GCPC Course 4 - Linux and SQL

Modul 2

Linux

An open-source operating system

Components of Linux

• User
• Applications
• Shell
• Filesystem Hierarchy Standard
• Kernel
• Hardware

Shell

The command-line interpreter

Filesystem Hierarchy Standard (FHS)

The component of the Linux OS that organizes data

Kernel

The component of the Linux OS that manages processes and memory

Distributions

The different versions of Linux

Parent distributions

• Red Hat Enterprise Linux (CentOS)
• Slackware (SUSE)
• Debian (Ubuntu and KALI LINUX)

Pentest tools in KALI LINUX

• Metasploit
• Burp Suite
• John the Ripper

Digital forensics

The practice of collecting and analyzing data to determine what has happened after an attack

Digital forensic tools in KALI LINUX

• tcpdump
• Wireshark
• Autopsy

Package managers

• Red Hat Package Manager (RPM)
  • .rpm
• dpkg for Debian
  • .deb

Package management tools

• Advanced Package tool (APT)
  • APT is a tool used with Debian-derived distributions. It is run from the command-line interface to manage, search, and install packages.
• Yellowdog Updater Modified (YUM)
  • YUM is a tool used with Red Hat-derived distributions. It is run from the command-line interface to manage, search, and install packages. YUM works with .rpm files.

Types of shells

• Bourne-Again Shell (bash)
• C Shell (csh)
• Korn Shell (ksh)
• Enhanced C shell (tcsh)
• Z Shell (zsh)

Standard input

Information received by the OS via the command line

Standard output

Information returned by the OS through the shell

Standard error

Error messages returned by the OS through the shell

echo

A Linux command that outputs a specified string of text

Modul 3

Security analysts

• Work with server logs
• Navigate, manage and analyze files remotely
• Verify and configure users and group access
• Give authorization and set file permissions

Bash

The default shell in most Linux distros

Root directory

The highest-level directory in Linux

pwd

Prints the working directory onto the screen

ls

Displays the names of files and directories in the current working directory

cd

Navigates between directories

cat

Displays the content of a file

head

Displays just the beginning of a file, by default 10 lines

Standard FHS directories

Directly below the root directory, you’ll find standard FHS directories. In the diagram, home, bin, and etc are standard FHS directories. Here are a few examples of what standard directories contain:

• /home:
  • Each user in the system gets their own home directory.
• /bin:
  • This directory stands for “binary” and contains binary files and other executables. Executables are files that contain a series of commands a computer needs to follow to run programs and perform other functions.
• /etc:
  • This directory stores the system’s configuration files.
• /tmp:
  • This directory stores many temporary files. The /tmp directory is commonly used by attackers because anyone in the system can modify data in these files.
• /mnt:
  • This directory stands for “mount” and stores media, such as USB drives and hard drives.

grep

Searches a specified file and returns all lines in the file containing a specified string

| (piping)

Sends the standard output of one command as standard input to another command for further processing

mkdir

Creates a new directory

rmdir

Removes or deletes a directory

touch

Creates a new file

rm

Removes or deletes a file

mv

Moves a file or directory to new location

cp

Copies a file or directory into a new location

Permissions

The type of access granted for a file or directory

• Read
• Write
• Execute

Types of owners

• User
• Group
• Other

Options

Modify the behaviour of the command

ls -l

Displays permissions to files and directories

ls -a

Displays hidden files

ls -la

Previous 2 options combined

chmod

Changes permissions on files and directories

Root user (superuser)

A user with elevated privileges to modify the system

Problems with logging in as root

• security risks
• Irreversible mistakes
• Accountability

sudo

Temporarily grants elevated permissions to specific users

useradd

Adds a user to the system

• -g: sets default group
• -G: set additional groups

userdel

Deletes a user from the system

usermod

Modifies existing users

• -a: used to append new groups
• .d: changes users home directory
• -l: changes users login name
• -L: Locks account

chown

Changes ownership of a file or directory

man

Displays information on other commands and how they work

whatis

Displays a description of a command on a single line

apropos

Searches the manual page descriptions for a specified string