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Home > Help Files >
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Security: SSH
CONTENTS:
o What is SSH?
o Download SSH
o WebSSH
o Instructions
o Logging in using SSH Passphrase
o SSH w/o passwords in 1111 Linux Cluster (manually)
o SSH w/o passwords in 1111 Linux Cluster (parallel computing)
o Running programs remotely with SSH and Exceed
o SSH info
o SSH Public and Private KEYS
o Features
o SSH-Agent
o How to replace rsh/rcp/rlogin with SSH
What is SSH?SSH (Secure Shell) is a program to log into another computer over a network, to execute commands in a remote machine, and to move files from one machine to another. It provides strong authentication and secure communications over insecure channels. It is intended as a replacement for rlogin, rsh, and rcp.SSH protects the user from illicit network snooping ("packet sniffing"), whereby un-encrypted passwords and text can be read by unscrupulous persons. SSH is most useful for logging into a UNIX computer from an Windows computer or from another UNIX computer, where the traditional 'telnet' and 'rlogin' programs would not provide password and session encryption; however, the DECF administrative personnel tend to use SSH exclusively in preference to telnet or rlogin, except in cases where SSH is not available. SSH serves a purpose that is similar to Kerberos, but it works consistently amongst different operating systems and is easier to administer (no ticket- server is required, sysadmin privileges are not required to set it up). SSH Secure Shell for Workstations includes several features of interest:
To use ssh to connect to a host, just type ssh hostname(the same way you would use telnet or rlogin) If you are connecting to a host for the first time, you will be asked for confirmation. Type "yes" and hit return. You now have an encrypted connection to that host. Additionally you should be able to transparently run X (graphical) applications without setting any additional variables. Download SSHSSH Clients
SSH Public and Private KEYSWhen you first use ssh, it asks you to invent an "RSA indentity passphrase". It generates public and private keys for you, in files called "identity.pub" and "identity". The "identity" file should not be readable by anyone but you. On UNIX, those files are located in your .ssh directory. On Windows, they are typically located in your lop-level home directory folder. FeaturesSSH has a number of excellent security features beyond the basic encryption of your password and login session as they pass over the net. SSH can provide a stronger encryption algorithm ("RSA") and it can allow X11 and other network protocols to securely "tunnel" through your encrypted SSH session as they pass over the net.
SSH commands include:
sshd Server program run on the server machine. This
listens for connections from client machines, and
whenever it receives a connection, it performs
authentication and starts serving the client.
ssh This is the client program used to log into another
machine or to execute commands on the other machine.
"slogin" is another name for this program.
scp Securely copies files from one machine to another.
ssh-keygen Used to create RSA keys (host keys and user
authentication keys).
ssh-agent Authentication agent. This can be used to hold RSA
keys for authentication.
ssh-add Used to register new keys with the agent.
make-ssh-known-hosts
Used to create the /etc/ssh_known_hosts file.
For more infomation, see the manual pages ssh(1), sshd(8), scp(1),
ssh-keygen(1), ssh-agent(1), ssh-add(1), and make-ssh-known-hosts(1).
What is SSH-Agent?Ssh-agent is a program to hold authentication private keys. The idea is that ssh-agent is started in the beginning of an X-session or a login session, and all other windows or programs are started as children of the ssh-agent program. ssh-agent is stores your (private) authentication keys for ssh. This means that if you're using it, you won't have to enter the passphrase to unlock it every time you ssh to a remote machine.How to Replace rsh/rcp/rlogin with SSH
If you want to be able to use ssh and scp without passwords, see the next section. Logging in using SSH PassphraseExample. Login from myclient.berkeley.edu into myserver.berkeley.edu using a passphrase.
Secure Remote Access Without Passwords (manually)Due to the unique setup of 1111 Etch lab, you can use ssh-agent to avoid entering your username/password when logging between machines in the cluster.
Secure Remote Access Without Passwords among DECF clustersTo be able to ssh among DECF clients w/o a password
The following SSH help files are available:
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