jfs_logdump

jfs_logdump [ -l ] [ -a address ] device

-l
    Lists all log entries sequentially from the beginning of the journal, providing a comprehensive view of recorded transactions.

-a

The jfs_logdump command is a utility designed to read and display the raw contents of the journal log for a JFS (Journaled File System) partition. JFS uses a journal to record metadata changes before they are written to the main filesystem, enabling rapid recovery after system crashes or power failures without requiring a full filesystem check.

This command is primarily a diagnostic and debugging tool for filesystem developers and advanced administrators. It allows users to examine the sequence of transactions and operations recorded in the journal, which can be invaluable for understanding filesystem behavior, diagnosing corruption, or recovering specific information from the log. The output is typically raw, hexadecimal, and requires a deep understanding of the JFS log format to interpret effectively.

Requires root privileges to access the raw device. The output is highly technical, often raw hexadecimal, and difficult to interpret without a deep understanding of JFS internal structures and journal formats. This command is primarily for advanced debugging and development purposes rather than routine administration. JFS is also less commonly used on modern Linux distributions compared to other journaling filesystems like ext4, XFS, or Btrfs.

While not a common user command, jfs_logdump can be invaluable during filesystem development, for post-mortem analysis of JFS filesystem corruption, or when attempting to understand specific operations that led to an issue on a JFS volume. It helps in verifying the integrity of the journal and identifying specific transaction boundaries for deeper investigation.

JFS (Journaled File System) was originally developed by IBM for its AIX and OS/2 operating systems. JFS version 2 (JFS2) was open-sourced by IBM in 2000 and subsequently integrated into the Linux kernel, starting around version 2.4.18. The jfs_logdump utility is part of the jfsutils package, which provides various tools for managing JFS filesystems on Linux. Its development is tied to the evolution and maintenance of the JFS filesystem support within the Linux ecosystem, primarily serving as a diagnostic component for an older, though still supported, filesystem.

jfs_mkfs(8), jfs_fsck(8), jfs_debugfs(8), mount(8)