LPIC-102

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LPIC-102



Title

LPIC-102
Author


Tytus Kurek (NobleProg)
Subfooter

LPIC-102          

Tytus Kurek (NobleProg)


What does Linux mean?⌘

LPIC-102-01.png
http://upload.wikimedia.org/wikipedia/commons/thumb/3/35/Tux.svg/512px-Tux.svg.png

LINUX = LINUs' uniX

Outline⌘

  • First Day:
    • Session I:
      • Introduction to the course
    • Session II:
      • Topic 105: Shells, Scripting and Data Management
    • Session III:
      • Topic 106: User Interfaces and Desktops
    • Session IV:
      • Topic 107: Administrative Tasks

Outline #2⌘

  • Second Day:
    • Session I:
      • Topic 108: Essential System Services
    • Session II:
      • Topic 109: Networking Fundamentals
    • Session III:
      • Topic 110: Security
    • Session IV:
      • Case Study, Certification and Surveys

First Day - Session I⌘


Introduction


LPIC-102-02.gif
http://shop.linuxnewmedia.com/media/catalog/product/cache/17/image/9df78eab33525d08d6e5fb8d27136e95/l/p/lpic1_large_6.gif

LPI certification path⌘

LPIC-102-10.png

LPIC-101 exam⌘

Introduction to the lab⌘

Lab components:

  • Laptop with Windows
  • Virtual Machines with Linux on:
    • VMs: Debian, CentOS
    • Credentials:
      • admin user: root / terminal
      • non-admin user: terminal / terminal
  • VirtualBox:
    • 64-bit version (click here to download)
    • Snapshots (top right corner)
    • Press right "Control" key to release

First Day - Session II⌘


Topic 105: Shells, Scripting and Data Management


LPIC-102-03.jpg
http://www.thelinuxblog.com/uploads/optimizing-shell-scripts.jpg

105.1 Customize and use the shell
environment⌘



LPIC-102-11.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Environmental Variables⌘

  • Environmental variable - variable defining a behavior of the environment
  • Management tools:
    • env - displays set environmental variables
    • export - causes the environmental variable to be inherited by child processes
    • set - sets a value of the environmental variable
    • unset - unsets a value of the environmental variable
  • The most common environmental variables:
    • HOSTNAME - system hostname
    • USERNAME - username
    • PATH - paths in which to search executables
    • PWD - current working directory
    • LANG - locale category

Bash configuration files⌘

  • Common bash configuration files:
Type of File Login File Location Non-Login File Location
Global /etc/profile and files in /etc/profile.d directory /etc/bashrc or /etc/bash.bashrc
User ~/.bash_login, ~/.profile or ~/.bash_profile ~/.bashrc
  • Additional bash configuration files and directories:
    • /etc/skel - skeleton directory for new user accounts
    • ~/.bash_logout - user logout script
    • ~/.inputrc - keyboard shortcuts configuration

Other bash customization tools⌘

  • Aliases:
    • defined by an alias built-in:
alias [alias]="[command]"
  • Functions:
    • defined by a function keyword
function [name] {
    ...
} 
  • Lists:
list=(item1 item2)
list[2]=item3
echo ${list[0]} ${list[1]} ${list[2]}
  • Lab Exercise 105.1

105.2 Customize or write simple scripts⌘

LPIC-102-12.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Bash scripting foudations⌘

  • Execution permissions
  • #! (shebang) - defines a path to the interpreter
  • The most common Linux interpreters:
    • /bin/bash (Bourne Again SHell)
    • /bin/sh - standard shell
    • /bin/tcsh (The C Shell)
    • /usr/bin/expect
    • /usr/bin/perl
    • /usr/bin/python

IO Operations⌘

  • Input operation:
read [variable]
  • Output operation:
echo [output]
  • Reading from file:
cat [file]
  • Writing to file:
[command] > [file]

Conditional expressions⌘

  • test:
test [expression] && [true command] || [false command]
  • if:
if [ [expression] ]
then
    [true command]
else
    [false command]
fi
  • case:
case [word] in
    [pattern 1]) [command 1] ;;
    [pattern 2]) [command 2] ;;
    ...
    *)           [command n] ;;
esac

Loops⌘

  • for:
for [variable] in [list]
do
    [command]
done
  • seq:
seq [start] [stop]
  • while:
while [ [condition] ]
do
    [command]
done
  • Lab Exercise 105.2

