Some hints on things only needed in rescue situations, i.e. easily forgotten between emergencies.
A lot of these got easier over the years, but under stress ...
Changing keyboard layout
Example for German (.de):
loadkeys de
Assembling Software RAID devices
mdadm --assemble --scan
Accessing LVM volumes
# find vgscan # activate vgchange -ay # list lvdisplay # mount something mount /dev/volumegroup/logicalvolume /mountpoint