Activating md raid or lvm means that the kernel changes the metadata like
timestamps and mount counts of the devices and writes them to disk.
Also reconstructing degraded md raid devices is automatically activated.
There are cases when writing to disks is absolutely not wanted. For example
when restoring data from broken disks or when doing forensics.
The nomdlvm boot commandline option prevents any activation and thus
not wanted writes. If the user wants to use md or lvm with the option
set, all md or lvm devices have to be manually found and activated.
nomdlvm is only implemented as boot commandline option and does not use
the YAML config file. The reason is that the udev rules are evaluated
before sysrescue-configuration.lua is run, so the YAML config is not
ready yet. Moving nomdlvm after sysrescue-configuration.lua would be
an invasive operation and modify the activation order of all md and lvm
devices for all cases, increasing the probability of regressions.
Also udev rules offer a direct access to boot commandline options, making
implementation straightforward and robust.
