Ellhniko Linux Partition HOWTO
Kristan Koehntopp,
[email protected]
Ekdosh 2.4, 3 Noembrioy 1997
Gia opoiadhpote sxolia, dior8wseis, klp sxetika me thn ellhnikh
metafrash epikoinwnhste me ton Panagiwth Boydourh sth dieu8ynsh:
[email protected] To sygkekrimeno mini-HOWTO sas didaskei
pws na sxediazete kai na xrhsimopoieite to xwro stoys diskoys sas gia
ena susthma Linux. Mila gia to yliko, tis katatmhseis, periorismous
sto mege8os kai thn topo8ethsh xwroy enallaghs(swap) sto disko, systh�
mata arxeiwn, tainies kai alla sxetika 8emata. O skopos toy einai na
dwsei basikes gnwseis, opote milame perissotero gia arxes leitoyrgias
para gia th xrhsh ergaleiwn.
______________________________________________________________________
Table of Contents
1. Eisagwgh
1.1 Ti einai ayto;
1.2 Ti yparxei se ayto; kai sxetika HOWTO.
2. Telos pantwn, ti einai mia katatmhsh;
2.1 Ta antigrafa einai shmantika
2.2 Ari8moi kai onomata syskeywn
3. Ti katatmhseis xreiazomai;
3.1 Poses katatmhseis xreiazomai;
3.2 Poso megalos prepei na einai o xwros enallaghs;
3.3 Pou prepei na balw to xwro enallaghs;
3.4 Merika gegonota gia ta systhmata arxeiwn kai ton katakermatismo
3.5 Diarkeia zwhs arxeiwn kai kukloi antigrafwn asfaleias ws krithria katatmhsewn
4. Ena paradeigma
4.1 Proteinomeno montelo gia filodojoys arxarioys
5. Pws to ekana sto mhxanhma moy
______________________________________________________________________
1. Eisagwgh
1.1. Ti einai ayto;
To eggrafo ayto einai ena Linux Mini-HOWTO. Ena Mini-HOWTO einai ena
suntomo keimeno poy ejhgei otidhpote sxetiko me to Linux ws odhgos
egkatastashs kai synthrhshs. Einai mini epeidh eite to keimeno h to
8ema einai polu mikro gia ena pragmatiko HOWTO h akoma ki ena biblio.
To HOWTO den einai odhgos anaforas: gia ayto yparxoyn oi selides
boh8eias (man pages).
1.2. Ti yparxei se ayto; kai sxetika HOWTO.
To sygkekrimeno mini-HOWTO sas didaskei pws na sxediazete kai na
xrhsimopoieite to xwro stoys diskoys sas gia ena susthma Linux. Mila
gia to yliko, tis katatmhseis, periorismous sto mege8os kai thn
topo8ethsh eikonikhs mnhmhs sto disko, systhmata arxeiwn, kasetes kai
alla sxetika 8emata. O skopos toy einai na dwsei basikes gnwseis,
opote milame perissotero gia arxes leitoyrgias para gia th xrhsh
ergaleiwn.
Idanika, ayto to eggrafo 8a prepei na diabastei prin thn prwth sas
egkatastash, pragma duskolo gia toys perissoteroys. Oi prwtarhdes
exoyn kai alla problhmata apo th beltistopoihsh toy diskoy. Etsi,
pi8anon eiste kapoios poy molis teleiwse thn egkatastash toy Linux kai
skeftetai tropoys na thn beltistopoihsei h pws na apofugei la8h gia
thn epomenh. Pantws, na perimenete oti meta to telos aytou toy
keimenoy 8a exete mia epi8ymia gia mia kainouria egkatastash. :-)
Ayto to mini-HOWTO periorizetai ston programmatismo kai sxediasmo toy
xwroy sto disko. Den perigrafei th xrhsh twn fdisk, LILO, mke2fs h
programmatwn gia antigrafa asfaleias. Yparxoyn alla HOWTO gia ayta ta
problhmata. Parakalw, deite to Linux HOWTO Index gia plhrofories gia
Linux HOWTO. Yparxoyn kai plhrofories sto index gia to pws na
apokthsete ta HOWTO.
Gia na ma8ete pws na ypologizete ta mege8h kai tis apaithseis
taxuthtas gia diafora tmhmata toy systhmatos arxeiwn, deite to "Linux
Multiple Disks Layout mini-HOWTO", apo ton Gjoen Stein
<
[email protected]>.
Gia plhrofories kai periorismous sxetika me diskoys me perissoteroys
apo 1024 kulindroys, deite to "Linux Large Disk mini-HOWTO", toy
Andries Brouwer <
[email protected]>.
Gia odhgies toy pws na periorisete th xrhsh diskoy ana xrhsth
(quotas), deite to "Linux Quota mini-HOWTO", toy Albert M.C. Tam
<
[email protected]>
Th stigmh ayth den yparxei kapoio geniko eggrafo gia antigrafa
asfaleias, alla yparxoyn arketa eggrafa poy anaferontai se
sygkekrimenes luseis. Deite to "Linux ADSM Backup mini-HOWTO", toy
Thomas Koenig <
[email protected]> gia odhgies sxetika
me to pws na oloklhrwsete to Linux se ena IBM ADSM periballon. Deite
to "Linux Backup with MSDOS mini-HOWTO", toy Christopher Neufeld
<
[email protected]> gia plhrofories sxetika me antigrafa
asfaleias toy Linux mesw MS-DOS.
