1. CEG 2400 FALL 2012 Linux/UNIX Network Operating Systems

2. UNIX and Linux Popular NOSs – UNIX/Linux operating system comes in many varieties, or distributions – Provide resource sharing – Older UNIX develop in 1969 – Most Internet servers run UNIX Some difficulty to master UNIX – Not controlled, distributed by single manufacturer – Some version nonproprietary and freely distributed 2

3. 3 Varieties of UNIX Many varieties (flavors, distributions) – Share several features UNIX operating system – Divided into two main categories Proprietary Open source (Linux, many varieties, free) – Ubuntu, OpenSUSE, etc Can be GUI or GUI-less

4. UNIX and Linux

5. 5 Proprietary UNIX Available only by purchasing licensed copy Vendors – Apple Computer: Mac OS X Server – Sun Microsystems: Solaris – IBM: AIX – Novell: SUSE – HP: hp-ux – Red Hat – Others

6. UNIX and Linux operating system UNIX and Linux operating system share the following features: – The ability to support multiple, simultaneously logged-on users – The ability to coordinate multiple, simultaneously running tasks (or programs) – The ability to mount —or to make available—disk partitions upon demand – The ability to apply permissions for file and directory access and modification – A uniform method of issuing data to or receiving data from hardware devices, files, and running programs – The ability to start a program without interfering with a currently running program

7. UNIX and Linux operating system UNIX and Linux operating system share the following features: (con’t) – Hundreds of subsystems, including dozens of programming languages – Programs necessary for routing, firewall protection, DNS services, and DHCP services – Source code portability, or the ability to extract code from one UNIX system and use it on another – Window interfaces that the user can configure, the most popular of which is the X Window system

8. 8 UNIX and Linux operating system UNIX and Linux operating system share the following features: (con’t) TCP/IP protocol suite Applications to support networking infrastructure Support non-IP protocols Operates over many different network topologies, physical media Efficiently and securely handle growth, change, stability Source code used, thoroughly debugged

9. 9 UNIX Multiprocessing UNIX and Linux – Support processes and threads – Allocate separate resources (memory space) to each process When created Manage access to resources Advantage: prevents one program from disrupting system – Support symmetric multiprocessing – Different versions support different number of processors

10. The UNIX Memory Model Use physical, virtual memory efficiently Allocate memory area for each application – Share memory between programs when possible Use 32-bit addressing scheme – Programs access 4 GB memory Most systems also run on CPUs employing 64- bit addresses Virtual memory – Disk partition or file 10

11. 11 The UNIX Kernel Kernel – Core of all UNIX and Linux systems – Loads into memory – Primary function is to coordinate access to computer’s hardware Kernel module – File containing instructions for performing specific task EX. Reading data from and writing data to hard drive

12. The UNIX Kernel

13. 13 UNIX System File and Directory Structure Hierarchical file system – Disk directories may contain files, other directories /boot directory: kernel, system initialization files /sbin directory: applications, services /var directory: variable data /home directory: created for new users Some versions have other directories

14. 14 UNIX System File and Directory Structure (cont’d.) UNIX file system hierarchy

15. 15 Disk File Systems Organizing, managing, accessing files – Through logical structures, software routines Linux native file system type – ext4: “fourth extended” file system – There are so many others Solaris native file system – UFS (UNIX file system)

16. 16 UNIX and Linux Network File Systems Similar to Windows shares – Attach shared file systems (drives) From Windows, other UNIX servers – Share files with users on other computers UNIX and Linux popular remote file system type – Sun Microsystems’ NFS (Network File System) Open source application implementing Windows SMB, CIFS file system protocols – Samba

17. 17 A UNIX and Linux Command Sampler Many system administrators prefer command line GUI executes commands – Responds to mouse clicks Command interpreter (shell) – Accepts keyboard commands and runs them Man pages (manual pages) – Full documentation of UNIX command – Similar to windows help

18. 18 A UNIX and Linux Command Sampler Commands function like sentences Significant UNIX and Windows command-line interface difference – Character separating directories Windows separator character: ( \ ) UNIX separator character: ( / )

19. 19 Commonly used UNIX commands

20. 20 A UNIX and Linux Command Sampler Most frequently used UNIX command – ls – Provides file information Stores in file inode (information node) – ls –l command Access permissions field Files type designations Pipe – Direct one command output to input of another command – Unix: vertical bar ( | )

21. 21 Example of output from ls -l

22. 22 Anatomy of ls –l output

23. 23 Summary Many varieties Proprietary vs Open source Many common features Memory model Kernel File System

24. End of Linux/UNIX Questions