dm-linear with secure deletion (wipe, erase) on discard
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dm-linear like target which provides discard, but replaces it with write of random data to a discarded region. Thus, discarded data is securely deleted. Because of abstract nature it could support many file-systems which support discard (such as ext3, ext4, xfs, btrfs).

Operation notes:

Create mapped device with secdelsetup tool. Make sure file-system is mounted from that device and not from underlying device. Make sure file-system is mounted with -o discard option. Do not enable data journaling (such as -o data=journal do not enable it). Note, that when you rm files discard and, thus, erasing will go asynchronously, so, to make sure data is already erased issue sync or mount file-system with -o sync option before rm. If you wish that filenames are wiped too - delete directory itself, so its blocks are discarded and erased. If you issue fstrim all free blocks of file-system will be discarded and thus erased too (make sure that file-system is still mounted with -o discard though.)


secdelsetup /dev/sda5 [/dev/mapper/secdel5]
  • will map sda5 to secdel5. Then, file-system on secdel5 should be mounted with -o discard.
secdeltab --all or secdeltab --list
  • show current maps.
secdelsetup --save
  • save current maps to /etc/secdeltab which will be automatically activated after reboot (by secdeltab.service systemd unit).
secdeltab --detach-all
  • detach all active maps.

Based on the code of dm-linear from Linux kernel of their respective authors. (C) 2018; License GPLv2.