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LINUX System Administration Perspectives, Practices and Expectations Eunuchs or UNIX? System Administration? • • • • • • • • • • • • • • • General user administration Disk administration Application Administration Scripting and automation Security Network Performance – CPU, memory, disk, network Application installation, configuration and maintenance System software installation, configuration and maintenance OS installation, configuration and maintenance Virtualization Storage/Backup/Restore Hardware selection and design Architectural design Platform Interface Why UNIX? • • • • • • • Technical strengths – Common platform, commands and services The original “portable” OS Multi-user OS Disk/process oriented Highly configurable Basis of most modern open source technologies and platforms – File Systems, Inter-process communication, script languages, “C” language, Language roject Packaging (IDEW/SCCS) Regex, Internet – TCP/IP, MAC OSx (BSD) , IBM and Windows UNIX Services • Many vendors – software, hardware platforms • At some level not proprietary? (snicker) Commercial UNIX Versions • • • • • • • • • • IBM AIX SunOS, Solaris Ultrix, Digital Unix (DEC/Compaq)) HP-UX Irix (SGI) SCO (Inte) UnixWare -> Novell -> SCO -> Caldera ->SCO Xenix: -> SCO OSF Standardization (Posix, X/Open, OSF-1) Coherent (RIP) UNIX Source Code License • Developed in 1960’s on DEC PDP with 6 bit hardware. Later ported to AT&T 3B hardware for automated switching systems. • Internal development continues. BSD developed at UC Berkley in mid-70’s by Ken Thompson and Bill Joy with features like “vi”, TCP/IP. • After internal and academic distribution, AT&T enters computer business in 1982-3 with System III after AT&T breakup. Commercial variants expand Sun, IBM, HP and smaller vendors. PC development leads to SCO – only Intel based commercial version. • System V and BSD continue parallel development until terminal versions AT&T SVR4 and BSD4.3 LINUX in late 1980’s. BSD “Tahoe”, “Reno” versions continue into early 90’s. • USL passws from AT&T Bell Labs, Lucent/Alcatel, Caldera, Novell (licensed to SCO) and then Attachmate and Microsoft. The SCO Story • 1980s: Started by Intel (Santa Cruz Operations). Only Intel based commercial UNIX • 1980s-1990s: Post AT&T breakup, USL changes hands several time winding up with Novell. “Licenses” USL to SCO. • March 2003: SCO sues IBM for $3 billion. Alleges contributions to Linux come from proprietary licensed code. AIX is based on System V r4, now owned by SCO? • Aug 2003: Evidence released. Some code traced to Ancient UNIX but isn’t in 90% of all running Linux distributions. Suspect code dropped from Linux in July • • • • Aug 2005: Linux Kernel Code May Have Been in SCO - 2009: Lawsuit proceeds supported by “patent trolls” 2009 – 2010: Lawsuit dismissed. Goodbye SCO. 2011: Netware dead. USL sold to Attachmate and Microsoft(?) UNIX Structure shell scripts system calls signal handler device drivers terminal disk User Space Kernel Devices utilities C programs compilers scheduler swapper printer RAM What is the kernel? • The kernel is … – a program loaded into memory during the boot process, and always stays in physical memory. – responsible for managing CPU and memory for processes, managing file systems, and interacting with devices. – The Operating System – Microkernel architecture, HAL Kernel Subsystems • Process management – Schedule processes to run on CPU – Inter-process communication (IPC) • Memory management – Virtual memory – Paging and swapping • I/O system – – – – File system Device drivers Buffer cache Network I/O, protocol stacks System Calls to OS • Interface to the kernel – microkernel level 3 • Over 1,000 system calls available on Linux • 3 main categories – File/device manipulation • e.g. mkdir(), unlink() – Process control • e.g. fork(), execve(), nice() – Information manipulation • e.g. getuid(), time() System call in code • The kernel implements a set of special routines • A user program invokes a routine in the kernel by issuing a hardware TRAP • The trap switches the CPU into a privileged mode and the kernel executes the system call • The CPU goes back to user mode • A C language API exists for all system calls Why LINUX? • • • • • • • • • • • • • “Free” open source via GPL with all the UNIX advantages Multitude of available software Multi-vendor support some even commercial level (i.e. RedHat) Desktop of the future? (see Android) Few proprietary competitors (i.e. Apple, IBM, Novell) Even fewer *NIX competitors – SCO (dead), Open/Free BSD Few viable Intel based competitors, even fewer ARM based competitors “Frozen” USL at System V R4 Proprietary UNIX hardware/software vendors falling by the wayside Convergence of hardware and software platforms Services not systems - “the cloud” New technologies – Android, Redhat, Centos, Ubuntu Basis for a lot of other proprietary technologies - database frontends, network appliances Administrivia • • • • [email protected], all day, every day. Or Division II office if necessary. See syllabus for class schedule Be on time, eat a good breakfast, it’s a long day, short lunch Check the website regularly: HTTP://www.oakton.edu/~rjtaylor and follow links. Class material always being updated. • • • • Office hour: Just after class Labs 75% of grade, attendance is a good idea Read ahead, online text, supplementary material, Internet reading assignments Acceptable Use Policy – Systems are on the school and Internet. Personal systems OK, wirelesss is unencrypted. If you wouldn’t do it in front of your mother/wife/girlfriend/kids/significant other/life partner, don’t do it here. Bad/impolitic/wife/mother-in-law/current event humor OK (see instructor), keep your politics and biases to yourself. Removeable disc procedures. • • Who cares, how do I get an A? Labs: 75% Midterm, Final: 25% Got to be there (Michael Jackson)