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Some history

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

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Some history

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  1. 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

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

  3. 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.

  4. 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

  5. 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

  6. 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

  7. 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)

  8. 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)

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

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

  11. 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

  12. 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

  13. 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

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

  15. 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

  16. 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

  17. 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

  18. 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!

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