LPI Updated 101-500 Exam Questions and Answers by kaia

The dd command is used to copy data from one device or file to another, with optional parameters to specify the block size (bs), the number of blocks to copy (count), and other options. The bootloader is typically located in the first 440 bytes of the disk, which is the Master Boot Record (MBR) area. The MBR also contains the partition table, which starts at byte 446 and occupies 64 bytes. Therefore, to overwrite the bootloader without affecting the partition table or any data following it, the command should copy 440 bytes from /dev/zero (a special device that provides null bytes) to /dev/sda (the disk device) and stop after one block. This is achieved by the command: dd if=/dev/zero of=/dev/sda bs=440 count=1 References:

• LPI Exam 101 Detailed Objectives, section 1.101.3
• dd man page
• Master Boot Record

The command grub-install is used to install GRUB on a device or a partition. The option --root-directory specifies the directory where GRUB images are put. The default is /boot/grub. The argument /dev/sda specifies the device where GRUB is installed, usually the Master Boot Record (MBR) of the disk. Therefore, the command grub-install --root-directory=/custom-grub /dev/sda will install GRUB on the MBR of /dev/sda and put the GRUB images under the directory /custom-grub/boot/grub. This means that the new configuration files, such as grub.cfg, will be found in the directory /custom-grub/boot/grub. References:

• GNU GRUB Manual 2.06: Installing GRUB using grub-install
• Installing GRUB using grub-install - GNU GRUB Manual 0.97

 When removing a package on a system using dpkg package management, the --purge option ensures that configuration files are removed as well. The --purge option is equivalent to the --remove option followed by the --purge-config-files option, which removes any configuration files that are marked as obsolete. The --remove option only removes the package files, but leaves the configuration files intact. The --clean option removes any .deb files from the local cache, but does not affect the installed packages. The --delete option is not a valid option for dpkg. References:

• 1, 102.4 Lesson 1
• 3, 101-500 Exam - Free Questions and Answers - ITExams.com
• man dpkg

The yum command is a tool for managing software packages on Red Hat Enterprise Linux and other RPM-based systems. The yum update option will update the entire system by checking the versions of the installed packages and installing the latest available versions from the repositories. The yum upgrade option will do the same, but it will also remove any obsolete packages that are no longer needed by the system. Both options will prompt the user to confirm before proceeding with the update or upgrade process. References:

• Yum Command Cheat Sheet for Red Hat Enterprise Linux
• "yum update" Explained for Beginners!
• How to Install Updates on CentOS 7
• Which option to the yum command will update the entire system?