Introduction to Unix Administration

1. 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

2. Unix - PDP/7 Unix 1st edition - PDP/11 BSD Unix System III BSD 4.1 XENIX Amdahl UTS Unix System V BSD 4.2 SCO Unix BSD 4.3 AIX Unix System V.3 SunOS 4 AIX 3.1 Solaris 1.0 UnixWare 1.0 Unix SVR4.2 Solaris 2.0 AIX 4.1 UnixWare 2.0 Unix - Genealogy Systems Date 1969 1972 1975 1978 1981 1983 1985 1987 1989 1991 1993 1995 1 25 500 100000 2800000 5000000 Unix 5/6th edition - C Unix 7th edition - non PDP SunOS Unix System V.4 - SVR4

3. 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/1 ICL DRX SVR4 SNI/Pyramid DC/OSx SVR4 Silicon Graphics Inc IRIX SVR4 SCO UnixWare SVR4 Sun Microsystems Solaris 2 SVR4 SCO SCO Unix SVR3.2 Sequent Dynix/PTX SVR3.2 + security Sun Microsystems SunOS 4 BSD DEC Digital Unix OSF/1 + SVR4 IBM AIX OSF/1 + SVR4

4. 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)

5. 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

6. Discussion - Administration Roles • What are the typical jobs performed by a Unix System Administrator in the following categories? Operations Administration Technical Support ? ? ?

7. 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?

8. 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

9. 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

10. 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 - root password: work as root, with root's environment

11. 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 # more /root/.bash_profile

12. 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"

13. 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...

14. 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 http SuSE YaST tty & X AIX SMIT tty & X Digital Unix setup tty HP/UX SAM X IRIX Cadmin X SCO Unix sysadmsh tty Solaris 2 admintool X SVR4 sysadm tty

15. 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.