Slides null puliya linux basics

LINUX PULIYA

ANANT SHRIVASTAVA Information Security Consultant Admin - Dev - Security null + OWASP + G4H http://anantshri.info and @anantshri Trainer : Blackhat, RuxCon, NullCon, g0s, c0c0n Speaker : Nullcon, c0c0n, ClubHack, RootConf Android Tamer Code Vigilant

WHAT ARE WE COVERING 1. Understanding *nix 2. File System Basics 3. Understanding I/O 4. Basic Commands 5. How to Exit VIM 6. Shell Script basics 7. Automation

NIX 1. Family of OS ranging from Unix, Linux, *BSD (FreeBSD, OpenBSD etc) 2. Follow same standards in terms of file systems, directory layout etc

LINUX 1. Free as in free speech not free beer 2. Everyone can create there own Distro 3. Hanna Montanna Linux and more

LINUX DISTRIBUTIONS 1. Various Linux Distributions 2. Debian Based (apt-get / dpkg) 3. RedHat based (yum / rpm) 4. LTS or not

FILE SYSTEM BASICS 1. Everything is a file 2. File System Layout 3. Standard File system layout 1. / as highest level 2. /etc for all configuration 3. /home : users home folder

FILE SYSTEM TYPES ext2 Maximum file size = 16 GB to 2 TB File system size = 2 TB to 32 TB ext3 1. Journaling (Linux Kernel 2.4.15) 2. Maximum file size = 16 GB to 2 TB 3. File system size = 2 TB to 32 TB ext4 1. Starting from Linux Kernel 2.6.19 ext4 2. Maximum file size = 16 GB to 16 TB 3. File system size = 1 EB 1. 1 EB = 1024 PB 2. 1 PB = 1024 TB

MORE FILE SYSTEM BASIC 1. File System Permissions -rwxrwxrwx 2. Suid bits -rwsrwxrwx 3. sgid bit -rwxrwsrwx 4. sticky bit -rwxrwxrwt 5. First bit can be l,c,b,d,-

SUDO 1. id 0 is omnipotent 2. its suggested not to use root access 3. So how do we do high privilege actions

STANDARD I/O 1. Input (<) 2. Output (>) 3. Error (2>)

USEFUL COMMANDS 1. ls, cd, mkdir 2. cut 3. grep 4. sed 5. sort 6. uniq 7. xargs 8. find 9. tr 10. ps 11. screen 12. netstat -lntp 13. file

EDITOR 1. Vim 2. Nano 3. EMACS

INSTALLING SOFTWARES 1. Debian apt-get install 2. Redhat yum install 3. python pip install 4. ruby gem install 5. npm / nodejs npm install

MORE USEFUL COMMANDS 1. python -m SimpleHTTPServer Port 2. !! 3. cd ~ 4. cd 5. mtr 6. mount and format 7. setting environment Variables

CRONTAB 1. Automate periodic execution * * * * * * CMD |||||| | | | | | +— Year (range: 1900-3000) | | | | +—— Day of the Week (range: 1-7, 1 standing for Monday) | | | +——— Month of the Year (range: 1-12) | | +———— Day of the Month (range: 1-31) | +————— Hour (range: 0-23) +—————— Minute (range: 0-59)

CONFIGURING SERVICES SSH Configuration file : /etc/ssh/sshd_config

USING SSH 1. SSH Authentication 1. Password 2. SSH Key 2. How to Configure SSH Login via Key 3. ~/.ssh/authorized_keys

SHELL SCRIPT BASICS 1. Shebang 2. $1 $2, $* $@ $0 3. read 4. echo 5. cat 6. Conditions 7. Loop 8. Expansion {}

WRITING CUSTOM SCRIPTS 1. Write a shell script to calculate simple interest 2. Write a shell script to check whether no is even or odd 3. Print prime numbers from 1 to 5000

OVERLOAD COMMANDS 1. alias 2. Why alias and why not 3. find location add path before everything else and then overload

EXAMPLE

QUESTIONS

THANK YOU