本文主要是介绍SSH连接慢(GSS惹的祸)，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
维护linux经常需要使用ssh进行连接，但是有时会很郁闷的发现ssh连接部分机器的时候特别的慢。之前写过一篇文章<SSHl连接慢(DNS惹的祸)>今天就跟大家说一下GSS导致的慢的问题。
首先普及一下linux服务器上在/etc/ssh目录下存在两个配置文件一个是ssh_config，一个是sshd_config。区别就在于d上，带d的是ssh服务使用的配置文件，不带的是ssh客户端程序使用的。
当大家发现ssh慢的时候可以使用ssh -vv 192.168.0.30的方式测试一下慢出现在什么地方。(是两个v奥)
显示的调试信息如下：
OpenSSH_4.3p2, OpenSSL 0.9.8e-fips-rhel5 01 Jul 2008 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug2: ssh_connect: needpriv 0 debug1: Connecting to 192.168.0.30 [192.168.0.30] port 22. debug1: Connection established. debug1: permanently_set_uid: 0/0 debug1: identity file /root/.ssh/identity type -1 debug2: key_type_from_name: unknown key type '-----BEGIN' debug2: key_type_from_name: unknown key type '-----END' debug1: identity file /root/.ssh/id_rsa type 1 debug1: identity file /root/.ssh/id_dsa type -1 debug1: loaded 3 keys debug1: Remote protocol version 2.0, remote software version OpenSSH_4.3 debug1: match: OpenSSH_4.3 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_4.3 debug2: fd 3 setting O_NONBLOCK debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 debug2: kex_parse_kexinit: ssh-rsa,ssh-dss debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@lysator.liu.se,aes128-ctr,aes192-ctr,aes256-ctr debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@lysator.liu.se,aes128-ctr,aes192-ctr,aes256-ctr debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 debug2: kex_parse_kexinit: ssh-rsa,ssh-dss debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@lysator.liu.se,aes128-ctr,aes192-ctr,aes256-ctr debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@lysator.liu.se,aes128-ctr,aes192-ctr,aes256-ctr debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,zlib@openssh.com debug2: kex_parse_kexinit: none,zlib@openssh.com debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2: mac_init: found hmac-md5 debug1: kex: server->client aes128-cbc hmac-md5 none debug2: mac_init: found hmac-md5 debug1: kex: client->server aes128-cbc hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug2: dh_gen_key: priv key bits set: 122/256 debug2: bits set: 530/1024 debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Host '192.168.0.30' is known and matches the RSA host key. debug1: Found key in /root/.ssh/known_hosts:8 debug2: bits set: 535/1024 debug1: ssh_rsa_verify: signature correct debug2: kex_derive_keys debug2: set_newkeys: mode 1 debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug2: set_newkeys: mode 0 debug1: SSH2_MSG_NEWKEYS received debug1: SSH2_MSG_SERVICE_REQUEST sent debug2: service_accept: ssh-userauth debug1: SSH2_MSG_SERVICE_ACCEPT received debug2: key: /root/.ssh/identity ((nil)) debug2: key: /root/.ssh/id_rsa (0x90f7ef8) debug2: key: /root/.ssh/id_dsa ((nil)) debug1: Authentications that can continue: publickey,gssapi-with-mic,password debug1: Next authentication method: gssapi-with-mic Address 192.168.0.30 maps to localhost, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT!debug1: Unspecified GSS failure. Minor code may provide more information No credentials cache founddebug1: Unspecified GSS failure. Minor code may provide more information No credentials cache founddebug1: Unspecified GSS failure. Minor code may provide more information No credentials cache founddebug2: we did not send a packet, disable method debug1: Next authentication method: publickey debug1: Trying private key: /root/.ssh/identity debug1: Offering public key: /root/.ssh/id_rsa debug2: we sent a publickey packet, wait for reply debug1: Server accepts key: pkalg ssh-rsa blen 277 debug2: input_userauth_pk_ok: SHA1 fp 0e:7e:08:29:03:3f:92:4e:80:90:0e:fd:ab:9b:d9:f7:3d:f9:59:04 debug1: read PEM private key done: type RSA debug1: Authentication succeeded (publickey). debug1: channel 0: new [client-session] debug2: channel 0: send open debug1: Entering interactive session. debug2: callback start debug2: client_session2_setup: id 0 debug2: channel 0: request pty-req confirm 0 debug1: Sending environment. debug1: Sending env LANG = zh_CN.UTF-8 debug2: channel 0: request env confirm 0 debug2: channel 0: request shell confirm 0 debug2: fd 3 setting TCP_NODELAY debug2: callback done debug2: channel 0: open confirm rwindow 0 rmax 32768 debug2: channel 0: rcvd adjust 2097152Last login: Wed Aug 27 22:50:26 2014 from 192.168.0.10
当机器出现GSS导致慢的问题的时候会看到
从以上的输出可以看到耗时最长的就是Unspecified GSS failure的地方，这是因为验证的时候启用的GSSAPIAuthentication验证方式导致的。
那我们只要关闭就可以了，这个时候有两个地方是需要设置的，sshd_config里面设置的是服务端，ssh_config里面设置的是客户端的。两台相互连接的机器只要把一方设置为no即可。但是服务端一定要设置sshd_config，客户端设置ssh_config。
这篇关于SSH连接慢(GSS惹的祸)的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！
