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Plink (PuTTY Link) is a command-line connection tool similar to UNIX
ssh. It is mostly used for automated operations, such as making CVS access a repository on a remote server.
Plink is probably not what you want if you want to run an interactive session in a console window.
Plink is a command line application. This means that you cannot just double-click on its icon to run it and instead you have to bring up a console window. In Windows 95, 98, and ME, this is called an "MS-DOS Prompt", and in Windows NT and 2000 it is called a "Command Prompt". It should be available from the Programs section of your Start Menu.
In order to use Plink, the file
plink.exe will need either to be on your
PATH or in your current directory. To add the directory containing Plink to your
PATH environment variable, type into the console window:
This will only work for the lifetime of that particular console window. To set your
PATH more permanently on Windows NT, use the Environment tab of the System Control Panel. On Windows 95, 98, and ME, you will need to edit your
AUTOEXEC.BAT to include a
set command like the one above.
This section describes the basics of how to use Plink for interactive logins and for automated processes.
Once you've got a console window to type into, you can just type
plink on its own to bring up a usage message. This tells you the version of Plink you're using, and gives you a brief summary of how to use Plink:
Z:\sysosd>plink PuTTY Link: command-line connection utility Release 0.50 Usage: plink [options] [user@]host [command] Options: -v show verbose messages -ssh force use of ssh protocol -P port connect to specified port -pw passw login with specified password
Once this works, you are ready to use Plink.
To make a simple interactive connection to a remote server, just type
plink and then the host name:
Z:\sysosd>plink login.example.com Debian GNU/Linux 2.2 flunky.example.com flunky login:
You should then be able to log in as normal and run a session. The output sent by the server will be written straight to your command prompt window, which will most likely not interpret terminal control codes in the way the server expects it to. So if you run any full-screen applications, for example, you can expect to see strange characters appearing in your window. Interactive connections like this are not the main point of Plink.
In order to connect with a different protocol, you can give the command line options
-raw. To make an SSH connection, for example:
Z:\sysosd>plink -ssh login.example.com login as:
If you have already set up a PuTTY saved session, then instead of supplying a host name, you can give the saved session name. This allows you to use public-key authentication, specify a user name, and use most of the other features of PuTTY:
Z:\sysosd>plink my-ssh-session Sent username "fred" Authenticating with public key "fred@winbox" Last login: Thu Dec 6 19:25:33 2001 from :0.0 fred@flunky:~$
More typically Plink is used with the SSH protocol, to enable you to talk directly to a program running on the server. To do this you have to ensure Plink is using the SSH protocol. You can do this in several ways:
-sshoption as described in section 7.2.1.
PLINK_PROTOCOLto the word
Usually Plink is not invoked directly by a user, but run automatically by another process. Therefore you typically do not want Plink to prompt you for a user name or a password.
To avoid being prompted for a user name, you can:
-loption to specify a user name on the command line. For example,
plink login.example.com -l fred.
To avoid being prompted for a password, you should almost certainly set up public-key authentication. (See chapter 8 for a general introduction to public-key authentication.) Again, you can do this in two ways:
Once you have done all this, you should be able to run a remote command on the SSH server machine and have it execute automatically with no prompting:
Z:\sysosd>plink login.example.com -l fred echo hello, world hello, world Z:\sysosd>
Or, if you have set up a saved session with all the connection details:
Z:\sysosd>plink mysession echo hello, world hello, world Z:\sysosd>
Then you can set up other programs to run this Plink command and talk to it as if it were a process on the server machine.
You may also find it useful to use the
-batch command-line option; see section 220.127.116.11.
This section describes the command line options that Plink accepts.
-vshow verbose messages
By default, Plink only displays any password prompts and the output of the remote command. The
-v option makes it print extra information about the connection being made, for example:
Server version: SSH-1.5-OpenSSH-1.2.3 We claim version: SSH-1.5-PuTTY Using SSH protocol version 1 Received public keys Host key fingerprint is: 1023 e3:65:44:44:bd:b1:04:59:bc:e2:3d:a1:4d:09:ce:99 Encrypted session key Using 3DES encryption Trying to enable encryption... Successfully started encryption Sent username "fred". Sent username "fred" email@example.com's password:
This information can be useful for diagnosing problems.
