keygen -L [-f input_keyfile]
ssh-keygen -A [-f prefix_path]
ssh-keygen -k -f krl_file [-u] [-s ca_public] [-z version_number]
file ...
ssh-keygen -Q -f krl_file file ...
ssh-keygen -Y check-novalidate -n namespace -s signature_file
ssh-keygen -Y sign -f key_file -n namespace file ...
ssh-keygen -Y verify -f allowed_signers_file -I signer_identity
-n namespace -s signature_file [-r revocation_file]在本地生成的key文件，推送到服务器上，在此之前先看下服务器的ssh服务开启了没有，没有开启的打开就好。
shell
systemctl status sshd
systemctl start sshd在服务器上，设置一下.ssh和authorized_keys的权限，网上有部分资料将权限设置之后，免密登录才生效。
shell
sudo chmod 700 ~/.ssh
sudo chmod 600 ~/.ssh/authrized_keys设置之后，测试一下，看看免密登录能不能成功：
shell
ssh root@101.101.101.101只要可以正常进入云服务器就说明已经生效了，如果还不行的，检查一下配置文件的路径或者是权限。
最后，在本地的.ssh目录，新增一个配置文件config:
shell
Host aliyun
user root
hostname 192.168.1.1
IdentityFile /Users/root/.ssh/id_rsa (密钥的本地地址)执行一下ssh aliyun，就可以登录云服务器了。