resize_reiserfs

resize_reiserfs [-s size] [-f] [-q] [-V] [-p] device [new_size]

-s size
    Specifies the new size of the filesystem in blocks. If omitted, the filesystem will be extended to fill the entire underlying block device.

-f
    Forces the resize operation. Particularly relevant for shrinking, though unmounting the filesystem is still highly recommended for safety.

-q
    Enables quiet mode, suppressing most output during the resize process.

-V
    Displays the version information for the resize_reiserfs utility and exits.

-p
    Shows progress of the resize operation, displaying percentage completed.

resize_reiserfs is a utility designed to change the size of an existing ReiserFS filesystem. It allows administrators to expand a ReiserFS filesystem to fill a larger underlying block device or, with certain precautions, shrink it to fit a smaller device. This command is typically used in conjunction with logical volume management (LVM) tools like lvextend or lvreduce, or partition management tools like fdisk or parted, which first modify the size of the block device itself. resize_reiserfs then updates the ReiserFS filesystem's metadata to reflect the new size. While it can often grow a filesystem online (while mounted), shrinking usually requires the filesystem to be unmounted for safety. ReiserFS, though once popular, has largely been superseded by more modern filesystems like Ext4 or XFS, so resize_reiserfs is primarily relevant for legacy systems.

resize_reiserfs is primarily for legacy ReiserFS filesystems, as more modern alternatives like Ext4 and XFS are generally preferred.
When shrinking a ReiserFS filesystem, it is highly recommended to unmount it first, even when using the -f (force) option, to prevent data loss or corruption.
Always ensure a full backup of your data before performing any filesystem resizing operations.
Remember that the underlying block device (partition or logical volume) must be resized before resize_reiserfs is used to adjust the filesystem size. Shrinking the block device without shrinking the filesystem first will lead to data loss.

Typically, resize_reiserfs is used in two main scenarios:
1. Growing the filesystem: After extending the underlying block device (e.g., with lvextend or resizing a partition), this command expands the ReiserFS filesystem to utilize the newly available space. This operation can often be performed online (while the filesystem is mounted).
2. Shrinking the filesystem: This involves reducing the size of the filesystem. It requires careful planning and typically an offline operation (unmounting the filesystem) to prevent data corruption. The filesystem must be shrunk before the underlying block device is reduced.

Growing a ReiserFS filesystem with resize_reiserfs can generally be done while the filesystem is mounted and in use (online). However, shrinking a ReiserFS filesystem requires it to be unmounted (offline) to ensure data integrity. Attempting to shrink an online filesystem, even with the force option, carries a significant risk of data loss or filesystem corruption. Always back up critical data before any resize operation.

ReiserFS was developed by Hans Reiser and his company Namesys in the late 1990s and early 2000s, aiming to be a high-performance journaling filesystem. The resize_reiserfs utility is part of the reiserfsprogs user-space tools package, which provides various utilities for managing ReiserFS filesystems. While ReiserFS gained some traction, particularly in its early days for its efficient handling of small files and journaling capabilities, its adoption significantly declined following Hans Reiser's legal troubles and the emergence and maturation of alternative filesystems like Ext3, Ext4, and XFS, which offered comparable or superior performance and stability. Consequently, the development and widespread usage of resize_reiserfs have diminished over time, making it primarily a tool for maintaining older systems.

fdisk(8), parted(8), lvextend(8), lvreduce(8), reiserfsck(8), mkfs.reiserfs(8), mount(8)