Some history PDP versions BSD/Version 7 split VAX virtual memory implementations End of line 4.4 BSD System V merges Modern versions OSF/1, Solaris, HPUX 10 Standards

Jobs to do Add users Backup filespace User support Update software/install new System Security Performance issues Networking problems

Tools for the job ps – shows what is going on df – disc space usage netstat – network activity su – gain admin rights kill – delete a process + thought to understand why a situation has happened.

GUI’s make life easy … HPUX – SAM is a mature product Linux – –usrcfg –netcfg –rpm GUI’s can bring benefits –single machines –less understanding needed –does not help with a lot of machines

File Systems removable media –floppies –CDs discs –mount’ing – usually at startup but things may go wrong –fsck’ing - done automatically unless disc is corrupt –lost+found – where the damaged files are dropped

Files ls – modes drwxrwxrwx + t,c,b chmod – {o,g,o,a} +/- {r,w,x} –symbolic safer than numeric hidden files umask – default mode (777 – umask value) ln and ln –s

Where things live /sbin – files needed at boot time /usr/sbin – files used only by the administrator /bin and /usr/bin – main place for applications for users /etc – configuration files /dev – device file (the Unix view of the world is everything looks like a file)

How processes run command looked up in PATH –take care of order of search – this is a security risk –can also bring performance issues fork and exec –child – parent relationship for communications (or use sockets) –exit and zombies –signals (eg HUP)

More essential tools grep awk sed all subsumed into PERL –scripting version of C –wide platform availability

Starting up the machine boot process (prom to disc) single user multi-user levels –inittab –shutdown lilo –configuration of PC for multiple OS’s

Scripts in charge /etc/rc – things to do at startup now more complicated –/etc/rc? when ? is the level –/etc/rc?.d directory holding many scripts –S??name – run at startup –K??name – run at shutdown

Users and groups uid is the Unix security token groups allow sharing passwords should not be guessable –ageing –shadow files shell – bash home directory becoming another person –su - name

Backups What should be backed up? –configuration files –users files Frequency of backup –logically after every change –practically as often as can Where too? –somewhere safe! –multiple tapes in multiple locations

Restoring Need to have organised backups Takes a lot of time Educate users to use RCS Using a good backup system will automate this.

The network Security issues –no telling where a connection is from, just know last hop Services you run –keep to a minimum –keep them logged Are you protected? –block connections to certain ports –block connections from certain sites ssh rather than telnet

Printing and printers networked or hardwired –networked are dearer but simpler to manage spool machine needed – with free disc space printers break down a lot printers need a lot of consumables

What if disaster strikes corrupt kernel –have a backup kernel especially if you reconfigure the machine damaged files stop booting –have a alternative boot method – perhaps CD hackers break-in –use something like tripwire –info.cert.org –you will be down a long time

Books etc O’Reilly Guides –Essential System Administration (Frisch) –Practical Unix Security (Garfinkel/Spafford) –Programming Perl (Wall/Christiansen/Schwartz) Unix manuals for command News groups (low signal to noise) Go on a course or two!