Delete files securely on Linux – Journaled file systems
Few days ago I write about shred, which work fine for old systems, like EXT2, but not so nice with journaled file systems. Modern file systems need something more robust, like dd and srm (a secure replacement for rm). Unlike the standard rm, srm overwrites and rename the files before unlinking them. This makes it very hard to recovery of the data.
Create test file:
echo "secure content" > /tmp/secure.txt
dd and srm command usage
Fill free space with zeroes (Use very carefully):
dd if=/dev/zero of=/tmp/secure.txt
Write buffered data from the memory out to disk
syncDelete file with srm:
# Basic example srm /tmp/secure.txt # US Dod compliant 7-pass overwrite. srm -D /tmp/secure.txt # US DoE compliant 3-pass overwrite. # Twice with a random pattern, finally with the bytes "DoE". # See http://cio.energy.gov/CS-11_Clearing_and_Media_Sanitization_Guidance.pdf for details. srm -E /tmp/secure.txt # OpenBSD compatible rm. Files are overwritten three times, first with the byte pattern # 0xff, then 0x00, and then 0xff again, before they are deleted. # Files with multiple links will be unlinked but not overwritten. srm -P /tmp/secure.txt
Delete directory:
srm -r /tmp/secure-directory
Write buffered data from the memory out to disk
syncConclusion of commands
# Create echo "secure content" > /tmp/secure.txt # Remove dd if=/dev/zero of=/tmp/secure.txt sync srm -D /tmp/secure.txt sync
More info about options with commands:
man dd man srm
Related posts:
- Delete files permanently with shred command in Linux – Remove absolutely
- Linux Encrypt Files/Decrypt Files – GPG Interactive/Non Interactive Modes
- Linux: Create Text File on Linux Shell / Command Line
- Linux: Display / Show File Contents (tabs, line breaks, non-printing characters)
- Linux locate command: Find Files and Directories Quickly and Efficiently
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