LINUX/UNIX/SOLARIS Interview Questions & Answers

  1. Question 1. What Are The Basic Components Of Linux?

    Answer :

    Linux is an operating system based on UNIX, and was first introduced by Linus Torvalds. It is based on the Linux Kernel, and can run on different hardware platforms manufactured by Intel, MIPS, HP, IBM, SPARC and Motorola. Another popular element in Linux is its mascot, a penguin figure named Tux.

  2. Question 2. What Is The Difference Between Unix And Linux?

    Answer :

    Unix originally began as a propriety operating system from Bell Laboratories, which later on spawned into different commercial versions. On the other hand, Linux is free, open source and intended as a non-propriety operating system for the masses.

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  4. Question 3. What Is Bash?

    Answer :

    BASH is short for Bourne Again SHell. It was written by Steve Bourne as a replacement to the original Bourne Shell (represented by /bin/sh). It combines all the features from the original version of Bourne Shell, plus additional functions to make it easier and more convenient to use. It has since been adapted as the default shell for most systems running Linux.

  5. Question 4. What Is Linux Kernel?

    Answer :

    The Linux Kernel is a low-level systems software whose main role is to manage hardware resources for the user. It is also used to provide an interface for user-level interaction.

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  7. Question 5. What Is Lilo?

    Answer :

    LILO is a boot loader for Linux. It is used mainly to load the Linux operating system into main memory so that it can begin its operations.

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  9. Question 6. What Is A Swap Space?

    Answer :

    A swap space is a certain amount of space used by Linux to temporarily hold some programs that are running concurrently. This happens when RAM does not have enough memory to hold all programs that are executing.

  10. Question 7. What Is The Advantage Of Open Source?

    Answer :

    Open source allows you to distribute your software, including source codes freely to anyone who is interested. People would then be able to add features and even debug and correct errors that are in the source code. They can even make it run better, and then redistribute these enhanced source code freely again. This eventually benefits everyone in the community.

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    Linux Interview Questions

  12. Question 8. Does It Help For A Linux System To Have Multiple Desktop Environments Installed?

    Answer :

    In general, one desktop environment, like KDE or Gnome, is good enough to operate without issues. It’s all a matter of preference for the user, although the system allows switching from one environment to another. Some programs will work on one environment and not work on the other, so it could also be considered a factor in selecting which environment to use.

  13. Question 9. What Is The Basic Difference Between Bash And Dos?

    Answer :

    The key differences between the BASH and DOS console lies in 3 areas:

    1. BASH commands are case sensitive while DOS commands are not.
    2. under BASH, / character is a directory separator and acts as an escape character. Under DOS, / serves as a command argument delimiter and is the directory separator.
    3. DOS follows a convention in naming files, which is 8 character file name followed by a dot and 3 character for the extension. BASH follows no such convention.
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  15. Question 10. What Is The Importance Of The Gnu Project?

    Answer :

    This so-called Free software movement allows several advantages, such as the freedom to run programs for any purpose and freedom to study and modify a program to your needs. It also allows you to redistribute copies of a software to other people, as well as freedom to improve software and have it released to the public.

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  17. Question 11. Describe The Root Account?

    Answer :

    The root account is like a systems administrator account, and allows you full control of the system. Here you can create and maintain user accounts, assigning different permissions for each account. It is the default account every time you install Linux.

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  19. Question 12. What Is Cli?

    Answer :

    CLI is short for Command Line Interface. This interface allows user to type declarative commands to instruct the computer to perform operations. CLI offers an advantage in that there is greater flexibility. However, other users who are already accustom with using GUI find it difficult to remember commands including attributes that come with it.

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  21. Question 13. How Do You Open A Command Prompt When Issuing A Command?

    Answer :

    To open the default shell (which is where the command prompt can be found), press Ctrl-Alt-F1. This will provide a command line interface (CLI) from which you can run commands as needed.

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  23. Question 14. How Can You Find Out How Much Memory Linux Is Using?

    Answer :

    From a command shell, use the “concatenate” command: cat /proc/meminfo for memory usage information. You should see a line starting something like: Mem: 64655360, etc. This is the total memory Linux thinks it has available to use.

  24. Question 15. What Is Typical Size For A Swap Partition Under A Linux System?

    Answer :

    The preferred size for a swap partition is twice the amount of physical memory available on the system. If this is not possible, then the minimum size should be the same as the amount of memory installed.

