![]() ![]() To name the whole device with all partitions type the letters without the number. The third letter indicates the device number, so an "a" would be the first SATA and a "b" would be the second. The first letter indicates the storage type, in this case SATA, but an "s" could also mean SCSI, FireWire, or USB. The second partition on the first SATA hard-drive would be sda2. The name of each device (not the name that the admin gave each partition or device) that is given by the system follows a predictable scheme. So, the user has the file, but the file is useless.īefore we continue, here is some information that will aid in directing the undelete utilities to the correct storage unit. For instance, recovering a corrupted JPEG file will be pointless because the image viewer will not be able to generate an image from the file. The file can usually be recovered, but the contents will be useless. If a part of the file has been written over, then the whole file will be corrupted. Then, the user can select which deleted files to recover. Other undelete programs search for all magic numbers. The user may want a PDF, so the program searches for the hex magic number "25504446" which is the ASCII code for "%PDF". Some undelete programs can look for a specific file type. So, an undelete program would find "CAFEBABE" and copy that file to another storage unit. For example, the magic number of a compiled JAVA class is the hex number "CAFEBABE". All files have a specific string of code that is at the very beginning of the file. The program searches the storage unit for file headers. If a filesystem does, this is how an undelete program undeletes the file. Rarely do filesystems erase the allocation table entry. If the files were copied to the same storage unit, then the user could lose other deleted files that are needed. With these filesystems, the undelete program looks at the file allocation list and copies the deleted file to another storage unit. The majority of filesystems only mark the space as empty. When a deleted file is to be recovered, the user must not manipulate any files because if the "empty space" is used, then the file can never be retrieved. After the new file is written to the "empty space", the deleted file is now gone forever. Now, if a file needs to be placed on the storage unit, the operating system will put the file in the space marked as empty. The file's entry on the file allocation table marked as "free space" or the file's entry on the list is erased and then the space is marked as free. When a file is deleted, the filesystem will perform one of two tasks on the allocation table. This list keeps track of what files are where on the storage unit (hard-drive, MicroSD card, flash-drive, etc.). On a filesystem, the system has what is called a file allocation list. When a user deletes a file, it is not gone, only hidden for some time. Often times, a computer user will delete a needed file accidentally and not have an easy way to regain or recreate the file. ![]()
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