e2fsck

Check filesystem, reporting any damaged blocks

$ sudo e2fsck [/dev/sdXN]

$ sudo e2fsck -p [/dev/sdXN]

$ sudo e2fsck -c [/dev/sdXN]

$ sudo e2fsck -fccky [/dev/sdXN]

e2fsck [-pacnyrdfkvtDFV] [-b superblock] [-B blocksize] [-l|-L bad_blocks_file] [-C fd] [-j external-journal] [-E extended_options] device

-p
    Automatically repair the filesystem without user intervention. Equivalent to -a.

-a
    Same as -p; automatically repair the filesystem.

-c
    Check for bad blocks by doing a read-only scan.

-n
    Open the filesystem read-only and answer 'no' to all questions.

-y
    Assume an answer of 'yes' to all questions; use with caution.

-r
    Interactive repair; ask questions even if using -p or -a.

-d
    Print debugging output (for developers).

-f
    Force checking even if the filesystem appears clean.

-k
    Keep the bad blocks list when using -c or -l.

-v
    Verbose mode.

-t
    Print timing statistics.

-D
    Detect bad blocks by doing a destructive write test. USE WITH EXTREME CAUTION!

-F
    Flush the filesystem device's buffers before beginning.

-V
    Print version information and exit.

-b superblock
    Use the specified superblock number instead of the default.

-B blocksize
    Use the specified blocksize when examining the filesystem.

-l bad_blocks_file
    Add the blocks listed in bad_blocks_file to the bad blocks list.

-L bad_blocks_file
    Set the bad blocks list to be only the blocks listed in bad_blocks_file.

-C fd
    Output progress information to the specified file descriptor.

-j external-journal
    Locate the external journal device.

-E extended_options
    Set extended options. See man page for specific extended options.

device
    The device file to be checked (e.g., /dev/sda1).

e2fsck is an essential command-line utility in Linux systems used to check and repair ext2, ext3, and ext4 filesystems. Filesystem corruption can occur due to power outages, hardware failures, or software bugs. e2fsck scans the filesystem for inconsistencies and attempts to fix them. It operates directly on the disk partition, analyzing the filesystem metadata (such as inodes, superblock, and group descriptors) to identify errors.

The program operates in several phases, including checking inodes, blocks, directories, and filesystem connectivity. e2fsck can be run in read-only mode to check for errors without making any changes. In repair mode, it prompts the user for confirmation before making significant changes, although an auto-repair mode (-y or -a) can be used to automatically fix issues. Regularly running e2fsck on important filesystems is critical to maintaining data integrity and system stability. It's crucial to unmount the filesystem before running e2fsck in repair mode to avoid further corruption.

Running e2fsck on a mounted filesystem can lead to severe data corruption. Always unmount the filesystem before running e2fsck in repair mode.

The exit code returned by e2fsck is the sum of the following conditions:

0 - No errors
1 - Filesystem errors corrected
2 - System should be rebooted
4 - Filesystem errors left uncorrected
8 - Operational error
16 - Usage or syntax error
128 - Shared library error

It's recommended to run e2fsck after a system crash, power outage, or any other event that might have interrupted disk writes. It can also be run proactively as part of a routine system maintenance schedule to detect and fix potential issues before they cause data loss.

e2fsck was originally designed as part of the extended file system tools (e2fsprogs) created by Theodore Ts'o. It has evolved alongside the ext2, ext3, and ext4 filesystem formats. Its development closely followed the needs of journaling and advanced filesystem features. Over time, performance enhancements and features like online checking (with limitations) have been added. It remains a critical tool for system administrators to diagnose and resolve filesystem issues, ensuring data integrity.

mkfs.ext4(8), tune2fs(8), fsck(8)