105.3 SQL data management⌘

LPIC-102-13.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

SQL and RDBMS⌘

  • RDBMS (Relational DataBase Management system):
  • SQL (Sequential Query Language):
    • programming language designed for managing data held in a RDBMS
    • SQL is an interpreted language
    • de facto standard for managing structured data

Basic SQL commands⌘

  • SELECT - retrieves data from one or more tables
  • FROM - specifies the table(s) from which data is to be retrieved
  • WHERE - includes a comparison predicate, which restricts the rows returned by the query
  • GROUP BY - used to project rows having common values into a smaller set of rows
  • ORDER BY - identifies which columns are used to sort the resulting data
  • JOIN - used to join query results from two tables into one table
  • INSERT - adds data to a table in a form of row
  • INTO - specifies the table into which data is to be insterted
  • VALUES - specifies the data to be insterted
  • UPDATE - modifies a set of existing table rows
  • SET - specifies the data to be modified
  • DELETE - removes existing rows from a table
  • Lab Exercise 105.3

First Day - Session III⌘


Topic 106: User Interfaces and Desktops


LPIC-102-04.png
http://www.blogporta80.com.br/conteudo/2011/09/07/gnome_kde_xfce.png

106.1 Install and configure X11⌘

LPIC-102-14.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

What is X11?⌘

  • X11 - The X Window System - http://www.x.org/wiki/
  • Windowing system for bitmap displays
  • The most common GUI for UNIX-like operating systems
  • Responsibilities:
    • interacting with mouse and keyboard as an input device
    • interacting with displays as an output device
    • X11 does not mandate user interface!
  • Principles of operations:
    • client / server architecture
    • network awareness
    • x window manager
  • List of supported video cards: http://www.x.org/wiki/Projects/Drivers/

History of X11⌘

  • 1973 - first bitmap diplay system by Xeros (Alto)
  • 1983 - initial idea of the X Window System
  • 1985 - first release of the UWM (Ultrix Window Manager)
  • 1987 - first release of the X11 system
  • 1988 - first release of the XDM (X Display Manager)
  • 1991 - fork between the MIT X Consortium and the XFree86 Project, Inc.
  • 1993 - the MIT X Consortium transitions into the X Consortium, Inc.
  • 1997 - the X Consortium, Inc. transitions into The Open Group

History of X11 #2⌘

  • 1998 - first release of the KDE (K Desktop Environment) desktop
  • 1999 - first release of the Gnome desktop
  • 2004 - establishment of the X.Org Foundation
  • 2004 - fork between the X.Org Foundation and the XFree86 Project, Inc.
  • 2008 - last release of the XFree86 server
  • 2009 - last commit into the XFree86 project
  • 2014 - latest release of the X.Org Server

Desktops⌘

X11 installation⌘

  • Standard installation:
cd /usr/src
wget http://xorg.freedesktop.org/releases/individual/xserver/xorg-server-1.15.99.903.tar.gz
tar -xzf xorg-server-1.15.99.903.tar.gz
cd xorg-server-1.15.99.903
./configure
make
make install
  • Package-based installation:
    • CentOS:
yum groupinstall "X Window System"
    • Debian:
apt-get install x-window-system
  • Some distributions support installation of both X11 and default desktop in one:
    • Ubuntu:
apt-get install ubuntu-desktop

X11 configuration⌘

  • /etc/X11/xorg.conf - main X11 configuration file:
Section [SectionName]
    [SectionEntry]
    ...
EndSection
man xorg.conf
  • Section entries:
    • InputDevice - keyboard and mouse
    • Monitor - monitor
    • Device - video card
    • Screen - monitor and video card combination
    • Display - video mode
    • Files - font server
  • Automatic X11 configuration (X Server must be stopped):
X -configure
mv /root/xorg.conf /etc/X11/xorg.conf

X11 management⌘

  • Management tools:
    • startx - starts the X Server
    • xdpyinfo - displays information about the X Server
    • xwininfo - displays information about windows
    • xhost - access control program for the X Server
  • DISPLAY environmental variable:
    • [hostname]:[display].[screen]
    • example: localhost:0.1
  • Lab Exercise 106.1

106.2 Setup a display manager⌘

LPIC-102-15.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Display manager⌘

Logging into the system⌘

  • Logging into the system without display manager:
    • CLI logon
    • startx
  • Logging into the system with display manager:
    • GUI logon
  • Runlevels with graphical modes:
    • 2 on Debian
    • 5 on RedHat
  • Changing runlevels:
    • telinit - temporarily
    • /etc/inittab - permanently