Gia odhgies pws na gracete kai na paradwsete ena HOWTO, deite to Linux
HOWTO Index, toy Tim Bynum <
[email protected]>.
Epishs, koitazontas to /usr/src/linux/Documentation mporei na einai
polu xrhsimo. Koitajte ta ide.txt kai scsi.txt gia plhrofories sxetika
me tis idiothtes twn odhgwn diskwn kai rijte mia matia kai ston
ypokatalogo filesystems/.
2. Telos pantwn, ti einai mia katatmhsh;
Otan efeyre8hkan oi sklhroi diskoi, oi xrhstes suntoma h8elan na
egkatasthsoyn diafora leitoyrgika systhmata, akoma ki an eixan mono
ena disko sto susthma toys. Etsi, xreiazotan enas mhxanismos poy na
xwrizei ton ena fysiko disko se pollaples logikes monades. Ayto einai
h katatmhsh: ena synexes tmhma toy diskoy poy symperiferetai san enas
teleiws jexwristos diskos sta perissotera leitoyrgika systhmata.
Einai emfanes oti oi katatmhseis den prepei na yperkaluptoyn h mia thn
allh: Sigoyra ena leitoyrgiko de 8a htan eyxaristhmeno an ena allo
leitoyrgiko susthma egrafe panw se shmantika toy dedomena epeidh oi
katatmhseis sygkaluptontai. Epishs, de 8a prepei na yparxoyn kena
metaju twn katatmhsewn. An kai ta endiamesa kena den einai epiblabh,
xaramizoyn ton polutimo xwro toy diskoy.
O diskos de xreiazetai na katatmh8ei teleiws. Mporei na apofasisete na
afhsete ligo xwro sto telos toy diskoy poy na mh xrhsimopoieitai apo
kanena leitoyrgiko susthma. Argotera, otan jeka8arisei poio
leitoyrgiko xrhsimopoieite perissotero, mporeite na xrhsimopoihsete
ton keno xwro gia to susthma ayto.
Oi katatmhseis de mporoun na metakinh8oun h na allajoyn mege8os xwris
na katastrafei to susthma arxeiwn toys. Ayto shmainei pws h ek neoy
diairesh toy diskoy se katatmhseis apaitei thn lhch antigrafwn
asfaleias kai meta thn anadiairesh thn epanafora twn dedomenwn apo ta
antigrafa ayta. Sthn pragmatikothta, einai polu syxno to na
katastrefontai ta panta kata thn anadiairesh, opote 8a prepei na
kanete antigrafa olwn twn dedomenwn se oloys toys diskoys prin
akoymphsete programmata san to fdisk.
Parola ayta, merikes katatmhseis me sygkekrimena systhmata arxeiwn
mporoun na diaire8oun xwris na xa8oun dedomena (an eiste tyxeroi).
Gia paradeigma, yparxei ena programma onomati "fips" poy diairei
katatmhseis MS-DOS sta duo gia na kanei xwro gia mia egkatastash Linux
xwris na xreiastei epanegkatastash toy MS-DOS. Omws pali de 8a to
aggijete xwris na parete antigrafa, etsi den einai;
2.1. Ta antigrafa einai shmantika
Oi tainies einai oi filoi sas gia ta antigrafa. Einai grhgores,
ajiopistes kai eukoles sth xrhsh, opote mporeite na kanete antigrafa
asfaleias syxna kai kata protimhsh aytomata kai xwris mpelades.
Prosoxh: Milaw gia alh8ines tainies, oxi ekeines tis ftape ahdies poy
elegxontai apo ton elegkth diskoy. Agoraste SCSI: to Linux exei eggenh
yposthrijh SCSI. Den xreiazetai na fortwsete ASPI odhgous, de xanete
polutimh HMA kai efoson o elegkths SCSI egkatasta8ei, apla pros8etete
diskoys, kasetes kai CD-ROMs epanw toy. Oute alles I/O diey8unseis,
paijimo me IRQ h syndyasmoi Master/Slave kai PIO.
Epishs: Oi kaloi SCSI elegktes sas dinoyn ychlh epidosh I/O xwris
megalo fortio ston epejergasth. Akomh kai katw apo baria xrhsh toy
diskoy 8a exete kalh apokrish. Ean sxediazete na xrhsimopoihsete ena
susthma Linux san basiko USENET trofodoth h ean 8a asxolh8eite ws ISP
mhn dianoh8eite na parete susthma xwris SCSI.
2.2. Ari8moi kai onomata syskeywn
O ari8mos twn katatmhsewn se basizomena se Intel systhmata htan
periorismenos apo thn arxh: O arxikos pinakas katatmhsewn htan
egkatesthmenos ws tmhma toy tomea ekkinhshs kai eixe xwro gia mono
tesseris eggrafes. Aytes oi tesseris katatmhseis onomazontai
prwtarxikes. Otan egine emfanes oti oi xrhstes xreiazontan
perissoteres, oi logikes katatmhseis efeyre8hkan. O ari8mos toys den
einai periorismenos: ka8e logikh katatmhsh periexei ena deikth sthn
epomenh, opote einai dynaton na yparxei mia alysida apo apeires
eggrafes.
