AFAICT dracut has dracut-shutdown(8) which you can extend at will, or
convince the maintainer to ship the required logic for everyone.
However Debian’s default initramfs, namely initramfs-tools(7) currently
has no interface to hook into at shutdown, and init doesn’t even hand
execution over to the initramfs during the shutdown phase (#778849).
When such an interface is available we can ship shutdown scripts into
Note: There’s a chance it might freeze a VM or host operating system. It didn’t happen to me yet but better to have this in mind.
sudo apt update
sudo apt install secure-delete time
Disabling swap is required. Otherwise smem would fill up all RAM and the system highly likely to permanently freeze.
sudo swapoff --all
To verify that swap is off:
sudo swapon --show ; echo $?
sudo sdmem -h
time sudo sdmem
time sudo sdmem -v
Probably better because it shows some progress.
For just a single pass of RAM wipe with zeros:
without verbose mode:
time sudo sdmem -l -l
with verbose mode:
time sudo sdmem -l -l -v
The time command is optional. Can be dropped. But useful here to measure how long it takes.
Default mode does, quote:
27 passes with special values defined by Peter Gutmann.
Not sure that is really necessary because if I remember right, Peter Gutmann was about hard drives, not RAM. Is there any research how many passes RAM wipe requires?
Should RAM wipe be skipped inside VMs for faster reboot / shutdown times? I am not sure about the dynamics of RAM wipe in VMs. In worst case, the VM might start use swap file on the host operating system. Therefore I tend to say RAM wipe should be skipped if a VM is detected.
secure-delete* package name in debian (sdmem: secure-delete memory)
Wipe mode is secure (38 special passes)
Using /dev/urandom for random input.
Wipe mode is insecure (one pass with 0x00)
Happen to me, i opened xfce-terminal and start moving it right and left until the screen freezed permanently (play for less than 3 minutes with anything like browse some stuff and open close terminal…).