Logging In to a Remote System (ssh)

The Secure Shell feature of Oracle Solaris provides secure access to a remote host over an unsecured network. In Secure Shell, authentication is provided by the use of passwords, public keys, or both. All network traffic is encrypted. Thus, Secure Shell prevents a would-be intruder from being able to read an intercepted communication. Secure Shell also prevents an adversary from spoofing the system.

If the system you are logging in to is in a remote domain, be sure to append the domain name to the system name. In the following example, example.com is the name of the remote domain, venus is the host name, and jdoe is the user:

ssh —l jdoe venus.example.com

Authentication for Remote Logins (ssh)

Authentication (establishing who you are) for ssh logins is provided by a combination of system passwords and public host keys. Authentication operations can be performed either by the remote system or by the network environment.

The /etc/ssh_known_hosts and .ssh/known_hosts Files

The /etc/ssh_known_hosts and the .ssh/known_hosts files contain the list of known host keys on the system or account. By default, the ssh command verifies the remote host's key. The ssh command next checks the host keys stored in the /etc/ssh_known_hosts and ~/.ssh/known_hosts files. If there is no host key for the remote host in either file, the user is asked whether they trust the new remote host's key. If the user confirms, the remote host's key is then added to the user's ~/.ssh/known_hosts file before the user is prompted for their password.

In the following example, user jsmith is logging in to the remote host mars.example.com for the first time.

$ ssh -l jsmith mars.example.com
The authenticity of host 'mars.example.com (10.80.226.105)' can't be established.
RSA key fingerprint is 06:55:4d:4e:d2:4a:e6:d9:8a:c4:13:15:18:9a:ef:dd.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'mars.example.com' (RSA) to the list of known hosts.
Password: 
Last login: Thu Jun 21 15:44:54 2012 from venus.example
Oracle Corporation      SunOS 5.11      11.1    June 2012
$ 

The RSA key fingerprint for mars.example.com is now in jsmith/.ssh/known_hosts. Subsequent logins by jsmith to mars.example.com will prompt for a system password. For example:

$ ssh -l jsmith mars.example.com
Password: 
Last login: Thu Jun 21 15:45:47 2012 from mars.example
Oracle Corporation      SunOS 5.11      11.1    June 2012
$ 

For further information on Secure Shell authentication, refer to Secure Shell Authentication in Oracle Solaris 11.1 Administration: Security Services.

What Happens After You Log In Using Secure Shell

When you attempt to log in to a remote system with the ssh command, the sshd daemon on the remote system starts the login program. The login program then performs the same tasks as when you log in locally. The program authenticates the user, and if successful, it executes the user's login shell.

If the home directory for the user cannot be found, you are then assigned to the remote system's root (/) directory. For example:

Unable to find home directory, logging in with / 

How to Log In to a Remote System (ssh)

• Log in to a remote system by using the ssh command.

  ssh [-l login-name] hostname | login-name@hostname

  login-name

  Logs you in to the remote system with the user name you supply

  hostname

  The name of the remote system that you are logging into

  If the system's host key is verified, you are asked to provide a password. If the password is typed incorrectly, the system states the number of authentication failures and the last date of successful login.

  If the operation succeeds, the following is displayed: information about your last remote login to that system, the version of the operating system that is running on the remote system, and whether you have mail waiting for you in your home directory.

Example 3-1 Logging In to a Remote System (ssh)

The following example shows the output of a remote login to pluto. The system's host key has not been identified in either the /etc/ssh_known_hosts or the .ssh/known_hosts file, and the user has incorrectly entered in the password at the first attempt:

$ ssh -l amy pluto
The authenticity of host 'pluto (10:120:100:12)' can't be established.
RSA key fingerprint is 06:55:4d:4e:d2:4a:e6:d9:8a:c4:13:15:18:9a:ef:dd.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'pluto' (RSA) to the list of known hosts.
Password:
Password:
Warning: 1 failed authentication attempt at Wed Jun 27 12:47 2012 since last successful authentication.

Last login: Wed Jun 27 12:19:04 2012 from venus.us.
Oracle Corporation      SunOS 5.11      11.1    June 2012
$

Logging Out of a Remote System (exit or logout)

You can log out of a remote system by using either the exit or the logout command.

$ exit
 

$ logout

The Control-D command sequence also ends a session on a remote system. For example, on the host venus:

$ Control-D
Connection to venus closed.