e2fsck

e2fsck is a filesystem check and repair utility for the ext2, ext3, and ext4 filesystems. It is part of the e2fsprogs package and is used to detect and correct inconsistencies in filesystem metadata, including inodes, block bitmaps, directory structures, and link counts. The tool helps ensure filesystem integrity after events such as improper shutdowns, crashes, or disk errors. It can operate in a purely diagnostic mode or perform repairs as needed, often by writing changes back to the filesystem.

Operationally, e2fsck examines the filesystem’s metadata and data structures to identify corruption or inconsistencies. It can fix issues such as orphaned inodes, incorrect block counts, and directory mislinks. In general, repairs should be performed on unmounted filesystems or from a maintenance environment; running with the filesystem mounted read-write is risky and discouraged. It supports non-interactive modes suitable for automatic checks, and interactive prompts allow the user to approve repairs.

Typical usage involves invoking e2fsck on a device or image, with common options such as -p to preen (repair without prompting), -y to assume “yes” for all questions, -f to force a check, and -C fd to display a progress bar. It can operate on block devices or filesystem images, and it can use backup superblocks to recover when the primary superblock is damaged. After repairs, a filesystem should be remounted cleanly and a backup plan should be in place.

e2fsck is closely related to fsck, serving as the ext family’s specific checker within the broader file-system integrity toolkit. It is widely used by system administrators and during boot-time filesystem checks.