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Operating Systems: Virtualization, Concurrency & Persistence

Solution #1: The File System Checker

Learn how the fsck tool ensures file system crash consistency by checking the superblock, inodes, and directories for errors. Understand its operation phases, limitations, and performance challenges when repairing file systems after crashes.

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What is fsck

Early file systems took a simple approach to crash consistency. Basically, they decided to let inconsistencies happen and then fix them later (when rebooting). A classic example of this lazy approach is found in a tool that does this: fsckPronounced either “eff-ess-see-kay”, “eff-ess-check”, or, if you don’t like the tool, “eff- suck”. Yes, serious professional people use this term.. fsck is a UNIX tool for finding such inconsistencies and repairing them; similar tools to check and repair a disk partition exist on different systems. Note that such an approach can’t fix all problems. Consider, for example, the case above where the file system looks consistent but the inode points to garbage data. The only real goal is to make sure the file system metadata is internally consistent.

What does fsck do

The tool fsck operates in a number of phases, as summarized in McKusick and Kowalski’s paper“Fsck – The UNIX File System Check Program” by Marshall Kirk McKusick and T. J. Kowalski. Revised in 1996. Describes the first comprehensive file-system checking tool, the eponymous fsck. Written by some of the same people who brought you FFS.. It is run before the file system is mounted and made available (fsck assumes ...