reiserfstune

reiserfstune [ options ]
device

device
    The special file (e.g., /dev/sdb1) corresponding to the ReiserFS filesystem to be tuned.

-j journal_size
    Sets the journal size in blocks. Larger journals can improve performance and recovery but consume more space. Must be within the allowed range (e.g., 512-32768 blocks).

-o [+|-]option
    Modifies default mount options stored in the superblock. For example, +notail enables tail packing, while -notail disables it. Other options may include no_unhashed_relocation or unhashed_relocation.

-s
    Displays the current tunable parameters of the specified ReiserFS filesystem without making any changes.

-t
    Performs a test run. It will show what would be done without actually committing any changes to the filesystem.

-b block_size
    (Rarely used after mkfs) Attempts to change the filesystem block size. This is a highly dangerous operation and can lead to data loss if not handled correctly. Block size is usually set during filesystem creation with mkfs.reiserfs.

-f
    Forces the operation, overriding some safety checks. Use with extreme caution as it can increase the risk of data loss.

-q
    Runs quietly, suppressing most output.

-V
    Displays the version information of reiserfstune.

reiserfstune is a utility from the reiserfsprogs package designed to modify various tunable parameters of an unmounted ReiserFS filesystem. It allows administrators to adjust characteristics like the journal size, block allocation policies, and default mount options stored within the filesystem's superblock. This tool is primarily used for performance optimization or to alter default behaviors, such as enabling or disabling the 'notail' feature, which affects how small files are stored. It is crucial that the filesystem targeted by reiserfstune be unmounted before any operations are performed, as modifying an active filesystem can lead to data corruption. The changes made by reiserfstune are persistent and stored in the filesystem's metadata, affecting future mounts.

Filesystem Must Be Unmounted: It is absolutely critical that the ReiserFS filesystem targeted by reiserfstune is unmounted before executing the command. Operating on a mounted filesystem can lead to severe data corruption and loss.

Risk of Data Loss: Incorrect usage, especially with options like -b (block size change) or -f (force), can result in irreversible data loss. Always back up critical data before making significant changes.

Deprecated Status: ReiserFS itself is largely considered a legacy filesystem and is not actively developed or widely recommended for new deployments. Its tooling, including reiserfstune, reflects this status.

To view the current tunable parameters of a ReiserFS filesystem without making any changes, use the -s option (e.g., reiserfstune -s /dev/sdb1). This is a safe way to inspect the filesystem's configuration before attempting any modifications.

Adjusting parameters like journal size (-j) can significantly impact filesystem performance. A larger journal can reduce the frequency of metadata writes to disk and improve recovery times after crashes, but it consumes more disk space. Similarly, the notail option affects how small files are stored; enabling it can improve performance for workloads with many small files, while disabling it might be better for systems with large files and fewer small ones, potentially at the cost of disk space efficiency for tiny files.

The reiserfstune utility is an integral part of the reiserfsprogs suite, which was developed by Hans Reiser and his company Namesys. ReiserFS was a prominent journaling filesystem in the early 2000s, offering features like tail packing and efficient handling of small files that were innovative for its time. reiserfstune was created as a companion tool to allow administrators to fine-tune these features post-creation. Its development paralleled the evolution of the ReiserFS filesystem itself. While ReiserFS saw significant adoption in its heyday, its usage has declined considerably over the years, largely due to the rise of more modern and actively maintained filesystems like ext4, XFS, and Btrfs, as well as the legal issues surrounding its creator. Consequently, reiserfstune is now primarily encountered in environments managing older ReiserFS installations.

mkfs.reiserfs(8), fsck.reiserfs(8), resize_reiserfs(8), mount(8)