BESTURINGSSYSTEMEN
Academiejaar 2018 - 2019
Jakob Lierman
HoGent
,Jakob Lierman Besturingssystemen
Inhoud
INLEIDING .................................................................................................................................................. 8
WAT IS LINUX ........................................................................................................................................................... 8
AAN DE SLAG MET LINUX ............................................................................................................................................ 8
De terminal ...................................................................................................................................................... 8
Het Linux bestandssysteem.............................................................................................................................. 8
Oriëntatie in het bestandssysteem .................................................................................................................. 8
Met de shell leren werken ................................................................................................................................ 8
Enkele commando’s ....................................................................................................................................................... 8
Hulp (man pages) ........................................................................................................................................... 10
WAT IS EEN BESTURINGSSYSTEEM ............................................................................................................................... 10
Functies .......................................................................................................................................................... 10
Historisch overzicht ........................................................................................................................................ 10
Soorten besturingssystemen .......................................................................................................................... 11
Single-tasking ............................................................................................................................................................... 11
Multitasking (single-user) ............................................................................................................................................ 11
Multi-user-systemen .................................................................................................................................................... 11
Virtuele machines ........................................................................................................................................................ 12
Concepten van besturingssystemen .............................................................................................................. 12
Proces........................................................................................................................................................................... 12
Resources ..................................................................................................................................................................... 12
Concurrency ................................................................................................................................................................. 12
Ontwerp-criteria .......................................................................................................................................................... 13
Compromissen ............................................................................................................................................................. 13
SCHEDULING ............................................................................................................................................ 14
2
,Jakob Lierman Besturingssystemen
NOODZAAK TOT SCHEDULING..................................................................................................................................... 14
DOELSTELLINGEN VAN SCHEDULING ............................................................................................................................ 14
UITVOEREN VAN EEN PROCES ..................................................................................................................................... 15
SYSTEEMBEELD VAN EEN PROCES ................................................................................................................................ 16
Procestoestand-diagram................................................................................................................................ 17
Procestoestanden ........................................................................................................................................................ 17
Toestandsovergangen.................................................................................................................................................. 17
Process Control Blocks (PCB) .......................................................................................................................... 18
Niveaus van scheduling.................................................................................................................................. 18
STRATEGIEËN VOOR LOW-LEVEL SCHEDULING................................................................................................................ 18
Round Robin scheduling (RR) ......................................................................................................................... 19
First-In-First-Out scheduling (FIFO) of First-Come-First-Served scheduling (FCFS) ........................................ 19
Multilevel feedback queues (MFQ) ................................................................................................................ 20
Shortest-Job-First scheduling (SJF) ................................................................................................................. 20
Starvation....................................................................................................................................................... 21
Samenvatting strategieën low-level scheduling ............................................................................................ 21
SCRIPTING IN LINUX ................................................................................................................................. 22
INLEIDING .............................................................................................................................................................. 22
Eigenschappen van een goed script ............................................................................................................... 22
Structuur van een shell script ......................................................................................................................... 22
Instructies bovenaan het script ................................................................................................................................... 22
Debuggen van een bash script ....................................................................................................................... 22
VARIABELEN EN PARAMETERS .................................................................................................................................... 23
Variabele koppelen ........................................................................................................................................ 23
Variabele aanroepen...................................................................................................................................... 23
3
,Jakob Lierman Besturingssystemen
Soorten variabelen ......................................................................................................................................... 23
Constanten ................................................................................................................................................................... 23
Lokale variabelen ......................................................................................................................................................... 23
Omgevingsvariabelen .................................................................................................................................................. 23
Shell-variabelen ........................................................................................................................................................... 24
Werken met invoer......................................................................................................................................... 24
Positionele parameters ................................................................................................................................................ 24
Speciale parameters .................................................................................................................................................... 24
Commando substitution................................................................................................................................. 25
REGULIERE EXPRESSIES ............................................................................................................................................. 25
PROGRAMMEERBARE FILTERS .................................................................................................................................... 26
SED: Stream EDitor......................................................................................................................................... 26
Substitutieopdrachten.................................................................................................................................... 27
FLOW-CONTROL ...................................................................................................................................................... 28
Exit-status, exit............................................................................................................................................... 28
Return en test................................................................................................................................................. 28