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  26. Question 16. What Are Symbolic Links?

    Answer :

    Symbolic links act similarly to shortcuts in Windows. Such links point to programs, files or directories. It also allows you instant access to it without having to go directly to the entire pathname.

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  28. Question 17. Does The Ctrl+alt+del Key Combination Work On Linux?

    Answer :

    Yes, it does. Just like Windows, you can use this key combination to perform a system restart. One difference is that you won’t be getting any confirmation message and therefore, reboot is immediate.

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  30. Question 18. How Do You Refer To The Parallel Port Where Devices Such As Printers Are Connected?

    Answer :

    Whereas under Windows you refer to the parallel port as the LPT port, under Linux you refer to it as /dev/lp . LPT1, LPT2 and LPT3 would therefore be referred to as /dev/lp0, /dev/lp1, or /dev/lp2 under Linux.

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  32. Question 19. Are Drives Such As Hard Drive And Floppy Drives Represented With Drive Letters?

    Answer :

    No. In Linux, each drive and device has different designations. For example, floppy drives are referred to as /dev/fd0 and /dev/fd1. IDE/EIDE hard drives are referred to as /dev/hda, /dev/hdb, /dev/hdc, and so forth.

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  34. Question 20. How Do You Change Permissions Under Linux?

    Answer :

    Assuming you are the system administrator or the owner of a file or directory, you can grant permission using the chmod command. Use + symbol to add permission or – symbol to deny permission, along with any of the following letters: u (user), g (group), o (others), a (all), r (read), w (write) and x (execute). For example the command chmod go+rw FILE1.TXT grants read and write access to the file FILE1.TXT, which is assigned to groups and others.

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  36. Question 21. In Linux, What Names Are Assigned To The Different Serial Ports?

    Answer :

    Serial ports are identified as /dev/ttyS0 to /dev/ttyS7. These are the equivalent names of COM1 to COM8 in Windows.

  37. Question 22. How Do You Access Partitions Under Linux?

    Answer :

    Linux assigns numbers at the end of the drive identifier. For example, if the first IDE hard drive had three primary partitions, they would be named/numbered, /dev/hda1, /dev/hda2 and /dev/hda3.

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  39. Question 23. What Are Hard Links?

    Answer :

    Hard links point directly to the physical file on disk, and not on the path name. This means that if you rename or move the original file, the link will not break, since the link is for the file itself, not the path where the file is located.

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  41. Question 24. What Is The Maximum Length For A File Name Under Linux?

    Answer :

    Any filename can have a maximum of 255 characters. This limit does not include the path name, so therefore the entire pathname and filename could well exceed 255 characters.

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  43. Question 25. What Are File Names That Are Preceded By A Dot?

    Answer :

    In general, filenames that are preceded by a dot are hidden files. These files can be configuration files that hold important data or setup info. Setting these files as hidden makes it less likely to be accidentally deleted.

  44. Question 26. What Is Unix?

    Answer :

    It is a portable operating system that is designed for both efficient multi-tasking and mult-user functions. Its portability allows it to run on different hardware platforms. It was written is C and lets user do processing and control under a shell.

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  46. Question 27. What Is The Use Of The Tee Command?

    Answer :

    The tee command does two things: one is to get data from the standard input and send it to standard output; the second is that it redirects a copy of that input data into a file that was specified.

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  48. Question 28. What Is The Standard Convention Being Followed When Naming Files In Unix?

    Answer :

    One important rule when naming files is that characters that have special meaning are not allowed, such as * / & and %. A directory, being a special type of file, follows the same naming convention as that of files. Letters and numbers are used, along with characters like underscore and dot characters.

  49. Question 29. Is It Possible To See Information About A Process While It Is Being Executed?

    Answer :

    Every process is uniquely identified by a process identifier. It is possible to view details and status regarding a process by using the ps command.

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  51. Question 30. How Do You Determine And Set The Path In Unix?

    Answer :

    Each time you enter a command, a variable named PATH or path will define in which directory the shell will search for that command. In cases wherein an error message was returned, the reason maybe that the command was not in your path, or that the command itself does not exist. You can also manually set the path using the “set path = [directory path]” command.

