CEG 2400 FALL 2012 Linux/UNIX Network Operating Systems

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 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

UNIX and Linux

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

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

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 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 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

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 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

The UNIX Kernel

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

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 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 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 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 Commonly used UNIX commands

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 Example of output from ls -l

22 Anatomy of ls –l output

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

End of Linux/UNIX Questions