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Linux basics

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Linux Basics for Server Management

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Linux basics

  1. 1. Linux Basics Geeta Vinnakota
  2. 2. Outline • Terms • Releases • File System • Package Management • Environment Variables • Processes • User Management • Command Enhancements • Aliases • Network Management • Terminal Tips & Misc 1/23/2016 2
  3. 3. Philosophy of Linux • Linux does not assume anything. • Lets you install what you need rather than give you a bunch of things you may not need • Linux commands and case sensitive 1/23/2016 3
  4. 4. Terms Term Kernel Takes care of resource allocation Shell Accepts command and passes it to kernel Service Application that runs in the background 1/23/2016 4
  5. 5. Releases lsb_release -a Prints the release, codename and description lsb_release -sc Prints the codename ubuntu-support-status Check status of the release and packages uname -r prints kernel version Release Upgrade Steps sudo apt-get update Step-1 sudo apt-get update update-manager-core Step-2 sudo do-release-upgrade Step-3 1/23/2016 5
  6. 6. File System - Important Directories /var/run pids for important processes /var/log log files /etc/init Configuration Files /etc/init.d Scripts that respond to start and stop /etc/hosts DNS /etc/passwd User database /etc/ssh SSH configuration /etc/my.cnf MySQL configuration /opt/ Optional packages not part of the default installation ~ Home directory ~/.ssh Known Hosts, Authentication Keys ~/.bash_profile Startup File. Defines aliases and configuration 1/23/2016 6
  7. 7. Package Management apt Advanced Packaging Tool /etc/apt/sources.list Stores the list of available packages deb – Repos containing binarires deb-src – Repos containing source code for packages sudo apt-get update Checks for new versions sudo apt-get install nmap To install the package nmap sudo apt-get remove nmap To remove the package nmap 1/23/2016 7
  8. 8. Environment Variables env View all environment variables env | grep PATH echo $PATH echo $USER prints current user 1/23/2016 8
  9. 9. Processes Processes are the core of Linux OS. A process is an instance of a running command. init First process with id 1. Cannot be killed. Every other process is a child of init daemon is a background process htop interactive tool to list and manage processes Prints CPU & memory utilization of each process crontab –l list all background scheduled processes crontab –e edit the crontab 1/23/2016 9
  10. 10. User Management compgen –u List all users compgen –g List all groups sudo su – user2 Switch to user2 sudo Run commands as root user 1/23/2016 10
  11. 11. Command Enhancements time cmd prints the time taken to execute cmd cmd1 | cmd2 pass the output of the previous cmd1 to in the input of the next cmd2 cmd & Execute cmd in the background and return ./cmd bypass an alias man cmd Manual entry for cmd whatis cmd Documentation for cmd screen -x screen sharing between users 1/23/2016 11
  12. 12. Aliases Aliases help replace 1 string with another while execution. Aliases are usually defined in the configuration file like .bash_profile alias ll=“ls—l” Creates an alias alias ll gets the alias single quotes variables are not expanded double quotes variables are expanded 1/23/2016 12
  13. 13. Network Management netstat -ntlp Network Statistics - List of ports listening telnet host port Check if the port on the host is listening iostat Input Output Statistics host google.com DNS lookup ping google.com Check is server is active du disk usage statistics ifconfig Configure network interface parameters 1/23/2016 13
  14. 14. Terminal Tips & Misc cmd + R clears terminal ctrl + R Search through command history sudo reboot reboot machine & logout #! /bin/bash Hash bang. First line of a script. Uses bash interpreter 1/23/2016 14