undelete sto linux

[Christos Ricudis]

Hello Linux-greek-users!

  On 20 Nov 99, Linux-greek-users wrote to All with subject "undelete sto
linux":

 L> Geia sas.. Etsi aplws anarwtieme, giati sto Linux den exw dei pote kapoio
 L> tool pou na prospa8ei na epanaferei kapoio arxeio pou egine prosfata rm.

Den kserw, isws na prepei na foreseis gyalia. Egw to blepw pentaka8ara :^). 

 L> Mipws to ext2 den parexei ayti ti dinatotita? (p.x. otan sbinei
 L> ena entry apo to directory area, na sbinei mazi kai tis plirofories
 L> tou size kai tou inode number). 'H aplws logo tou oti to linux 
 L> einai multitasking kai oi pi8anotites na epikalif8oun ta dedomena 
 L> tou arxeiou pou sbistike einai poli megales, ara kai oi pi8anotites 
 L> na to kanoume recover elaxistes,

H dynatothta yparxei. Yparxei kapoy ena ext2-undelete-HOWTO kai kapoia analoga
utilitakia. O midnight commander epishs exei ena undelete mode, mono poy prepei
na to kaneis configure sto compilation (ta perissotera binary distributions den
to exoyn kanei compile). 

Otan sbhnetai ena arxeio, diagrafetai to directory entry toy (ara xaneis to
onoma toy) kai to inode toy metaferetai sthn "Megalh 8anaterh Lista Twn
Skotwmenwn Inodes". 

Psaxnontas mesa sth lista mporeis na breis to inode poy antistoixouse sto
arxeio poy esbhses (apo ta permissions, ton owner, to mege8os kai thn
hmeromhnia tou arxeioy). An to file exei mege8os mexri 12 blocks, eisai
tyxeros, kai olh h plhroforia poy xreiazesai brisketai mesa sto inode. Aplws
diabazeis ta blocks, kai ta swzeis se kapoio arxeio. An to file exei mege8os
megalytero apo 12 blocks tote xrhsimopoieitai enas mhxanismos 1-2-3-level
indirection. Dhladh, ta prwta 12 blocks periexontai sto inode, kai sto amesws
epomeno block yparxei mia lista (indirect block) me alla 256 block numbers. Ean
to arxeio einai megalytero apo 256+12 blocks, h lista (doubly indirect block)
periexei 256 block numbers poy deixnoyn se antistoixa indirect blocks. Ktl ktl
mexri to 3. (4-way indirection den yparxei, 8ewreitai asymforo na kratas OLO to
sympan se ena arxeio ;>)

Mexri ton 2.0.38, ta indirect blocks ka8arizontai otan diagrafetai to arxeio,
kai h monh sou elpida einai na mhn einai poly fragmented to filesystem, kai na
katafereis na breis to arxeio sou se adjacent blocks. (den kserw ti ginetai me
ta block groups wstoso). Meta ton 2.0.38, ta (1-2-3-indirect blocks den
ka8arizontai, ektos an paei kapoios allos kai grapsei apo epanw toys fysika. 

--
Christos Ricudis
Prof:    So the American government went to IBM to come up with a data
         encryption standard and they came up with ...
Student: EBCDIC!
--
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