CS 550: Comparative Operating System Saie MulayCS 550COMPARATIVE OPERATING SYSTEMAMOEBA - A DISTRIBTED O!ERATI"# S$STEMSu%mitte& %y: SAIE M'A$SID: (5) )* +((),CS 550: Comparative Operating System Saie MulayCO"TE"TSABSTRACT-----------------------.-. (I"TRODCTIO"----------------------. (/0AT IS AMOEBA1--------------------.. 2ARC0ITECTRE----------------------. 20ARD/ARE ARC0ITECTRE----------------. 2SO3T/ARE ARC0ITECTRE----------------- 4DESI#" #OA'S A"D C0IE3 DESI#" 3EATRES--------. 5!ROTECTIO" A"D CA!ABI'ITIES--------------. )3I'E S$STEM------------------------. ,,!ROCESS MA"A#EME"T------------------- ,+MAC0I"ES O" /0IC0 AMOEBA R"S------------... ,(!RICI"#--------------------------... ,(CO"C'SIO"------------------------.. ,2+CS 550: Comparative Operating System Saie MulayAbstract:T6is paper attempts to &es7ri%e a &istri%ute& operating system 7alle& Amoe%a8 9it6 spe7ial re:eren7e to its 6ar&9are ar76ite7ture8 so:t9are ar76ite7ture8 :ile system an& pro7ess management. /e also stu&y t6e &esign goals an& 76ie: &esign :eatures in %rie:.Apart :rom t6ese I 6ave also &es7ri%e& prote7tion an& 7apa%ilities o: Amoe%a.Introduction:/e 7an &ivi&e t6e 6istory o: mo&ern 7omputing into t6e :ollo9ing eras: ,)40;s: Times6aring ,0,, se7on&s8 or a%out *8(00 years. T6e same argument 7an %e applie& to t6e 25-%it server port i&enti:ier8 to s6o9 t6at a pro7ess not @no9ing t6e target pro7ess;s port i&enti:ier is 6ig6ly unli@ely to su77ee& in guessing itusing %rute :or7e.A maCor &isa&vantage o: 7apa%ilities is t6at t6ey &o not solve pro%lems o: eaves&ropping an& replaying: an intru&er 7an e>amine messages %eing sent over t6e net9or@8 an& 7opy 7apa%ilities ample: I: Smit6 an& Lones 6ave ea76 %een given 7apa%ilities to a77ess a 7ertain :ile8 6o9 is it possi%le to retra7t Lones;s rig6ts to a77ess t6e :ile8 %ut not Smit6;s1 T6e only 9ay is :or t6e server to asso7iate a &i::erent set o: 7apa%ilities 9it6 t6e :ile8 an& to give a ne9 7apa%ility to Smit68 %ut to ensure t6at it is not given to Lones. 0o9ever8 i: Smit6 &e7i&es ,0CS 550: Comparative Operating System Saie Mulayto grant a77ess to t6e :ile to Lones8 t6en s6e 6as only to pass t6e 7apa%ility to Lones8 t6us t69arting t6e o9ner;s 9is6es.%i,! S*st!:"aming in t6e Amoe%a operating system is an intrinsi7 part o: t6e o%Ce7t 7apa%ilities. T6is is a%stra7te&8 6o9ever :or users. T6ere is an e>tra level o: mapping :rom sym%oli78 6ierar76i7al pat6 names to 7apa%ilities. T6roug6 t6is system a user sees lo7al o%Ce7ts as 9ell as pu%li7 o%Ce7ts.T6is also provi&es a user a77ess system t6at 7an %e relate& to ni>;s. Mem%ers o: a groupmay %e given 7apa%ility o: a &ire7tory. All ot6ers are not given t6e 7apa%ility o: t6e &ire7tory. T6us only mem%ers o: t6e group 7an see t6e &ire7tory. T6e o%Ce7t property o: &ire7tories also ensures t6e 6ierar76i7al properties o: &ire7tories t6roug6 t6eir 7apa%ilities. In reality &ire7tories are nameB7apa%ility pairs.In t6e implementation o: an Amoe%a operating system in Amster&am8 t6e :ile server use& is t6e %ullet :ile servi7e. It supports t6ree operations: rea& :ile8 7reate :ile8 an& &elete :ile.Sin7e no 9rite :ile is supporte&8 96en a :ile is 7reate& all in:ormation in7lu&ing si?e an& nameB7apa%ility must %e provi&e&. 3iles 7annot %e 76ange& on7e t6ey are 7reate&. T6is ma@es :or a relia%ility 7onvenien7e. Sin7e :iles &on;t 76ange t6e :ile server may %a7@ up at any time. 