Recently I stumbled upon some mystery that I can't understand.
My Google search bring no results.

I have 3 VM with different Linuxes that run under QEMU and now I noticed that
all of them don't have /proc/sys/vm/mmap_min_addr files (/proc is mounted)

I am sure that this file was here some time ago.
I didn't recompile kernel in any of those VMs, don't upgrade QEMU - nothing of the sort.

But those VMs where started and stopped multiple times.

So my questions:
1. What happened, where this file gone?
2. How can I get it back?

My host system (Fedora 12, x86-64) has this file.
One of VM is Fedora 12 ARM, another - Fedora Core 3 x86-64, ant yet another ARM OABI debian - all of them miss mmap_min_addr file.

Thank you,
Valery.

From within the VMs, what does 'sysctl vm.mmap_min_addr' show?

Admittedly for Debian, this Debian wiki entry on mmap_min_addr implies that older versions of Qemu needed mmap_min_addr set to zero to work (newer versions are ok). Are you running an older version?

Also, "Fedora qemu mmap_min_addr" throws up a lot of hits showing Fedora did once have an issue with mmap_min_addr set to 0. Are you convinced you remember accurately (not that I'm doubting you, I mis-remember things all the time).

Turns out that you are quite right - I remembered wrong.
Now I boot QEMU with other (Ubuntu's) kernel for ARM and got my mmap_min_addr back.

Thank you anyway