Net::SSH is a library for interacting, programmatically, with remote processes via the SSH2 protocol. Sessions are always initiated via Net::SSH.start. From there, a program interacts with the new SSH session via the convenience methods on Net::SSH::Connection::Session, by opening and interacting with new channels (Net::SSH::Connection:Session#open_channel and Net::SSH::Connection::Channel), or by forwarding local and/or remote ports through the connection (Net::SSH::Service::Forward).

The SSH protocol is very event-oriented. Requests are sent from the client to the server, and are answered asynchronously. This gives great flexibility (since clients can have multiple requests pending at a time), but it also adds complexity. Net::SSH tries to manage this complexity by providing some simpler methods of synchronous communication (see Net::SSH::Connection::Session#exec!).

In general, though, and if you want to do anything more complicated than simply executing commands and capturing their output, you’ll need to use channels (Net::SSH::Connection::Channel) to build state machines that are executed while the event loop runs (Net::SSH::Connection::Session#loop).

Net::SSH::Connection::Session and Net::SSH::Connection::Channel have more information about this technique.

“Um, all I want to do is X, just show me how!“

X == “execute a command and capture the output“

Net::SSH.start("host", "user", :password => "password") do |ssh|
  result = ssh.exec!("ls -l")
  puts result
end

X == “forward connections on a local port to a remote host“

Net::SSH.start("host", "user", :password => "password") do |ssh|
  ssh.forward.local(1234, "www.google.com", 80)
  ssh.loop { true }
end

X == “forward connections on a remote port to the local host“

Net::SSH.start("host", "user", :password => "password") do |ssh|
  ssh.forward.remote(80, "www.google.com", 1234)
  ssh.loop { true }
end

Methods

Classes and Modules

Module Net::SSH::Authentication
Module Net::SSH::BufferedIo
Module Net::SSH::Connection
Module Net::SSH::ForwardedBufferedIo
Module Net::SSH::Loggable
Module Net::SSH::PromptMethods
Module Net::SSH::Proxy
Module Net::SSH::Service
Module Net::SSH::Test
Module Net::SSH::Transport
Module Net::SSH::Verifiers
Class Net::SSH::AuthenticationFailed
Class Net::SSH::Buffer
Class Net::SSH::ChannelOpenFailed
Class Net::SSH::ChannelRequestFailed
Class Net::SSH::Compat
Class Net::SSH::Config
Class Net::SSH::Disconnect
Class Net::SSH::Exception
Class Net::SSH::HostKeyMismatch
Class Net::SSH::KeyFactory
Class Net::SSH::KnownHosts
Class Net::SSH::Packet
Class Net::SSH::Version

Constants

Prompt	=	begin require 'highline'		Try to load Highline and Termios in turn, selecting the corresponding PromptMethods module to use. If neither are available, choose PromptMethods::Clear.
VALID_OPTIONS	=	[ :auth_methods, :compression, :compression_level, :config, :encryption, :forward_agent, :hmac, :host_key, :kex, :keys, :key_data, :languages, :logger, :paranoid, :password, :port, :proxy, :rekey_blocks_limit, :rekey_limit, :rekey_packet_limit, :timeout, :verbose, :global_known_hosts_file, :user_known_hosts_file, :host_key_alias, :host_name, :user, :properties, :passphrase, :keys_only ]		This is the set of options that Net::SSH.start recognizes. See Net::SSH.start for a description of each option.

Public class methods

configuration_for (host, use_ssh_config=true)

Returns a hash of the configuration options for the given host, as read from the SSH configuration file(s). If use_ssh_config is true (the default), this will load configuration from both ~/.ssh/config and /etc/ssh_config. If use_ssh_config is nil or false, nothing will be loaded (and an empty hash returned). Otherwise, use_ssh_config may be a file name (or array of file names) of SSH configuration file(s) to read.

See Net::SSH::Config for the full description of all supported options.

[show source]

     # File lib/net/ssh.rb, line 209
209:     def self.configuration_for(host, use_ssh_config=true)
210:       files = case use_ssh_config
211:         when true then Net::SSH::Config.default_files
212:         when false, nil then return {}
213:         else Array(use_ssh_config)
214:         end
215:       
216:       Net::SSH::Config.for(host, files)
217:     end

start (host, user, options={}) {|connection| ...}

The standard means of starting a new SSH connection. When used with a block, the connection will be closed when the block terminates, otherwise the connection will just be returned. The yielded (or returned) value will be an instance of Net::SSH::Connection::Session (q.v.). (See also Net::SSH::Connection::Channel and Net::SSH::Service::Forward.)

