SSH Without a Password

[fabiodelorenzo]

The following steps can be used to ssh from one system to another without specifying a password.
Notes:

* The system from which the ssh session is started via the ssh command is the client.
* The system that the ssh session connects to is the server.
* These steps seem to work on systems running OpenSSH.
* The steps assume that a RSA key is being used. To use a DSA (insecure) key substitute 'rsa' with 'dsa'.
* The steps assume that you are using a Bourne-like shell (sh, ksh or bash)



Steps:

1. On the client run the following commands:

$ mkdir -p $HOME/.ssh
$ chmod 0700 $HOME/.ssh
$ ssh-keygen -t rsa -f $HOME/.ssh/id_rsa -P "your_private_pass_key"

SKIP the -P private_pass_key if you don't wanna be prompted for password

This should result in two files, $HOME/.ssh/id_rsa (private key) and $HOME/.ssh/id_rsa.pub (public key).

NOTE: steps [2,3,4 and 5] can be skipped using:
ssh-copy-id -i .ssh/id_rsa.pub user@domain.com

2. Copy $HOME/.ssh/id_rsa.pub to the server.

3. On the server run the following commands:

$ cat id_dsa.pub >> $HOME/.ssh/authorized_keys2
$ chmod 0600 $HOME/.ssh/authorized_keys2

Depending on the version of OpenSSH the following commands may also be required:

$ cat id_dsa.pub >> $HOME/.ssh/authorized_keys
$ chmod 0600 $HOME/.ssh/authorized_keys

An alternative is to create a link from authorized_keys2 to authorized_keys:

$ cd $HOME/.ssh && ln -s authorized_keys2 authorized_keys

4. On the client test the results by ssh'ing to the server:
$ ssh -i $HOME/.ssh/id_rsa server

5. (Optional) Add the following $HOME/.ssh/config on the client:

Host server
IdentityFile ~/.ssh/id_rsa

This allows ssh access to the server without having to specify the path to the id_dsa file as an argument to ssh each time.

Helpful manpages:

* ssh(1)
* ssh-keygen(1)
* ssh_config(5)