Overview of Unix System - Essay Example

1 UNIX Overview It is possible for an operating system to be matured as well as of the art simultaneously? If it is UNIX, then the answer wouldbe “Yes.” UNIX has contributed in the Information technology sector for the last 25 years. Millions of installations conducted on various platforms and UNIX has proved to be organized and scalable. UNIX invented in 1969, by the computer scientists Dennis Ritchie and Kenneth Thompson employed at AT&T bell labs. Operating systems are compared by their functionality and performance. UNIX has contributed immensely in recent years. UNIX communication capabilities has also contributed in High performance computing sector as a company named Computer Associated International implemented a powerful system “Advantage Gen (release 6.5)”on UNIX platform to speed up the development of J2EE applications and web services (Ohio Supercomputing Center to Deploy Hp Linux Supercomputer. 2002). UNIX back end server support the automatic generation of enterprise java beans facilitated the development teams to develop the J2EE application more efficiently. By the UNIX fast XML proxy support, web services are developed in no time on a distributed system as compared to the previous server architecture. IBM 32 way UNIX servers were also launched in year 2001 with the code name “Regatta”. The microprocessor architecture comprises of 1 GHz 64 Bit Power 4. This UNIX server is capable of self-healing technology and to decrease system failures. The system is capable to divide into 16 virtual servers which enable the businesses to unite several machines in to one (Popovich 2001). The Client-server model of UNIX was the core components for the growth of Internet and reshaping of the distributed systems networks. Inter process communication in the UNIX operating system involves the connection between the system components logically and physically. It supports real time network applications which allow the user to exchange messages in an interactive session. UNIX is known as a command line interface due to nonexistence of a GUI environment Today UNIX is equipped with a GUI along with dynamic communication functionalities. Some of the registered UNIX products are HP-UX, IBM AIX, SCO UnixWare, SGI IRIX, Sun Solaris etc. 2 UNIX Administration UNIX system administrator is responsible for installing software, patches, administer file system, analyze and constantly monitor the performance. If any issue occurs, system administrator troubleshoots the issue with the help of available tools and commands. Hardware and software configuration management, liaison with data center, software and hardware migration also add to the responsibilities of a UNIX system administrator. The UNIX administration is divided in to two separate groups. System Administration Network Administration 2.1 System Administration To administer Linux / UNIX, there are many commands and tools available. To perform useful tasks, following commands are illustrated below with screen shots where possible. 2.1.1 “MAN” Command ‘MAN’ command “displays the online documentation for almost any command or program in UNIX. An incredible amount of information is stored in man pages, but you must know the name of the command you are looking for to be able to search” (, UNIX man command). This command extracts the title from the online reference manuals. As in the below mentioned snapshot, there is no manual installed. 2.1.2 “su” Command ‘Su’ is used to create a shell with a specific used id. It is used for switching between accounts as compared to Windows “switch user” option. See the snapshot for example 2.1.3 ‘Who’ Command This command displays the information regarding the users who is logged in, from how long, and how many users are logged in. As the below mentioned snapshot shows the username, time, date and how many users are logged in. Common switches are activity, state, line, time and name. 2.2 Network Administration Network administrator utilized ICMP “by routers, intermediary devices, or hosts to communicate updates or error information to other routers, intermediary devices, or hosts” (, Internet Control Message Protocol (ICMP) Basics). 2.2.1 For blocking/Unblocking the ICMP On the root console terminal, type the following commands; 2.2.1.1 For blocking ICMP SUDO Iptables –t filter –A OUTPUT –p icmp –j DROP To verify whether the command has been executed or not, it is executed on the terminal server. The above snapshot shows ICMP request are blocked by pinging www.google.com. 2.2.1.2 For unblocking ICMP SUDO Iptables –t filter –D OUTPUT –p icmp –j DROP To verify whether the command has been executed or not, it is is executed on the terminal server. The above snapshot shows ICMP request is unblocked by pinging www.google.com. 2.2.2 For blocking/Unblocking TCP On the root console, type the following commands; 2.2.2.1 For blocking TCP SUDO Iptables –t filter –A OUTPUT –p tcp –j DROP 2.2.2.2 For unblocking TCP SUDO Iptables –t filter –D OUTPUT –p tcp –j DROP 3 UNIX Communication Mechanism Features 3.1 Pipes Pipe is used to transfer information between two processes. The pipes are also called special files, which only save a limited amount of data. The pipe uses FIFO (First in First Out) mechanism to retrieve data. The data is written at one end of the pipe and can be read on the other end. The system cannot identify the processes at the other end of the pipe. The system also provides synchronization between reading and writing process. The system block the pipes already involved in processing data and constantly monitor the pipes to assure the processes are running at both ends of the pipes. The deadlock prevention is handled by the programmers. Pipes can be divided in to two categories: 3.1.1 Named Pipes: They exist in the form of directories with complete permissions. Unrelated processes can use them. 3.1.2 Un Named Pipes: They can only be used by related programs 3.2 PIPES FUNCTIONALITY IN UNIX UNIX has limited the pipes to 512 K. Write ( ) un buffered is used to add data to the pipes. The system assured that no interleaving will occur even if the pipes fill on a temporary basis. For the retrieval of data, read ( ) is used. The pipes ( ) call is used to rename unnamed pipes in UNIX. The command retrieves two pipes supporting bi directional communication. Pipe is used for sending the output of one process to another process as input. When a pipe process in initialized, both processes run concurrently and the system cannot assure on which sequence each process is allowed to run. UNIX communication mechanism manages the producer and the consumer issue, both processes proceed and the system provides automatic blocking when required. 3.3 To print the contents on the Terminal Screen The snapshot below shows the files in a temporary directory of a server that was created by user “Alice” and modified in the month of “January” by the order of size. 3.4 To Search the Contents ‘cat’ command is executed in the terminal for displaying the contents of a file names as ‘’OS.txt. ‘grep’ command is executed in the terminal window to display the total number of lines that contain the string “Unix” but not the string “Linux”. The below mentioned snap shot displays the results. “Ps” command lists the processes which are currently running. Common switches are –a,-c,-d,-e. The snapshot below shows 2 processes which are currently running. 3.5 References Ohio Supercomputing Center to Deploy Hp Linux Supercomputer. 2002. UNIX Update, 13(12), pp. 7. POPOVICH, K., 2001. IBMs new 32-way Unix server turns heads. eWeek, 18(38), pp. 11. Nasa Goddard Space Center Selects Linux Networx Supersystem. 2006. UNIX Update, 17(6), pp. 8-8. , UNIX man command . Available: http://www.cheme.cornell.edu/cheme/facilities/computing/unix/commands/man.cfm [1/12/2011, 2011]. , Internet Control Message Protocol (ICMP) Basics . Available: http://support.microsoft.com/kb/170292 [1/12/2011, 2011]. Read More