sftp  [用户名@]IP地址
 sftp -oPort=220 [用户名@]IP地址     //修改了默认端口的情况下，需要指定端口号
 例：
 sftp 192.168.72.129
 sftp root@192.168.72.129
 #sftp连接后，进入的是当前登录用户的家目录。例如使用root登录，则sftp连接后进入的是/root/目录.
 #文件的上传和下载，不能使用绝对路径。文件必须位于当前目录下。
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get        #下载文件
 get -r     #下载目录
 put        #上传文件
 put -r     #上传目录
 quit、exit、bye      #退出
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ssh-keygen -t ecdsa
 ssh-copy-id -i id_ecdsa.pub zhangsan@192.168.72.129
 ssh-add 
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[root@localhost ~]# ssh-keygen -t ecdsa     //生成密钥文件
 Generating public/private ecdsa key pair.
 Enter file in which to save the key (/root/.ssh/id_ecdsa): 
 Enter passphrase (empty for no passphrase): 
 Enter same passphrase again: 
 Your identification has been saved in /root/.ssh/id_ecdsa.
 Your public key has been saved in /root/.ssh/id_ecdsa.pub.
 The key fingerprint is:
 SHA256:7chFnJIV8f9fOJhVCk1U+F+3EtGX1NqCWaX5rZZnQEI root@localhost.localdomain
 The key's randomart image is:
 +---[ECDSA 256]---+
 |          +oE.===|
 |         + + +o=o|
 |        o + ++*+o|
 |         +  o*o+*|
 |        S o   *.B|
 |       . +   = B.|
 |        o . o B =|
 |             . +o|
 |                .|
 +----[SHA256]-----+
 [root@localhost ~]# cd ~/.ssh          //切换到sshd服务的家目录下
 [root@localhost .ssh]# ls 
 id_ecdsa  id_ecdsa.pub  known_hosts    //同时生成公钥和私钥文件
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[root@localhost .ssh]# ssh-copy-id -i /root/.ssh/id_ecdsa.pub root@192.168.72.129
 /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_ecdsa.pub"
 /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
 /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
 root@192.168.72.129's password: 
 Number of key(s) added: 1
 Now try logging into the machine, with:   "ssh 'root@192.168.72.129'"
 and check to make sure that only the key(s) you wanted were added.
 [root@localhost .ssh]#
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[root@localhost .ssh]# ssh 192.168.72.129
 Last failed login: Wed Mar 23 01:32:09 CST 2022 from 192.168.72.10 on ssh:notty
 There were 13 failed login attempts since the last successful login.
 Last login: Tue Mar 22 23:57:20 2022 from 192.168.72.10
 [root@192 ~]# 
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[root@192 ~]# vim /etc/hosts.allow
 ---------------
 sshd:192.168.72.10，192.168.72.20    //允许这两个地址使用sshd服务进行访问
 sshd：192.168.4.0/255.255.255.0      //允许该网段的所有地址使用sshd服务进行访问
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[root@192 ~]# vim /etc/hosts.deny
 ---------------
 sshd:ALL            //禁止所有地址使用sshd服务进行访问
 sshd：192.168.0.0/255.255.255.0  EXCEPT 192.168.0.10   //禁止该网段的所有地址使用sshd服务进行访问，除了192.168.0.10 
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