Linux Command Line Interface

The server we will be using for the Linux units is a secure server. We will need to use a secure Telnet client, like PuTTY, to access it. The Telnet client will give us console access to the server. Thus, we will be able to enter commands at the system prompt and see the results from our computer through the Telnet client. OC uses a SSH connection for cis2.oc.ctc.edu for security reasons. See details below. NOTE: Since we are sending and receiving commands over the Internet, the speed of your local connection may impact the overall user experience like slow response times.

SSH uses public-key cryptography to authenticate the remote computer and allow it to authenticate the user, if necessary. Anyone can produce a matching pair of different keys (public and private). The public key is placed on all computers that must allow access to the owner of the matching private key (the owner keeps the private key secret). While authentication is based on the private key, the key itself is never transferred through the network during authentication. SSH only verifies if the same person offering the public key also owns the matching private key. Hence, in all versions of SSH it is important to verify unknown public keys, i.e. associate the public keys with identities, before accepting them as valid. Accepting an attacker's public key without validation will authorize an unauthorized attacker as a valid user. [Wikipedia]

To make a connection to the cis2 sever, you will need to know the following. If you have issues connecting, please contact the OC Help Desk at 360-475-7600. Make sure they know you are referring to the cis2 server since many at the OC Help Desk may not be aware of this server existence since it is primarily used for this class and a few other CIS classes. Please note that I do not have admin control over this server.

Host: cis2.oc.ctc.edu
Port: 22
Cnct: SSH (for secure shell connection)

When you connect to the server, you will be asked to enter your user name. Use your standard OC user name you use for any OC network. They all use the same authentication server. Your password will not be display on the screen, including dots. You will just have to believe it is being entered.

User: (see unit outline for details)
Pswd: (see unit outline for details, note: no keystrokes will be displayed)

Once connect, you should see the system prompt which is a "$" dollar sign on most Linux systems. You are now in the Bash shell and should be in your home directory (~) which acts as your root. Every user on the system has a home directory. It is referenced by the ~ tilde. You control what you can do and what you will let others can see and do from this location down. It is the same for other users on the server. Some quick commands to verify you have a working connection is to enter "clear" to clear the screen and "whoami" to see your system name.

A user's home directory is intended to contain that user's files; including text documents, music, pictures or videos, etc. It may also include their configuration files of preferred settings for any software they have used there and might have tailored to their liking: web browser bookmarks, favorite desktop wallpaper and themes, passwords to any external services accessed via a given software, etc. The user can install executable software in this directory, but it will only be available to users with permission to this directory. The home directory can be organized further with the use of sub-directories. The content of a user's home directory is protected by file system permissions, and by default is accessible to all authenticated users and administrators. Any other user that has been granted administrator privileges has authority to access any protected location on the filesystem including other users home directories. Separating user data from system-wide data avoids redundancy and makes backups of important files relatively simple. Furthermore, Trojan horses, viruses and worms running under the user's name and with their privileges will in most cases only be able to alter the files in the user's home directory, and perhaps some files belonging to workgroups the user is a part of, but not actual system files. [Wikipedia]

A user's account allows a user to authenticate to a system and to be granted authorization to access resources provided by or connected to that system; however, authentication does not imply authorization. To log into an account, a user is typically required to authenticate oneself with a password or other credentials for the purposes of accounting, security, logging, and resource management. Once the user has logged on, the operating system will often use an identifier such as an integer to refer to them, rather than their username, through a process known as identity correlation. In Unix systems, the username is correlated with a user identifier or user id. Each user account on a multi-user system typically has a home directory, in which to store files pertaining exclusively to that user's activities, which is protected from access by other users (though a system administrator may have access). User accounts often contain a public user profile, which contains basic information provided by the account's owner. [Wikipedia]

✏ Self Quiz!

Key terms: Linux, Telnet, client, connection, home directory, server, user account, whoami

Resources:
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Linux Command Line Interface

Logon to cis2.oc.ctc.edu with Telnet

✏ Self Quiz!

Embedded Resources