Slides null puliya linux basics
A presentation at Null Meet Bangalore Chapter in in Bengaluru, Karnataka, India by Anant Shrivastava
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
covering following
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Basic’s of linux file system hirarchy
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Useful commands
- cut
- grep
- sed
- sort
- uniq
- xargs
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Interaction with std input, output and error
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VIM Editor Basics
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Automating Routine Tasks
- Interacting with other commands
- overloading existing command to do more
- writing shell scripts (Introduction)
Resources
The following resources were mentioned during the presentation or are useful additional information.
