As asked by udev-181 I built a ramdisk to mount /usr. I use genkernel for that. Genkernel mount /usr right, and read-only. But init scripts (localmount ?) try to remount it, fails, and thus not remount it read-write.
1) Please post your `emerge --info' output in a comment. 2) Please post your `emerge -vpq sys-fs/udev sys-apps/openrc' output in a comment.
Ahum... I figure out that due to genkernel-3.4.25.1 openrc should be 0.9.9. It was not. I update, and everything goes well : /usr remounted rw.