Gia logoys symbatothtas, o xwros poy xrhsimopoieitai apo oles tis
logikes katatmhseis prepei na katametrh8ei. Ean xrhsimopoieite logikes
katatmhseis, mia eggrafh twn prwtarxikwn katatmhsewn shmeiwnetai ws
"ektetamenh katatmhsh" enw ta arxiko kai teliko shmeio ths shmeiwnei
ton xwro poy xrhsimopoieitai apo tis logikes katatmhseis. Ayto yponoei
oti o xwros poy dinetai stis logikes katatmhseis prepei na einai
synexomenos. Mporei na yparxei mono mia ektetamenh katatmhsh: kanena
fdisk programma de 8a dhmioyrghsei parapanw apo mia ektetamenh
katatmhsh.
To Linux de mporei na xeiristei panw apo ena sygkekrimeno ari8mo
katatmhsewn ana disko. Etsi, sto Linux exete 4 prwtarxikes katatmhseis
(3 apo aytes xrhsimes, ean xrhsimopoieite logikes katatmhseis) kai to
polu 15 katatmhseis synolika se ena disko SCSI (63 synolika se ena
disko IDE).
Sto Linux, oi katatmhseis apeikonizontai ws arxeia syskeywn. To arxeio
syskeyhs einai ena arxeio tupoy c (gia syskeyh xarakthrwn=character,
poy de xrhsimopoioun endiamesh mnhmh-buffer chache) h tupoy b (gia
syskeyh temaxiwn=block, poy perna mesa apo thn endiamesh mnhmh). Sto
Linux, oloi oi diskoi apeikonizontai ws block syskeyes. Se anti8esh me
alla Unix systhmata, to Linux den prosferei akatergastes ekdoseis
xarakthrwn (raw character) twn diskwn kai twn antistoixwn katatmhsewn
toys.
To mono shmantiko se ena arxeio syskeyhs einai o meizwn kai o mikros
ari8mos syskeyhs, poy deixnontai anti toy mege8oys toy arxeioy:
______________________________________________________________________
$ ls -l /dev/hda
brw-rw---- 1 root disk 3, 0 Jul 18 1994 /dev/hda
^ ^
| minor device number
major device number
______________________________________________________________________
Otan xrhsimopoieitai ena arxeio syskeyhs, o meizwn ari8mos epilegei
poios odhgos syskeyhs 8a klh8ei gia na ektelestei h ergasia
eisodoy/ejodoy. H klhsh ayth ginetai me ton mikro ari8mo ws parametro
kai ejartatai apokleistika apo ton odhgo pws 8a metafrastei o mikros
ari8mos. H tekmhriwsh toy odhgou synh8ws ejhgei pws o odhgos
xrhsimopoiei toys mikrous ari8mous. Gia IDE diskoys h tekmhriwsh
brisketai sto /usr/src/linux/Documentation/ide.txt. Gia SCSI diskoys,
8a perimenate na toys breite sto
/usr/src/linux/Documentation/scsi.txt, alla den einai ekei. Prepei na
koitajete ston kwdika toy odhgou gia na eiste sigoyroi
(/usr/src/linux/driver/scsi/sd.c:184-196). Eytyxws yparxei kai h lista
ari8mwn kai onomatwn odhgwn toy Peters Anvin sto
/usr/src/linux/Documentation/devices.txt; koitajte tis anafores gia
block syskeyes, meizwn 3, 22, 33, 34 gia IDE kai meizwn 8 gia SCSI
diskoys. Oi meizwn kai mikroi ari8moi einai ena byte o ka8enas kai gia
ayto o ari8mos katatmhsewn ana disko einai periorismenos.
Kata sumbash, ta arxeia syskeywn exoyn sygkekrimena onomata kai polla
programmata exoyn gnwsh twn onomatwn aytwn kata th metaglwttish toys.
Perimenoyn oi IDE diskoi na onomazontai /dev/hd* kai toys SCSI diskoys
/dev/sd*. Oi diskoi ari8mountai ws a, b, c klp, opote to /dev/hda
einai o prwtos IDE diskos kai o /dev/sda einai o prwtos sas SCSI
diskos. Kai oi dyo syskeyes antiproswpeuoyn oloklhroys diskoys,
jekinwntas apo to block ena. Grafontas stis syskeyes aytes me ta la8os
ergaleia 8a katastrecei tis eggrafes ekkinhshs kai katatmhsewn,
ka8istwntas ola ta dedomena ston disko mh prosbasima h kanontas to
susthma sas adunato na jekinhsei. Na jerete ti kanete, kai jana, parte
antigrafa prin kanete otidhpote.
Oi prwtarxikes katatmhseis toy diskoy einai oi 1, 2, 3 kai 4. Etsi
/dev/hda1 einai h prwth prwtarxikh katatmhsh ston prwto IDE disko kok.
Logikes katatmhseis exoyn noumera 5 kai anw, opote /dev/sdb5 einai h
prwth logikh katatmhsh ston deutero SCSI disko.