Configuration⌘

  • GDM:
    • /etc/X11/gdm/gdm.conf - main configuration file
    • key=value pairs grouped by sections
  • KDM:
    • /etc/X11/kdm/kdmrc - main configuration directory
    • key=value pairs grouped by sections
  • XDM:
    • /etc/X11/xdm/xdm-config - main configuration file
    • key: value pairs grouped by sections
  • LightDM:
    • /etc/lightdm/lightdm.conf - main configuration file
    • key=value pairs grouped by sections

Remote access⌘

106.3 Accessibility⌘

LPIC-102-16.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Keyboard and mouse accessibility settings⌘

  • Keyboard repeat time - repeat rate and delay of the keyboard
  • Sticky keys - causes keyboard modifier keys (Ctrl, Alt and Shift) to "stick" when pressed
  • Slow keys - requires a key to be pressed for longer than a specified period of time
  • Bounce/debounce keys - treats multiple press of a key as a single press
  • Mouse tracking and click options - adjusts mouse tracking and click options
  • Simulated mouse clicks - simulates mouse click / double click
  • Mouse emulation/mouse navigation - enables mouse emulation by cursor keypad
  • Mouse gestures - keyboard shortcuts for mouse
  • Online keyboard - keyboard emulator

Screen accessibility settings⌘

  • Fonts - adjust fonts used by the system
  • Contrast - adjust display contrast
  • Magnifier - enlarges part of the screen

Assistive technologies⌘

First Day - Session IV⌘


Topic 107: Administrative Tasks


LPIC-102-05.png
http://itekblog.com/wp-content/uploads/2013/03/crontab.png

107.1 Manage user and group accounts and
related system files⌘



LPIC-102-17.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

User and group accounts management⌘

  • Configuration files:
    • /etc/passwd - user database
    • /etc/shadow - user password database
    • /etc/group - group database
    • /etc/gshadow - group password database
  • Management tools:
    • groupadd - creates a group
    • groupdel - deletes a group
    • groupmod - modifies a group
    • passwd - modifies user password
    • useradd - creates a user
    • userdel - deletes a user
    • usermod - modifies a user

/etc/passwd file⌘

  • Structure:
[username]:[password information]:[UID]:[GID]:[GECOS]:[home directory]:[program]
  • username - user name / login
  • password information:
    • empty - no password
    • x - password hash in /etc/shadow file
    • * - account locked
    •  ! - account locked
  • UID (User IDentifier) - user number
  • GID (Group IDentifier) - user group number
  • GECOS (General Electric Comprehensive Operating System) - user full name and contact information
  • home directory - a path to user home directory
  • program - a program which is started when the user logs into the system (e.g. shell)

/etc/shadow file⌘

  • Structure:
[username]:[hash]:[change date]:[min age]:[max age]:[warn period]:[grace period]:[exp date]:[reserved]
  • username - user name / login
  • hash - user password hash
  • change date - last password change date:
    • counted in days starting from the 1st of January 1970
    • 0 - user will be asked to change its password during the next login
    • empty - date checking disabled
  • min age - minimum number of days after which the password can be changed
  • max age - maximum number of days after which the password can be changed
  • warn period - how many days before password expiration date is the user warned
  • grace period - how many days after password expiration date can the user log in
  • exp date - account expiration date counted in days starting from the 1st of January 1970
  • reserved - reserved for future use

/etc/group file⌘

  • Structure:
[group name]:[password information]:[GID]:[members]
  • group name - group name
  • password information:
    • empty - no password
    • x - password hash in /etc/gshadow file
    • * - account locked
    •  ! - account locked
  • GID - group number
  • members - comma-separated list of users
  • Lab Exercise 107.1

107.2 Automate system administration tasks
by scheduling jobs⌘



LPIC-102-18.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Scheduling jobs in Linux⌘

  • Jobs run on regular basis:
    • on computers running continuously:
      • cron daemon
    • on computers not running continuously:
      • anacron utility
  • Jobs run once:
    • at command

Scheduling jobs to be run on regular basis
on computers running continuously⌘



  • Configuration files:
    • /etc/cron.allow - contains new-line separated list of users allowed to access cron service
    • /etc/cron.deny - contains new-line separated list of users denied to access cron service
    • /var/spool/cron/* - physical location of crontab files
  • Management tools:
    • crontab - crontab management utility
    • crond - cron daemon binary

