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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 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 3 UNIX and Linux 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 5 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 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 8 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 9 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 64bit addresses • Virtual memory – Disk partition or file 10 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 11 The UNIX Kernel 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 13 UNIX System File and Directory Structure (cont’d.) UNIX file system hierarchy 14 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) 15 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 16 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 17 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: ( / ) 18 19 commands Commonly used UNIX 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 ( | ) 20 Example of output from ls -l 21 Anatomy of ls –l output 22 Summary • • • • • • Many varieties Proprietary vs Open source Many common features Memory model Kernel File System 23 End of Linux/UNIX Questions