


RDEV(8)		Linux Programmer's Manual		RDEV(8)


NNAAMMEE
       rdev  - query/set image root device, swap device, RAM disk
       size, or video mode

SSYYNNOOPPSSIISS
       rrddeevv [[ --rrssvvhh ]] [[ --oo offset ]] [[ image [[ value [[ offset ]] ]] ]]
       rrddeevv [[ --oo offset ]] [[ image [[ root_device [[ offset ]] ]] ]]
       rraammssiizzee [[ --oo offset ]] [[ image [[ size [[ offset ]] ]] ]]
       rroooottffllaaggss [[ --oo offset ]] [[ image [[ value ]] ]]
       sswwaappddeevv [[ --oo offset ]] [[ image [[ swap_device [[ offset ]] ]] ]]
       vviiddmmooddee [[ --oo offset ]] [[ image [[ mode [[ offset ]] ]] ]]

DDEESSCCRRIIPPTTIIOONN
       With no arguments, rrddeevv outputs an _/_e_t_c_/_m_t_a_b line for  the
       current	root  file  system.   With  no	arguments,  rraamm--
       ssiizzee,rroooottffllaaggss,sswwaappddeevv, and vviiddmmooddee print  usage	informa-
       tion.

       In  a  bootable image for the Linux kernel, there are sev-
       eral pairs of bytes which specify  the  root  device,  the
       video mode, the size of the RAM disk, and the swap device.
       These pairs of bytes, by	default,  begin  at  offset  504
       (decimal) in the kernel image:

	       502 Read Only
	       504 RAM Disk Size
	       506 VGA Mode
	       508 Root Device
	      (510 Boot Signature)

       rrddeevv will change these values.

       Typical	values	for  the  _i_m_a_g_e	parameter,  which  is	a
       bootable Linux kernel image, are as follows:

	      /vmlinux
	      /vmlinux.test
	      /vmunix
	      /vmunix.test
	      /dev/fd0
	      /dev/fd1

       When using the rrddeevv, or sswwaappddeevv commands, the  _r_o_o_t___d_e_v_i_c_e
       or _s_w_a_p___d_e_v_i_c_e parameter are as follows:

	      /dev/hda[1-8]
	      /dev/hdb[1-8]
	      /dev/sda[1-8]
	      /dev/sdb[1-8]

       For  the rraammssiizzee command, the ssiizzee parameter specifies the
       size of the RAM disk in kilobytes.

       For the rroooottffllaaggss command, the vvaalluuee parameter should be 11



Linux 0.99		13 March 1993				1





RDEV(8)		Linux Programmer's Manual		RDEV(8)


       to set read-only mode, and 00 to set read-write mode.

       For  the vviiddmmooddee command, the mmooddee parameter specifies the
       video mode:

	      -3 = Prompt
	      -2 = Extended VGA
	      -1 = Normal VGA
	       0 = as if "0" was pressed at the prompt
	       1 = as if "1" was pressed at the prompt
	       2 = as if "2" was pressed at the prompt
	       n = as if "n" was pressed at the prompt

       If the _v_a_l_u_e is not specified, the _i_m_a_g_e will be	examined
       to determine the current settings.

OOPPTTIIOONNSS
       --ss     Causes rrddeevv to act like sswwaappddeevv.

       --rr     Causes rrddeevv to act like rraammssiizzee.

       --vv     Causes rrddeevv to act like vviiddmmooddee.

       --hh     Provides help.

BBUUGGSS
       For historical reasons, there are two methods for specify-
       ing alternative values for the offset.

       The  user  interface  is	cumbersome,  non-intuitive,  and
       should  probably be re-written from scratch, allowing mul-
       tiple kernel image parameters to be  changed  or	examined
       with a single command.

       If  LILO is used, rrddeevv is no longer needed for setting the
       root device and the VGA mode, since these parameters  that
       rrddeevv  modifies  can  be	set from the LILO prompt during a
       boot.  However, rrddeevv is still needed at this time for set-
       ting  the RAM disk size.	Users are encouraged to find the
       LILO documentation for more information, and to	use  LILO
       when booting their systems.

AAUUTTHHOORRSS
       Originally by Werner Almesberger (almesber@nessie.cs.id.ethz.ch).
       Modified by Peter MacDonald (pmacdona@sanjuan.UVic.CA) and by Stephen
       Tweedie (sct@dcs.ed.ac.uk).











Linux 0.99		13 March 1993				2


