Free LPI 101-500 Practice Exam with Questions & Answers | Set: 7

 The main configuration file for GNU GRUB is grub.cfg, which is usually located in /boot/grub/ or /boot/grub2/ depending on the distribution. This file contains the menu entries for the boot loader, each with a title, a kernel image, an initrd image, and optional parameters. The grub.cfg file is not meant to be edited manually, as it is generated by the grub-mkconfig command, which reads the settings from /etc/default/grub and the scripts in /etc/grub.d/. The /etc/default/grub file contains the global options for GRUB, such as the default menu entry, the timeout, the theme, etc. The /etc/grub.d/ directory contains executable scripts that are run by grub-mkconfig to generate the menu entries for each operating system or kernel found on the system. For example, the script 10_linux generates the entries for the Linux kernels installed by the package manager, while the script 30_os-prober generates the entries for other operating systems detected on the system, such as Windows. To make changes to the GRUB configuration, one should edit the /etc/default/grub file and/or the scripts in /etc/grub.d/, and then run grub-mkconfig -o /boot/grub/grub.cfg to update the grub.cfg file. References:

• 2, 102.2 Install a boot manager
• 4, 102.2 Install a boot manager
• man grub-mkconfig

 The command that lists all currently installed packages when using RPM package management is rpm --query --all. This command displays information about all the packages that are currently installed on the system, including their name, version, release, and architecture1. The output can be customized by using various query options and format specifiers2.

The other commands are either invalid or related to YUM, not RPM. yum --query --all is not a valid YUM command, as YUM does not have a --query option3. yum --list --installed is a valid YUM command, but itlists the packages from the YUM repositories, not the RPM database3. rpm --list --installed is not a valid RPM command, as RPM does not have a --list option2.

References:

• RPM Command in Linux | Linuxize
• rpm(8) - Linux manual page
• Linux package management with YUM and RPM | Enable Sysadmin

 The dpkg-reconfigure command is used to reconfigure an already installed package. It asks configuration questions for the package, just as if the package were being installed for the first time. This can be useful if the user wants to change some settings or options for the package without reinstalling it. The dpkg-reconfigure command can also be used to fix a broken package configuration or to restore the default settings. References:

• dpkg-reconfigure(8) - Linux man page
• Linux Professional Institute: Exam 101 Objectives

 The command that updates the linker cache of shared libraries is ldconfig. This command creates, updates, and removes the necessary links and cache for the run-time linker, ld.so, to the most recent shared libraries found in the specified directories. To add a new library directory to the cache, you need to edit the /etc/ld.so.conf file and rerun ldconfig. You can use the -p option to print the current cache contents1.

The other commands are either invalid or unrelated to the linker cache. mkcache, soconfig, and mkldconfig are not standard Linux commands. lddconfig is a typo for ldd, which is a command that prints the shared libraries required by a program2.

References:

• Linux Commands For Shared Library Management & Debugging Problem
• ldd(1) - Linux manual page

The environment variable that overrides or extends the list of directories holding shared libraries is LD_LIBRARY_PATH. This variable is used to specify a colon-separated list of directories where the dynamic linker should look for shared libraries when loading a program1. The directories in LD_LIBRARY_PATH are searched before the default directories, such as /lib and /usr/lib, or the directories specified in/etc/ld.so.conf or the executable’s rpath1. This variable can be useful for testing or debugging purposes, or for running programs that require a specific version of a library that is not installed in the system1.

The other options are incorrect for the following reasons:

• LD_LOAD_PATH. This is not a standard environment variable for shared libraries. It may be confused with LD_PRELOAD, which is a variable that allows the user to specify one or more shared libraries that should be loaded before any other library, even the C library2. This variable can be used to override or modify the behavior of certain functions or symbols in the libraries2.
• LD_LIB_PATH. This is not a standard environment variable for shared libraries. It may be confused with LIBPATH, which is a variable that is used on some Unix variants, such as AIX, to specify the search path for shared libraries3. On Linux, this variable has no effect4.
• LD_SHARE_PATH. This is not a standard environment variable for shared libraries. It may be confused with LD_RUN_PATH, which is a variable that allows the user to specify a list of directories that should be embedded in the executable as the rpath5. The rpath is a attribute that tells the dynamiclinker where to look for shared libraries at run time5. Unlike LD_LIBRARY_PATH, LD_RUN_PATH is only effective at link time, not at run time5.
• LD_RUN_PATH. This is not an environment variable that overrides or extends the list of directories holding shared libraries, but rather one that sets the rpath of the executable at link time. See the explanation for LD_SHARE_PATH above.