Ka8e eggrafh ston pinaka katatmhsewn exei mia arxikh kai telikh
dieu8ynsh kai enan tupo. O tupos einai enas ari8mhtikos kwdikos (ena
byte) poy ka8orizei th sygkekrimenh katatmhsh se ena sygkekrimeno
leitoyrgiko susthma. Oi kwdikoi katatmhsewn den einai monadikoi, opote
yparxei h pi8anothta dyo leitoyrgika na xrhsimopoioun ton idio kwdiko.
To Linux xrhsimopoiei ton kwdiko 0x82 gia katatmhseis enallaghs kai
0x83 gia "eggenh" systhmata arxeiwn (ext2 dhladh). To kapote dhmofiles
alla twra parwxhmeno Linux/Minix susthma xrhsimopoiouse ton kwdiko
0x81. To OS/2 xrhsimopoiei ton tupo 0x07 kai to idio kai to NTFS
susthma twn Windows NT. To MS-DOS xrhsimopoiei arketous kwdikous gia
tis diafores ekdoseis toy FAT systhmatos toy: 0x01, 0x04 kai 0x06
einai gnwsta. To DR-DOS xrhsimopoiouse to 0x81 gia tis prostateyomenes
FAT katatmhseis toy, dhmioyrgwntas problhmata me to Linux/Minix ston
kairo toy, alla shmera oute to Linux/Minix oute kai to DR-DOS
xrhsimopoiountai pia. H ektetamenh katatmhsh poy xrhsimopoieitai apo
tis logikes katatmhseis exei kwdiko 0x05.
Oi katatmhseis dhmioyrgountai kai katastrefontai me to fdisk. Ka8e
leitoyrgiko poy sebetai ton eayto toy exei ena fdisk poy paradosiaka
kaleitai fdisk (h FDISK.EXE) sta perissotera systhmata. Merika fdisk,
kyriws toy DOS, einai kapws periorismena otan xeirizontai katatmhseis
allwn leitoyrgikwn. Tetoioi periorismoi exoyn na kanoyn me thn
adynamia xeirismou otidhpote me jenoy kwdiko, me ari8mo kylindroy
megalutero toy 1024 kai thn adynamia na dhmioyrghsoyn h na katalaboyn
katatmhseis poy den teleiwnoyn se orio kylindroy. Gia paradeigma, to
fdisk toy MS-DOS de mporei na sbhsei katatmhseis NTFS, to fdisk toy
OS/2 exei anafer8ei oti kryfa "dior8wnei" katatmhseis poy
dhmioyrgh8hkan me to fdisk toy Linux poy den teleiwnoyn se orio
kylindroy, enw kai ta duo, toy DOS kai toy OS/2, exoyn problhmata me
diskoys me perissoteroys apo 1024 kylindroys (deite to "large-disk"
mini-howto gia leptomereies gia tetoioys diskoys).
3. Ti katatmhseis xreiazomai;
3.1. Poses katatmhseis xreiazomai;
Wraia, poses katatmhseis xreiazeste dhladh; Loipon, merika leitoyrgika
systhmata de 8eloyn na jekinoun apo logikes katatmhseis gia logoys poy
jefeugoyn ths logikhs. Etsi, pi8ana na 8elete na krathsete tis
prwtarxikes katatmhseis sas gia thn ekkinhsh twn MS-DOS, OS/2 kai
Linux h otidhpote allo xrhsimopoieite. 8ymh8eite oti mia prwtarxikh
katatmhsh xreiazetai gia na ginei ektetamenh, wste na dra san doxeio
gia tis logikes katatmhseis toy diskoy sas.
H ekkinhsh leitoyrgikwn systhmatwn perilambanei to BIOS kai toys
periorismous twn 1024 kylindrwn. Etsi, mallon 8a 8elete na balete oles
tis katatmhseis ekkinhshs stoys prwtoys 1024 kylindroys toy diskoy
sas, wste na apofugete ta problhmata. 3ana, diabaste to "large-disk"
mini-howto, gia perissoteres leptomereies.
Gia na egkatasthsete to Linux, 8a xreiasteite toylaxiston mia
katatmhsh. Ean o pyrhnas fortwnetai apo aythn thn katatmhsh (gia
paradeigma apo to LILO), h katatmhsh ayth prepei na diabazetai apo to
BIOS. Ean xrhsimopoieite alla mesa gia na fortwsete ton pyrhna (apo
disketa ekkinhshs h me to LOADLIN.EXE mesw toy MS-DOS) h katatmhsh
mporei na einai opoydhpote. Se opoiadhpote periptwsh, h katatmhsh 8a
einai tupoy 0x83 "Linux native".
To susthma sas 8a xreiastei kai xwro enallaghs. Ektos ean
xrhsimopoieite arxeia ws xwro enallaghs, 8a xreiasteite mia katatmhsh
afierwmenh gia ayth th doyleia. Efoson h katatmhsh ayth
xrhsimopoieitai apo ton pyrhna toy Linux kai o pyrhnas den exei tis
adynamies toy BIOS, h katatmhsh ayth mporei na brisketai opoydhpote
sto disko. Systhnw na xrhsimopoihsete mia logikh katatmhsh (/dev/?d?5
h megaluterh). Oi katatmhseis afierwmenes ws xwros enallaghs einai
tupoy 0x82 "Linux swap".
