Exactprep 101-500 Questions

The lspci command can display information about the system hardware, such as:

• Device IRQ settings1: The lspci command can show the interrupt request (IRQ) number assigned to each device by using the -v option. The IRQ number indicates how the device communicates with the CPU.
• PCI bus speed2: The lspci command can show the speed of the PCI bus by using the -vv option. The speed is expressed in megahertz (MHz) or gigahertz (GHz) and indicates how fast the data can be transferred between the device and the bus.
• Device vendor identification3: The lspci command can show the name and identification number of the device vendor by using the -n or -nn option. The vendor identification helps to identify the manufacturer and model of the device.

References: 1: https://www.man7.org/linux/man-pages/man8/lspci.8.html  2: https://phoenixnap.com/kb/lspci-command  3: https://en.wikipedia.org/wiki/Lspci

 udev is a device manager that dynamically creates and removes device nodes in the /dev/ directory. It also handles device events, such as adding, removing, or changing the attributes of devices. udev uses rules to match devices and assign properties, permissions, names, symlinks, and other actions. The rules are stored in files under /lib/udev/rules.d/ and /etc/udev/rules.d/. The latter directory can be used to create additional or override existing rules. The /dev/ directory is not a regular directory on the root filesystem, but a virtual filesystem of type tmpfs that is mounted by udev during system startup. tmpfs is a filesystem that resides in memory and can grow and shrink dynamically. The content of /dev/ is not stored in /etc/udev/dev, but is created by udev based on the rules and the available devices. udev does not prevent the creation of block or character devices in /dev/ using mknod, but it may overwrite or remove them if they conflict with the rules or the device events. References: LPI Linux Essentials - 1.101.2, LPI Linux Administrator - 102.4

The GRUB boot process consists of three stages1:

• Stage 1: This stage is located in the Master Boot Record (MBR) of the first hard disk or the boot sector of a partition. Its main function is to load either Stage 1.5 or Stage 22.
• Stage 1.5: This stage is located in the first 30 KB of hard disk immediately following the MBR or in the boot sector of a partition. It contains the code to access the file system that contains the GRUB configuration file. Its main function is to load Stage 22.
• Stage 2: This stage is located in an ordinary file system, usually in the /boot/grub directory. It contains the code to display the GRUB menu and to load the kernel and initrd images. It can also load additional modules to support other file systems or features2.

The message “Hard Disk Error” is displayed on the screen during Stage 1 of the GRUB boot process. This indicates that the next Stage (either Stage 1.5 or Stage 2) cannot be read from the hard disk because GRUB was unable to determine the size and geometry of the disk3. This could occur because the BIOS translated geometry has been changed by the user or the disk is moved to another machine or controller after installation, or GRUB was not installed using itself (if it was, the Stage 2 version of this error would have been seen during that process and it would not have completed the install)3.

The other options in the question are not correct because:

• A. The kernel was unable to execute /bin/init: This error would occur in Stage 2, after the kernel and initrd images are loaded, not in Stage 14.
• C. One or more of the filesystems on the hard disk has errors and a filesystem check should be run: This error would also occur in Stage 2, when GRUB tries to access the file system that contains the GRUB configuration file, not in Stage 15.
• D. The BIOS was unable to read the necessary data from the Master Boot Record to begin the boot process: This error would prevent GRUB from starting at all, not in Stage 16.

References:

1: GRUB - ArchWiki 2: GNU GRUB Manual 0.97 3: Stage1 errors - GNU GRUB Manual 0.97 4: [Kernel panic - Wikipedia] 5: [Stage2 errors - GNU GRUB Manual 0.97] 6: [Master Boot Record - Wikipedia] : How to Fix GRUB Load Errors and Recover Data? - MiniTool Home Data Recovery

The usual way to pass this change to the kernel from the boot loader is to pass init=/bin/sh on the kernel parameter line12. The init kernel parameter is used to specify the program that is run as the first process after the kernel is loaded3. By default, this program is /sbin/init, which is responsible for starting and managing other processes and services4. However, by passing init=/bin/sh, the kernel will run /bin/sh instead, which is a shell program that allows the user to execute commands interactively or from a script5. This way, the user can bypass the usual initialization process and run /bin/sh as the root user, which can be useful for troubleshooting or recovery purposes12.

The other options in the question are not correct because:

• A. Start in runlevel 1: This option would not bypass the /sbin/init program, but rather instruct it to start the system in single-user mode, which is a mode that allows only the root user to log in, and disables all network services and graphical interfaces. To start in runlevel 1, the user would need to pass single or 1 on the kernel parameter line, not init=/bin/sh.
• C. Pass /bin/sh on the kernel parameter line: This option would not work, because the kernel would not recognize /bin/sh as a valid parameter and would ignore it. The kernel only accepts parameters that have a specific format, such as name=value or name.flag3. To specify the init program, the user would need to use the init= prefix, as in init=/bin/sh3.
• D. Pass start=/bin/sh on the kernel parameter line: This option would also not work, because the kernel does not have a start parameter. The user would need to use the init parameter, as in init=/bin/sh3.

References:

1: How to pass arguments to a Linux kernel init= bootparam? - Unix & Linux Stack Exchange 2: kernel parameter init=/bin/bash not working? (RHEL7, RHCSA test) - Unix & Linux Stack Exchange 3: The kernel’s command-lineparameters — The Linux Kernel documentation 4: [init - Wikipedia] 5: [sh - Wikipedia] : [Single-user mode - Wikipedia] : How to Change Runlevels (targets) in SystemD - Tecmint