Stages of fsck

Stages of fsck

The phases (passes) performed by the UFS version of the fsck command are:

Initialization.

Phase 1 – Check Blocks and Sizes.

Phase 2a – Check Duplicated Names.

Phase 2b – Check Pathnames.

Phase 3 – Check Connectivity.

Phase 3b – Verify Shadows/ACLs.

Phase 4 – Check Reference Counts.

Phase 5 – Check Cylinder Groups.

fsck sets up tables for storing inodes and comparisons, verifies validity of fsck options, then runs through the 6 phases. After initializing it's tables fsck runs through:

Phase 1: Check Blocks and Sizes - checks inodes for inconsistencies

Phase 2: Check Path-Names - checks directory <-> inode consistencies

Phase 3: Check Connectivity - checks that all directories are connected to the file system

Phase 4: Check Reference Counts - compares link count information from Phases 2 & 3, correcting discrepancies

Phase 5: Check Cylinder Groups - checks free blocks and the used inode maps for consistency

Phase 6: Salvage Cylinder Groups - update the tables to reflect any changes made in earlier passes