Aytes einai oi elaxistes apaithseis. 8a htan xrhsimo na dhmioyrghsete
perissoteres katatmhseis gia to Linux. Diabaste parakatw.
3.2. Poso megalos prepei na einai o xwros enallaghs;
Ean apofasisate na xrhsimopoihsete mia katatmhsh ws xwro enallaghs,
poy genika einai Kalh Idea, akoloy8hste tis parakatw odhgies gia na
ypologisete to mege8os ths:
� Sto Linux, h mnhmh RAM kai o xwros enallaghs xrhsimopoiountai ws to
sunolo ths eikonikhs mnhmhs poy einai dia8esimh (kati poy den einai
alh8eia gia ola ta Unix). Gia paradeigma an exete 8MB RAM kai 12MB
xwro enallaghs, exete ena sunolo peripoy 20MB eikonikhs mnhmhs.
� Otan ka8orizete to mege8os toy xwroy enallaghs, 8a prepei na exete
peripoy 16MB eikonikhs mnhmhs synolika. Etsi, gia 4MB RAM 8a
xreiasteite toylaxiston 12MB ws xwro enallaghs, gia 8MB RAM 8a
xreiasteite toylaxiston 8MB xwro enallaghs kok.
� Sto Linux, mia katatmhsh enallaghs de mporei na einai megaluterh
apo 128MB. Dhladh, h katatmhsh mporei na einai megaluterh apo
128MB, alla o parapanw xwros de xrhsimopoieitai pote. Ean 8elete
parapanw apo 128MB xwroy enallaghs, 8a xreiasteite pollaples
katatmhseis.
� Otan dhmioyrgeite ton xwro enallaghs, 8ymh8eite oti polus xwros
mporei na einai kai axrhstos.
Ka8e diergasia exei ena "sunolo ergasias". Ayto to sunolo selidwn
sth mnhmh 8a xrhsimopoih8ei apo ton epejergasth sto suntomo mellon.
To Linux prospa8ei na problecei thn prosbash sth mnhmh (ypo8etontas
oti oi teleytaia xrhsimopoihmenes selides 8a xrhsimopoih8oun jana
suntoma) kai krata aytes tis selides sth RAM an einai dynaton. Ean
to programma exei kalh "topikothta anaforas" h ypo8esh ayth 8a
einai swsth kai o algori8mos problechs 8a doylecei.
To na krath8ei to sunolo ergasias sth mnhmh doyleuei mono ean
yparxei arketh mnhmh RAM. Ean exete polles diergasies na trexoyn se
ena mhxanhma, o pyrhnas anagkazetai na bazei selides ston disko poy
8a tis xrhsimopoihsei suntoma (anagkazontas thn ejodo mias selidas
apo allo sunolo ergasias kai thn eisagwgh ths selidas poy
zhteitai). Ayto synh8ws katalhgei se baria enallagh selidwn kai
katakoryfh ptwsh ths apodoshs. Ena mhxanhma se ayth thn katastash
legetai oti kanei "thrashing".
Se ena tetoio mhxanhma oi diergasies trexoyn sthn oysia apo ton
disko anti ths RAM. Etsi h apodosh peftei peripoy oso h sxesh
metaju ths taxuthtas prosbashs mnhmhs kai ths taxuthtas prosbashs
toy diskoy.
Enas palios kanonas apo tis meres toy PDP kai toy Vax leei oti to
sunolo ergasias enos programmatos einai to 25% toy eikonikou toy
mege8oys. Gia ayto einai mallon askopo na exete xwro enallaghs
megalutero apo treis fores to mege8os ths RAM.
Prosejte omws oti aytos einai enas aplos kanonas. Einai eukolo na
dhmioyrgh8oun senaria opoy programmata exoyn ejairetika megala h
mikra sunola ergasias. Gia paradeigma ena programma ejomoiwshs exei
megala sunola dedomenwn poy prosballontai tyxaia kai xwris kamia
topikothta, etsi to sunolo ergasias einai polu megalo.
Apo thn allh, to xv me arketa anoixta JPEG arxeia 8a exei ena polu
megalo sunolo dedomenwn. Omws oi metasxhmatismoi 8a ginontai se ena
mono arxeio, opote h perissoterh mnhmh poy katalambanetai apo to xv
den prosballetai pote. To idio isxuei kai me enan epejergasth
keimenoy me polla anoixta eggrafa, alla mono ena na dior8wnetai.
Etsi, ta programmata ayta - an exoyn sxediastei swsta - exoyn polu
megalh topikothta kai megala tmhmata toys mporoun na krath8oun sto
xwro enallaghs xwris megalh ptwsh taxuthtas.
8a perimene kaneis oti to 25% apo thn epoxh ths grammhs entolwn de
8a einai swsto stis meres twn grafikwn periballontwn kai pollaplwn
eggrafwn, alla den jerw gia nees meletes poy epibebaiwnoyn ayta ta
noumera.
