根本無法通過 ssh 連接到遠端主機——選項？

更新： 不知道為什麼不贊成。無論如何，經過無數次嘗試，我確實短暫地連接了 ssh。我註銷了，但無法再次登錄，ssh 只是掛起。這是對使用者帳戶的無密鑰 ssh。

現在它工作正常。只是花了很長時間才可以登錄。 為什麼？

我禁用了基於密碼的 ssh，但可能無意中禁用了基於密鑰的身份驗證：

thufir@doge:~$ 
thufir@doge:~$ ssh -vvv thufir@foo.example.com
OpenSSH_7.2p2 Ubuntu-4ubuntu1, 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 *
debug2: resolving "foo.example.com" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to foo.example.com [123.123.123.12] port 22.
debug1: connect to address 123.123.123.12 port 22: Connection timed out
ssh: connect to host foo.example.com port 22: Connection timed out
thufir@doge:~$ 


thufir@doge:~$ 
thufir@doge:~$ ssh -vvv root@foo.example.com
OpenSSH_7.2p2 Ubuntu-4ubuntu1, 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 *
debug2: resolving "foo.example.com" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to foo.example.com [123.123.123.12] port 22.
debug1: Connection established.
debug1: identity file /home/thufir/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/thufir/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/thufir/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/thufir/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/thufir/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/thufir/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/thufir/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/thufir/.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-4ubuntu1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3
debug1: match: OpenSSH_5.3 pat OpenSSH_5* compat 0x0c000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to foo.example.com:22 as 'root'
debug3: hostkeys_foreach: reading file "/home/thufir/.ssh/known_hosts"
debug3: record_hostkey: found key type RSA in file /home/thufir/.ssh/known_hosts:2
debug3: load_hostkeys: loaded 1 keys from foo.example.com
debug3: order_hostkeyalgs: prefer hostkeyalgs: ssh-rsa-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: ssh-rsa-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256,ssh-rsa,ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519
debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: MACs ctos: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib@openssh.com,zlib
debug2: compression stoc: none,zlib@openssh.com,zlib
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: host key algorithms: ssh-rsa,ssh-dss
debug2: ciphers ctos: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: ciphers stoc: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: MACs ctos: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: MACs stoc: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: compression ctos: none,zlib@openssh.com
debug2: compression stoc: none,zlib@openssh.com
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug1: kex: algorithm: diffie-hellman-group-exchange-sha256
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: aes128-ctr MAC: umac-64@openssh.com compression: none
debug1: kex: client->server cipher: aes128-ctr MAC: umac-64@openssh.com compression: none
debug3: send packet: type 34
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(2048<3072<8192) sent
debug3: receive packet: type 31
debug1: got SSH2_MSG_KEX_DH_GEX_GROUP
debug2: bits set: 1546/3072
debug3: send packet: type 32
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug3: receive packet: type 33
debug1: got SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Server host key: ssh-rsa SHA256:A/1ufRNwhmB0KfYD5HFRAlrtYgVt2vnv1W4YNkNAs6s
debug3: hostkeys_foreach: reading file "/home/thufir/.ssh/known_hosts"
debug3: record_hostkey: found key type RSA in file /home/thufir/.ssh/known_hosts:2
debug3: load_hostkeys: loaded 1 keys from foo.example.com
debug3: hostkeys_foreach: reading file "/home/thufir/.ssh/known_hosts"
debug3: record_hostkey: found key type RSA in file /home/thufir/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from 123.123.123.12
debug1: Host 'foo.example.com' is known and matches the RSA host key.
debug1: Found key in /home/thufir/.ssh/known_hosts:2
debug2: bits set: 1589/3072
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug2: set_newkeys: mode 0
debug1: rekey after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS received
debug2: key: /home/thufir/.ssh/id_rsa (0x55933276ea90), agent
debug2: key: /home/thufir/.ssh/id_dsa ((nil))
debug2: key: /home/thufir/.ssh/id_ecdsa ((nil))
debug2: key: /home/thufir/.ssh/id_ed25519 ((nil))
debug3: send packet: type 5
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic
debug3: start over, passed a different list publickey,gssapi-keyex,gssapi-with-mic
debug3: preferred gssapi-keyex,gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup gssapi-keyex
debug3: remaining preferred: gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_is_enabled gssapi-keyex
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug2: we did not send a packet, disable method
debug3: authmethod_lookup gssapi-with-mic
debug3: remaining preferred: publickey,keyboard-interactive,password
debug3: authmethod_is_enabled gssapi-with-mic
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available

debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available

debug1: Unspecified GSS failure.  Minor code may provide more information


debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available

debug2: we did not send a packet, disable method
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/thufir/.ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic
debug1: Trying private key: /home/thufir/.ssh/id_dsa
debug3: no such identity: /home/thufir/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /home/thufir/.ssh/id_ecdsa
debug3: no such identity: /home/thufir/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /home/thufir/.ssh/id_ed25519
debug3: no such identity: /home/thufir/.ssh/id_ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (publickey,gssapi-keyex,gssapi-with-mic).
thufir@doge:~$ 

VPS上沒什麼特別的，我可以重新安裝。我還有什麼其他選擇？遠端主機執行 CentOS。

伺服器端（您連接的主機）的一些常見故障（或緩慢）原因：

• dns問題？在某些系統上，在連接時使用 DNS 以檢查連接客戶端上的資訊：損壞的 DNS 然後使通過 ssh 的初始登錄變慢：嘗試查看是否在 /etc 中添加帶有“IP.OF.YOUR.CLIENT a_name”的行/hosts 提升登錄？（這只是為了測試，但不是解決方案：一般來說，一旦它再次可靠地工作，它就會下注修復 DNS 並從 /etc/hosts 中刪除該添加的行。）
• 記憶問題？當 sshd 程序試圖啟動你的 shell 環境時，你通常會得到一個“無法分叉”或類似的程序……你似乎沒有在這種情況下

並且可能有更多類型的故障：檢查伺服器（和客戶端）端的日誌，如果可以啟用更詳細的級別（如果您是這些伺服器的管理員）

引用自：https://unix.stackexchange.com/questions/334497