Crontab⌘

  • Structure:
[minute] [hour] [DoM] [month] [DoW] [username] [command]
  • minute - job is executed specified number of minutes after a full hour
  • hour - job is executed at specified hour
  • DoM - job is executed on specified day of the month
  • month - job is executed in specified month
  • DoW - job is executed on specified day of the week
  • command - command to be executed by cron
  • Crontab tricks:
    • 1-n - 1, 2, ... , n
    • */m - 0, m, 2m, ...
    • 0-n/m - 0, m, 2m, ... , n
    • x,y,z - x, y, z

Scheduling jobs to be run on regular basis
on computers not running continuously⌘



  • Anacron utility execution:
    • /etc/crontab - on Debian-based systems
    • /etc/anacrontab - on RedHat-based systems
  • Anacron jobs definitions:
    • /etc/cron.hourly/* - jobs run on an hourly basis
    • /etc/cron.daily/* - jobs run on a daily basis
    • /etc/cron.weekly/* - jobs run on a weekly basis
    • /etc/cron.monthly/* - jobs run on a monthly basis

Anacrontab⌘

  • Structure:
[period / period name] [delay] [job-identifier] [command]
  • period - job is executed each period of days
  • period name - job is executed daily, weekly, monthly, yearly or annualy
  • delay - job is executed delay minutes after a full hour
  • job-identifier - used to identify jobs in anacron messages
  • command - command to be executed by anacron

Scheduling jobs to be run once⌘

  • Configuration files:
    • /etc/at.allow - contains new-line separated list of users allowed to run the at and batch commands
    • /etc/at.deny - contains new-line separated list of users denied to run the at and batch command
  • Management tools:
    • at - queues job for later execution
    • atq - lists users's pending jobs
    • atrm - deletes user's pending job
  • Lab Exercise 107.2

107.3 Localisation and internationalisation⌘

LPIC-102-19.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Encoding⌘

  • Unicode:
    • standard for consistent representation of text expressed in most of the world's writing systems
    • character set - a list of characters with unique numbers
  • Character encoding standards:
    • ASCII - 7-bit encoding
    • ISO-8859 - single-byte encoding
    • UTF-8 - multi-byte encoding
  • Encoding conversion - iconv

Locale⌘

  • Locale - set of parameters that define user's language, country and other preferences
  • Structure:
[language]_[territory].[codeset]@[modifier]
    • language - language code
    • territory - territory code
    • codeset - encoding system
    • modifier - optional parameters
  • Management tools:
    • locale - displays current locale
    • locale-gen - generates locale
  • Lab Exercise 107.3

Second Day - Session I⌘


Topic 108: Essential System Services


LPIC-102-06.jpg
http://wecai.org/wordpress/wp-content/uploads/2012/09/email1.jpg

108.1 Maintain system time⌘

LPIC-102-20.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Basic concepts⌘

  • Hardware Clock - maintains the time while the computer is turned off
  • Software Clock - maintains the time while the computer is turned on
  • GMT (Greenwich Mean Time) - local time in Greenwich adjusted for DST (Daylight Saving Time)
  • UTC (Coordinated Universal Time) - local time in Greenwich not adjusted for DST
  • Local Time - GMT adjusted for the time zone
  • NTP (Network Time Protocol) - a protocol used for time adjustment over the network

Time, date and timezone configuration⌘

  • Time and date manual configuration:
    • hwclock - displays / configures hardware clock
    • date - displays / configures software clock
  • Timezone configuration:
    • /usr/share/zoneinfo/* - contains timezones configuration files
    • /etc/localtime:
      • specifies timezone used by the system
      • links into a file from /usr/share/zoneinfo directory
    • /etc/timezone - specifies timezone name
    • dpkg-recofigure tzdata - reconfigures timezone on Debian systems
    • tzselect - reconfigures timezone on RedHat systems

NTP configuration⌘

    • /etc/ntp.conf - main NTP configuration file:
  • Client-side configuration and administration tools:
    • pointing a client to the server via ntp.conf:
server [server]
    • manual update of software time from the server:
ntpdate [server]
  • Server-side configuration:
    • ntpd - NTP server daemon
    • ntpq - verifies NTP server operations
  • pool.ntp.org - virtual cluster of publicly available and reliable time servers
  • Lab Exercise 108.1

108.2 System logging⌘

LPIC-102-21.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Syslog configuration⌘

  • /etc/syslog.conf - main syslog configuration file:
    • structure:
[facility].[priority] [action]
    • facility:
      • specifies a code word for the type of program or tool that generated the message to be logged
      • valid codes: auth, authpriv, cron, daemon, kern, lpr, mail, mark, news, security, syslog, user, uucp, local[0-7], *
    • priority:
      • specifies a code word for the priority the message below which it is not logged
      • valid codes: *, debug, info, notice, warning, warn, error, err, crit, alert, emerg, panic
    • action:
      • specifies a file into which the messages is logged
      • a file can be a log file, device, remote syslog server ('@server') or all logged users ('*')
  • /etc/rsyslog.conf - main rsyslog configuration file