Etsi gia ena susthma me 16MB RAM, xwros enallaghs de xreiazetai gia
mia elaxisth diamorfwsh kai panw apo 48MB einai mallon axrhsta. To
akribes poso mnhmhs ejartatai apo to migma twn efarmogwn sto mhxanhma
(ti perimenate;).
3.3. Pou prepei na balw to xwro enallaghs;
� Ta mhxanika einai arga, ta hlektronika einai grhgora.
Oi monternoi diskoi exoyn polles kefales. H metabash metaju kefalwn
sto idio aylaki einai grhgorh, afou einai ka8ara hlektronikh. H
metabash metaju aylakiwn einai argh, afou apaitei th metakinhsh
fysikwn antikeimenwn.
Etsi an exete ena disko me polles kefales kai enan me ligoteres me
idies tis alles parametroys toys, o diskos me tis perissoteres
kefales 8a einai grhgoroteros.
Parola ayta, to na xwrisete to xwro enallaghs kai na ton moirasete
stoys dyo diskoys 8a einai akoma grhgorotero.
� Oi palioteroi diskoi exoyn ton idio ari8mo tomewn se ola ta
aylakia. Me aytous toys diskoys 8a einai pio grhgoro na balete to
xwro enallaghs sth mesh toy diskoy, ypo8etontas oti h kefalh toy
diskoy 8a kinh8ei apo mia tyxaia perioxh pros to xwro enallaghs.
� Oi neoteroi diskoi xrhsimopoioun ZBR (zone bit recording). Exoyn
perissoteroys tomeis sta ejwterika aylakia. Me sta8ero ry8mo
peristrofhs, ayto dinei shmantika ayjhmenh apodosh sta ejwterika
aylakia se sxesh me ta eswterika. Balte to xwro enallaghs sta
ejwterika aylakia.
� Fysika h kefalh toy diskoy de 8a kineitai tyxaia. Ean exete to xwro
enallaghs sth mesoy toy diskoy, metaju mias polyasxolhs katatmhshs
home kai mias sxedon axrhsimopoihths katatmhshs arxeioy, 8a htan
kalutera na to balete sth mesh ths katatmhshs home, gia akoma
mikroteres kinhseis ths kefalhs. Fysika 8a htan kalutera an eixate
to xwro enallaghs se enan allo axrhsimopoihto disko.
Perilhch: Balte to xwro enallaghs se ena grhgoro disko me polles
kefales poy den kanei alles doyleies. Ean exete pollous diskoys:
moiraste to kai skorpiste to se oloys toys diskoys h akomh kai se
diaforetikous elegktes.
Akomh kalutera: Agoraste perissoterh RAM.
3.4. Merika gegonota gia ta systhmata arxeiwn kai ton katakermatismo
O xwros sto disko diaxeirizetai apo to leitoyrgiko susthma se monades
kai tmhmata enothtwn (blocks). Sto ext2, ta tmhmata kai oi enothtes
prepei na exoyn to idio mege8os, opote mporoume na periorisoyme th
syzhthsh mas stis enothtes.
Ta arxeia erxontai se opoiodhpote mege8os. De teleiwnoyn sta oria twn
enothtwn. Etsi, gia ka8e arxeio, ena tmhma ths teleytaias enothtas
xaramizetai. Ypo8etontas oti ta mege8h twn arxeiwn einai tyxaia,
xaramizetai peripoy mish enothta gia ka8e arxeio poy yparxei sto disko
sas. O Tanenbaum to onomazei ayto "eswteriko katakermatismo" sto
biblio toy "Leitoyrgika systhmata".
Mporeite na mantecete ton ari8mo twn arxeiwn ston disko sas apo ton
ari8mo twn xrhsimopoihmenwn kombwn (inodes) toy diskoy sas.
______________________________________________________________________
# df -i
Filesystem Inodes IUsed IFree %IUsed Mounted on
/dev/hda3 64256 12234 52022 19% /
/dev/hda5 96000 43058 52942 45% /var
______________________________________________________________________
Yparxoyn peripoy 12000 arxeia sto / kai peripoy 44000 arxeia sto /var.
Me mege8os kommatiou 1KB, peripoy 6+22 = 28MB xanontai sta telika
kommatia twn arxeiwn. An eixa epilejei mege8os kommatiou 4KB, 8a eixa
xasei 4 fores perissotero xwro.
H metafora dedomenwn, omws, einai grhgoroterh gia synexhs enothtes
dedomenwn. Gia ayto, to ext2 prospa8ei na proana8esei to xwro se 8
synexhs enothtes gia epekteinomena arxeia. An o xwros de
xrhsimopoih8ei eley8erwnetai, opote de xaramizetai ka8oloy xwros.
H asynexhs ana8esh kommatiwn se ena arxeio einai kakh gia thn apodosh,
efoson ta arxeia diabazontai me ena synexh tropo. Ayto anagkazei to
leitoyrgiko na moirasei thn prosbash sto disko kai thn kefalh na
kinh8ei. Ayto onomazetai "ejwterikos katakermatismos" h apla
"katakermatismos" kai einai ena syxno problhma se systhmata arxeiwn
DOS.
