02 - Linux Directory and File System

Question 1

What the three varieties of file systems in Linux?

Answer 1

1. Disk-based
2. Network-based
3. Memory-based

Question 2

What is disk-based file system?

Answer 2

Disk-based file systems are typically created on physical media such as hard drive or a USB flash drive.

Question 3

What is network-based file system?

Answer 3

Network-based file systems are essentially disk-based file systems that are shared over the network for remote access.

Question 4

What is memory-based file systems?

Answer 4

Memory-based file systems are virtual; they are created automatically at system startup and destroyed when the system goes down.

Question 5

What is /etc?

Answer 5

The /etc directory holds system configuration files. Some common sub directories are systemd, sysconfig, lvm, and skel, which comprise configuration files for systemd, most system services, logical volume manager (lvm) and per-use shell startup template files, respectively.

Question 6

What is /root?

Answer 6

The /root is the default home directory location for the root user.

Question 7

What is /mnt?

Answer 7

The /mnt is used to mount a file system temporarily.

Question 8

What is /boot?

Answer 8

The /boot file system contains the linux kernel, boot support files, and boot configuration files.

Question 9

What is /home?

Answer 9

The /home directory is designed to store user home directories and other user contents. Each user is assigned a home directory to save personal files, and the user can block access to other users.

Question 10

What is /opt?

Answer 10

The /opt (optional) directory can be used to hold additional software that may need to be installed on the system. A subdirectory is created for each installed software.

Question 11

What is /usr?

Answer 11

The /usr (Unix System Resources) directory contains most of the system files. Some of the subdirectories are: /usr/bin, /usr/sbin, /usr/lib, /usr/lib64, /usr/include, /usr/local, /usr/share, /usr/src.

Question 12

What is /usr/bin and /usr/sbin?

Question 13

What is /usr/lib and /usr/lib64?

Question 14

What is usr/include?

Answer 14

This directory contains header files for C language.

Question 15

What is usr/local?

Question 16

What is usr/share?

Answer 16

This is the directory for manul pages, documentation, sample template, configuration files, etc., that may be shared with other linux platforms.

Question 17

What is /var?

Answer 17

The /var (variable) directory contains data that frequently changes while the system is operational. Files in this directory contain log, status, spool, lock, and other dynamic data. Some /var/log, /var/opt, /var/spool, /var/tmp

Question 17

What is usr/src?

Answer 17

This directory is used to store source code.

Question 18

What is /var/log?

Question 19

What is /var/opt?

Question 20

What is /var/spool?

Question 21

What is /var/tmp?

Question 22

What is /tmp?

Answer 22

This directory is a repository for temporary files. Many program crate temporary files here during runtime or installation. These files survive system reboots and are automatically removed if they are not accessed or modified for a period of 10 days.

Question 23

What is /dev?

Answer 23

The Devices (device file system) file system is accessible via the /dev directory and is used to store device nodes for physical hardware and virtual devices. The linux kernel communicates with these devices through corresponding device nodes located here. These devices automatically created and deleted by the udevd service (a linux service for dynamic device management) as necessary.

Question 24

What are character device files?

Answer 24

Character device files are the devices that are accessed serially with streams of bits transferred during kernel and device communication. Examples of such devices are console, serial printer, mice, keyboards, terminal, etc.

Question 25

What are block device files?

Answer 25

Block device files are the devices that are accessed in parallel fashion with data exchanged in blocks (parallel) during kernel and device communication. Data on block devices is accessed randomly. Examples of such devices are hard disk drives, optional drives, parallel printers, etc.

Question 26

What is /proc?

Answer 26

The Procfs (process file system) file system is accessible via the /proc directory, and it is used to maintain information about the current state of the running kernel. This includes the details for current hardware configuration an status information on CPU, memory, disks, partitioning, file systems, networking, running processes, and so on. This information is stored in a hierarchy of subdirectories that contain thousands of zero-length pseudo files. These files point to relevant data maintained by the kernel in the memory. This virtual directory structure simply provides an easy interface to interact with kernel-maintained information. The Procfs file system is dynamically managed by the system.

The contents in /procs are created in memory at system boot time, update during runtime, and destroyed at system shutdown.

Question 27

What is /run?

Answer 27

The Runtime file system is a virtual file system. This virtual file system is a repository of data for processes on the system. One of its subdirectories, /run/media, is also used to automatically mount external file systems such as those that are on optical and flash USB.

Question 28

What is /sys?

Answer 28

The system file system. Information about hardware devices, drivers, and some kernel features is stored and maintained in the /sys file system. This information is used by the kernel to load necessary support for the devices, create device nodes in /dev, and configure the devices. This file system is auto-maintained as well.

