After upgrading the kernel from sys-kernel/gentoo-sources:3.17.8-r1 to sys-kernel/gentoo-sources:3.18.7 my LTSP thinclient loses the /proc mount during boot. On two of my servers (rootfs on disk) I use the same kernel sources without any problem. Even when booted in single user mode and repeatedly executing stuff like: `# mount ls /proc` after some time /proc is empty and mount fails. I also tried sys-kernel/gentoo-sources:3.19.1 and sys-kernel/vanilla-sources:3.19.1 with the same result. This is similar to http://forums.gentoo.org/viewtopic-p-7695378.html but I use openrc and the /sys mount does not disappear.
Made another try today: With sys-kernel/gentoo-sources-3.19.8 the problem is gone.