File testers.................................................................................................................................................................... 29
File comparisons .......................................................................................................................................................... 30
String tests ................................................................................................................................................................... 30
Integer tests - operators .............................................................................................................................................. 30
If then else ...................................................................................................................................................... 30
Case ................................................................................................................................................................ 31
For .................................................................................................................................................................. 31
While / until ................................................................................................................................................... 31
REKENEN IN EEN SCRIPT ............................................................................................................................................ 32
FUNCTIES ............................................................................................................................................................... 32
4
,Jakob Lierman Besturingssystemen
Waarden uit functie teruggeven .................................................................................................................... 32
OPTIES .................................................................................................................................................................. 33
Manueel parsen ............................................................................................................................................. 33
Grep parsen.................................................................................................................................................... 33
Getopts parsen ............................................................................................................................................... 34
CONCURRENCY – PARALLELLE PROCESSEN................................................................................................. 35
WAT IS CONCURRENCY? ........................................................................................................................................... 35
WEDERZIJDSE UITSLUITINGEN (MUTUAL EXCLUSION) ...................................................................................................... 35
Concurrency met meerdere processors ......................................................................................................... 35
Concurrency met één processor ..................................................................................................................... 35
Wederzijdse uitsluiting................................................................................................................................... 36
PROGRAMMEREN VAN WEDERZIJDSE UITSLUITINGEN ...................................................................................................... 36
Eerste poging ................................................................................................................................................. 36
Tweede poging ............................................................................................................................................... 36
Derde poging.................................................................................................................................................. 36
ALGORITME VAN DEKKER .......................................................................................................................................... 37
ALGORITME VAN PETERSON ...................................................................................................................................... 38
SEMAFOREN ........................................................................................................................................................... 39
Inleiding.......................................................................................................................................................... 39
Sterke semaforen ........................................................................................................................................... 41
Implementatie semaforen ............................................................................................................................. 43
MONITOREN .......................................................................................................................................................... 44
SYNCHRONISATIE ..................................................................................................................................................... 44
DEADLOCK ............................................................................................................................................................. 44
Aspecten van deadlock .................................................................................................................................. 45
5
,Jakob Lierman Besturingssystemen
Preventie ...................................................................................................................................................................... 45
Vermijding .................................................................................................................................................................... 45
Signalering.................................................................................................................................................................... 45
Herstel .......................................................................................................................................................................... 45
THREADS ............................................................................................................................................................... 46
PROCESSEN IN LINUX ................................................................................................................................ 47
WAT IS EEN PROCES? ............................................................................................................................................... 47
SOORTEN PROCESSEN ............................................................................................................................................... 47
Interactieve processen ................................................................................................................................... 47
Automatische (batch) processen ................................................................................................................... 47
Daemons ........................................................................................................................................................ 47
BACKGROUND ........................................................................................................................................................ 47
EIGENSCHAPPEN ..................................................................................................................................................... 48
INFORMATIE WEERGEVEN ......................................................................................................................................... 48
Korte info........................................................................................................................................................ 48
Uitgebreide info ............................................................................................................................................. 48
top commando ............................................................................................................................................... 49
pstree commando .......................................................................................................................................... 49
PROCESSEN BEHEREN ............................................................................................................................................... 49
Prioriteit veranderen ...................................................................................................................................... 50
PROCESSEN ONDERBREKEN........................................................................................................................................ 50
kill commando ................................................................................................................................................ 50
xkill commando .............................................................................................................................................. 50
PROCESSEN PROGRAMMEREN VOOR AUTOMATISCHE UITVOERING .................................................................................... 50
LEVENSCYCLUS ........................................................................................................................................................ 51
6
,Jakob Lierman Besturingssystemen
Proces aanmaken ........................................................................................................................................... 51
systemd .......................................................................................................................................................... 51
Proces beëindigen .......................................................................................................................................... 51
7
,Jakob Lierman Besturingssystemen
Inleiding
Wat is Linux
Besturingssysteem ontwikkeld vanuit UNIX door Linus Torvalds.
Aan de slag met Linux
De terminal
# commando [-opties] [argument(en)]
# Bijvoorbeeld:
ls -l /etc
Het Linux bestandssysteem
Oriëntatie in het bestandssysteem
Absoluut pad: start vanaf de root en begint met een slash (/).
Relatief pad: start vanaf de huidige map.
Met de shell leren werken
Een shell is een programma dat wordt opgestart in een terminal venster.
