Unix technical interview questions and answers are frequently asked in system administration, DevOps, backend development, and support engineering roles. Unix forms the base for Linux and macOS, so companies expect candidates to understand file permissions, commands, shell scripting, process management, filters, pipes, and environment variables. Interviews in TCS, Infosys, Wipro, Cognizant, Capgemini, and Accenture often include Unix questions during both technical rounds and written tests. This guide explains frequently asked Unix commands and concepts using simple language, making it easy for freshers and experienced candidates to prepare. You can also download Unix interview questions PDFs and practice mock commands for better preparation.
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31. What are the criteria for choosing a process for swapping into memory from the swap device?
The resident time of the processes in the swap device, the priority of the processes and the amount of time the processes had been swapped out.
32. What are the criteria for choosing a process for swapping out of the memory to the swap device?
The processs memory resident time,
Priority of the process and
The nice value.
33. What are conditions on which deadlock can occur while swapping the processes?
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 are swapped out of the main memory.
There is no space in the main memory for the new incoming process.
34. What are conditions for a machine to support Demand Paging?
Memory architecture must based on Pages,
The machine must support the ‘restartable instructions.
35. What is ‘the principle of locality?
Its the nature of the processes that they refer only to the small subset of the total data space of the process. i.e. the process frequently calls the same subroutines or executes the loop instructions.
36. What is the working set of a process?
The set of pages that are referred by the process in the last ‘n, references, where ‘n is called the window of the working set of the process.
37. What is the window of the working set of a process?
The window of the working set of a process is the total number in which the process had referred the set of pages in the working set of the process.
38. What is called a page fault?
Page fault is referred to the situation when the process addresses a page in the working set of the process but the process fails to locate the page in the working set. And on a page fault the kernel updates the working set by reading the page from the secondary device.
39. What are data structures that are used for Demand Paging?
Kernel contains 4 data structures for Demand paging. They are,
Page table entries,
Disk block descriptors,
Page frame data table (pfdata),
Swap-use table.
40. How the Kernel handles the fork() system call in traditional Unix and in the System V Unix, while swapping?
Kernel in traditional Unix, makes the duplicate copy of the parents address space and attaches it to the childs process, while swapping. Kernel in System V Unix, manipulates the region tables, page table, and pfdata table entries, by incrementing the reference count of the region table of shared regions.