1. What is UNIX? UNIX is an Operating System (OS). An operating system is a control program that helps the user communicate with the computer hardware. UNIX was developed long before Windows, about 30 years ago at AT&T Bell Labs in the US (95% written in “C” programming language). UNIX was designed as an operating system for experts, used on high-end workstations, servers and hosts. UNIX is an Operating System (OS). An operating system is a control program that helps the user communicate with the computer hardware. UNIX was developed long before Windows, about 30 years ago at AT&T Bell Labs in the US (95% written in “C” programming language). UNIX was designed as an operating system for experts, used on high-end workstations, servers and hosts.

2. What is UNIX? UNIX provides some powerful features: –Security - private and shared files –Multi-user support –Inter-process communication –Extensive network support –Data sent to display, files, or printers in same way Windows NT was developed by Microsoft to try to replace UNIX as the “OS for experts”. UNIX provides some powerful features: –Security - private and shared files –Multi-user support –Inter-process communication –Extensive network support –Data sent to display, files, or printers in same way Windows NT was developed by Microsoft to try to replace UNIX as the “OS for experts”.

3. Most Important Feature of UNIX Most important feature of UNIX: STABILITY –30 years to get the bugs out –Important in shared environments and critical applications Shared Environments Example: University –Windows98/NT crashes at least once a day in labs –UNIX servers crash about once a semester (usually due to hard disk failure) –UNIX more than 100 times more reliable than Windows! Critical Applications –Hospital - Don’t want to wait for reboot during operation! –Airport - Air traffic control landing planes. –Telecom - Don’t want phone system going down! Most important feature of UNIX: STABILITY –30 years to get the bugs out –Important in shared environments and critical applications Shared Environments Example: University –Windows98/NT crashes at least once a day in labs –UNIX servers crash about once a semester (usually due to hard disk failure) –UNIX more than 100 times more reliable than Windows! Critical Applications –Hospital - Don’t want to wait for reboot during operation! –Airport - Air traffic control landing planes. –Telecom - Don’t want phone system going down!

4. UNIX Versions There are two main types of UNIX: –BSD (Berkeley Software Distribution) –System V (developed at AT&T) There are many different versions of UNIX for different hardware: –Sun Microsystem’s Solaris (and SunOS) –Hewlett-Packard’s HP-UX –IBM’s AIX –SGI’s IRIX Many UNIX dialects for PCs –“Free”: Linux (distributions such as Red Hat, Caldera,Corel, SuSE, TurboLinux, WinLinux), FreeBSD (see http://www.linux.org/; http://www.linux.org/dist/index.html)http://www.linux.org/http://www.linux.org/dist/index.html –Commercial: SCO UNIX (Xenix), Sun OS There are two main types of UNIX: –BSD (Berkeley Software Distribution) –System V (developed at AT&T) There are many different versions of UNIX for different hardware: –Sun Microsystem’s Solaris (and SunOS) –Hewlett-Packard’s HP-UX –IBM’s AIX –SGI’s IRIX Many UNIX dialects for PCs –“Free”: Linux (distributions such as Red Hat, Caldera,Corel, SuSE, TurboLinux, WinLinux), FreeBSD (see http://www.linux.org/; http://www.linux.org/dist/index.html)http://www.linux.org/http://www.linux.org/dist/index.html –Commercial: SCO UNIX (Xenix), Sun OS

5. PC UNIX Linux basically free Also runs well on older PCs Many free, reliable software & development tools with source code e.g.,Web/Mail Server, Database Server, File Server (NFS for UNIX, Samba for Windows clients), Firewall, Dialup Extremely fast PC for hosts and servers –Multiple (2,4,8) CPUs in one PC – Symmetric Multi- Processing (SMP) –PC clusters for scientific computing More powerful than and therefore alternative for older expensive mini/mainframe & some super computers, especially if they are running UNIX Linux basically free Also runs well on older PCs Many free, reliable software & development tools with source code e.g.,Web/Mail Server, Database Server, File Server (NFS for UNIX, Samba for Windows clients), Firewall, Dialup Extremely fast PC for hosts and servers –Multiple (2,4,8) CPUs in one PC – Symmetric Multi- Processing (SMP) –PC clusters for scientific computing More powerful than and therefore alternative for older expensive mini/mainframe & some super computers, especially if they are running UNIX

6. Who Uses UNIX? Computer manufacturers such as Sun, SGI, IBM, and HP Computer chip manufacturers like Motorola & Intel Software companies Banks Hospital Authority Universities Internet Service Providers (ISP) Web Companies Web servers of many organization and for personal use Computer manufacturers such as Sun, SGI, IBM, and HP Computer chip manufacturers like Motorola & Intel Software companies Banks Hospital Authority Universities Internet Service Providers (ISP) Web Companies Web servers of many organization and for personal use

