Ans: Cluster is a very high availability type of cluster which can be improve the performance of software like data base, file sharing on network

Ans:
open(pathname,flag,mode) - open file
create (pathname, mode) - create file
close(filedes) - close an open file
read(filedes,buffer,bytes) - read data from an open file
write(filedes,buffer,bytes) - write data to an open file
lseek(filedes,offset,from) - position an open file
dup(filedes) - duplicate an existing file descriptor
dup2(oldfd,newfd) - duplicate to a desired file descriptor
fcntl(filedes,cmd,arg) - change properties of an open file
ioctl(filedes,request,arg) - change the behaviour of an open file
The difference between fcntl and ioctl is that the former is intended for any open file, while the latter is for device-specific operations.

Ans: In situations like, where the copy on write bit of a page is set and that page is shared by more than one process, the Kernel allocates new page and copies the content to the new page and the other processes retain their references to the old page. After copying the Kernel updates the page table entry with the new page number. Then Kernel decrements the reference count of the old pfdata table entry. In cases like, where the copy on write bit is set and no processes are sharing the page, the Kernel allows the physical page to be reused by the processes. By doing so, it clears the copy on write bit and disassociates the page from its disk copy (if one exists), because other process may share the disk copy. Then it removes the pfdata table entry from the page-queue as the new copy of the virtual page is not on the swap device. It decrements the swap-use count for the page and if count drops to 0, frees the swap space.

Ans: ex is UNIX line editor and vi is the standard Unix screen editor.

Ans: A pipe is two or more commands separated by pipe char '|'. That tells the shell to arrange for the output of the preceding command to be passed as input to the following command.

Example: ls -l | pr
The output for a command ls is the standard input of pr.
When a sequence of commands is combined using pipe, then it is called pipeline.

Ans: The page is first checked for the validity fault, as soon as it is found that the page is invalid (valid bit is clear), the validity fault handler returns immediately, and the process incur the validity page fault. Kernel handles the validity fault and the process will incur the protection fault if anyone is present.

Ans: The two paging states are:
The page is aging and is not yet eligible for swapping.
The page is eligible for swapping but not yet eligible for reassignment to other virtual address space.

Ans: All processes in the main memory are asleep.
All ‘Ready-to-run’ Processes are swapped out.
There is no space in the swap device for the new incoming process that is swapped out of the main memory.
There is no space in the main memory for the new incoming process.

Ans: who > file1

who command lists all the users currently working & output can be stored in a file named file1.

Ans: The ‘Sticky Bit’ Is a permission bit that can be set on either a file or a directory.

If it is set on a file, then that file will remain in memory after execution, thus ‘sticking’ in memory. This is useful when running a multi-user program (such as a bulletin board system that I ran once) to make the program execute faster for the next user. This was a common programming tactic earlier in the history of computer programming when speed and disk space were at a premium.

If the sticky bit is set on a directory, only the owner of files in that directory will be able to modify or delete files in that directory - even if the permissions set on those files would otherwise allow it.

It executes from user and behaves as it executing from the root.