Net::SSH.start("host", "user") do |ssh|
  ssh.exec! "cp /some/file /another/location"
  hostname = ssh.exec!("hostname")

  ssh.open_channel do |ch|
    ch.exec "sudo -p 'sudo password: ' ls" do |ch, success|
      abort "could not execute sudo ls" unless success

      ch.on_data do |ch, data|
        print data
        if data =~ /sudo password: /
          ch.send_data("password\n")
        end
      end
    end
  end

  ssh.loop
end

This method accepts the following options (all are optional):

:auth_methods => an array of authentication methods to try
:compression => the compression algorithm to use, or true to use whatever is supported.
:compression_level => the compression level to use when sending data
:config => set to true to load the default OpenSSH config files (~/.ssh/config, /etc/ssh_config), or to false to not load them, or to a file-name (or array of file-names) to load those specific configuration files. Defaults to true.
:encryption => the encryption cipher (or ciphers) to use
:forward_agent => set to true if you want the SSH agent connection to be forwarded
:global_known_hosts_file => the location of the global known hosts file. Set to an array if you want to specify multiple global known hosts files. Defaults to %w(/etc/ssh/known_hosts /etc/ssh/known_hosts2).
:hmac => the hmac algorithm (or algorithms) to use
:host_key => the host key algorithm (or algorithms) to use
:host_key_alias => the host name to use when looking up or adding a host to a known_hosts dictionary file
:host_name => the real host name or IP to log into. This is used instead of the host parameter, and is primarily only useful when specified in an SSH configuration file. It lets you specify an “alias”, similarly to adding an entry in /etc/hosts but without needing to modify /etc/hosts.
:kex => the key exchange algorithm (or algorithms) to use
:keys => an array of file names of private keys to use for publickey and hostbased authentication
:key_data => an array of strings, with each element of the array being a raw private key in PEM format.
:keys_only => set to true to use only private keys from keys and key_data parameters, even if ssh-agent offers more identities. This option is intended for situations where ssh-agent offers many different identites.
:logger => the logger instance to use when logging
:paranoid => either true, false, or :very, specifying how strict host-key verification should be
:passphrase => the passphrase to use when loading a private key (default is nil, for no passphrase)
:password => the password to use to login
:port => the port to use when connecting to the remote host
:properties => a hash of key/value pairs to add to the new connection’s properties (see Net::SSH::Connection::Session#properties)
:proxy => a proxy instance (see Proxy) to use when connecting
:rekey_blocks_limit => the max number of blocks to process before rekeying
:rekey_limit => the max number of bytes to process before rekeying
:rekey_packet_limit => the max number of packets to process before rekeying
:timeout => how long to wait for the initial connection to be made
:user => the user name to log in as; this overrides the user parameter, and is primarily only useful when provided via an SSH configuration file.
:user_known_hosts_file => the location of the user known hosts file. Set to an array to specify multiple user known hosts files. Defaults to %w(~/.ssh/known_hosts ~/.ssh/known_hosts2).
:verbose => how verbose to be (Logger verbosity constants, Logger::DEBUG is very verbose, Logger::FATAL is all but silent). Logger::FATAL is the default. The symbols :debug, :info, :warn, :error, and :fatal are also supported and are translated to the corresponding Logger constant.

[show source]

     # File lib/net/ssh.rb, line 156
156:     def self.start(host, user, options={}, &block)
157:       invalid_options = options.keys - VALID_OPTIONS
158:       if invalid_options.any?
159:         raise ArgumentError, "invalid option(s): #{invalid_options.join(', ')}"
160:       end
161: 
162:       options[:user] = user if user
163:       options = configuration_for(host, options.fetch(:config, true)).merge(options)
164:       host = options.fetch(:host_name, host)
165: 
166:       if !options.key?(:logger)
167:         options[:logger] = Logger.new(STDERR)
168:         options[:logger].level = Logger::FATAL
169:       end
170: 
171:       if options[:verbose]
172:         options[:logger].level = case options[:verbose]
173:           when Fixnum then options[:verbose]
174:           when :debug then Logger::DEBUG
175:           when :info  then Logger::INFO
176:           when :warn  then Logger::WARN
177:           when :error then Logger::ERROR
178:           when :fatal then Logger::FATAL
179:           else raise ArgumentError, "can't convert #{options[:verbose].inspect} to any of the Logger level constants"
180:         end
181:       end
182: 
183:       transport = Transport::Session.new(host, options)
184:       auth = Authentication::Session.new(transport, options)
185: 
186:       user = options.fetch(:user, user)
187:       if auth.authenticate("ssh-connection", user, options[:password])
188:         connection = Connection::Session.new(transport, options)
189:         if block_given?
190:           yield connection
191:           connection.close
192:         else
193:           return connection
194:         end
195:       else
196:         raise AuthenticationFailed, user
197:       end
198:     end