使用 *nix 服务器肯定会用到 ssh，它是一个链接到远程服务器终端的工具。
$ man ssh ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c cipher_spec] [-D [bind_address:]port] [-e escape_char] [-F configfile] [-I pkcs11] [-i identity_file] [-L [bind_address:]port:host:hostport] [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port] [-R [bind_address:]port:host:hostport] [-S ctl_path] [-W host:port] [-w local_tun[:remote_tun]] [user@]hostname [command]
ssh [user@]hostname [-p port]
登录到远程服务器和登录本地电脑系统没什么大的区别，都需要用户名，密码，除此之外我们还需要知道远程服务器的地址（IP 地址或域名均可）及允许的端口（默认 22 端口）。
$ ssh email@example.com -p 22
有些时候大家发现一些教程没有提到用户，实际上 ssh 很聪明，默认会使用当前系统的用户名：
(icyleaf) $ ssh 10.10.10.10
$ ssh firstname.lastname@example.org
$ ssh email@example.com -p 2020
呐，你可能因为 GFW 的威力，尝试使用 ssh 的 socket 代理，实际上就是用到的
-D [bind_address:]port Specifies a local ``dynamic application-level port forwarding. This works by allocating a socket to listen to port on the local side, optionally bound to the specified bind_address. Whenever a connection is made to this port, the connection is forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine. Currently the SOCKS4 and SOCKS5 protocols are supported, and ssh will act as a SOCKS server. Only root can forward privileged ports.
|----client----| |-----server----| | | | | | local port<| <incoming | | | ssh port<>| <--------------> |<> ssh port | | forwarding>| >outgoing connection <<<------------local network-----------
它首先需要登录到远程服务器，并把本地的请求全部转发到服务器指定的端口上，然后通过由服务器再去请求。例如我们设置 8624 端口：
$ ssh -D8624 firstname.lastname@example.org -p 22
这样保持这个连接，我们在设置浏览器或系统的 socket4/5 代理就能达到翻墙的目的。当前这个最大的前提是你的服务器在不手 GFW 的控制下（任意海外未被 GFW 服务器）
或许曾经你在看某本黑客杂志或电影出现过这样的片段，黑客使用肉鸡跳板不断的增加难度避开警察的追踪，实际上我们通过 ssh 也能非常简单又很酷的实现。
-L [bind_address:]port:host:hostport Specifies that the given port on the local (client) host is to be forwarded to the given host and port on the remote side. This works by allocating a socket to listen to port on the local side, optionally bound to the specified bind_address. Whenever a con- nection is made to this port, the connection is forwarded over the secure channel, and a connection is made to host port hostport from the remote machine.
|----client----| |-----server----| |-----host-----| | | | | | | | local port<| <incoming | | | | | ssh port<>| <--------------> |<> ssh port | | | | forwarding>| -------------> |>host port | <<<------------local network------------------->>>
-L [bind_address:]port:host:hostport 即可。这里假设我们想登录的目标服务器 target(10.10.10.10)，而我们希望在肉鸡 chicken(22.214.171.124) 上做成跳板：
$ ssh -L2020:126.96.36.199:22 10.10.10.10
Host linode HostName 10.10.10.10 Port 22 User icyleaf
AddressFamily BatchMode BindAddress ChallengeResponseAuthentication CheckHostIP Cipher Ciphers ClearAllForwardings Compression CompressionLevel ConnectionAttempts ConnectTimeout ControlMaster ControlPath ControlPersist DynamicForward EscapeChar ExitOnForwardFailure ForwardAgent ForwardX11 ForwardX11Timeout ForwardX11Trusted GatewayPorts GlobalKnownHostsFile GSSAPIAuthentication GSSAPIDelegateCredentials HashKnownHosts Host HostbasedAuthentication HostKeyAlgorithms HostKeyAlias HostName IdentityFile IdentitiesOnly IPQoS KbdInteractiveAuthentication KbdInteractiveDevices KexAlgorithms LocalCommand LocalForward LogLevel MACs NoHostAuthenticationForLocalhost NumberOfPasswordPrompts PasswordAuthentication PermitLocalCommand PKCS11Provider Port PreferredAuthentications Protocol ProxyCommand PubkeyAuthentication RekeyLimit RemoteForward RequestTTY RhostsRSAAuthentication RSAAuthentication SendEnv ServerAliveInterval ServerAliveCountMax StrictHostKeyChecking TCPKeepAlive Tunnel TunnelDevice UsePrivilegedPort User UserKnownHostsFile VerifyHostKeyDNS VisualHostKey XAuthLocation
~/.ssh/config 是配置 ssh 服务器的文件，其实除了这些还有好多，比如大家可能会经常见到的：