7. UNIX BSD Berkeley Standard Distribution (univ at CA) Tools: –C shell –VI editor –File managers –Network applications Berkeley Standard Distribution (univ at CA) Tools: –C shell –VI editor –File managers –Network applications

8. Unix System V “Standard” unix AT&T version Improved file sharing in the network Version 4.0 developed by AT&T and Sun Microsystems “Standard” unix AT&T version Improved file sharing in the network Version 4.0 developed by AT&T and Sun Microsystems

9. X-Windows GUI for Unix Many tools Standard for every system Provides: windows, menus, buttons, dialog boxes etc… GUI for Unix Many tools Standard for every system Provides: windows, menus, buttons, dialog boxes etc…

10. Applications File Managers Shells Editors Databases Web Servers Mail server Network applications and utilities File Managers Shells Editors Databases Web Servers Mail server Network applications and utilities

11. Programming Many tools: compilers, debuggers etc.. Supports: C, C++, Fortran, Pascal, Java, Basic, Cobol, Lisp, APL, Logo, RPG Easy Connection between Application with the standard input and output. Shell Programming Many tools: compilers, debuggers etc.. Supports: C, C++, Fortran, Pascal, Java, Basic, Cobol, Lisp, APL, Logo, RPG Easy Connection between Application with the standard input and output. Shell Programming

12. General UNIX Architecture Hardware Kernel System Call Interface Unix applications/commands Hardware Kernel System Call Interface Unix applications/commands

13. What is a file system? A means of organizing information on the computer. A file system is a logical view, not necessarily a physical view. What does the file system provide: –Ways to create, move, and remove files –Ways to order files –Security Examples of file systems: –DOS, Macintosh, CD-ROM, UNIX, NFS (networked file system) What is a file system? A means of organizing information on the computer. A file system is a logical view, not necessarily a physical view. What does the file system provide: –Ways to create, move, and remove files –Ways to order files –Security Examples of file systems: –DOS, Macintosh, CD-ROM, UNIX, NFS (networked file system) Unix File System

14. Hierarchical Organization Single root of tree is at top denoted by ‘/’ Kinds of files: –Directory files (the branches in the tree) –Regular files (leaves in the tree) Hierarchical Organization Single root of tree is at top denoted by ‘/’ Kinds of files: –Directory files (the branches in the tree) –Regular files (leaves in the tree) UNIX File Systems / binlibhomes horner.mailrctop10111 jbond...

15. Home and Working Directories Home directory –The directory you are in when you first login in –This is your space; you control security –Place to put your personalized,startup files –Your working directory after typing cd with no arguments Working directory –Can access files in your working directory by simply typing the filename –To access files in other directories, must use a pathname –pwd command prints the working directory –cd command changes the working directory Home directory –The directory you are in when you first login in –This is your space; you control security –Place to put your personalized,startup files –Your working directory after typing cd with no arguments Working directory –Can access files in your working directory by simply typing the filename –To access files in other directories, must use a pathname –pwd command prints the working directory –cd command changes the working directory

16. Directory Shorthands “.” is the directory itself “..” is the parent directory In most shells “~” means your home directory ~user means user’s home directory, so: ~jbond/.plan looks at the file.plan in /home/jbond, which is jbond’s home directory. “.” is the directory itself “..” is the parent directory In most shells “~” means your home directory ~user means user’s home directory, so: ~jbond/.plan looks at the file.plan in /home/jbond, which is jbond’s home directory.

17. Special Directories “/” (pronounced “slash” and also called “the “root”) is the ancestor of all files in the file system /bin and /usr/bin contain UNIX utilities (e.g., cat) /dev contains special files which describe “devices” such as terminals and printers /etc has administrative programs like password files /tmp is for temporary files; periodically deleted Every directory has at least two entries: “.” is the directory itself, and “..” is the directory’s parent “/” (pronounced “slash” and also called “the “root”) is the ancestor of all files in the file system /bin and /usr/bin contain UNIX utilities (e.g., cat) /dev contains special files which describe “devices” such as terminals and printers /etc has administrative programs like password files /tmp is for temporary files; periodically deleted Every directory has at least two entries: “.” is the directory itself, and “..” is the directory’s parent

18. Naming Files Files in the same directory can’t have the same name Case sensitive: secret and Secret are different Files are sometimes named with an extension (e.g., bond.cpp, 007.html) to show the file’s content. You cannot create a file named “.” or “..” “Invisible” files and directories (those that don’t appear using ls) have a period as the first character (e.g.,.plan,.xinitrc). Some programs use invisible files to store information. Files in the same directory can’t have the same name Case sensitive: secret and Secret are different Files are sometimes named with an extension (e.g., bond.cpp, 007.html) to show the file’s content. You cannot create a file named “.” or “..” “Invisible” files and directories (those that don’t appear using ls) have a period as the first character (e.g.,.plan,.xinitrc). Some programs use invisible files to store information.