wipefs3

Usage

Library

library “libutil ”

Overview

The wipefs family of functions wipe existing file systems on a volume. A DKIOCUNMAP ioctl is sent to the device to invalidate all of its content. Then zeroes are written to various locations that are used by various file systems to recognize their content and mount their volumes. This is usually used by the newfs_* utilities before they create new file systems on the volume, so that the existing file system will not be mounted accidentally after the new file system is created. NOTE: These routines do not overwrite all volume structures. These routines do not securely erase the previous content. They only overwrite enough to make sure that the normal utilities will no longer recognize any file system content. It is possible that previous file system content could be recovered by other means. The wipefs_alloc () function initializes a wipefs_ctx object (which is an opaque data type). file_desc is the file handle of the volume to be wiped, which can be a block device node, a character device node, or a file. file_desc must be opened with write access. If block_size is 0, this function calls ioctl(2 ) to get the block size. A valid block_size, must be supplied if file_desc is a regular file. This function does not write any data to the volume. The wipefs_include_blocks () function tells wipefs to write zeroes in the block range provided, in addition to any other ranges it would normally write. This may be more efficient than if the caller were to write this range separately, especially if the block range overlaps or is contiguous with other ranges that wipefs will write. This function does not write any data to the volume. If this function is called multiple times, the union of all the ranges provided will be written by wipefs_wipe(. ) The wipefs_except_blocks () function tells wipefs not to write anything in the block range provided. This function is used for performance optimizations if the caller will write to these blocks. It is the caller's responsibility to write to these blocks. Otherwise, some file systems may still be recognized on the volume. This function does not write any data to the volume. If this function is called multiple times, the union of all the ranges provided will be excluded from being written by wipefs_wipe(. ) The wipefs_wipe () function sends a DKIOCUNMAP ioctl and then writes data to the volume to wipe out existing file systems on it. CAUTION: this function destroys any file system or partition scheme on the volume represented by file_desc, . If file_desc represents the entire disk (e.g. /dev/diskX), the partition map of the disk will be destroyed. If file_desc represents a partition (e.g., /dev/diskXsY), only the file system in that partition is destroyed. Although the partition scheme or file system on file_desc may be beyond repair after wipefs_wipe(, ) this function is not designed as a means to safely delete all data. It is possible that some user data (or intact file systems in some partitions) may still be recovered. The wipefs_free () function frees the allocated wipefs_ctx handle and set *handlep to NULL.

Return values

The wipefs_alloc(, ) wipefs_include_blocks(, ) wipefs_except_blocks () and wipefs_wipe () functions return 0 on success, or will fail and return an error code. Each function may return ENOMEM if insufficient memory is available. In addition, if block_size is not provided, wipefs_alloc () may return any error ioctl(2 ) returns; wipefs_wipe () may return any error pwrite(2 ) returns.