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Difficulty[[Category: 3 How-To]][[Category:Computers]]'''SSH''', which stands for "secure shell", is a way to log into a server and execute commands on a [[command line]]. Here at Williams, you might SSH into [[Unix]] (unix.williams.edu) or to [[WSO]] (wso.williams.edu).

==Logging in with SSH without a password : Public-key authentication (UNIX and Mac OS X)==

NoteThe program doesn't need to be installed; just open the file you downloaded whenever you want to run PuTTY. 2. Open putty.exe 3. Enter "wso.williams.edu" (or whatever) for the host, and "SSH" for the protocol.  4. Click "Open"  5. Enter your user name and password when prompted.  6. If this is your first time connecting from this computer, you might get a message like this: Logging   The server's host key is not cached in the registry. You have no guarantee that the server is the computer you think it is. The server's key fingerprint is: ssh-rsa 1024 7b:e5:6f:a7:f4:f9:81:62:5c:e3:1f:bf:8b:57:6c:5a If you trust this host, hit Yes to add the key to PuTTY's cache and carry on connecting. If you want to carry on connecting just once, without a password will save adding the key to the cache, hit No. If you do not trust this host, hit Cancel to abandon the connection.  If this is your first time, don't sweat it, just say Yes. If you get this message and this is not your first time SSH'ing from this machine, you might drop us a few seconds out of every dayline. It comes howeverFor more information about host keys, with an added security riskread this page: if someone compromises   http://the.earth.li/~sgtatham/putty/0.55/htmldoc/Chapter2.html  7. You're in! Happy computing. ===Mac/Linux=== Let's say youruser name is ewilliam and you want to log in to wso.williams.edu. From a [[command line]], typemachine, they can then log into WSO with ssh ewilliam@wso.williams.edu Enter your accountpassword when prompted. If it's your first time and you are willing to bear this responsibilityget a warning about host keys, then read onjust say "yes".

The basic idea is that WSO's server will check for a special key on your computer every time you log in, and if it checks out, you'll be allowed ==Logging in without entering a password. Ifyou'd like a more in-depth explanation, read on: ==

httpNote://theLogging in without a password will save you a few seconds out of every day.earth.li/~sgtatham/putty/0It comes however, with an added security risk: if someone compromises yourmachine, they can then log into WSO with your account.54/htmldoc/Chapter8If you are willing to bear this responsibility, then read on.html#8

1.Open a terminal [[command line]]  2.Generate a public key and a private key. We'll copy the public key over to the server later.   ssh-keygen -t rsa -f ~/.ssh/id_rsa 3. When it says something like

3.When it says something like Enter passphrase (empty for no passphrase): Just press return. 4.Let's copy the public key to WSO. Type

$ scp 4.ssh/id_rsa.pub user@wso:~/.ssh/Let's copy the public key to WSO. Type

5scp .Cruise over to the WSO serverssh/id_rsa.pub user@wso: ~/.ssh/.

$ ssh user@wso5.williams.edu Cruise over to the WSO server:

6ssh user@wso.Hop into the SSH directory: williams.edu

$ cd 6.ssh Hop into the SSH directory:

7 cd .Append the key to your list of authorized keys: ssh

$ cat id_rsa7.pub >> authorized_keys2 Append the key to your list of authorized keys:

8 cat id_rsa.Change permissions: pub >> authorized_keys2

$ rm id_rsa9. Kill the key.pub

===Windows===This link will give you some background about public-Evan Millerkey authentication, and how to do it with PuTTY:  http://the.earth.li/~sgtatham/putty/0.54/htmldoc/Chapter8.html#8  A few tips: * Use RSA * Your authorized keys file is called .ssh/authorized_keys2  Best of luck!