Syslog central log server⌘

  • Client:
    • point syslog daemon to send messages to the remote syslog server
[facility].[priority] @[server]
  • Server:
    • install syslog-ng package
    • edit /etc/syslog-ng/syslog-ng.conf and include the following entries to accept all messages over the network:
source s_all {
    udp();
};
...
log { source(s_all); filter(f_syslog3); destination(d_syslog); };
    • perform additional configuration (man syslog-ng.conf)

Other logging tools⌘

  • logger:
    • used to create log entry manually
    • example:
logger Sample Message
  • klogd:
    • reads and logs Linux kernel messages
    • example:
klogd -o -f /var/log/kernel
  • logrotate:
    • used to automatically rotate logs
  • Lab Exercise 108.2

108.3 Mail Transfer Agent (MTA) basics⌘

LPIC-102-22.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Email foundations⌘

  • Email architecture:
    • MUA (Mail User Agent) - formats user message in email format and submits it into the MSA
    • MSA (Mail Submission Agent) - determines MTA into which an email should be send
    • MTA (Mail Transfer Agent) - delivers an email into another MTA
    • MDA (Mail Delivery Agent) - delivers an email into user mailbox
  • Email protocols:
    • SMTP (25) - used to send email between MTAs
    • Submission (587) - used to send email from MUA to MSA
    • POP3 (110) - used to get email from mailbox
    • IMAP (143) - used to manage mailbox
  • Email DNS records:
    • MX - edge MTAs in the domain
    • SPF - prevents email spoofing

MTA⌘

Aliases⌘

  • Define email address of system users
  • /etc/aliases.db - aliases database
  • /etc/aliases - aliases configuration file
    • format:
[alias]: [email address | alias], [email address | alias], ...
    • example:
postmaster:   root
root:         IT@mycompany.com, MyCompanyIT@gmail.com
  • newaliases - updates aliases database

MTA management⌘

  • Management tools:
    • mailq - displays mail queue
    • mail - displays mailbox content
    • ~/.forward - email forwarding configuration file:
      • list of forwarders
      • avoid infinite loops by using the '\' prefix
  • Lab Exercise 108.3

108.4 Manage printers and printing⌘

LPIC-102-23.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Print queue⌘

  • Holding area where files wait to be printed
  • /var/spool/cups/* - physical location of the print queue
  • A single compute can support many distinct print queues
  • Jobs are submitted to the print queue by the lpr program
  • Can be managed in terms of jobs monitoring, ordering, deleting, etc.
  • Network oriented - jobs can be submitted over the network

PostScript and Ghostscript⌘

  • PostScript:
    • printer language
    • de facto standard for Linux
  • Ghostscript:
    • PostScript interpreter
    • used for printers incompatible with PostScript

CUPS configuration⌘

  • /etc/cups - main configuration directory:
    • cupsd.conf - CUPS daemon configuration file
    • printers.conf - printer definitions
    • classes.conf - printer classes
    • client.conf - CUPS client configuration
    • lpoptions - printer options
    • subscriptions.conf - active subscriptions
    • ppd/* - additional options (PostScript Printer Definition)
  • The easiest way to add a printer is to do it from the GUI
  • CUPS web interface: http://localhost:631

CUPS management⌘

  • Management tools:
    • lpr - prints a file
    • lpq - displays print queue status
    • lpc - displays printers status
    • lprm - removes a job from the print queue
  • Lab Exercise 1.8.4

Second Day - Session II⌘


Topic 109: Networking Fundamentals


LPIC-102-07.jpg
http://villagecom.com/wp-content/uploads/2012/03/network_cabling1.jpg

109.1 Fundamentals of internet protocols⌘

LPIC-102-24.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

TCP/IP protocol stack⌘

LPIC-102-32.gif
http://www.phaedsys.com/principals/segger/seggerimages/embosip_struct1.gif

MAC address⌘

  • The most common link layer networks:
    • Ethernet (802.1)
    • WiFi (802.11)
  • MAC (Media Access Control) address:
    • used to uniquely identify a host in link layer
    • 48 bits
    • 12 hex values
    • consists of:
      • OUI (Organisationally Unique Identifier) - 24 bits
      • NIC (Network Interface Controller) - 24 bits
    • physically bound to the interface, but can be changed programmatically
    • can coexist in 2 networks separated by a router

