LPI 101-500 - LPIC-1 Exam 101, Part 1 of 2, version 5.0

The /tmp directory should be on a separate partition if possible because it is world writable. This means that any user can create, modify, or delete files and directories in /tmp. This can pose a risk of filling up the / partition, which can cause system instability or failure. By having /tmp on a separate partition, we can limit the amount of disk space that can be used by temporary files and prevent users from affecting the / partition. The /tmp 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. The /tmp directory is one of the few directories that are world writable by default, according to the Filesystem Hierarchy Standard (FHS)1. The other directories that are usually world writable are /var/tmp and /var/lock, which are also used for temporary or lock files. However, these directories are not as frequently used or as large as /tmp, so they are less likely to fill up the / partition. The /tmp directory also has the sticky bit set, which means that only the owner of a file or directory can delete or rename it2. This prevents users from deleting or modifying other users’ files in /tmp. However, this does not prevent users from creating new files or directories in /tmp, which can still consume disk space and resources. Therefore, it is advisable to have /tmp on a separate partition if possible. References:

Filesystem Hierarchy Standard

Sticky bit - Wikipedia

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 dynamic linker 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.

 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 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 /etc/apt/sources.list file is the main configuration file for the Advanced Package Tool (apt), which is used to manage Debian installation package files. This file contains a list of repositories, or sources, from which apt can download and install packages. Each repository is specified by a line that has the following format:

type uri suite [component1] [component2] […]

Where:

type is the access method, such as http, ftp, file, etc.

uri is the Uniform Resource Identifier (URI) of the repository, such as http://deb.debian.org/debian

suite is the distribution code name or archive name, such as stable, testing, unstable, etc.

component is an optional section of the repository, such as main, contrib, non-free, etc.

For example, a typical sources.list file for Debian stable could look like this:

deb http://deb.debian.org/debian stable main contrib non-free deb-src http://deb.debian.org/debian stable main contrib non-free

deb http://deb.debian.org/debian-security/ stable/updates main contrib non-free deb-src http://deb.debian.org/debian-security/ stable/updates main contrib non-free

deb http://deb.debian.org/debian stable-updates main contrib non-free deb-src http://deb.debian.org/debian stable-updates main contrib non-free

The first two lines specify the main repository for Debian stable, with both binary (deb) and source (deb-src) packages. The next two lines specify the security updates repository for Debian stable, which contains important security fixes. The last two lines specify the stable-updates repository, which contains packages that have been updated after the release of Debian stable.

By editing the /etc/apt/sources.list file, one can select the network locations from which Debian installation package files are loaded. However, it is recommended to use a graphical or command-line tool, such as aptitude or synaptic, to manage the sources.list file, as they can handle the syntax and avoid errors.

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 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 it lists 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.

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

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.