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 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 1.0Unix 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 HPHP/UXSVR4 + OSF/1 ICLDRXSVR4 SNI/PyramidDC/OSxSVR4 Silicon Graphics IncIRIXSVR4 SCOUnixWareSVR4 Sun MicrosystemsSolaris 2SVR4 SCOSCO UnixSVR3.2 SequentDynix/PTXSVR3.2 + security Sun MicrosystemsSunOS 4BSD DECDigital UnixOSF/1 + SVR4 IBMAIXOSF/1 + SVR4 HPHP/UXSVR4 + OSF/1 ICLDRXSVR4 SNI/PyramidDC/OSxSVR4 Silicon Graphics IncIRIXSVR4 SCOUnixWareSVR4 Sun MicrosystemsSolaris 2SVR4 SCOSCO UnixSVR3.2 SequentDynix/PTXSVR3.2 + security Sun MicrosystemsSunOS 4BSD DECDigital UnixOSF/1 + SVR4 IBMAIXOSF/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? OperationsAdministrationTechnical 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 - root password: work as root, with root's environment $ su - root password: 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

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 LinuxWebMinhttp SuSEYaSTtty & X AIXSMITtty & X Digital Unixsetuptty HP/UXSAMX IRIXCadminX SCO Unixsysadmshtty Solaris 2admintoolX SVR4sysadmtty LinuxWebMinhttp SuSEYaSTtty & X AIXSMITtty & X Digital Unixsetuptty HP/UXSAMX IRIXCadminX SCO Unixsysadmshtty Solaris 2admintoolX SVR4sysadmtty

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.