IP address⌘

  • IP (Internet Protocol) address:
    • used to uniquely identify a host in network layer
    • 32 bits
    • 4 decimal octests separated by dots
    • consists of:
      • Network Part delimited by a Subnet Mask
      • Host Part delimited by a Subnet Mask
    • special purpose addresses:
      • network address
      • broadcast address
    • programmatically bound to the interface
    • can not coexist in 2 networks separated by a router

Default gateway⌘

LPIC-102-33.png

IPv4 vs IPv6⌘

Feature IPv4 IPv6
IP address 32 bits 128 bits
Checksum Header includes checksum Header does not include checksum
Options Header includes options Extension headers
Broadcast IP address Available Not available; link-local IP address
IP address configuration Manual or DHCP-based Auto-configuration

ICMP, TCP and UDP protocols⌘

  • ICMP (Internet Control Message Protocol):
    • used to send error messages between network hosts
    • used to test network connectivity (ping)
  • TCP (Transmission Control Protocol):
    • the most widely used transport-layer protocol in the TCP/IP stack
    • creates full connection for with error checking, acknowledgements, etc.
    • used to ensure reliable data transmission
  • UDP (User Datagram Protocol):
    • best-effort transport-layer protocol
    • does not create a connection between network hosts
    • used in cases when reliable data transmission is not important or is provided by upper layer protocols

Network services⌘

Port Protocol Service Example Linux Implementation
20 TCP FTP data ProFTPd
21 TCP FTP ProFTPd
22 TCP SSH OpenSSH
23 TCP Telnet in.telnetd
25 TCP SMTP Postfix
53 TCP / UDP DNS BIND
80 TCP HTTP Apache
110 TCP POP3 Dovecot

Network services #2⌘

Port Protocol Service Example Linux Implementation
119 TCP NTTP InterNetNews
139 TCP Windows file sharing Samba
143 TCP IMAP Dovecot
161 UDP SNMP Net-SNMP
443 TCP HTTPS Apache
465 TCP SMTPS Postfix
993 TCP IMAPS Dovecot
995 TCP POP3S Dovecot

Basic IP configuration⌘

  • Configuration files:
    • /etc/protocols - IP protocols and their numbers
[protocol number] [protocol name] [protocol aliases] #[comment]
    • /etc/services - TCP / UDP services and their ports
[service name] [port]/[protocol] [service aliases] #[comment]
  • Lab Exercise 109.1

109.2 Basic network configuration⌘

LPIC-102-25.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Network interfaces configuration⌘

  • Configuration files:
    • /etc/network/interfaces - on Debian systems
    • /etc/sysconfig/network-scripts/ifcfg-[interface name] - on RedHat systems
  • Configuration tools:
    • ifconfig - network interface configuration tool
    • ifup - brings network interface up
    • ifdown - brings network interfac down

Network interfaces configuration - Debian⌘

auto [interface name]
iface [interface name] inet [dhcp | static]
address [IP]
netmask [SM]
network [network IP]
broadcast [broadcast IP]
gateway [DG]

Network interfaces configuration - RedHat⌘

DEVICE=[interface name]
ONBOOT=[no | yes]
BOOTPROTO=[dhcp | none]
IPADDR=[IP]
NETMASK=[SM]
NETWORK=[network IP]
BROADCAST=[broadcast IP]
GATEWAY=[DG]

Routing configuration⌘

  • Manual:
    • route command:
route add -net [network IP] netmask [SM] gw [next hop IP] [interface name]
    • ip route command:
ip route add [network IP / SM] via [next hop IP] dev [interface name]
  • Via configuration files:
    • Debian (/etc/network/interfaces):
up [manual command]
    • RedHat (/etc/sysconfig/network-scripts/route-[interface name]):
[network IP/ SM] via [next hop IP] dev [interface name]
  • Lab Exercise 109.2

109.3 Basic network troubleshooting⌘

LPIC-102-26.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Network troubleshooting tools⌘

  • host - simple DNS lookup tool
  • dig - advance DNS lookup tool
  • hostname - system hostname management tool
  • ping - sends ICMP ECHO_REQUEST packet to network host
  • traceroute - prints the route packets trace to network host
  • tracepath - prints the route and MTU packets trace to network host
  • telnet - establishes TCP session with any server
  • ftp - establishes TCP session with FTP server
  • Lab Exercise 109.3

