Password for SSH and SCP – How to Set Up

clusterscpssh

(1) I want to upload some files to a server

for (( i=0 ; i < 23 ; i+=1 )); do  
    echo mypassword | scp tim@xxx.xxx.xxx.xxx:project/$i/train10000/finer_search_c_g ~/project/$i/train10000/  
done

I hope that by pipe my password to scp, the loop will be executed without interaction. However it still asks me to manually input the password. How should I specify mypassword to scp?

(2) I do not use authentication keys generated by ssh-keygen because the server actually is a head node of a cluster. I found that if I use ssh-keygen to generate authentication keys, the files under ~/.ssh will make the access between nodes requiring password, which I cannot find a solution. Is it possible to make the access between nodes with empty password while using authentication keys to access head node from outside the cluster?

THanks and regards!

Best Answer

Use a key file. Place the private keyfile on your client and use ssh-agent to keep the key file loaded in memory, decrypted. Place the public key file on each of the systems you want to access.

Use authentication forwarding to create connections between various hosts without being prompted for authentication.

Related Solutions

SSH – System for Distributing SSH Public Keys

As already mentioned by pulegium, any generic configuration management software like Puppet, Chef, Bcfg2 or cfengine could accomplish the task.

Since the authorized_keys file is not that complicated, you could also use rsync or a (D)SCM like git or hg to manage this file. You have the "master" file on one of your servers and serve it via rsync/git/hg/…. On every other server you run a cron job which periodically retrieves the master copy (if it was changed) and copies it to the correct local location. Heck, this would even work with pure HTTP or FTP.

The bottom line is: Have one "master" copy of your authorized_keys file and update it. Let the "clients" (the computers, which should have the current authorized_keys file) fetch it from your master server and deploy it locally.

Ssh – How to automate SSH login with password

Don't use a password. Generate a passphrase-less SSH key and push it to your VM.

If you already have an SSH key, you can skip this step… Just hit Enter for the key and both passphrases:

$ ssh-keygen -t rsa -b 2048
Generating public/private rsa key pair.
Enter file in which to save the key (/home/username/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/username/.ssh/id_rsa.
Your public key has been saved in /home/username/.ssh/id_rsa.pub.

Copy your keys to the target server:

$ ssh-copy-id id@server
id@server's password:

Now try logging into the machine, with ssh 'id@server', and check-in:

.ssh/authorized_keys

Note: If you don't have .ssh dir and authorized_keys file, you need to create it first

to make sure we haven’t added extra keys that you weren’t expecting.

Finally, check to log in…

$ ssh id@server

id@server:~$

You may also want to look into using ssh-agent if you want to try keeping your keys protected with a passphrase.

Best Answer

Related Solutions

SSH – System for Distributing SSH Public Keys

Ssh – How to automate SSH login with password

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