Question 29

What is tree command?

Answer 29

Tree command lists a hierarchy of directories and files.

-a = includes hidden files in the output
-d = excludes files from the output
-h = displays file sizes in human-friendly format
-f = prints the full path for each file
-p = includes file permissions in the output

Question 30

What does command prompt # and $ signifies?

Answer 30

is for the root user and $ is for the normal user.

Question 31

What are options and arguments in a command?

Answer 31

Optional are optional. You can specify zero or more options with a command. An option modifies the behavior of the command. An option may start with - (short format) or – (long format).

Arguments, in contrast, may be optional or mandatory depending on the command and its usage. An argument supplies a target on which to perform the command action.

Question 32

Listing files and directories

Answer 32

-a = include hidden files and directories in the output. (hidden files start with .)
-l = Displays a long listing with detailed file information including the file type, permissions, link count, owner, group, size, date and time of the last modification, and name of the file.
-ld = Display long listing of the specified directory but hides its content.
-lh = Displays long listing with files sizes shown in human-friendly format
-ltr = List all files sorted by date and time with the older file first
-R = Lists contents of the specified directory and all its subdirectories

Question 33

What is pwd?

Answer 33

The pwd (print working directory or present working directory) command displays a user’s current location in the directory tree.

Question 34

How do you identify terminal device file?

Answer 34

Linux allocates unique pseudo (or virtual) numbered device files to represent terminal sessions opened by users on the system. It uses these files to communicate with individual sessions. By default, these files are stored in the /dev/pts ( pseudo terminal session) directory. These files are created by the system and they are removed on its closure. The destroyed files are recreated and reused for new terminal sessions.

tty - teletype

Question 35

Inspecting system’s uptime and processor load

Answer 35

uptime

1. current system time
2. up duration
3. no. of logged users
4. CPU load averages for past 1, 5, and 15 mins

Question 36

Clear screen

Answer 36

clear

Question 37

Determining command path

Answer 37

RHEL provides a set of tools that can be used to identify path of the command that will be executed when you run it without you specifying the full path.

These tools are the which, whereis, and type commands.

Question 38

System information

Answer 38

The uname command identifies elementary information about the system including its hostname.

uname
uname -a

Displays:
1. Kernel name (-s)
2. hostname of the system (-n)
3. Kernel release (-r)
4. Date and time of the kernel built (-v)
5. Machine hardware name (-m)
6. Processor type (-p)
7. Hardware platform (-i)
8. Operating system name (-o)

Question 39

Viewing CPU specs

Answer 39

A CPU has many architectural pieces that can be looked using the lscpu command. These pieces include the CPU architecture, its opering modes, vendor family, model, speed, cache memory, and whether it supports virtualization.

Question 40

man help

Answer 40

:f = displays line number and bytes being viewed
q = quits the man pages
/pattern = searches forward for the specified pattern
?pattern = searches backward for the specified pattern
n / N = Find the next / previous occurrence
h - Gives help on navigational keys

man passwd
man 5 passwd

Question 41

Headings in the manual

Answer 41

NAME = Name of the command or file with a short description
SYNOPSIS = Syntax summary
DESCRIPTION = An overview of the command or file
OPTIONS = options available for use
EXAMPLES = some examples to explain the usage
FILE = a list of related files
SEE ALSO = reference to other manual pages or topics
BUGS = any reported bugs or issues
AUTHOR = contributor information

Question 42

Manual sections

Answer 42

The default behavior of the man command is to search through section 1 and each successive section until it finds a match.

When you run man passwd, the man command scans through the manual pages and the first occurrence it finds is of the passwd command that’s stored in section 1. If you want to consult the manual pages of the passwd configuration file, you would have to specify the section number with the command (man 5 pages) to instruct it to scan that one particular section only.

Question 43

Searching by keyword

Answer 43

Linux allows you to perform a keyword search on manual pages using the man command. But, before that you have to run mandb command.

catdir = /var/cache/overrides

1. man -k xfs
2. apropos xfs

Question 44

Exposing short description

Answer 44

The ‘whatis’ command searches for a short description of the specified command or file in the manual database.

1. whatis yum.conf
2. whatis passwd
3. man -f yum.conf
4. man -f passwd

Question 45

info and pinfo commands

Answer 45

The info and pinfo commands display command documentation in a document-like format in great detail. Documentation is divided into sections called nodes. The header across the top of the screen shows the name of the file being displayed, names of the current, next, and previous nodes, and name of the prior to the current node.

Question 46

Documentation in the /usr/share/doc directory

Answer 46

The /usr/share/doc directory stores general documentation for installed packages under subdirectories that match their names