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Question number: 380

» Basic CS » Operating System

Essay Question▾

Describe in Detail

What is logical volume group?


  • Logical volume group or LVM A relatively new approach to UNIX disks and file systems.

  • Provides abstraction layer between operating system and physical hard drives.

  • Provides a virtual disk space which can be flexibly mapped to real physical disks.

  • The commands in LVM are very similar to the actual physical disks.

Every valid command is preceded by physical volume and volume group as shown below:

  • Physical Volume = pv

  • Volume Group = vg

  • Logical Volume = lv

Physical volume and volume group

Physical Volume and Volume Group

Physical volume and volume group

Advantages of logical volume group.

  • Offer greater flexibility for disk partitioning.

  • Size of logical volumes can be modified according to need, while the operating system is running

  • Logical volumes can span multiple disks.

  • Disk mirroring is often supported, for greater data reliability

Question number: 381

» Operating System » Unix

Essay Question▾

Describe in Detail

What are various IDs associated with a process?


  • Every process in unix is identified with a unique integer called processed.

  • Each process also associated with a particular user called the ‘owner’ – whose privileges transfer to the process.

  • ‘UserId’ is the identification of the user.

  • Owner is the user who executes the process.

  • ‘Effective UserID’ determines the access privileges for accessing resources like files.

  • getpid ()
    • process id

  • getppid ()

    • parent process id

  • getuid ()

    • user id

  • geteuid ()

    • effective user id