109.4 Configure client side DNS⌘

LPIC-102-27.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

NSS, resolver, DNS and hostname configuration⌘

  • Resolver and DNS configuration files:
    • /etc/nsswitch.conf - NSS (Name Service Switch) configuration file:
hosts: files dns
    • /etc/hosts - resolver configuration file:
[IP] [domain name]
    • /etc/resolv.conf - DNS (Domain Name System) configuration file:
search [domain 1] [domain 2] ...
nameserver [IP 1]
nameserver [IP 2]
...
    • Hostname configuration file:
      • /etc/hostname - on Debian-based systems
      • /etc/sysconfig/network - on RedHat-based systems
  • Lab Exercise 109.4

Second Day - Session III⌘


Topic 110: Security


LPIC-102-08.jpg
http://blogs.salleurl.edu/nice-rack/files/2014/05/infosec.jpg

110.1 Perform security administration tasks⌘

LPIC-102-28.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Security audit⌘

  • Security audit definition (via searchcio.techtarget.com):

"A security audit is a systematic evaluation of the security of a company's information system by measuring how well it conforms to a set of established criteria."

  • Security audit types:
    • system scans
    • network scans
    • processes reviews
    • policies reviews
    • attacks

SUID and SGID bits⌘

  • SUID (Set User ID):
    • causes that users executing the program will inherit owner's permissions, UID and GID
    • setup as an s character on third bit in standard access rights
    • dangerous if an owner of the program is root
  • SGID (Set Group ID):
    • causes that newly created files and subdirectories in the directory will inherit GID
    • setup as an s character on sixth bit in standard access rights
    • dangerous if a group of the directory is root
  • Finding files and directories with SUID and SGID bits setup:
find / -perm -u+s
find / -perm -g+s
  • Listing open files:
lsof

Password management⌘

  • Changing user password:
passwd [username]
  • Password and account expiration management:
    • chage - used for password expiration management
    • usermod - used for account expiration management
    • examples:
      • 1 year password expiration period:
chage -M 365 user
      • 1 month account expiration period:
usermod -f 30 user

Network scans⌘

  • nmap - scans open ports on a system by sending a bunch of TCP / UDP packets over the network:
    • useful options:
      • -p - specifies port, ports or a port range to scan
      • -sU - specifies that UDP scan should be performed
    • example:
nmap -p 80,443 google.com
  • netstat - scans open ports on a local system by displaying a list of open sockets:
    • useful options:
      • -t - limits the output to show TCP connections only
      • -a - shows both listening and non-listening sockets
      • -p - shows PID of the process to which the socket belongs to
      • -n - does not attempt to reverse resolve domain names
    • example:
netstat -atpn | grep 631 | head -n 1 | awk '{print $7}'

Security limits⌘

  • /etc/security/limits.conf - main security limits configuration file:
    • structure:
[domain] [type] [item] [value]
    • domain - username or group ('@')
    • type - 'soft' or 'hard'
    • item - system resource
    • value - limit value
  • ulimit - security limits management tool:
ulimit -a

Sudo configuration⌘

  • Management tools:
    • sudo - executes single command as another user
    • su - switches into another user space
    • gksudo / gksu - graphical versions of sudo / su
    • visudo - used to edit /etc/sudoers file
  • /etc/sudoers - sudo configuration file:
    • example:
admin ALL=(ALL:ALL)NOPASSWD ALL
    • explanation:
      • admin - the rule applies to admin user
      • first ALL - the user can run commands from any host
      • second ALL - the user can run commands as any user
      • third ALL - the user can run commands as any group
      • NOPASSWD - the user does not need to type a password to run commands
      • fourth ALL - the rule applies to any commands
  • Lab Exercise 110.1

110.2 Setup host security⌘

LPIC-102-29.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

Super server⌘

  • Listens for network connections on behalf of another program
  • When a connection is initiated, hands off control of that connection to the intended server
  • Reduces memory load if the super server handles many small servers that are seldom used
  • Enhanced security thanks to the tcp wrappers
  • Linux super servers:
    • inetd - standard super server
    • xinetd - enhanced super server

Inetd configuration⌘

  • /etc/inetd.conf - main inetd configuration file:
    • structure:
[service name] [socket type] [protocol] [wait / nowait] [user] [server name] [parameters]
    • service name - name of the service from /etc/services file
    • socket type - type of connection: stream, dgram, raw, seqpacket
    • protocol - name of the protocol from /etc/protocols file
    • wait / nowait - specifies whether all packets are processed before closing the socket
    • user - username used to run the server
    • server name - server executable path
    • parameters - server parameters
  • service inetd restart - restarts inetd super server

