Unix

Seven columns are printed - one for each day of the week.

The samba software package implements the netbios protocol which is used by Microsoft Windows Lan Manager under TCP/IP to share files. Samba is open software and available free for non-windows platforms such as linux, unix and OpenVMS. Properly configuring samba makes Unix folders appear as shared folders on a Windows system.

The 'system' API will run a command string in a subshell and return to the calling program. The 'execl' API will overlay the current process with a different program; it can never return to the calling program because the calling program is no longer there (it has been overlayed by the new program from execl).

The fork and exec command are used to spawn other activities or processes from a currently running program.

Different versions of Unix use different methods of page replacement depending on situations; there is no one size fits all. You will need to check for the specific version of Unix you are interested in and ask the vendor.

Yes, you can.

)With a neat diagram explain different layer of Unix OS? Also explain interaction between Shell an kernel using any suitable commands.

or

Architecture of Unix.

Ans- The part of UNIX that manages the hardware and the executing processes is called the kernel. The kernel is a collection of programs written in C which directly communicate with the hardware. Each hardware device is viewed as a file and is called a device file. This allows the same simple method of reading and writing files to be used to access each hardware device. The file system manages read and write access to user data and to devices, such as printers, attached to the

system. It implements security controls to protect the safety and privacy of information. In executing processes the kernel allocates resources, including use of the CPU and mediates accesses to the hardware.

The user commands are translated into action by the shell which acts as an interpreter. The shell forms the outer part of the operating system and forms the interface between the user and the kernel. For each user logged in, there is shell in action. When a command is given by the user, it is examined by the shell and communicated to the kernel for execution. The functions used to communicate with the kernel are called system calls and are built into the kernel. The system calls are in all the flavors of UNIX are the same. Hence, software developed on one UNIX system can be easily run on another UNIX system.

UNIX's layered design insulates the application from the different types of hardware. This allows the software developer to support the single application on multiple hardware types with minimal effort. The application writer has lower development costs and a larger potential customer base. Users not only have more applications available, but can rely on being able to use the same applications on different computer hardware.

You can see this yourself by looking at the passwd file - it is the colon symbol.

A GUI can be used in Unix (in fact, several). Most power users don't use the GUI because it can be too limiting. The power of what you can do in Unix is at the command line, not using a GUI to click on buttons.

Of course, this could be said about most operating systems; the GUI is there for user convenience but most administrators use the command line for most of their work.

For Unix based systems the first field is the user-id; there is no beginning plus symbol.

You will need to provide more information in order to completely answer the question.

The two links are for the current directory (.) and the parent directory (..). This is allow for easy directory traversal.

The 'type' command does approximately (but not exactly) the same thing as the 'cat' command.

smb umount

PWD

Although pwd will tell you where you are it won't change back to your home directory. For that, use the 'cd' command without any parameters

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That would be IRIX.

Run level 1 is considered an adminstrative mode, usually for installing packages and so forth. In this situation, you want a minimal set of processes running, no other users logged in, and local filesystems mounted. It usually requires the /etc/inittab file for the definitions of what processes to start at different run levels.

Run level s is for single user mode, usually considered an administrative mode as well, but for more of a basic environment; local file systems are not mounted and the /etc/inittab file does not have to exist. Usually, single user level is for repairing systems or troubleshooting the system.

'cat' is short for concatenation; it is a Unix utility program to print the contents of 1 or more files on the standard output. It is similar to the 'type' command in Windows.

They give different information, for one thing. The 'who' command is only useful for users who are currently logged into the system. It also gives log in information about when they logged in and from where. It won't tell you who they are (other than there log in name).

The finger command will give information like a white pages - who the person is, where their office is, telephone number, a plan and project if they have one. It may be used whether or not the user is logged in. It also will tell you if you can communicate with them.

Heap file organization

Sequential File Organization

Hashing File organization

The question is rather vague; the applications used in Unix are similar or identical to those used in other operating systems, such as Windows.

OpenBSD is a free an open-source Unix-like operating system, with a primary focus on security.

To ignore the special meaning of a meta-character, use the escape character (back-slash) in front of it.

For example, echo $USER would cause the shell variable $USER to be substituted. But if you wanted to actually echo $USER, then use 'echo \$USER'

Unix has the following categories of users:

Superuser - root account, can do anything on the system

ordinary user - has no special privileges

restricted user - is restricted in what they can do in the shell and programs they can run.

The main reason is vendor support; as part of the contract the vendor agrees to enhance and fix problems in a timely manner. Also, a number of proprietary UNIX systems are better suited for heavy environments than some of the open source versions.

It should be indicated, however, that you can buy a support contract for the open source versions as well.

One of the things that determine whether or not to use the open source version versus a proprietary one is what applications you intend to use on the platform. Not all versions of either may support the program you want to use.