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

system calls

device drivers

shell scripts utilities

compilers

signal handler scheduler

swapper

terminal

disk

printer

RAM

C programs

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

• 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)