解決centos的SSH遠端連線服務慢的方法

解決centos的SSH遠端連線服務慢的方法

串連慢的主要原因是DNS解析導致

解決方案：

1、在ssh服務端上更改/etc/ssh/sshd_config檔案中的配置為如下內容：
UseDNS no
# GSSAPI options
GSSAPIAuthentication no
然後，執行/etc/init.d/sshd restart重啟sshd進程使上述配置生效，在串連一般就不慢了。

如果還慢的話，檢查ssh服務端上/etc/hosts檔案中，127.0.0.1對應的主機名稱是否和
uname -n的結果一樣，或者把本機ip和hostname(uname -n結果)加入到/etc/hosts裡。

[python]view plaincopy

1. [root@C64~]#uname-n
2. C64
3. [root@C64~]#cat/etc/hosts
4. #modibyoldboy11:122013/9/24
5. 127.0.0.1C64localhostlocalhost.localdomainlocalhost4localhost4.localdomain4
6. ::1localhostlocalhost.localdomainlocalhost6localhost6.localdomain6
7. 10.0.0.18C64
8. ################

利用ssh-v的調試功能尋找慢的原因
其實可以用下面的命令調試為什麼慢的細節（學習這個思路很重要）。

[python]view plaincopy

1. [root@C64~]#ssh-vroot@IP地址
2. OpenSSH_5.3p1,OpenSSL1.0.0-fips29Mar2010
3. debug1:Readingconfigurationdata/etc/ssh/ssh_config
4. debug1:Applyingoptionsfor*
5. debug1:Connectingto10.0.0.19[10.0.0.19]port22.
6. debug1:Connectionestablished.
7. debug1:permanently_set_uid:0/0
8. debug1:identityfile/root/.ssh/identitytype-1
9. debug1:identityfile/root/.ssh/id_rsatype-1
10. debug1:identityfile/root/.ssh/id_dsatype-1
11. debug1:Remoteprotocolversion2.0,remotesoftwareversionOpenSSH_4.3
12. debug1:match:OpenSSH_4.3patOpenSSH_4*
13. debug1:Enablingcompatibilitymodeforprotocol2.0
14. debug1:LocalversionstringSSH-2.0-OpenSSH_5.3
15. debug1:SSH2_MSG_KEXINITsent
16. debug1:SSH2_MSG_KEXINITreceived
17. debug1:kex:server->clientaes128-ctrhmac-md5none
18. debug1:kex:client->serveraes128-ctrhmac-md5none
19. debug1:SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192)sent
20. debug1:expectingSSH2_MSG_KEX_DH_GEX_GROUP
21. debug1:SSH2_MSG_KEX_DH_GEX_INITsent
22. debug1:expectingSSH2_MSG_KEX_DH_GEX_REPLY
23. Theauthenticityofhost'10.0.0.19(10.0.0.19)'can'tbeestablished.
24. RSAkeyfingerprintisca:18:42:76:0e:5a:1c:7d:ef:fc:24:75:80:11:ad:f9.
25. Areyousureyouwanttocontinueconnecting(yes/no)?yes
26. =======>這裡就是提示儲存密鑰的互動提示。
27. Warning:Permanentlyadded'10.0.0.19'(RSA)tothelistofknownhosts.
28. debug1:ssh_rsa_verify:signaturecorrect
29. debug1:SSH2_MSG_NEWKEYSsent
30. debug1:expectingSSH2_MSG_NEWKEYS
31. debug1:SSH2_MSG_NEWKEYSreceived
32. debug1:SSH2_MSG_SERVICE_REQUESTsent
33. debug1:SSH2_MSG_SERVICE_ACCEPTreceived
34. debug1:Authenticationsthatcancontinue:publickey,password
35. debug1:Nextauthenticationmethod:publickey
36. debug1:Tryingprivatekey:/root/.ssh/identity
37. debug1:Tryingprivatekey:/root/.ssh/id_rsa
38. debug1:Tryingprivatekey:/root/.ssh/id_dsa
39. debug1:Nextauthenticationmethod:password
40. root@10.0.0.19'spassword:
41. <strong>=======>這裡就是提示輸入密碼的互動提示。</strong>
42. debug1:Authenticationsucceeded(password).
43. debug1:channel0:new[client-session]
44. debug1:Enteringinteractivesession.
45. debug1:Sendingenvironment.
46. debug1:SendingenvLANG=en_US.UTF-8
47. Lastlogin:TueSep2410:30:022013from10.0.0.18
48. <strong>在遠端連線時如果慢就可以確定卡在哪了。</strong>
49. [root@C64_A~]#ssh-voldboy@IP地址
50. OpenSSH_5.3p1,OpenSSL1.0.0-fips29Mar2010
51. debug1:Readingconfigurationdata/etc/ssh/ssh_config
52. debug1:Applyingoptionsfor*
53. debug1:Connectingto10.0.0.17[10.0.0.17]port22.
54. debug1:Connectionestablished.
55. debug1:permanently_set_uid:0/0
56. debug1:identityfile/root/.ssh/identitytype-1
57. debug1:identityfile/root/.ssh/id_rsatype-1
58. debug1:identityfile/root/.ssh/id_dsatype2
59. debug1:Remoteprotocolversion2.0,remotesoftwareversionOpenSSH_5.3
60. debug1:match:OpenSSH_5.3patOpenSSH*
61. debug1:Enablingcompatibilitymodeforprotocol2.0
62. debug1:LocalversionstringSSH-2.0-OpenSSH_5.3
63. debug1:SSH2_MSG_KEXINITsent
64. debug1:SSH2_MSG_KEXINITreceived
65. debug1:kex:server->clientaes128-ctrhmac-md5none
66. debug1:kex:client->serveraes128-ctrhmac-md5none
67. debug1:SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192)sent
68. debug1:expectingSSH2_MSG_KEX_DH_GEX_GROUP
69. debug1:SSH2_MSG_KEX_DH_GEX_INITsent
70. debug1:expectingSSH2_MSG_KEX_DH_GEX_REPLY
71. debug1:Host'10.0.0.17'isknownandmatchestheRSAhostkey.
72. debug1:Foundkeyin/root/.ssh/known_hosts:2
73. debug1:ssh_rsa_verify:signaturecorrect
74. debug1:SSH2_MSG_NEWKEYSsent
75. debug1:expectingSSH2_MSG_NEWKEYS
76. debug1:SSH2_MSG_NEWKEYSreceived
77. debug1:SSH2_MSG_SERVICE_REQUESTsent
78. debug1:SSH2_MSG_SERVICE_ACCEPTreceived
79. debug1:Authenticationsthatcancontinue:publickey,gssapi-keyex,gssapi-with-mic,password
80. debug1:Nextauthenticationmethod:gssapi-keyex
81. debug1:NovalidKeyexchangecontext
82. debug1:Nextauthenticationmethod:gssapi-with-mic

上述配置沒配就發現卡到gssapi這。就大概知道是gssapi的問題。

實際上在linux系統最佳化部分就應該最佳化SSH服務的此處。