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Welcome to Securing Linux Intro to Linux. WK 1 Objectives. Syllabus Intro to Linux ppt Basic commands, Directory structure, & File permissions Remotely log into the Linux network Class Project, Homework. Course Text. Additional Linux Books. Distro types.

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wk 1 objectives
WK 1 Objectives

Syllabus

  • Intro to Linux ppt
  • Basic commands, Directory structure, & File permissions
  • Remotely log into the Linux network
  • Class Project, Homework
distro types
Distro types
  • Installable versions installed to a disk
  • Live versions – bootable cd /dvd
  • VirtualBox – is a virtual engine you can run Linux under VB on windows
  • Unetbootin –
    • utility to make a bootable usb key
  • Embedded versions - DSL embedded

Download to windows runs on top of windows in a virtual session

slide6
GNU
  • 1973 Richard Stallman proposed the idea of a free Unix, started the GNU project
  • Started the Free Software Foundation and formulated the General Public License (GPL)
  • Hackers began assisting on projects
  • Became know as the Open Source Movement
question
Question?
  • What does Open Source mean to you?
linux highlights
Linux Highlights
  • Based on TEXT! Everything treated as a file!
  • ONE Hierarchical file system verse many in Window & DOS
  • Security, file attributes, users groups, privileges, permissions, etc
  • Multi-processing
  • Safe, Stable & Strong!
what is linux
What is Linux
  • Short answer = like UNIX
  • Long answer = a REVOLUTION
linux is like unix so what is unix
Linux is like UNIX ... So, what is UNIX?
  • developed by Ken Thompson at Bell Labs in 1969
  • was joined Dennis Ritchie (founder of C language)
  • MULTICS had a strong influence on UNIX
  • Ran on PDP-7, PDP-11
  • Both completely rewritten in 1973 using the C programming language (making it portable)
  • due to legal issues, UNIX could not be sold – so AT&T distributed it to educational and research communities
  • once the legal issues were settled, several commercial versions appeared
  • http://plan9.bell-labs.com/who/dmr/
slide11
UNIX
  • a true multi-user and multi-tasking environment
  • designed by programmers for programmers
  • small enough to understand, algorithms based on simplicity, kernel, shell, and library structure is easily expandable yet powerful
  • UNIX was intimately involved with the development of the Internet
  • UNIX erred regarding the desktop PC market
    • Could be as bad as IBM & Microsoft blunder
unix s strength
Unix’s strength
  • Logical Volume Manager (LVM)
  • Low Cost, Simple, Stable, Scalable, Customizability, Minimalistic and Purpose-built
  • Internet subset of tools
    • TCP/IP
    • FTP
    • Rlogin Slogin
    • Send Mail
    • Telnet
linux kernel
LINUX kernel
  • In 1991 Linus Torvalds a student rewrote the UNIX kernel and publish it on the Internet (Minix)
  • His instructor said it would never take off
  • Small kernel ran on Intel’s 386 (32-bit cpu)
  • GNU Libraries + Linux kernel = Full functional operating system
  • The rest is history!
linux kernel poster
Linux kernel Poster
  • http://www.linuxdriver.co.il/kernel_map_poster
pro s
Pro’s
  • $$$$$$$$ FREE $$$$$$$$$$
  • TCP/IP subset = Internet
  • LVM
  • Low Cost, Simple, Stable, Scalable, Customizability, Minimalistic and Purpose-built
  • Supports many file systems
  • Portable – runs on gas pumps
  • Transferable to routers, sans, PDA’s, Phones, etc
  • Example: Google’s 450,000 RedHat servers
  • Open Source more Secure?
con s
Con’s
  • Too Many Variant\'s (maybe 315)????
  • Welcome to the dark side
  • Concurrence not yet there in driver package.
  • Open Source less Secure?
distributions
Distributions
  • Red Hat most popular
  • SuSE most popular in Europe
  • Debian most popular with hackers
  • Standard $30-$50
  • Professional $60-$100
  • Enterprise $100-$200
  • Linux is FREE! You pay for distribution integration the OS, software & support
linux kernel1