  52. Question 31. What Is A Superuser?

    Answer :

    A superuser is a special type user who has open access to all files and commands on a system. Note that the superuser’s login is usually root, and is protected by a so-called root password.

  53. Question 32. What Is Piping?

    Answer :

    Piping, represented by the pipe character “|”, is used to combine two or more commands together. The output of the first command serves as input the next command, and so on.

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  55. Question 33. What Is The Use Of -l When Listing A Directory?

    Answer :

    -l, which is normally used in listing command like ls, is used to show files in a long format, one file per line. Long format refers to additional information that is associated with the file, such as ownership, permissions, data and filesize.

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  57. Question 34. Differentiate Cmp Command From Diff Command?

    Answer :

    The cmp command is used mainly to compare two files byte by byte, after which the first encountered mismatch is shown. On the other hand, the diff command is used to indicate the changes that is to be made in order to make the two files identical to each other.

  58. Question 35. Enumerate Some Of The Most Commonly Used Network Commands In Unix?

    Answer :

    • telnet – used for remote login
    • ping – an echo request for testing connectivity
    • su – user switching command
    • ftp – file transfer protocol used for copying files
    • finger – information gathering command
  59. Question 36. What Is Bash Shell?

    Answer :

    It is a free shell designed to work on the UNIX system. Being the default shell for most UNIX-based systems, it combines features that are available both in the C and Korn Shell.

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  61. Question 37. What Are The Differences Among A System Call, A Library Function, And A Unix Command?

    Answer :

    A system call is part of the programming for the kernel. A library function is a program that is not part of the kernel but which is available to users of the system. UNIX commands, however, are stand-alone programs; they may incorporate both system calls and library functions in their programming.

  62. Question 38. What Are Shell Variables?

    Answer :

    Shell variables are a combination of a name ( identifier), and an assigned value, which exist within the shell. These variables may have default values, or whose values can be manually set using the appropriate assignment command. Examples of shell variable are PATH, TERM and HOME.

  63. Question 39. Explain The Importance Of Directories In A Unix System?

    Answer :

    Files in a directory can actually be a directory itself; it would be called a subdirectory of the original. This capability makes it possible to develop a tree-like structure of directories and files, which is crucial in maintaining an organizational scheme.

  64. Question 40. Differentiate Relative Path From Absolute Path?

    Answer :

    Relative path refers to the path relative to the current path. Absolute path, on the other hand, refers to the exact path as referenced from the root directory.

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  66. Question 41. Describe File Systems In Unix?

    Answer :

    Understanding file systems in UNIX has to do with knowing how files and inodes are stored on a system. What happens is that a disk or portion of a disk is set aside to store files and the inode entries. The entire functional unit is referred to as a file system.

  67. Question 42. Briefly Describe The Shell’s Responsibilities?

    Answer :

    • program execution
    • variable and file name substitution
    • I/O redirection
    • pipeline hookup
    • environment control
    • interpreted programming language
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  69. Question 43. What Is Inode?

    Answer :

    An inode is an entry created on a section of the disk set aside for a file system. The inode contains nearly all there is to know about a file, which includes the location on the disk where the file starts, the size of the file, when the file was last used, when the file was last changed, what the various read, write and execute permissions are, who owns the file, and other information.

  70. Question 44. What Is A Directory?

    Answer :

    Every file is assigned to a directory. A directory is a specialized form of file that maintains a list of all files in it.

  71. Question 45. Differentiate Multiuser From Multitask?

    Answer :

    Multiuser means that more than one person can use the computer at the same time. Multitask means that even a single user can have the computer work on more than one task or program at the same time.

  72. Question 46. What Is Command Substitution?

    Answer :

    Command substitution is one of the steps being performed every time commands are processed by the shell. Commands that are enclosed in backquotes are executed by the shell. This will then replace the standard output of the command and displayed on the command line.

  73. Question 47. What Is Kernel?

    Answer :

    Kernel is the UNIX operating system. It is the master program that controls the computer’s resources, allotting them to different users and to different tasks. However, the kernel doesn’t deal directly with a user. Instead, it starts up a separate, interactive program, called a shell, for each user when he/she logs on.

  74. Question 48. What Is Shell?

    Answer :

    A shell acts as an interface between the user and the system. As a command interpreter, the shell takes commands and sets them up for execution.