'astly8 t6is means t6at :ile store& 7ontiguously. T6e %ullet :ile server is %ot6 e::i7ient at :ile storage an& is 6ig6 per:orman7e &is@ &rive.Relia%ility an& se7urity rely 6eavily on t6e &ire7tory servi7e. All t6e internal ta%les are repli7ate& so t6at t6e loss o: a no&e 7an;t 7ause a system 6alt %e7ause it 6as no &ire7tory servi7e. T6e &ire7tory servi7e also :un7tions to grant or &eny a77ess &epen&ing on 7apa%ilities.,,CS 550: Comparative Operating System Saie MulayImplemente& in t6e &ire7tory servi7e8 is &ire7tory prote7tion. An en7ryption @ey is generate& an& t6en e>7lusive-ORe& 9it6 a ran&om num%er. T6is result is store& along si&e t6e &ire7tory an& t6e ran&om num%er put in t6e &ire7tory;s 7apa%ility. 3inally t6e 7apa%ility is given to t6e o9ner an& t6e &ire7tory servi7e K:orgetsH t6e ran&om num%er. /6en a 7lient ma@es a reEuest :or an operation on t6e &ire7tory8 t6e ran&om num%er8 96i76 is store& in t6e 7apa%ility8 is re7eive& %y t6e &ire7tory servi7e. T6e &ire7tory servi7e 7an t6en &e7rypt t6e &ire7tory.T6e &ire7tory servi7e is also responsi%le :or %a7@up o: t6e :ile system. T6e :a7t t6at :iles are immuta%le means t6at in:ormation t6at is 7a76e& %y t6e &ire7tory servi7e never %e7omes out&ate&. Immuta%le :iles8 in a&&ition8 are a spee& issue8 %e7ause o: 7a76ing8 see@ing8 an& 7ontiguousness.Proc!ss Mana&!!nt:In Amoe%a pro7ess 6ave a segmente& virtual a&&ress. T6ese pro7esses may 6ave one or more t6rea&s. T6rea&s are allo7ate& to pro7essors until all pro7essors are use&. T6e resulting pro7ess management me76anism provi&es :or %etter utili?ation o: pro7essor 7y7les %y minimi?ing 7onte>t s9it76ing among more 6eavy9eig6t pro7esses8 ea76 o: 96i76 9oul& o77upy an entire a&&ress spa7e. !ro7esses 7ontrol t6eir a&&ress spa7e. T6ey may a&& or remove segments :rom t6eir virtual a&&ress spa7e t6roug6 a mapping operation. A :ile-li@e o%Ce7t 7ontains a 7apa%ility8 an& is rea&y %y t6e @ernel an&8 i: t6e pro7ess is allo9e&8 it 7an t6en map or unmap segments :or its virtual a&&ress spa7e.To 7reate a pro7ess8 a pro7ess &es7riptor is sent to t6e @ernel. T6is is @no9n as t6e e>e7ute pro7ess reEuest. A pro7ess &es7riptor 7ontains t6e 6ost &es7riptor8 t6e pro7ess 7apa%ility8 t6e 6an&ler 7apa%ility an& num%er o: segments. ,+CS 550: Comparative Operating System Saie MulayT6e 6ost &es7riptor 7ontains t6e in:ormation a%out 96at @in& o: system t6e potential pro7ess 7an %e run on. T6is in7lu&es instru7tion set8 memory nee&s8 ma76ine 7lass in:ormation8 et7. T6e @ernel must mat76 t6e 6ost &es7riptor to 7ontinue.T6e pro7ess 7apa%ility is t6e integral part o: t6e pro7ess8 saying 96at 7an %e &one to an& %y t6e pro7ess8 as 9ell as %y 96om. T6e 6an&ler 7apa%ility is similar8 %ut its 7apa%ilities are :or a%normal pro7ess a7tions.!ro7ess a&&ress is en7apsulate& in an internal memory map. T6is map 6as an entry :or every segment o: a&&ress :or a potential pro7ess. An entry 7ontains t6e virtual a&&ress8 segment lengt68 segment mapping8 an& 7apa%ility o: t6e o%Ce7t :rom 96i76 t6e segment isinitiali?e&.T6ere is also a t6rea& map t6at &es7ri%es ot6er attri%utes. T6ese in7lu&e initial state o: t6rea&8 pro7essor status8 program 7ounter8 sta7@ pointer8 t6e sta7@ %ase8 register values8 an& t6e system 7all state. T6is allo9s :or pro7ess &es7riptor to %e use& on pro7esses.!ro7esses 6ave t9o possi%le states in t6e Amoe%a operating system. T6ese are running or stunne&. T6e stunne& state is 96en a pro7ess e>ists8 &oes not6ing in t6e sense o: e>e7ution8 an& is %eing &e%ugge&. /6en a pro7ess is stunne& t6e @ernel tells all attempte& 7ommuni7ators