Agenda Networking with Linux & UNIX OS –Overview –Setup –Common Utilities

Networking with Linux & UNIX OS The UNIX and Linux operating systems are well suited for allowing connections and transferring data between file servers (servers). Many individuals create their own servers as home to allow data to be transferred to school, etc...

Networking with Linux & UNIX OS Because students tend to gain access to more servers throughout their program (Phobos, Tux, Poseidon, Linux server at home) there is a need to protect access into their accounts, as well as use a set of tools to connect and transfer data among these servers

Networking Setup For Linux OS - Step 1: –Use editor to check settings in file /etc/hosts.allow should have nothing in it except comments and maybe your localALL:LOCALHOST at most if you see anything like ALL:ALL You should remove it! This says that EVERYONE has ACCESS to your computer!!!!

Networking Setup For Linux OS- Step 2: –Use editor to check settings in file /etc/hosts.deny You should have the following line: ALL:ALL what that means is everyone is not allowed in just in case you have any problems - remember to have in your hosts.allow ALL:localhost

Networking Setup Linux & Unix OS –Similar to Linux, a file requires to be setup to allow the user to transfer data between systems (or containing different login names). –A file called.rhosts should be setup in the user’s home directory containing the server name and /or static IP address followed by a space followed by the account’s username. –This will allow the system to “trust” you to use special “remote commands” (rlogin, rcp, rsh)

ATTENTION One weakness with the “remote” commands is that other users may view your data! Most servers (to protect themselves) use “secure” commands. You cannot use “remote” commands on servers such as Phobos, Tux, Gothic, etc, but you can use “secure” commands

.shosts In order to use “secure” commands, A file called.shosts should be setup in the user’s home directory containing the server name and/or static I.P. address followed by a space followed by the account’s username

Common Utilities for Networking telnet –Used to remotely connect to remote server (eg. telnet tux.senecac.on.ca) ftp –Used to transfer files between servers - very similar to MS-DOS FTP in terms of get and put commands. (eg. ftp tux.senecac.on.ca) rlogin(“secure” command is slogin) –Used to connect to remote server (eg. rlogin tux ) CRTL-D to return back to original server rcp

Common Utilities for Networking rwho –Displays users who are actively logged onto other remote systems rsh (“secure” command is ssh) –Allows user to run commands, scripts, programs remotely in other servers talk / write –Commands to intiate text-based conversion among users (check previous notes for usage)

Common Utilities for Networking rcp (“secure” commands is scp) – Used to transfer files between two between servers (works like copy & requires.rhosts file in home directories –For example: rcp doc1 tux:reports/doc1.txt This command copies file doc1 on your account on the current server to your other account on the tux server.

Common Utilities for Networking wall –Used to broadcast a message to all users currently logged onto server that allow message reception. (eg. echo hi everyone | wall ) ping –Used to test network connection (see how well server is running - if running). Can use both static IP address and DNS address. Examples: ping ping tux.senecac.on.ca

Common Utilities for Networking ruptime –determines how long remote server has been running since last “shut-down” Note: depending on UNIX administration, some of these command may or may not work….