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 User Space Kernel Devices shell scripts utilities C programs system calls compilers signal handler scheduler Kernel device drivers swapper terminal printer Devices disk 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 Memory management I/O system 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 rjtaylor@oakton.edu, 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)