Enkele commando’s
Werken met mappen:
8
,Jakob Lierman Besturingssystemen
# Map aanmaken (meerdere namen mag)
mkdir
# Map verwijderen (enkel lege mappen) (meerdere namen mag)
rmdir
Werken met tekstbestanden:
# Laat de inhoud van een tekstbestand over het scherm lopen
cat
# Toon tekst in omgekeerde volgorde
tac
# Laat toe om de tekst scherm per scherm te bekijken
less
# Toont de eerste 10 lijnen
head
# Toont de laatste 10 lijnen
tail
# Tekstbestanden aanmaken
touch bestand1 bestand2
# Bestanden kopiëren
cp bronmap/bronbestand doelmap/doelbestand
# Enkele opties:
# -r recursive
# -v verbose
# Bestanden verplaatsen
mv bronmap/bronbestand doelmap/doelbestand
# Enkele opties:
# -i interactive
# -v verbose
# -f force
# Bestanden verwijderen
rm map/bestand
# Enkele opties:
# -r recursive
# -v verbose
Tekst zoeken in bestanden:
grep [opties] tekenreeks [bestanden]
# Enkele opties:
# -i --ignore-case
# -n --line-number
# -s --silent
9
, Jakob Lierman Besturingssystemen
Zoeken:
# Zoeken op bestandsnaam
locate bestandsnaam
find zoekmap zoekoptie(s) [tests] [acties]
# Zoeken naar commando’s
which commandonaam
Hulp (man pages)
# Man page opvragen
man commando
Vaak ook bij het commando beschikbaar als optie --help.
Wat is een besturingssysteem
Besturingssysteem = programma dat het mogelijk maakt de hardware van een computer te
gebruiken.
Functies
- Opslaan en ophalen van informatie
- Programma’s afschermen
- Gegevensstroom regelen
- Prioriteiten regelen
- Het mogelijk maken om bronnen te delen
- Tijdelijke samenwerking tussen onafhankelijke programma’s mogelijk maken
- Reageren op fouten
- Tijdsplanning maken
Historisch overzicht
1e computers → Geen OS
Jaren 50 → Eenvoudig OS:
- Sequentieel opladen & opstarten v programma’s
- Alle bronnen bruikbaar door slechts 1 programma
Begin jaren 60 → Geavanceerder OS:
- Verscheidene programma’s konden tegelijk opgeslagen worden in geheugen
- Beurtelingse uitvoering programma’s
- Gemeenschappelijke bronnen
10
Academiejaar 2018 - 2019
Jakob Lierman
HoGent
,Jakob Lierman Besturingssystemen
Inhoud
INLEIDING .................................................................................................................................................. 8
WAT IS LINUX ........................................................................................................................................................... 8
AAN DE SLAG MET LINUX ............................................................................................................................................ 8
De terminal ...................................................................................................................................................... 8
Het Linux bestandssysteem.............................................................................................................................. 8
Oriëntatie in het bestandssysteem .................................................................................................................. 8
Met de shell leren werken ................................................................................................................................ 8
Enkele commando’s ....................................................................................................................................................... 8
Hulp (man pages) ........................................................................................................................................... 10
WAT IS EEN BESTURINGSSYSTEEM ............................................................................................................................... 10
Functies .......................................................................................................................................................... 10
Historisch overzicht ........................................................................................................................................ 10
Soorten besturingssystemen .......................................................................................................................... 11
Single-tasking ............................................................................................................................................................... 11
Multitasking (single-user) ............................................................................................................................................ 11
Multi-user-systemen .................................................................................................................................................... 11
Virtuele machines ........................................................................................................................................................ 12
Concepten van besturingssystemen .............................................................................................................. 12
Proces........................................................................................................................................................................... 12
Resources ..................................................................................................................................................................... 12
Concurrency ................................................................................................................................................................. 12
Ontwerp-criteria .......................................................................................................................................................... 13
Compromissen ............................................................................................................................................................. 13
SCHEDULING ............................................................................................................................................ 14
2
,Jakob Lierman Besturingssystemen
NOODZAAK TOT SCHEDULING..................................................................................................................................... 14
DOELSTELLINGEN VAN SCHEDULING ............................................................................................................................ 14
UITVOEREN VAN EEN PROCES ..................................................................................................................................... 15
SYSTEEMBEELD VAN EEN PROCES ................................................................................................................................ 16
Procestoestand-diagram................................................................................................................................ 17
Procestoestanden ........................................................................................................................................................ 17
Toestandsovergangen.................................................................................................................................................. 17
Process Control Blocks (PCB) .......................................................................................................................... 18
Niveaus van scheduling.................................................................................................................................. 18
STRATEGIEËN VOOR LOW-LEVEL SCHEDULING................................................................................................................ 18
Round Robin scheduling (RR) ......................................................................................................................... 19
First-In-First-Out scheduling (FIFO) of First-Come-First-Served scheduling (FCFS) ........................................ 19
Multilevel feedback queues (MFQ) ................................................................................................................ 20
Shortest-Job-First scheduling (SJF) ................................................................................................................. 20
Starvation....................................................................................................................................................... 21
Samenvatting strategieën low-level scheduling ............................................................................................ 21
