The “sfill” command is a Linux utility that is used to securely erase the contents of a hard drive’s free space and inodes. This is important for maintaining the privacy and security of sensitive data that may have been deleted from the drive, but could potentially be recovered through specialized software.
When a file is deleted from a hard drive, the data itself is not necessarily erased. Instead, the file’s directory entry is removed and the space it occupied on the drive is marked as “free.” However, until that space is overwritten with new data, the original contents can potentially be recovered through the use of data recovery software.
The “sfill” command works by securely overwriting the free space on a hard drive with random data multiple times. This makes it much more difficult, if not impossible, for data recovery software to recover any remnants of previously deleted files.
In addition to overwriting the free space, “sfill” can also overwrite the inodes of the partition where the specified directory resides. Inodes are data structures on a Unix-like file system that store information about files and directories, such as ownership, permissions, and timestamps. By overwriting the inodes, “sfill” can ensure that any residual information about previously deleted files is also erased.
sfil Command Examples
1. Overwrite free space and inodes of a disk with 38 writes (slow but secure):
# sfill /path/to/mounted_disk_directory
2. Overwrite free space and inodes of a disk with 6 writes (fast but less secure) and show status:
# sfill -l -v /path/to/mounted_disk_directory
3. Overwrite free space and inodes of a disk with 1 write (very fast but insecure) and show status:
# sfill -ll -v /path/to/mounted_disk_directory
4. Overwrite only free space of a disk:
# sfill -I /path/to/mounted_disk_directory
5. Overwrite only free inodes of a disk:
# sfill -i /path/to/mounted_disk_directory
Note
It is important to note that “sfill” should be used with caution, as it can potentially overwrite data that has not been deleted. Therefore, it is recommended to backup any important data before running “sfill.” It is also important to ensure that the correct partition is selected before running the command, as overwriting the wrong partition can result in data loss.