TCP wrapper⌘

  • TCP wrapper - allows access to particular services from specified IP addresses only
  • /usr/sbin/tcpd - TCP wrapper executable
  • /etc/hosts.allow, /etc/hosts.deny - TCP wrapper configuration files:
    • structure:
[daemon list]: [client list]
    • daemon list - list of services from the /etc/services file
    • client list - list of clients
  • Running services via TCP wrapper:
[service name] [socket type] [protocol] [wait / nowait] [user] /usr/sbin/tcpd [server name] [parameters]

Xinetd configuration⌘

  • /etc/xinetd.conf - main xinetd configuration file:
    • structure:
service [service name]
{
    socket_type   = [socket type]
    protocol      = [protocol]
    wait          = no / yes
    user          = [user]
    server        = [server name]
    server_args   = [parameters]
    only_from     = [hosts.allow file path]
    no_access     = [hosts.deny file path]
}
  • service xinetd restart - restarts xinetd super server

Additional security concerns⌘

  • Listing unused network services:
netstat -tap
  • Temporarily disabling login for non-root users:
    • /etc/nologin
    • file content is displayed and the loggin attempt fails
  • Lab Exercise 110.2

110.3 Securing data with encryption⌘

LPIC-102-30.png
https://www.lpi.org/linux-certifications/programs/lpic-1/exam-102/

SSH⌘

  • SSH (Secure SHell) - cryptographic network protocl to secure data communication
  • SSH packages:
    • openssh-server - SSH server
    • openssh-client - SSH client
  • SSH derivatives:
    • SCP (Secure CoPy) - used to copy files over the network via SSH
    • SSH Tunneling - used to wrap any kind of connection in an SSH

SSH architecture⌘

LPIC-102-31.gif
http://docstore.mik.ua/orelly/networking_2ndEd/ssh/figs/ssh_0304.gif

SSH configuration⌘

  • /etc/ssh/ssh_config - main client configuration file
  • /etc/ssh/sshd_config - main server configuration file
  • /etc/ssh/ssh_host_rsa_key - host private RSA key
  • /etc/ssh/ssh_host_rsa_key.pub - host public RSA key
  • /etc/ssh/ssh_host_dsa_key - host private DSA key
  • /etc/ssh/ssh_host_dsa_key.pub - host public DSA key
  • ~/.ssh/id_rsa - user private RSA key
  • ~/.ssh/id_rsa.pub - user public RSA key
  • ~/.ssh/id_dsa - user private DSA key
  • ~/.ssh/id_dsa.pub - user public DSA key
  • ~/.ssh/known_hosts - server fingerprints accepted by a user
  • ~/.ssh/authorized_keys - public keys of users allowed to SSH into the user account

SSH management⌘

  • Management tools:
    • ssh - runs SSH client
    • ssh-keygen - used to create and manage private-public key pairs
    • ssh-agent - program used to hold and remember the passphrace for private key
    • ssh-add - adds user public key into the ~/.ssh/authorized_keys file
  • SSH agent forwarding:
    • /etc/ssh/ssh_config:
ForwardAgent yes
    • /etc/ssh/sshd_config:
AllowAgentForwarding yes

SSH tunneling⌘

  • /etc/ssh/sshd_config:
AllowTcpForwarding yes
  • tunnel establishment:
ssh -N -f -L [local port]:[remote host]:[remote port] [username]@[remote host]

GPG⌘

  • GPG (GNU Privacy Guard) - email encryption tool
  • ~/.gnupg - user configuration directory
  • GPG private-public key pair generation:
gpg --gen-key
  • GPG public key export:
gpg --export [name] > [file]
  • GPG public key import:
gpg --import [file]
  • Listing GPG keys:
gpg --list

GPG usage⌘

  • Encrypting data with GPG:
gpg --out [encrypted file] --recipient [UID] --armor --encrypt [decrypted file]
  • Decrypting data with GPG:
gpg --out [decrypted file] --decrypt [encrypted file]
  • Signing messages with GPG:
gpg --clearsign [file]
  • Verifying signatures with GPG:
gpg --verify [file]
  • Lab Exercise 110.3

Second Day - Session IV⌘


Case Study, Certification and Surveys


LPIC-102-09.jpg
http://zone16.pcansw.org.au/site/ponyclub/image/fullsize/60786.jpg

Certification and Surveys⌘

Questions⌘


Thank you very much for your attention