  75. Question 49. What Is The Chief Difference Between The –v And –x Option S To Set?

    Answer :

    The –v option echoes each command before arguments and variables have been substituted for; the –x option echoes the commands after substitution has taken place.

  76. Question 50. Is There A Way To Erase All Files In The Current Directory, Including All Its Sub-directories, Using Only One Command?

    Answer :

    Yes, that is possible. Use “rm –r *” for this purpose. The rm command is for deleting files. The –r option will erase directories and subdirectories, including files within. The asterisk represents all entries.

  77. Question 51. Brief About Init Phases?

    Answer :

    There are 8 run level.

    1. Init0: Shutting down the system and bring back the system to OBP Prompt (OK)
    2. Init1: Single user mode for administrative
    3. Init2: Multi user mode without resource sharing
    4. Init3: Multi user mode with resource sharing
    5. Init4: Not in use
    6. Init5: Shutdown and power off the system
    7. Init6: Reboot the system to default run level
    8. Inits: Single user mode but user login are disabled
  78. Question 52. What Is The Difference Between Init 1 And Init S?

    Answer :

    If you switch from multiuser mode to init s and switch it back to multiuser mode.then remote useres automatically reconnects to the system. where as in the case of init 1. they have to reconnect manually means they have to relogin 

  79. Question 53. Explain The Boot Process?

    Answer :

    Boot process dived into 4 phases. 

    1. POST : Power on self test (POST), It will detect hardware, machine host ID,serial No, architecture type, memory and Ethernet address and it will load the primary program called bootblk. 
    2. OBPROM : Open boot programmable Diagnosing all the system hardware and memory. Initializing the boot parameter. Creating device trees and load the boot block from (0-15 sector), it is called as secondary boot — programmable ufsboot. 
    3. KERNEL INITIALIZATION : ufsboot load the kernel (generic unix) kernel will load all the necessary devices modules to mount the root partition to continue the booting process .
    4. INIT PHASES : It will started by executing of /etc/init program and start other process reading the /etc/inittab files, as the directory in the /etc/inittab files. 
  80. Question 54. Describe About Fsck?

    Answer :

    FSCK Utility is for checking and repairing the files system inconsistencies, It has 5 phases 

    Phase 1: Check Blocks and Sizes – checks inodes for inconsistencies
    Phase 2: Check Path-Names – checks directory inode consistencies
    Phase 3: Check Connectivity – checks that all directories are connected to the file system
    Phase 4: Check Reference Counts – compares link count information from Phases 2 & 3, correcting discrepancies
    Phase 5: Check Cylinder Groups – checks free blocks and the used inode maps for consistency
    Phase 6: Salvage Cylinder Groups – update the tables to reflect any changes made in earlier passes

  81. Question 55. What Is The Difference Between Dsk And Rdsk?

    Answer :

    • dsk: Block level devices, FS Which are formatted and mounted that device is called block device.
    • rdsk: Raw level device or character level device
  82. Question 56. Explain About Port Of Telnet, Ssh, Ftp, Http, Nfs, Ntp?

    Answer :

    • ftp port : 21 
    • ssh port : 22 
    • Telnet port : 23 
    • ntp port : 123
    • smtp port : 25
    • printer port : 515
  83. Question 57. How To View Vtoc (volume Table Of Contents)?and How To Copy?

    Answer :

    Print the VTOC
    # prtvtoc /dev/rdsk/c0t0d0s2

    Copy the VTOC to other disk
    # prtvtoc /dev/rdsk/c0t0d0s2|fmthard -s – /dev/rdsk/c1t0d0s2

  84. Question 58. Type Of Filesystems ?

    Answer :

    • Disk Based FS : ufs  (Unix FS), hsfs (High Sierra FS), pcfs (PC FS for DOS FAT32), 
    • udfs : Universal Disk Format FS  
    • Network FS      : nfs (Network FS) 
    • Memory based FS (Pseudo FS) :  tmpfs, swapfs, procfs, mntfs
  85. Question 59. Brief Filesystem Structure?

    Answer :

    VTOC present in the first sector in the raw disk area.
    VTOC – 512 sector
    Boot Block – 1-15 sector
    Super Block – 16-31
    First Cylinder Group – 32

  86. Question 60. How To Reduce The Reserved Space Of The Disk?

    Answer :

    This will reduce the reserved space to 2%
    # tunefs –m 2 /dev/rdsk/c1d0s0