Lect01 - Linux Intro

Question 1

What is Linux?

Answer 1

When we talk about the “Linux” operating system, we are actually talking about the GNU/Linux operating system (OS). Linux itself is not an OS. It is just a kernel. The OS is actually a combination of the Linux kernel and the GNU utilities that allow us (more specifically our hardware) to interact with the kernel.

Question 2

What is the Linux kernel?

Answer 2

The Linux kernel is the “brain” of the system. It is the base component of the Operating System that allows the hardware to interact with and manage hardware drivers and system resources. You can determine your current kernel version with the uname -a command.

Question 3

Name the three variations of desktop environment?

Answer 3

• X Window
• Windows Manager
• Desktop environment

Question 4

What is UEFI?

Answer 4

Unified Extensible Firmware Interface. EFI is a type of firmware, meaning that it’s software built into the computer to handle low-level tasks. Most importantly, the firmware controls the computer’s boot process, which in turn means that EFI-based computers boot differently than do BIOS-based computers.

Question 5

What is udev?

Answer 5

userspace /dev. Udev is a device manager for the Linux kernel. It manages device nodes in /dev directory. At the same time, udev also handles all user space events raised when hardware devices are added into the system or removed from it, including firmware loading as required by certain devices.

Question 6

What is systemd?

Answer 6

The systemd software suite provides fundamental building blocks for a Linux operating system. It includes the systemd “System and Service Manager”, an init system used to bootstrap user space and manage user processes. The name systemd adheres to the Unix convention of naming daemons by appending the letter d.

Question 7

Explain the following directory:

/

Answer 7

The root directory where the file system begins. In most cases the root directory only contains subdirectories.

Question 8

Explain the following directory:

/boot

Answer 8

This is where the Linux kernel and boot loader files are kept. The kernel is a file called vmlinuz.

Question 9

Explain the following directory:

/etc

Answer 9

The /etc directory contains the configuration files for the system. All of the files in /etc should be text files. Points of interest:

/etc/passwd

The passwd file contains the essential information for each user. It is here that users are defined.

/etc/fstab

The fstab file contains a table of devices that get mounted when your system boots. This file defines your disk drives.

/etc/hosts

This file lists the network host names and IP addresses that are intrinsically known to the system.

/etc/init.d

This directory contains the scripts that start various system services typically at boot time.

Question 10

Explain the following directory:

/bin

/usr/bin

Answer 10

These two directories contain most of the programs for the system. The /bin directory has the essential programs that the system requires to operate, while /usr/bin contains applications for the system’s users.

Question 11

Explain the following directory:

/sbin

/usr/sbin

Answer 11

The sbin directories contain programs for system administration, mostly for use by the superuser.

Question 12

Explain the following directory:

/usr

Answer 12

The /usr directory contains a variety of things that support user applications. Some highlights:

/usr/share/X11

Support files for the X Window system

/usr/share/dict

Dictionaries for the spelling checker. Bet you didn’t know that Linux had a spelling checker. See look and aspell.

/usr/share/doc

Various documentation files in a variety of formats.

/usr/share/man

The man pages are kept here.

/usr/src

Source code files. If you installed the kernel source code package, you will find the entire Linux kernel source code here.

Question 13

Explain the following directory:

/usr/local

Answer 13

/usr/local and its subdirectories are used for the installation of software and other files for use on the local machine. What this really means is that software that is not part of the official distribution (which usually goes in /usr/bin) goes here.

When you find interesting programs to install on your system, they should be installed in one of the /usr/local directories. Most often, the directory of choice is /usr/local/bin.

Question 14

Explain the following directory:

/var

Answer 14

The /var directory contains files that change as the system is running. This includes:

/var/log

Directory that contains log files. These are updated as the system runs. You should view the files in this directory from time to time, to monitor the health of your system.

/var/spool

This directory is used to hold files that are queued for some process, such as mail messages and print jobs. When a user’s mail first arrives on the local system (assuming you have local mail), the messages are first stored in /var/spool/mail

Question 15

Explain the following directory:

/lib

Answer 15

The shared libraries (similar to DLLs in that other operating system) are kept here.

Question 16

Explain the following directory:

/home

Answer 16

/home is where users keep their personal work. In general, this is the only place users are allowed to write files. This keeps things nice and clean

Question 17

Explain the following directory:

/root

Answer 17

This is the superuser’s home directory.

Question 18

Explain the following directory:

/tmp

Answer 18

/tmp is a directory in which programs can write their temporary files.

Question 19

Explain the following directory:

/dev

Answer 19

The /dev directory is a special directory, since it does not really contain files in the usual sense. Rather, it contains devices that are available to the system. In Linux (like Unix), devices are treated like files. You can read and write devices as though they were files. For example /dev/fd0 is the first floppy disk drive, /dev/sda (/dev/hda on older systems) is the first hard drive. All the devices that the kernel understands are represented here.

Question 20

Explain the following directory:

/proc

Answer 20

The /proc directory is also special. This directory does not contain files. In fact, this directory does not really exist at all. It is entirely virtual. The /proc directory contains little peep holes into the kernel itself. There are a group of numbered entries in this directory that correspond to all the processes running on the system. In addition, there are a number of named entries that permit access to the current configuration of the system. Many of these entries can be viewed. Try viewing /proc/cpuinfo. This entry will tell you what the kernel thinks of your CPU.

Question 21

Explain the following directory:

/media

/mnt

Answer 21

Finally, we come to /media, a normal directory which is used in a special way. The /media directory is used for mount points. As we learned in the second lesson, the different physical storage devices (like hard disk drives) are attached to the file system tree in various places. This process of attaching a device to the tree is called mounting. For a device to be available, it must first be mounted.

When your system boots, it reads a list of mounting instructions in the file /etc/fstab, which describes which device is mounted at which mount point in the directory tree. This takes care of the hard drives, but you may also have devices that are considered temporary, such as CD-ROMs, thumb drives, and floppy disks. Since these are removable, they do not stay mounted all the time. The /media directory is used by the automatic device mounting mechanisms found in modern desktop oriented Linux distributions. On systems that require manual mounting of removable devices, the /mnt directory provides a convenient place for mounting these temporary devices. You will often see the directories /mnt/floppy and /mnt/cdrom. To see what devices and mount points are used, type mount.

Question 22

Explain the following directory:

/opt

Answer 22

Often used for external software (optional)

Question 23

Explain the following directory:

/root

Answer 23

Root user’s home

Question 24

Explain the following directory:
/run

Answer 24

Per-user mount points (udisks 2)

Question 25

Explain the following directory:

/sys

Answer 25

Sysfs - kernel structures file system

Question 26

Explain the following directory:
/tmp

Answer 26

Temporary files