SCRIPTING IN LINUX ................................................................................................................................. 22
INLEIDING .............................................................................................................................................................. 22
Eigenschappen van een goed script ............................................................................................................... 22
Structuur van een shell script ......................................................................................................................... 22
Instructies bovenaan het script ................................................................................................................................... 22
Debuggen van een bash script ....................................................................................................................... 22
VARIABELEN EN PARAMETERS .................................................................................................................................... 23
Variabele koppelen ........................................................................................................................................ 23
Variabele aanroepen...................................................................................................................................... 23
3
,Jakob Lierman Besturingssystemen
Soorten variabelen ......................................................................................................................................... 23
Constanten ................................................................................................................................................................... 23
Lokale variabelen ......................................................................................................................................................... 23
Omgevingsvariabelen .................................................................................................................................................. 23
Shell-variabelen ........................................................................................................................................................... 24
Werken met invoer......................................................................................................................................... 24
Positionele parameters ................................................................................................................................................ 24
Speciale parameters .................................................................................................................................................... 24
Commando substitution................................................................................................................................. 25
REGULIERE EXPRESSIES ............................................................................................................................................. 25
PROGRAMMEERBARE FILTERS .................................................................................................................................... 26
SED: Stream EDitor......................................................................................................................................... 26
Substitutieopdrachten.................................................................................................................................... 27
FLOW-CONTROL ...................................................................................................................................................... 28
Exit-status, exit............................................................................................................................................... 28
Return en test................................................................................................................................................. 28
File testers.................................................................................................................................................................... 29
File comparisons .......................................................................................................................................................... 30
String tests ................................................................................................................................................................... 30
Integer tests - operators .............................................................................................................................................. 30
If then else ...................................................................................................................................................... 30
Case ................................................................................................................................................................ 31
For .................................................................................................................................................................. 31
While / until ................................................................................................................................................... 31
REKENEN IN EEN SCRIPT ............................................................................................................................................ 32
FUNCTIES ............................................................................................................................................................... 32
4
,Jakob Lierman Besturingssystemen
Waarden uit functie teruggeven .................................................................................................................... 32
OPTIES .................................................................................................................................................................. 33
Manueel parsen ............................................................................................................................................. 33
Grep parsen.................................................................................................................................................... 33
Getopts parsen ............................................................................................................................................... 34
CONCURRENCY – PARALLELLE PROCESSEN................................................................................................. 35
WAT IS CONCURRENCY? ........................................................................................................................................... 35
WEDERZIJDSE UITSLUITINGEN (MUTUAL EXCLUSION) ...................................................................................................... 35
Concurrency met meerdere processors ......................................................................................................... 35
Concurrency met één processor ..................................................................................................................... 35
Wederzijdse uitsluiting................................................................................................................................... 36
PROGRAMMEREN VAN WEDERZIJDSE UITSLUITINGEN ...................................................................................................... 36
Eerste poging ................................................................................................................................................. 36
Tweede poging ............................................................................................................................................... 36
Derde poging.................................................................................................................................................. 36
ALGORITME VAN DEKKER .......................................................................................................................................... 37
