Given that we boot into a modern Linux distribution with the "/run" toplevel
directory, we can easily mount move the whole /run directory to the real
root in the end and have the complete initramfs later on in
/run/initramfs. All log files and /run states are still accessible and
to save space /run/initramfs can be removed later on.
Because the kernel does not mount a tmpfs on /run prior to unpacking the
initramfs cpio image, we have to copy ourselves very early to a tmpfs
and mount it on /run.
Due to lazy umount the old initramfs binaries should
be removed in the end by switch_root.
This feature can be turned on with "--prefix".
We want all "/var/run" information to live in /dev/.run, until the real
root is mounted.
Therefore we mount a tmpfs on /dev/.run, which can/will be bind/move mounted
on /var/run later on.
Jóhann B. Guðmundsson