References:

• How to set the environmental variable LD_LIBRARY_PATH in Linux
• LD_PRELOAD - The secret of code injection into a running process without ptrace
• LIBPATH - Wikipedia
• linux - What is the difference between LD_LIBRARY_PATH and -L at link time? - Stack Overflow
• ld-linux(8) - Linux manual page

The top-level system directory that is used for files and data that change regularly while the system is running and are to be kept between reboots is /var. The /var directory contains variable data that changes in size as the system runs. For instance, log files, mail directories, databases, and printing spools are stored in /var. These files and data are not temporary and need to be preserved across system reboots. The /var directory is one of the few directories that are recommended to be on a separate partition, according to the Filesystem Hierarchy Standard (FHS)1. This is because the /var directory can grow unpredictably and fill up the / partition, which can cause system instability or failure. By having /var on a separate partition, we can limit the amount of disk space that can be used by variable data and prevent users from affecting the / partition. The /var directory is also a common target for malicious attacks, so having it on a separate partition can improve the security and isolation of the system. References:

• Filesystem Hierarchy Standard

The command that can be used to download the RPM package kernel without installing it is yumdownloader kernel. This command is part of the yum-utils package, which contains a suite of helper tools for yum package manager. To use this command, you need to install the yum-utils package first1. The downloaded package will be saved in the current directory. You need to use root privilege because yumdownloader will update package index files during downloading. Unlike yum command, yumdownloader will not download any dependent packages1.

The other commands are either invalid or do not have the desired functionality. yum download --no-install kernel is not a valid yum command, as yum does not have a --no-install option2. rpm --download --package kernel is not a valid rpm command, as rpm does not have a --download or a --package option3. rpmdownload kernel is not a standard Linux command. rpm has a native support to download a package from a URL and install it, but not to download a package without installing it4.

References:

• How to use yum to download an RPM package without installing it - Xmodulo
• yum(8) - Linux manual page
• rpm(8) - Linux manual page
• How to download an RPM package and install it in one line?

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?

 The apt-cache command is used to query the APT cache for information about packages. The depends option shows a listing of each dependency a package has and all the possible other packages that can fulfill that dependency. For example, apt-cache depends ubuntu-restricted-extras will show the dependencies of the ubuntu-restricted-extras package. The other options are not valid for the apt-cache command. References:

• How to Check Dependencies of a Package in Ubuntu/Debian-based Linux Distributions
• Check DEB package dependencies on Ubuntu / Debian

 The environment variable LD_LIBRARY_PATH is used to tell the dynamic linker to look in a specific directory for some of a program’s shared libraries. It is a colon-separated list of directories that are searched by the dynamic linker when looking for a shared library to load1. The directories are searched in the order they are mentioned in. For example, if we have a program that depends on a shared library libfoo.so that is located in /home/user/build/lib, we can run the program with:

LD_LIBRARY_PATH=/home/user/build/lib ./program

This will instruct the dynamic linker to search for libfoo.so in /home/user/build/lib before the default directories. The environment variable LD_LIBRARY_PATH can also be appended to an existing value with the += operator, for example:

LD_LIBRARY_PATH+=:/home/user/build/lib

This will add /home/user/build/lib to the end of the LD_LIBRARY_PATH list. The other options are not valid environment variables for the dynamic linker. LD_LOAD_PATH, LD_LIB_PATH, and LD_SHARE_PATH are not recognized by the dynamic linker. LD_RUN_PATH is a linker option that can be used to embed a librarysearch path in the executable at link time, but it is not an environment variable that can be set or modified at run time2. References:

• LPI Exam 101 Detailed Objectives, section 1.101.3
• ld-linux(8) — Linux manual page
• Setting the dynamic linker with an environment variable - narkive