Question

linux ssh无法连接。连接上的没问题。

ssh -v 192.168.0.145
OpenSSH_3.6.1p2, SSH protocols 1.5/2.0, OpenSSL 0x0090701f
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Rhosts Authentication disabled, originating port will not be trusted.
debug1: Connecting to 192.168.0.145 [192.168.0.145] port 22.
debug1: Connection established.
debug1: identity file /home/admins/aria/.ssh/identity type -1
debug1: identity file /home/admins/aria/.ssh/id_rsa type -1
debug1: identity file /home/admins/aria/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3
debug1: match: OpenSSH_5.3 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_3.6.1p2
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-cbc hmac-md5 none
debug1: kex: client->server aes128-cbc hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host '192.168.0.145' is known and matches the RSA host key.
debug1: Found key in /home/admins/aria/.ssh/known_hosts:5
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug1: Next authentication method: publickey
debug1: Trying private key: /home/admins/aria/.ssh/identity
debug1: Trying private key: /home/admins/aria/.ssh/id_rsa
debug1: Trying private key: /home/admins/aria/.ssh/id_dsa
debug1: Next authentication method: password
aria@192.168.0.145's password:
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
Permission denied, please try again.
aria@192.168.0.145's password:
debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug1: Entering interactive session.
debug1: channel_free: channel 0: client-session, nchannels 1
Read from remote host 192.168.0.145: Connection reset by peer
Connection to 192.168.0.145 closed.
debug1: Transferred: stdin 0, stdout 0, stderr 100 bytes in 0.0 seconds
debug1: Bytes per second: stdin 0.0, stdout 0.0, stderr 16241.8
debug1: Exit status -1
Accepted password for aria from 1.1.1.1 port 63477 ssh2
pam_unix(sshd:session): session opened for user aria by (uid=0)
fatal: setresuid 500: Resource temporarily unavailable
pam_unix(sshd:session): session closed for user aria

Answer 1

1、搜一下:ssh Read from remote host Connection reset by peer
2、SSH有一个 ClientAliveInterval 参数，在你的 /etc/ssh/sshd_config 配置文件中设置一个合适的值，比如：ClientAliveInterval 115 就可以让 OpenSSH 服务器端在空闲的时候定时向客户端请求一个数据包。
ISP或网关在使用NAT时，有时NAT设备会检测建立的session，如果无数据传输，就会拆掉该session，体现在ssh登录时，就会出现没有操作时无缘无故的断线。在NAT转换时，默认无传输session存活周期为120秒，把ClientAliveInterval值设成了115秒，这样就解决了SSH容易掉的问题！

Answer 2

貌似 "Read from remote host 192.168.0.145: Connection reset by peer" 表明服务端的 sshd 在 respawn 的时候资源不够而退出了, 所以需要检查一下服务端的 sshd 日志看看咋了 ...

追问

fatal: setresuid 500: Resource temporarily unavailable

这个大概会是什么原因引起的？

追答

恰如 "chassisd | 十级" 所言, "fatal: setresuid 500: Resource temporarily unavailable" 就是表明需要调用的资源暂时不够了, 是达到了与 nproc 有关的软设置上限, 适当配置 limits.conf 里的 nproc 数值即可 ...

Answer 3

看看你/etc/security/limits.conf里是否有用户数的限制。比如下面的：
* soft nproc 100
* hard nproc 150
到了100个用户，就会报下面的错：
sshd[21872]: Accepted password for user from 192.168.1.1 port 56193 ssh2
sshd[21875]: fatal: setresuid 500: Resource temporarily unavailable