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What is ssh?
ssh stands for secure shell. It is a secure way to login into other machines.
You should never use TELNET again if SSH is available (in fact I don't think you can use telnet on our network)
If ssh is not available on your machine or the one you are trying to access,
you should contact the appropriate system administrator.
How to use ssh
The implementation of MPI that is installed uses ssh to startup your parallel
processes on remote machines. By default, ssh prompts you for your password on
the remote machine. Go ahead, try this now.
For example, type ssh sun1 or ssh pc01
If you have never used ssh to connect with the machine, you may be
asked about an authentication key. It is okay to type "yes" at this
prompt. This will only happen the first time you use ssh to connect
to that machine. After the authentication key prompt (if any),
ssh should prompt you for your password on that machine.
So, this is great because now we can access our accounts on other machines in a
Except that for a parallel program that is going to use three machines, you'll get
prompted for the passwords to each of those machines! And this will happen each time
you execute the parallel program! Bummer, huh? But, read on!!
Bypassing the password prompt
It is possible to configure ssh to bypass the password prompt each time.
To do this, you need to create a "key" for ssh to use. So perform
the following steps. If you can already ssh around the EE network without
being prompted for a password you may be able to skip this. If you have any problems running the getmachines.sh script you should check that his step has been completed.
ssh-keygen -t rsa
- You will be prompted about what file to save the key in. Just accept the default
(it should be "id_rsa") by pressing ENTER.
- You will be prompted about a passphrase, just hit ENTER for no passphrase.
- Just hit ENTER again for the passphrase confirmation.
- Add the public key just generated to your list of authorized keys
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
- If you don't already have an authorized_keys file to
append to, just use one > in the
command above. You will know this file doesn't exist if the first cat command gives
you an error saying the file was not found or that there is no such file or directory
- Now do this for the RSA1 key (required by my getmachines.sh script) as well as the DSA key for good measure
ssh-keygen -t rsa1
ssh-keygen -t dsa
cat identity.pub id_dsa.pub >> authorized_keys