ALGORITME VAN PETERSON ...................................................................................................................................... 38
SEMAFOREN ........................................................................................................................................................... 39
Inleiding.......................................................................................................................................................... 39
Sterke semaforen ........................................................................................................................................... 41
Implementatie semaforen ............................................................................................................................. 43
MONITOREN .......................................................................................................................................................... 44
SYNCHRONISATIE ..................................................................................................................................................... 44
DEADLOCK ............................................................................................................................................................. 44
Aspecten van deadlock .................................................................................................................................. 45
5
,Jakob Lierman Besturingssystemen
Preventie ...................................................................................................................................................................... 45
Vermijding .................................................................................................................................................................... 45
Signalering.................................................................................................................................................................... 45
Herstel .......................................................................................................................................................................... 45
THREADS ............................................................................................................................................................... 46
PROCESSEN IN LINUX ................................................................................................................................ 47
WAT IS EEN PROCES? ............................................................................................................................................... 47
SOORTEN PROCESSEN ............................................................................................................................................... 47
Interactieve processen ................................................................................................................................... 47
Automatische (batch) processen ................................................................................................................... 47
Daemons ........................................................................................................................................................ 47
BACKGROUND ........................................................................................................................................................ 47
EIGENSCHAPPEN ..................................................................................................................................................... 48
INFORMATIE WEERGEVEN ......................................................................................................................................... 48
Korte info........................................................................................................................................................ 48
Uitgebreide info ............................................................................................................................................. 48
top commando ............................................................................................................................................... 49
pstree commando .......................................................................................................................................... 49
PROCESSEN BEHEREN ............................................................................................................................................... 49
Prioriteit veranderen ...................................................................................................................................... 50
PROCESSEN ONDERBREKEN........................................................................................................................................ 50
kill commando ................................................................................................................................................ 50
xkill commando .............................................................................................................................................. 50
PROCESSEN PROGRAMMEREN VOOR AUTOMATISCHE UITVOERING .................................................................................... 50
LEVENSCYCLUS ........................................................................................................................................................ 51
6
,Jakob Lierman Besturingssystemen
Proces aanmaken ........................................................................................................................................... 51
systemd .......................................................................................................................................................... 51
Proces beëindigen .......................................................................................................................................... 51
7
,Jakob Lierman Besturingssystemen
Inleiding
Wat is Linux
Besturingssysteem ontwikkeld vanuit UNIX door Linus Torvalds.
Aan de slag met Linux
De terminal
# commando [-opties] [argument(en)]
# Bijvoorbeeld:
ls -l /etc
Het Linux bestandssysteem
Oriëntatie in het bestandssysteem
Absoluut pad: start vanaf de root en begint met een slash (/).
Relatief pad: start vanaf de huidige map.
Met de shell leren werken
Een shell is een programma dat wordt opgestart in een terminal venster.
Enkele commando’s
Werken met mappen:
8
,Jakob Lierman Besturingssystemen
# Map aanmaken (meerdere namen mag)
mkdir
# Map verwijderen (enkel lege mappen) (meerdere namen mag)
rmdir
Werken met tekstbestanden:
# Laat de inhoud van een tekstbestand over het scherm lopen
cat
# Toon tekst in omgekeerde volgorde
tac
# Laat toe om de tekst scherm per scherm te bekijken
less
# Toont de eerste 10 lijnen
head
# Toont de laatste 10 lijnen
tail
# Tekstbestanden aanmaken
touch bestand1 bestand2
# Bestanden kopiëren
cp bronmap/bronbestand doelmap/doelbestand
# Enkele opties:
# -r recursive
# -v verbose
# Bestanden verplaatsen
mv bronmap/bronbestand doelmap/doelbestand
# Enkele opties:
# -i interactive
# -v verbose
# -f force
# Bestanden verwijderen
rm map/bestand
# Enkele opties:
# -r recursive
# -v verbose
Tekst zoeken in bestanden:
grep [opties] tekenreeks [bestanden]
# Enkele opties:
# -i --ignore-case
# -n --line-number
# -s --silent
9
, Jakob Lierman Besturingssystemen
Zoeken:
# Zoeken op bestandsnaam
locate bestandsnaam
find zoekmap zoekoptie(s) [tests] [acties]
# Zoeken naar commando’s
which commandonaam
Hulp (man pages)
# Man page opvragen
man commando
Vaak ook bij het commando beschikbaar als optie --help.
Wat is een besturingssysteem
Besturingssysteem = programma dat het mogelijk maakt de hardware van een computer te
gebruiken.
Functies
- Opslaan en ophalen van informatie
- Programma’s afschermen
- Gegevensstroom regelen
- Prioriteiten regelen
- Het mogelijk maken om bronnen te delen
- Tijdelijke samenwerking tussen onafhankelijke programma’s mogelijk maken
- Reageren op fouten
- Tijdsplanning maken
Historisch overzicht
1e computers → Geen OS
Jaren 50 → Eenvoudig OS:
- Sequentieel opladen & opstarten v programma’s
- Alle bronnen bruikbaar door slechts 1 programma
Begin jaren 60 → Geavanceerder OS:
- Verscheidene programma’s konden tegelijk opgeslagen worden in geheugen
- Beurtelingse uitvoering programma’s
- Gemeenschappelijke bronnen
10
