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Linux Intro

Linux Intro. Linux, the do it yourself OS Linux, successor to MINIX Linux, Unix for the masses (PC users) History: http://ragib.hypermart.net/linux/. Linux Organization. Central core of a Linux system is the kernel All CPU communication goes through the kernel

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Linux Intro

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  1. Linux Intro • Linux, the do it yourself OS • Linux, successor to MINIX • Linux, Unix for the masses (PC users) • History: http://ragib.hypermart.net/linux/

  2. Linux Organization • Central core of a Linux system is the kernel • All CPU communication goes through the kernel • Network devices are controlled via device drivers in the kernel • The TCP/IP network protocol stack is built into the kernel

  3. Linux Kernel • Can be modified by the user • Handles device drivers as needed by hardware • The kernel can be built for several different types of Linux applications

  4. Linux Devices • Devices communicate with the kernel through the /dev directory • Each device has a node number associated with it to point to a location in the kernel crw-rw---- 1 root tty 4, 64 Nov 26 15:39 0 crw-rw---- 1 root tty 4, 65 Nov 27 14:34 1 brw-------- 1 root root 8, 0 Oct 12 13:40 hda0

  5. Linux File system • Everything starts at the root (/) directory • /bin binary executables are here • /sbin system binary executables are here • /usr libraries, include files, system files are here • /tmp temporary storage • /var system logs, spool files, mail, accounting here • /lib library files • /etc system control files here • /dev devices • /proc process storage • /boot the boot files (kernel etc.) go here

  6. Linux File system • Linux always mounts and dismounts all file systems. • Floppies, Zips, Cdroms, and any other random access storage is mounted before use and dismounted after use. • Dismounting insures that all writes have completed and files are closed before removal of the media.

  7. Linux Swap • The swap partition is used for virtual memory and task swapping. • Depending on the applications, throughput desired, and amount of RAM memory the swap space can be from 1 to 3 times the size of RAM. • Swap space is unformatted disk space

  8. Linux Basics • Single boot or Dual boot? • Partitioning rules • Format (FAT32, ext2, ext3, swap) • Common disk partitions • Install operating system • Decide what features you need to add such as networking, server, development, ganes

  9. Linux Bootup • The linux boot program (lilo “Linux Loader” or grub “Grand Unified Boot loader”) starts the linux system. • After the kernel is loaded and the system can talk to it’s peripherals the initialization begins. • The /etc/inittab file tells the system what to start up, the first is usually rc.sysinit.

  10. Linux Bootup • rc.sysinit • Starts logging • Sets the hostname • Prepares the network for startup • Checks the clock • Sets up the host computer hardware • Sets up and mounts the filesystem

  11. Linux bootup • Depending on the run level that the system is to run to, different rc files will be executed. • Run level 0 is shutdown • Run level 1 is single user • Run level 2 is multiuser, no NFS • Run level 3 is ready to use full multiuser • Run level 4 is unused at present • Run level 5 is GUI • Run level 6 is reboot

  12. Linux Bootup • You don’t have the root password? Boot the system in single user mode Select command line mode from LILIO or GRUB linux –s or linux -single

  13. Linux bootup • To keep the startup files organized, they are put into a directory /etc/rc.d/init.d • Links to those programs are placed in the run level subdirectories back to init.d so changes are only needed in the init.d directory.

  14. Linux bootup • To control the sequence of startup processes, each start program is start sequentially by the numbers before the start script. • S98http (same as /etc/init.d/http start at sequence 98) • At shutdown the process reverses • K98http (same as /etc/init.d/http stop at sequence 98) • Init 2, init 3, init 4, and init 5 run the S##name scripts • Init 0, init 1 and init 6 run the K##name scripts

  15. Linux bootup last step • Once linux boots and loads the appropriate drivers and files it executes “login”. • Login provides a prompt for username, then prompts for a password. • The username is stored in /etc/passwd and the password is stored in /etc/shadow. • One the account is authenticated the user is given a command prompt (%)

  16. Linux configuration • Interfaces are configured using the linuxconf program (point and click) or command line programs. • The default network interface is called eth0 • The hardware board device drivers is selected via the linuxconf program

  17. GUI configuration • Linux uses the X window system for it’s graphical user interface • GUIs are typically installed at system installation time. • If the Linux box is in command line mode then the GUI can be installed with the Xconfigurator program. • Linux will probe for the correct video board but may need to be told what display is being used. • The GUI can be set up to start at boot time to provide a windows like login screen.

  18. Linux Networking • Linux normally will install networking with DHCP (Dynamic Host Control Protocol) enabled to receive TCP/IP configuration parameters. • Linux network programs are controlled either by starting the program and placing it in the background through the /etc/xinit.d dispatcher (httpd start) for CPU intensive programs, or by calling it as needed via /etc/xinetd.conf to save memory and CPU time.

  19. Linux Network apps • Shared password file • NIS (yellow pages) allows sharing of a single password file for a group of systems • NFS (Network File system) • Allows a group of systems to share a common disk farm.

  20. Linux Network Security • Linux can filter incoming and/or outgoing ip packets to control access to it’s resources. • The filter programs are called ipchains or iptables depending on the flavor of linux. • The tables may allow or deny certain ip addresses or ports to control access. • The xinetd program can control which services are available to the network

  21. Knoppix • Knoppix is the easy way to start into Linux • Knoppix boots from CD and starts a limited linux on any PC. • Knoppix is free!

  22. Linux terminal interface • Linux is ready to take requests from serial interfaces as soon as it boots. • The serial devices use terminal emulators to log in to the system (command line mode) • Modem’s use the serial ports to access the linux box and the system can also be used as a modem pool for PPP use.

  23. Interaction with Linux • Login • username user • Password may not be needed • Now what? • ls list files, ls –al list with attributes • man help files • man –k search for key word in man • ps –ef processor status, what is running on the system • df disk free, what disks are there and how much is left on them

  24. More Commands • grep search files for a string • paste put two files together • cut pull a pattern from a file • tr translate characters • sort sort a file • >, <, >> file redirection • | pipe (flow data between programs) • grep csh /etc/passwd | sort > file.temp

  25. Examples • sort < file1 > file2 • cut -d, -f4 file1 • paste file1 file2 > file3

  26. Linux Intro The End Check the website for homework Remember, no class next week

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