Introduction to Unix Administration• Objectives

– to identify the basic concepts of Unix administration

• Contents– history of Unix

– unix vendors and standards

– working as root

– system administration shells

• Practicals– evaluating an administration shell

• Summary

Unix

Unix - Genealogy

1969

1972

1975

1978

1981

1983

1985

1987

1989

1991

1993

1995

1

25

500

100000

2800000

5000000

Date Systems

SunOS

Amdahl UTS

Unix - PDP/7

Unix 1st edition - PDP/11

BSD

SunOS 4

SCO Unix

XENIX

Unix System V.3

AIX 3.1

Solaris 2.0

Solaris 1.0

BSD 4.2

BSD 4.3

UnixWare 2.0

BSD 4.1

AIX 4.1

AIX

Unix System III

Unix System V

UnixWare 1.0 Unix SVR4.2

Unix System V.4 - SVR4

Unix 7th edition - non PDP

Unix 5/6th edition - C

Major Unix Versions• AT&T System V

– currently release 4.2 (SVR4.2)

– most widely implemented version of Unix

• Berkeley Software Distribution (BSD)– pure BSD systems usually found as free Unix on PCs

– OSF/1 derived from BSD with SVR4 additions

HP HP/UX SVR4 + OSF/1ICL DRX SVR4SNI/Pyramid DC/OSx SVR4Silicon Graphics Inc IRIX SVR4 SCO UnixWare SVR4 Sun Microsystems Solaris 2 SVR4

SCO SCO Unix SVR3.2Sequent Dynix/PTX SVR3.2 + security

Sun Microsystems SunOS 4 BSDDEC Digital Unix OSF/1 + SVR4IBM AIX OSF/1 + SVR4

HP HP/UX SVR4 + OSF/1ICL DRX SVR4SNI/Pyramid DC/OSx SVR4Silicon Graphics Inc IRIX SVR4 SCO UnixWare SVR4 Sun Microsystems Solaris 2 SVR4

SCO SCO Unix SVR3.2Sequent Dynix/PTX SVR3.2 + security

Sun Microsystems SunOS 4 BSDDEC Digital Unix OSF/1 + SVR4IBM AIX OSF/1 + SVR4

Unix Standards• Unix has been standardised

– SVR4, OSF/1, POSIX, spec1170

– standards concentrate on kernel functionality and API

– administration not covered by standards

• Administration is similar for all Unix systems– command names can vary from one variant to another

– command options can vary

– some systems provide better support for administrators than others

• Unix administration is developing standards– Distributed Computing Environment (DCE)

– Domain Name Services (DNS)

– Common Desktop Environment (CDE)

Scope of this Course• To cover basic administrative functions

– describe underlying concepts and utilities

• Features described in a vendor independent manner– concentrate on SVR4

– reference to other systems where appropriate

• Cover common areas of administration in detail– users, processes, files & backups

– networking, terminals & printers

• Introduce less common administration– installing the system and software

– accounting & performance monitoring

• Useful commands are briefly described– use the on-line manual pages for full information

Discussion - Administration Roles• What are the typical jobs performed by a Unix System

Administrator in the following categories?

Operations Administration Technical Support

? ? ?

General Responsibilities• Identify your role and responsibilities

– can you delegate some of your work?

• Find out about your system– when was it purchased

– do you have hardware maintenance, if not why not?

– do you have OS maintenance, if not why not?

• What hardware does your system have?

• What software is installed?– is all the software necessary

• Who uses your system?

System Logbook• Keep a logbook for each system

• Record activities such as– system crashes

– maintenance,

– hardware problems

– system upgrades

– software installations

• Keep as paper copy, not an on-line copy

Working As Root• Nearly all Unix administration must be done as user root

– this superuser account (user id 0) has unrestricted access to the system

• Administration should be done by one person at a time– check that no one else is logged in as root

– if someone else is working as root, find out what they are doing

• In a secure room, keep the console logged in as root– useful for getting out of trouble if system starts to hang

– do all administration from the console

– disable root logins on other terminal lines for security

WARNING

root can irrevocably damage the system

take care when working as root

The su Command• The set user (su) command changes to another user

– runs a new shell for the new user

– exit from the new shell to resume original user's shell

• su changes your effective user id (and group id)– most commands use effective uid/gid for access control

– real uid/gid not changed

– be aware that some commands always use real uid/gid

• Root can use su without providing a password– other users must supply a password

$ su - rootpassword: work as root, with root's environment

$ su - rootpassword: work as root, with root's environment

Running Commands with su• su can be used to run a command as another user

– Use the -c option to specify a "command string"

– useful for including in shell scripts

• su defaults are in /root/.bash_profile– it it usual for root to have a separate su path

• su attempts are logged in /var/log/messages

• Permission file: /etc/sudoers tell who is allowed to su

• Permission file is edited with command visudo

# /bin/su - printer -c “cleanup”run the printer cleanup script

# /bin/su - printer -c “cleanup”run the printer cleanup script

# more /root/.bash_profile# more /root/.bash_profile

Exercise - Using su• What do the following commands do and which ones require

a password?

$ su

# su - henry

$ su -

# su - root -c poweroff

# exit

$ su root -c "rm /tmp/.lock321"

$ su

# su - henry

$ su -

# su - root -c poweroff

# exit

$ su root -c "rm /tmp/.lock321"

Traditional Administration

• Traditionally, Unix administration requires a good knowledge of the Unix operating system

• Administrators work directly with configuration files and special programs

• Administrators develop or borrow extra programs and scripts to support standard utilities

• Difficult for novice administrators even to get started...

Administration Shells• System manufacturers often provide menu driven

administration interfaces– some are better than others– some only work under X-Windows

• Admin shells are not as comprehensive as one would like– Unix administrators still need to know about underlying commands

• smit on AIX is awarded to be the most friendly and comprehensive front end to administration

Linux WebMin httpSuSE YaST tty & XAIX SMIT tty & XDigital Unix setup ttyHP/UX SAM XIRIX Cadmin XSCO Unix sysadmsh ttySolaris 2 admintool XSVR4 sysadm tty

Linux WebMin httpSuSE YaST tty & XAIX SMIT tty & XDigital Unix setup ttyHP/UX SAM XIRIX Cadmin XSCO Unix sysadmsh ttySolaris 2 admintool XSVR4 sysadm tty

Summary

• Unix administration is similar but not identical for all systems

• Unix administrators tend to learn a lot about how Unix works

• Nearly all administration is undertaken as the superuser (root)

• Administration shells such as sysadm or SMIT can simplify Unix for novice administrators

• Use the su command to run a shell as another user

• When you know one Unix system you can easly learn all other dialects.

• SuSE uses yast and yast2 for most common admin work.