Securely deleting files is an essential practice for maintaining privacy and security on your Linux system. When you delete a file using the standard methods, such as the rm command, the file is not actually erased from the disk; instead, the space it occupied is marked as available for new data. This means that the file can potentially be recovered using data recovery tools. To prevent this, you need to overwrite the file's data, making it irretrievable. This article will guide you through several methods to securely delete files on a Linux system.

Examples:

Using the shred Command

The shred command is a standard utility in Linux used to securely delete files by overwriting them multiple times.

Example:

shred -u -n 3 -z sensitive_file.txt

• -u: Remove the file after overwriting.
• -n 3: Overwrite the file 3 times. You can increase this number for more security.
• -z: Add a final overwrite with zeros to hide shredding.

Using the wipe Command

The wipe command is another tool designed to securely erase files and free disk space.

Example:

wipe -f sensitive_file.txt

• -f: Force the operation without asking for confirmation.

Using the dd Command

The dd command can be used creatively to overwrite a file with random data.

Example:

dd if=/dev/urandom of=sensitive_file.txt bs=1M count=1
rm sensitive_file.txt

• if=/dev/urandom: Use random data as input.
• of=sensitive_file.txt: Output to the file you want to overwrite.
• bs=1M: Block size of 1 Megabyte.
• count=1: Write 1 block of random data.

Using the srm Command

The srm command is part of the Secure Deletion Toolkit, which offers a secure way to delete files.

Example:

srm -v sensitive_file.txt

• -v: Verbose mode, shows progress.

To use srm, you may need to install the secure-delete package:

sudo apt-get install secure-delete

Considerations:

• SSD Drives: Secure deletion on SSDs can be more complex due to wear leveling. Using full disk encryption from the start is recommended for SSDs.
• Permissions: Ensure you have the necessary permissions to delete the files.
• Backups: Always ensure you have backups of important data before performing secure deletions.