Tänane küsimuste ja vastuste seanss tuleb meile viisakalt SuperUseriga, mis on Q & A veebisaitide kogukonna juhtimisgruppide Stack Exchange osakond.
Küsimus
SuperUseri lugeja FrozenKing tahab teada, kuidas tema arvuti teab, kui see on kukkunud või muul viisil sobimatu sulgemine olnud. Ta kirjutab:
Actually, this question struck me because of power cuts in my house. When there is a power cut, there is a sudden loss of power from the computer.
How does the computer know that the shutdown was not properly done?
See on huvitav küsimus; ilmselgelt kaasaegsed operatsioonisüsteemid on hästi teadlikud, et midagi on valesti läinud, kuid millise mehhanismi nad on teadlikud?
Vastused
SuperUseri toetaja David Schwartz pakub üldist vastust ja ülevaadet erinevatest operatsioonisüsteemidest:
For non-Windows based PCs, the detection is usually done on a per-filesystem basis. When a filesystem is mounted in read/write mode, an entry is written to the filesystem marking it dirty. When the filesystem is unmounted, an entry is written marking it clean. On startup, the operating system checks if its core filesystems are marked dirty, and if so it knows there wasn’t a clean shutdown - at least of those filesystems.
Teine kaasautor, ChrisF vastab täpsemalt Windowsi operatsioonisüsteemile:
When powered off as normal, the bit is switched off. However, in case of power outage or improper (forced) shutdown, the bit will still be on the next time the PC is started.
This means that Windows can suggest remedial action – such as booting into Safe Mode.
In addition a Windows based PC will write an entry into event log detailing when and why (if known) it was shut down. It also writes an event when the PC starts up.
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