Linux kernel
  • Numbering conventions
  • Even stable 2.0, 2.2, 2.4, 2.6
  • Developmental 2.1, 2.3, 2.5, 2.7
slide24
CLI
  • Like DOS
  • [doSomething] [how] [toFiles]
  • [doSomething] [how] [sourceFile] [destinationFile]
redirection
Redirection
  • [doSomething] [how] < [inputFile] > [outputFile]
piping
Piping
  • [doSomething] [how] | [doSomething] [how] | [doSomething] [how] > [outputFile]
tricks
Tricks
  • Wildcards : * and ?
  • >> redirect to append file
consoles
Consoles
  • Terminals emulators = xterm, konsole, etc
  • Virtual terminals
  • [alt]-[F1], … [alt]-[F6], [alt]-[F7] is GUI
  • [ctrl]-[alt]-[F1], … [ctrl]-[alt]-[F6] from GUI to Virtual terminal
  • Exiting Linux
  • [main menu] - [logout] from KDE
  • Exit or [ctrl]- D from text mode
getting help
Getting Help
  • man command
  • info command
  • −−help (command --help)
pathing
Pathing
  • [/] forward slash means from root dir
  • [/] = absolute pathing
  • [.] means current directory
  • [..] means parent directory
  • [./] explicitly means look here!
gui desktops
GUI desktops
  • CDE : Common Desktop Environment, commercial
  • KDE: K Desktop Environment utilities begin with “k” or “kde”
  • GNOME: GNU Network Object Model Environment, utilities begin with “g” or “gnome”
distribution installation
Distribution Installation
  • SuSE utilizes YAST: Yet Another Software Tool
  • Red Hat utilizes RPM: Red Hat Package Manager
  • Debian utilizes dpkg: Debian Package Manager
users and groups
users and groups
  • users are identified in the file /etc/passwd
    • user name and user id (uid)
  • groups are identified in the file /etc/group
    • group name and group id (gid)
  • important linux commands:
    • display uid and gids id
users and groups1
users and groups
  • root user uid = 0
  • regular user uid >= 500 ?
  • system user 0 < uid < 500
    • typically runs daemons (services)
    • does not login
users and groups2
users and groups
  • root user / system administrator / superuser
    • limit time as root user
    • it is too easy to do great damage!
      • example: rm -r *
  • becoming root user
    • at login
    • su (switch user) command
users and groups3
users and groups
  • regular user
    • unique account for each user
    • specify a default home directory
      • example: /home/joecool
    • specify a default shell
      • example: /bin/bash
users and groups4
users and groups
  • system user
    • typically does not require a home directory
    • typically does not require a default shell
  • a secure system should reflect this
    • /etc/passwd
users and groups5
users and groups

groups represent collections of users

having common needs

an individual user may belong to several groups

groups

users and groups6
users and groups
  • as a general rule: if a user requires access to certain files and/or to certain devices, then
    • it is better to add the user to the group that is permitted access than to modify the file access rights
file access rights
file access rights
  • the following command is essential in UNIX
  • ls -l
  • read – write – execute triples r w x
  • user – group – other triples u g o
  • chown command
  • chgrp command
  • chmod command
file access rights1
file access rights
  • octal notation is least ambiguous
    • read r 4
    • write w 2
    • execute x 1
  • example:
    • rwx r-x r-- equivalent to 7 5 4 octal
file attributes
file attributes
  • file attributes are an extension to file access rights
  • limited to linux native file systems: ext2 and ext3
  • basic commands:
    • to display attributes
      • lsattr
    • to set or modify attributes
      • chattr
file attributes1
file attributes
  • important attributes:
    • immutable +i
      • can not be modified, deleted, renamed, nor linked to
      • ideal for system files
    • append +a
      • only additions at the end of the file are permissible
      • ideal for log files
    • scrub +s
      • all blocks zeroed out when deleted
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