Plink is most useful when using the SSH protocol. However, it allows you to interface to all the protocols supported by PuTTY. You can specify the option
-ssh on the command line to select the SSH protocol; you can also specify
-raw to select other protocols.
-P portconnect to specified port
If your server machine is running its SSH service on a port other than the standard one, you can specify an alternative port number to connect to using the
-P option, like this:
plink -ssh login.example.com -P 5022
-pw passwlogin with specified password
A simple way to automate a remote login is to supply your password on the Plink command line. This is not recommended for reasons of security. If you possibly can, we recommend you set up public-key authentication instead. See chapter 8 for details.
-l usernamelogin with specified username
As described in section 7.2.2, you can specify the user name to log in as on the remote server using the
-l option. For example,
plink login.example.com -l fred.
-batchavoid interactive prompts
If you use the
-batch option, Plink will never give an interactive prompt while establishing the connection. If the server's host key is invalid, for example (see section 2.2), then the connection will simply be abandoned instead of asking you what to do next.
This may help Plink's behaviour when it is used in automated scripts: using
-batch, if something goes wrong at connection time, the batch job will fail rather than hang.
-m filenameread command from a file
If the command you want to run on the remote server is particularly large, you can read it from a file using the
-m option, instead of putting it directly on Plink's command line. On most Unix systems, you can even put multiple lines in this file and execute more than one command in sequence, or a whole shell script.
-Rset up port forwarding
Plink allows you to use port forwarding just as PuTTY does; if you have set up a PuTTY saved session that specifies port forwardings, and you connect to that session using Plink, then the same port forwardings will be set up.
For convenience, Plink also offers the option to set up port forwarding on the command line. The command-line options work just like the ones in Unix
To forward a local port (say 5110) to a remote destination (say
popserver.example.com port 110), you can write:
plink mysession -L 5110:popserver.example.com:110
And to forward a remote port to a local destination, just use the
-R option instead of
plink mysession -R 5023:mytelnetserver.myhouse.org:23
For general information on port forwarding, see section 3.5.
Once you have set up Plink to be able to log in to a remote server without any interactive prompting (see section 7.2.2), you can use it for lots of scripting and batch purposes. For example, to start a backup on a remote machine, you might use a command like:
plink root@myserver /etc/backups/do-backup.sh
Or perhaps you want to fetch all system log lines relating to a particular web area:
plink mysession grep /~fjbloggs/ /var/log/httpd/access.log > fredlogs
Any non-interactive command you could usefully run on the server command line, you can run in a batch file using Plink in this way.
To use Plink with CVS, you need to set the environment variable
CVS_RSH to point to Plink:
You also need to arrange to be able to connect to a remote host without any interactive prompts, as described in section 7.2.2.
You should then be able to run CVS as follows:
cvs -d :ext:user@sessionname:/path/to/repository co module
If you specified a username in your saved session, you don't even need to specify the "user" part of this, and you can just say:
cvs -d :ext:sessionname:/path/to/repository co module
Plink can also be used with WinCVS. Firstly, arrange for Plink to be able to connect to a remote host non-interactively, as described in section 7.2.2.
Then, in WinCVS, bring up the "Preferences" dialogue box from the Admin menu, and switch to the "Ports" tab. Tick the box there labelled "Check for an alternate
rsh name" and in the text entry field to the right enter the full path to
plink.exe. Select "OK" on the "Preferences" dialogue box.
Next, select "Command Line" from the WinCVS "Admin" menu, and type a CVS command as in section 7.4, for example:
cvs -d :ext:user@hostname:/path/to/repository co module
Select the folder you want to check out to with the "Change Folder" button, and click "OK" to check out your module. Once you've got modules checked out, WinCVS will happily invoke plink from the GUI for CVS operations.
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