On GNU/Linux with fdisk (util-linux 2.20.1), when using, say fdisk /dev/sda3 there are quite some options and the and even an expert mode (x). Most of these are explained through the m option.But I can't find an documentation on these, neither in the man not the info page. As I don't want to fumble around with my file systems at the moment - any idea?Just to make this clear: I'm not talking about the regular option, e.g. fdisk -v but the ones where fdiskfirst had to be started. My guess was that I might get luck in another, related manpage but I couldn't find anything so far. Did I miss something?
fdisk (expert mode) options
fdisk;options
This page says Expert mode can be used to force the drive geometry to match another drive: x: Enter expert mode c: Change the number of cylinders h: Change the number of heads r: Return to normal modeAdditionally, fdisk/README.fdisk on source package tells following story:Extra commands for experts--------------------------The eXtra command `x' puts `fdisk' into `expert' mode, in which aslightly different set of commands is available.  The Active, Delete,List, New, Type, Verify, and `eXpert' commands are not available inexpert mode.  The commands Write and Quit are available as in ordinarymode, the Print command is available, but produces output in a slightlydifferent format, and of course the Menu command prints the expertmenu.  There are several new commands.  1. The Return command brings you back to the main menu.  2. The Extended command prints the list of table entries which point     to other tables.  Ordinary users do not need this information.     The data is shown as it is stored.  The same format is used for     the expert Print command.  3. The dangerous Begin command allows you to move the start of data     in a partition away from its beginning.  Other systems create     partitions with this format, and it is sometimes useful to be able     to reproduce it.  4. The slightly dangerous Cylinders command allows you to change the     available number of cylinders.  For SCSI disk owners, note that we     require not the actual number of physical cylinders, but the     number of logical cylinders used by DOS and other operating     systems.  5. The extremely dangerous Heads and Sectors commands allow you to     change the number of heads and sectors.  It should not be     necessary to use these commands unless you have a SCSI disk, whose     geometry Linux is not always able to determine.  SCSI disk owners     note that we need not the actual number of heads or of sectors per     track, but the number believed to exist by DOS and other operating     systems.  *Warning*: If you set either of these numbers to a bad     value, you may lose all data on your disk.Always, after giving any of the commands Begin, Cylinder, Heads, orSectors, you should Return to the main menu and give the Verify command.