Ans: Protection fault refers to the process accessing the pages, which do not have the access permission. A process also incur the protection fault when it attempts to write a page whose copy on write bit was set during the fork () system call.

Ans: Redirection is the process by which input or output to or from a process is redirected to another process. This can be done using the pipe symbol "|", the greater than symbol ">" or the "tee" command. This is one of the strengths of UNIX allowing the output from one command to be redirected directly into the input of another command.

Ans:
$ ls > file1
writes the list of all the files in the folder into a file called file1
$ banner hi-fi > message
gives an error coz of the - i guess
$ cat par.3 par.4 par.5 >> report
writes the contents of the 3 files into a file called report
$ cat file1>file1
all contents of file1 are erased
$ date ; who
prints the current date and all the persons logged in
$ date ; who > log file
prints the current date and writes all the persons logged in into a file called log file
$ (date ; who) > log file the current date and the who details are inserted into a file called log file

Ans: Removing an open file under UNIX is possible, but not necessarily immediate; the file might not be removed until it has been closed by all openers.

Ans: The term IPC (Inter-Process Communication) describes various ways by which different process running on some operating system communicate between each other. Various schemes available are as follows: Pipes: One-way communication scheme th...  

Ans:  There are several commands to do this: du, DF, or bdf.

Ans: Process before swapping is residing in the primary memory in its original form. The regions (text, data and stack) may not be occupied fully by the process, there may be few empty slots in any of the regions and while swapping Kernel do not bother about the empty slots while swapping the process out. After swapping the process resides in the swap (secondary memory) device. The regions swapped out will be present but only the occupied region slots but not the empty slots that were present before assigning. While swapping the process once again into the main memory, the Kernel referring to the Process Memory Map, it assigns the main memory accordingly taking care of the empty slots in the regions.

Ans: The swapper works on the highest scheduling priority. Firstly it will look for any sleeping process, if not found then it will look for the ready-to-run process for swapping. But the major requirement for the swapper to work the ready-to-run process must be core-resident for at least 2 seconds before swapping out. And for swapping in the process must have been resided in the swap device for at least 2 seconds. If the requirement is not satisfied then the swapper will go into the wait state on that event and it is awaken once in a second by the Kernel.

Ans: The page stealer and the fault handler thrash because of the shortage of the memory. If the sum of the working sets of all processes is greater that the physical memory then the fault handler will usually sleep because it cannot allocate pages for a process. This results in the reduction of the system throughput because Kernel spends too much time in overhead, rearranging the memory in the frantic pace.

Ans: cd ~

This command will direct you to the user directory

cd $HOME

This command will direct you to the Home directory