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I use Knoppix (or other Live CDs/DVDs) as a secure environment for creating valuable crypto keys. Unfortunately entropy is a limited resource in such environments. I just noticed that each program start consumes quite some entropy. This seems to be due to some stack protection feature that needs address randomization.

Nice feature but completely useless and - worse - destructive in my scenario. Is there any possibility to disable this feature? I would prefer one that allows me to continue using the original Knoppix (or whatever) image and just need some configuration at runtime.

I read that this was caused by glibc. I am surprised that an strace -p $PID -f -e trace=open against bash does not show any accesses to /dev/random when I start programs. But I am not familiar with the interaction of execve() and the linker.

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If this is indeed due to address randomization (ASLR has to do with where the program is loaded, see here: http://en.wikipedia.org/wiki/Address_space_layout_randomization) then you can disable it by passing norandmaps to the kernel in the boot options (see here: http://www.linuxtopia.org/online_books/linux_kernel/kernel_configuration/re30.html).

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  • This kernel parameter indeed solves the problem. Apr 11, 2013 at 0:29

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