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96 строки
4.0 KiB
Plaintext
96 строки
4.0 KiB
Plaintext
\versionid $Id: intro.but,v 1.4 2001/11/25 16:57:45 simon Exp $
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\C{intro} Introduction to PuTTY
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PuTTY is a free SSH, Telnet and Rlogin client for 32-bit Windows
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systems.
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\H{you-what} What are SSH, Telnet and Rlogin?
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If you already know what SSH, Telnet and Rlogin are, you can safely
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skip on to the next section.
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SSH, Telnet and Rlogin are three ways of doing the same thing:
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logging in to a multi-user computer from another computer, over a
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network.
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Multi-user operating systems, such as Unix and VMS, usually present
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a command-line interface to the user, much like the \q{Command
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Prompt} or \q{MS-DOS Prompt} in Windows. The system prints a prompt,
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and you type commands which the system will obey.
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Using this type of interface, there is no need for you to be sitting
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at the same machine you are typing commands to. The commands, and
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responses, can be sent over a network, so you can sit at one
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computer and give commands to another one, or even to more than one.
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SSH, Telnet and Rlogin are \e{network protocols} that allow you to
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do this. On the computer you sit at, you run a \e{client}, which
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makes a network connection to the other computer (the \e{server}).
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The network connection carries your keystrokes and commands from the
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client to the server, and carries the server's responses back to
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you.
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These protocols can also be used for other types of keyboard-based
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interactive session. In particular, there are a lot of bulletin
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boards, talker systems and MUDs (Multi-User Dungeons) which support
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access using Telnet. There are even a few that support SSH.
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You might want to use SSH, Telnet or Rlogin if:
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\b you have an account on a Unix or VMS system which you want to be
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able to access from somewhere else
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\b your Internet Service Provider provides you with a login account
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on a web server. (This might also be known as a \e{shell account}.
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A \e{shell} is the program that runs on the server and interprets
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your commands for you.)
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\b you want to use a bulletin board system, talker or MUD which can
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be accessed using Telnet.
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You probably do \e{not} want to use SSH, Telnet or Rlogin if:
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\b you only use Windows. Windows computers have their own
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ways of networking between themselves, and unless you are doing
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something fairly unusual, you will not need to use any of these
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remote login protocols.
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\H{which-one} How do SSH, Telnet and Rlogin differ?
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This list summarises some of the differences between SSH, Telnet and
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Rlogin.
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\b SSH is a recently designed, high-security protocol. It uses
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strong cryptography to protect your connection against
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eavesdropping, hijacking and other attacks. Telnet and Rlogin are
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both older protocols offering minimal security.
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\b Telnet allows you to pass some settings on to the server, such as
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environment variables. (These control various aspects of the
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server's behaviour. You can usually set them by entering commands
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into the server once you're connected, but it's easier to have
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Telnet do it automatically.) SSH and Rlogin do not support this.
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However, most modern Telnet servers don't allow it either, because
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it has been a constant source of security problems.
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\b SSH and Rlogin both allow you to log in to the server without
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having to type a password. (Rlogin's method of doing this is
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insecure, and can allow an attacker to access your account on the
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server. SSH's method is much more secure, and typically breaking the
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security requires the attacker to have gained access to your actual
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client machine.)
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\b SSH allows you to connect to the server and automatically send a
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command, so that the server will run that command and then
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disconnect. So you can use it in automated processing.
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The Internet is a hostile environment and security is everybody's
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responsibility. If you are connecting across the open Internet, then
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we recommend you use SSH. If the server you want to connect to
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doesn't support SSH, it might be worth trying to persuade the
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administrator to install it.
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If you are behind a good firewall, it is more likely to be safe to
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use Telnet or Rlogin, but we still recommend you use SSH.
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