~/.ssh/config This is the per-user configuration file. The file format and configuration options are described in ssh_config(5). Because of the potential for abuse, this file must have strict permissions: read/write for the user, and not accessible by others. ~/.ssh/authorized_keys Lists the public keys (DSA/ECDSA/RSA) that can be used for log- ging in as this user. The format of this file is described in the sshd(8) manual page. This file is not highly sensitive, but the recommended permissions are read/write for the user, and not accessible by others. ~/.ssh/identity ~/.ssh/id_dsa ~/.ssh/id_ecdsa ~/.ssh/id_rsa Contains the private key for authentication. These files contain sensitive data and should be readable by the user but not acces- sible by others (read/write/execute). ssh will simply ignore a private key file if it is accessible by others. It is possible to specify a passphrase when generating the key which will be used to encrypt the sensitive part of this file using 3DES. ~/.ssh/identity.pub ~/.ssh/id_dsa.pub ~/.ssh/id_ecdsa.pub ~/.ssh/id_rsa.pub Contains the public key for authentication. These files are not sensitive and can (but need not) be readable by anyone. ~/.ssh/known_hosts Contains a list of host keys for all hosts the user has logged into that are not already in the systemwide list of known host keys. See sshd(8) for further details of the format of this file.
~/.rhosts This file is used for host-based authentication (see above). On some machines this file may need to be world-readable if the user's home directory is on an NFS partition, because sshd(8) reads it as root. Additionally, this file must be owned by the user, and must not have write permissions for anyone else. The recommended permission for most machines is read/write for the user, and not accessible by others. ~/.shosts This file is used in exactly the same way as .rhosts, but allows host-based authentication without permitting login with rlogin/rsh. ~/.ssh/ This directory is the default location for all user-specific con- figuration and authentication information. There is no general requirement to keep the entire contents of this directory secret, but the recommended permissions are read/write/execute for the user, and not accessible by others. ~/.ssh/environment Contains additional definitions for environment variables; see ENVIRONMENT, above. ~/.ssh/rc Commands in this file are executed by ssh when the user logs in, just before the user's shell (or command) is started. See the sshd(8) manual page for more information. /etc/hosts.equiv This file is for host-based authentication (see above). It should only be writable by root. /etc/shosts.equiv This file is used in exactly the same way as hosts.equiv, but allows host-based authentication without permitting login with rlogin/rsh. /etc/ssh/ssh_config Systemwide configuration file. The file format and configuration options are described in ssh_config(5). /etc/ssh/ssh_host_key /etc/ssh/ssh_host_dsa_key /etc/ssh/ssh_host_ecdsa_key /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys and are used for host-based authentication. If protocol version 1 is used, ssh must be setuid root, since the host key is readable only by root. For protocol version 2, ssh uses ssh-keysign(8) to access the host keys, eliminating the requirement that ssh be setuid root when host-based authentication is used. By default ssh is not setuid root. /etc/ssh/ssh_known_hosts Systemwide list of known host keys. This file should be prepared by the system administrator to contain the public host keys of all machines in the organization. It should be world-readable. See sshd(8) for further details of the format of this file. /etc/ssh/sshrc Commands in this file are executed by ssh when the user logs in, just before the user's shell (or command) is started. See the sshd(8) manual page for more information.
- [Linux] man ssh
- Advanced SSH usage