To ext2 exei arketes strathgikes gia na apofugei ton ejwteriko
katakermatismo. Kanonika, o katakermatismos den apotelei megalo
problhma gia to ext2, akomh kai se katatmhseis bareas xrhshs opws to
xwro newn toy USENET. An kai yparxei ena ergaleio apokatakermatismou
gia to ext2, kaneis de to xrhsimopoiei kai de symbadizei me thn
trexoysa ekdosh toy ext2. Xrhsimopoihste to, alla me dikh sas ey8unh.
To MS-DOS einai gnwsto gia thn pa8ologikh toy diaxeirish xwroy. Se
syndyasmo me thn apu8menh buffer cache, oi epiptwseis toy
katakermatismou arxeiwn sthn apodosh ginontai grhgora antilhptes. Oi
xrhstes toy DOS einai synh8ismenoi ston apokatakermatismo toy diskoy
ka8e liges ebdomades kai merikoi exoyn anaptujei eylabikes synh8eies
kai pisteuw gia ton apokatakermatismo. Kamia apo aytes tis synh8eies
de 8a prepei na metafer8ei sto Linux kai to ext2. Ta eggenh systhmata
arxeiwn toy Linux de xreiazontai apokatakermatismo katw apo kanonikes
syn8hkes, akomh kai se periptwseis me toylaxiston 5% eleu8ero xwro sto
disko.
To MS-DOS xanei kai megales posothtes xwroy logw toy eswterikou
katakermatismou. Gia katatmhseis anw twn 256KB, oi enothtes toy DOS
ginontai toso megales poy einai praktika mh xrhsimopoihsimes (ayto
exei dior8w8ei en merh me to FAT32).
To ext2 de sas anagkazei na xrhsimopoihsete megales enothtes gia
megala systhmata arxeiwn, ektos gia polu megala systhmata arxeiwn sthn
perioxh toy 0.5TB (dhladh terabytes me 1TB = 1024GB) kai anw, opoy oi
mikres enothtes ginontai mh apodotikes. Etsi, se anti8esh me to DOS,
den yparxei logos na xwrizete to disko se polles katatmhseis gia na
krathsete to mege8os twn enothtwn mikro. Xrhsimopoihste to 1KB opoy
einai dynaton. Isws na 8elete na xrhsimopoihsete ta 2KB gia merikes
katatmhseis, alla na perimenete merika aprosdokhta problhmata.
3.5. Diarkeia zwhs arxeiwn kai kukloi antigrafwn asfaleias ws
krithria katatmhsewn
Me to ext2, h katatmhseis prepei na ginoyn me bash toys periorismous
gia antigrafa asfaleias kai gia thn apofygh ejwterikou katakermatismou
logw ths diarkeias zwhs twn arxeiwn.
Ta arxeia exoyn diaforetikes diarkeies zwhs. Afou dhmioyrgh8ei ena
arxeio, 8a parameinei sto susthma gia kapoio xroniko diasthma kai meta
8a afaire8ei. H diarkeia zwhs twn arxeiwn diaferei polu mesa sto
susthma kai ejartatai, en merei, apo to xwro paramonhs toy arxeioy.
Gia paradeigma, arxeia sta /bin, /sbin, /usr/bin, /usr/bin kai
paromoioys katalogoys einai pi8anon na exoyn megalh diarkeia zwhs:
arketous mhnes kai parapanw. Arxeia sto /home einai pi8ano na exoyn
mia mesh diarkeia zwhs: peripoy arketes ebdomades. Arxeia sto /var
einai synh8ws braxubia: sxedon kanena arxeio sto /var/spool/news de 8a
parameinei gia perissoteres apo merikes meres, enw arxeia sto
/var/spool/lpd exoyn diarkeia zwhs merika lepta h ligotero.
Gia antigrafa asfaleias einai xrhsimo to poso toy ka8hmerinou
antigrafoy na einai mikrotero apo th xwrhtikothta toy enos mesoy. Ena
ka8hmerino antigrafo mporei na einai eite oloklhro eite prosayjhtiko.
Mporeite na apofasisete na krathsete tis katatmhseis sas mikres gia na
xwrane se ena meso (gia ka8hmerina plhrh antigrafa). Se opoiadhpote
periptwsh ka8e katatmhsh 8a prepei na einai arketa mikrh wste ta
ka8hmerina dedomena (ola ta allagmena arxeia) na xwrane se ena meso
(epilejte prosayjhtiko antigrafo kai na perimenete na allazete meso
gia to ebdomadiaio/mhniaio plhres antigrafo - den ginetai plhrhs
aytomatopoihmenh ergasia).
H strathgikh antigrafwn ejartatai apo ayth thn apofash.
Otan sxediazete na agorasete diskoys, 8ymh8eite na krathsete arketa
xrhmata gia ta antigrafa! Dedomena xwris antigrafa einai axrhsta! H
anaparagwgh dedomenwn kostizei polu perissotero apo to antigrafo gia
sxedon opoiondhpote!
Gia megaluterh apodosh einai xrhsimo na kratate arxeia me diaforetiko
xrono zwhs se diaforetikes katatmhseis. Me ayto ton tropo ta braxubia
arxeia sthn katatmhsh syzhthsewn 8a katakermatistoun polu. Ayto, omws,
de 8a exei kamia epiptwsh sthn apodosh twn / h /home katatmhsewn.
