[SSH]Too many ssh failures¶
昨天不小心删除了ubuntu用户，导致系统无法登录
今天重装了系统，使用公共镜像Ubuntu 18.04，重装完成后进行登录发现如下错误
$ ssh ubuntu@132.232.142.219
Received disconnect from 132.232.142.219 port 22:2: Too many authentication failures
Connection to 132.232.142.219 closed by remote host.
Connection to 132.232.142.219 closed.
解决¶
先到控制台的云服务器页面，选择左侧的SSH密钥选项，删除之前设置的密钥
然后关闭实例，重新设置密钥，输入本地的公钥内容，再次启动实例后就能够登录了
调试¶
使用参数-v能够打印出登录进度的调试信息
$ ssh -v ubuntu@132.232.142.219
OpenSSH_7.2p2 Ubuntu-4ubuntu2.7, OpenSSL 1.0.2g 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 132.232.142.219 [132.232.142.219] port 22.
debug1: Connection established.
debug1: identity file /home/zj/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/zj/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/zj/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/zj/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/zj/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/zj/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/zj/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/zj/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.7
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.6p1 Ubuntu-4
debug1: match: OpenSSH_7.6p1 Ubuntu-4 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 132.232.142.219:22 as 'ubuntu'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256@libssh.org
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:Jo/TLQ//NbUA3Sg3iZy3glGFLpf26BJtUOmBNMOtfdo
debug1: Host '132.232.142.219' is known and matches the ECDSA host key.
debug1: Found key in /home/zj/.ssh/known_hosts:12
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/zj/.ssh/id_rsa
debug1: Authentications that can continue: publickey
debug1: Offering RSA public key: gitee.com
debug1: Authentications that can continue: publickey
debug1: Offering RSA public key: github.com
debug1: Authentications that can continue: publickey
debug1: Offering RSA public key: zj@zj-ThinkPad-T470p
debug1: Authentications that can continue: publickey
debug1: Offering RSA public key: coding.com
debug1: Authentications that can continue: publickey
debug1: Offering RSA public key: zj@zj-ThinkPad-T470p
debug1: Server accepts key: pkalg rsa-sha2-512 blen 279
debug1: Authentication succeeded (publickey).
Authenticated to 132.232.142.219 ([132.232.142.219]:22).
...
...
上述调试信息是修改后的认证成功信息，可以看出ssh会遍历~/.ssh目录下的私钥文件，所以最开始的Too many authentication failures表明服务器端设置了认证的次数，可以通过配置文件修改
$ cat /etc/ssh/sshd_config | grep MaxAuth
#MaxAuthTries 6
配置¶
比如修改ssh服务端配置文件/etc/ssh/sshd_config，设置认证次数为100次，然后重启服务端即可
$ sudo vim /etc/ssh/sshd_config
MaxAuthTries 100
$ service sshd restart