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4. H megalh anamonh gia thn apoprosarthsh (unmount)

Merikoi apo esas blepontas ta deyterolepta anamonhs, 8a skefthkan oti einai arketos xronos perimenontas na bgei mia disketa. Isws na sygxroniza toys diskoys (sync) kai na thn ebgaza prosarthmenh, xwris kaneis na katalabei tipota. Epitrecte moy na proteinw asfalesteroys tropoys. Prwta apo ola, mporeite na allajete to xroniko diasthma. Alla ayto mporei na einai ligo aneparkes, legontas sto susthma na apoprosarthsei kati meta apo molis 15 deyterolepta h kati allo. Ejartwmeno apo thn dikh sas egkatastash, mporei na eiste se 8esh na ektelesete thn entolh umount ws aplos xrhsths. Alla sthn pragmatikothta yparxei tropos na zhthsete apo to automount programma na apoprosarthsei. An steilete (me to programma kill) to shma (signal) SIGUSR1 pros th diergasia automount, 8a apoprosarthsei otidhpote mporei. Alla protou arxisete na ftiaxnete plhktra apoprosarthshs stoys diaxeiristes para8urwn sas, yparxei ena mikro problhma.

H diergasia toy automount trexei apo ton xrhsth root, kai signals 8a dex8ei mono apo ton idio xrhsth. Oi misoi apo toys logoys gia toys opoioys pi8anon kanete aytomath prosarthsh einai wste na mporeite na prosarteite kati apoprosarthmeno xwris na eiste root. 8a htan eukolo na gracete ena suid-root programma se C to opoio na kanei th bromikh doyleia. Wstoso, xrhsimopoiwntas th sudo einai pi8ano na epitrecete stoys xrhstes na steiloyn to katallhlo kill signal. To monadiko problhma einai oti h sudo den 8a sas epitrecei na xrhsimopoihsete ` gia na epejergasteite ypoentoles, poy 8a 8elate na kanete gia na breite to trexon PID. 8a prepei na exete ena programma poy legetai killall, poy 8a sas epitrecei na kanete ayto: (eyxaristw gia tis protaseis)

ALL     ALL=NOPASSWD:/usr/bin/killall -USR1 automount
Diaforetika, 8a prepei na epitrecete stoys xrhstes sas na stelnoyn -SIGUSR1 se oles tis diergasies. Ayto exei poikiles epidraseis sta programmata. Mporei na anakyklwsei arketous diaxeiristes para8urwn, alla 8a skotwsei (kill) ton xemacs. Etsi loipon elpizete na mhn yparxoyn jexeilismata sthn endiamesh mnhmh (buffer overrun) ths killall...


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