4. Ena paradeigma
4.1. Proteinomeno montelo gia filodojoys arxarioys
Ena syxno montelo dhmioyrgei tis /, /home kai /var katatmhseis opws
proanafer8hke. Einai arketa aplo sthn egkatastash kai synthrhsh kai
diaforopoiei arketa tis katatmhseis wste na apofeyx8oun problhmata apo
th diarkeia zwhs twn arxeiwn. Boleuei kai gia antigrafa: sxedon
kanenas den krata antigrafo toy USENET kai mono merika arxeia toy /var
ajizoyn na krath8oun (/var/spool/mail gia paradeigma). Apo thn allh,
to / spania allazei kai mporei na antigrafei kata boulhsh (gia
paradeigma meta apo allages sth diamorfwsh) kai einai arketa mikro gia
na xwresei se ena monterno meso (peripoy 250 me 500MB, analoga me to
poses efarmoges exoyn egkatasta8ei). To /home perilambanei polutima
dedomena xrhstwn, opote 8a prepei na dhmioyrgeitai antigrafo
ka8hmerina. Merikes egkatastaseis exoyn polu megala /home kai prepei
na kanoyn prosayjhtika antigrafa.
Merika systhmata bazoyn to /tpm se jexwristh katatmhsh, enw alla
dhmioyrgoun ena symboliko desmo sto /var/tmp gia na exoyn to idio
apotelesma (shmeiwste oti ayto mporei na ephreasei to single user
mode, opoy to /var de 8a einai dia8esimo mexri na dhmioyrgh8ei ena h
na to anarthsete xeirokinhta sto /var) h to bazoyn se RAM disk (opws
kanei to Solaris gia paradeigma). Ayto krata to /tmp ejw apo to /, mia
kalh idea.
To montelo ayto einai boliko kai gia anaba8miseis h epanegkatastaseis:
krathste ta arxeia diamorfwshs (h oloklhro to /etc) se kapoio /home
katalogo, petajte to /, epanegkatasthsete kai janafortwste thn palia
diamorfwsh apo to /home.
5. Pws to ekana sto mhxanhma moy
Eixa sto rafi enan palio ISA 386/40, poy egkateleica prin dyo xronia
epeidh eixe texnologika jeperastei. Sxediaza na to kanw ena mikro
ejyphreth xwris X-Windows gia to oikiako topiko moy diktyo.
Na pws to ekana: phra ton 386 kai toy ebala 16MB RAM. Pros8esa ena
fthno EIDE disko, to mikrotero poy mporousa na brw (800MB), kai mia
karta ethernet. Ebala kai mia palia karta grafikwn Hercules epeidh
eixa akoma mia o8onh. Egkatesthsa to Linux kai etsi egine enas NFS,
SMB, HTTP, LPD/LPR, NNTP server ka8ws kai diakomisths taxydromeioy kai
ejyphrethths POP3. Me mia pros8eth ISDN karta to mhxanhma egine kai o
TCP/IP router kai firewall.
O perissoteros xwros toy diskoy phge stoys katalogoys /var,
/var/spool/mail, /var/spool/news kai /var/htppd/html. Ebala to /var
se jexwristh, megalh katatmhsh. De 8a yparxoyn sxedon ka8oloy xrhstes
sto mhxanhma, opote den ekana home katatmhsh alla thn prosarthsa sto
/home apo kapoio allo sta8mo ergasias mesw NFS.
Linux xwris X-Windows syn arketa topika egkatesthmena ergaleia 8a
einai mia xara me 250MB sto /. To mhxanhma exei 16MB RAM, alla 8a
trexei pollous servers. 16MB xwroy enallaghs 8a einai aparaithta, 32MB
8a einai aneta. Xwro exoyme, opote to mhxanhma 8a parei 32MB. Gia
synais8hmatikous logoys mia katatmhsh MS-DOS peripoy 20MB kratietai.
Apofasisa na eisagw to /home apo allo mhxanhma, opote ta ypoloipa
500+MB 8a katalhjoyn ws /var. 8a einai parapanw apo arketa gia oikiakh
trofodosia USENET.
Exoyme
______________________________________________________________________
Device Mount point Size
/dev/hda1 /dos_c 25 MB
/dev/hda2 - (swap space) 32 MB
/dev/hda3 / 250 MB
/dev/hda4 - (extended partition) 500 MB
/dev/hda5 /var 500 MB
homeserver:/home /home 1.6 GB
______________________________________________________________________
Kanw ta antigrafa asfaleias toy mhxanhmatos mesw toy diktuoy
xrhsimopoiwntas tainies sto homeserver. Efoson ola se ayto to mhxanhma
exoyn egkatasta8ei apo CD-ROM ta mona poy prepei na swsw einai ta
arxeia diamorfwshs apo to /etc, ta parametropoihmena moy, topika
egkatesthmena *.tgz arxeia apo to /root/Source/Installed kai ta
/var/spool/mail kai /var/httpd/html. Ta antigrafw se ena katalogo
/home/backmeup ston homeserver ka8e nuxta, opoy to programmatismeno
antigrafo gia ton homeserver ta grafei.
