The legal values are all, most and none. All modules are included on the image if it is set to all. Setting it to most will cause mkinitrd(8) to exclude modules which are considered unlikely to be necessary in the process of bringing up a root file system. Setting it to none will cause mkinitrd(8) to not include any modules, even if modules were specified in /etc/mkinitrd/modules.
The number of seconds the linuxrc script should wait to allow the user to interrupt it before the system is brought up.
If this is set to probe, mkinitrd(8) will try to determine the modules needed to bring up the root file system using /etc/fstab. It will also insert code onto the image in order to setup a software RAID device if necessary. This can be disabled by setting it to a null string. If you wish to use an alternative root device, you can specify it here and mkinitrd(8) will use that to figure out what is needed.
You can also set the file system type of your root device by appending it to the value of ROOT with a space in between. You will need to quote the entire value as otherwise the shell will interpret the file system type as a command.
This variable replaces the obsolete PROBE variable. The values probe and the null string correspond to the values on and off for PROBE.
The umask is used during the construction of the directory structure and the final image.