FDISK(8) FreeBSD System Manager's Manual FDISK(8) NNAAMMEE ffddiisskk - NEC PC-98x1 slice table maintenance utility SSYYNNOOPPSSIISS ffddiisskk [--BBIIaaiissttuuvv] [--1122334455667788] [_d_i_s_k] ffddiisskk --ff _c_o_n_f_i_g_f_i_l_e [--iittvv] [_d_i_s_k] PPRROOLLOOGGUUEE In order for the BIOS to boot the kernel, certain conventions must be adhered to. Sector 0 of the disk must contain boot code, a slice table, and a magic number. BIOS slices can be used to break the disk up into several pieces. The BIOS brings in sector 0 and verifies the magic number. The sector 0 boot code then searches the slice table to determine which slice is marked ``active''. This boot code then brings in the bootstrap from the active slice and, if marked bootable, runs it. Under DOS, you can have one or more slices with one active. The DOS ffddiisskk utility can be used to divide space on the disk into slices and set one active. DDEESSCCRRIIPPTTIIOONN The FreeBSD utility, ffddiisskk, serves a similar purpose to the DOS utility. The first form is used to display slice information or to interactively edit the slice table. The second is used to write a slice table using a _c_o_n_f_i_g_f_i_l_e, and is designed to be used by other scripts/programs. Options are: --aa Change the active slice only. Ignored if --ff is given. --BB Reinitialize the boot code contained in sector 0 of the disk. Ignored if --ff is given. --ff _c_o_n_f_i_g_f_i_l_e Set slice values using the file _c_o_n_f_i_g_f_i_l_e. The _c_o_n_f_i_g_f_i_l_e always modifies existing slices, unless --ii is also given, in which case all existing slices are deleted (marked as ``unused'') before the _c_o_n_f_i_g_f_i_l_e is read. The _c_o_n_f_i_g_f_i_l_e can be `--', in which case standard input is read. See _C_O_N_F_I_G_U_R_A_T_I_O_N _F_I_L_E, below, for file syntax. _W_A_R_N_I_N_G: when --ff is used, you are not asked if you really want to write the slices table (as you are in the interactive mode). Use with caution! --ii Initialize sector 0 of the disk. This implies --uu, unless --ff is given. --II Initialize sector 0 slice table for one FreeBSD slice covering the entire disk. Some space at the start of the disk will reserved for the IPL program and the pc98 slice table itself. --ss Print summary information and exit. --tt Test mode; do not write slice values. Generally used with the --ff option to see what would be written to the slice table. Implies --vv. --uu Update (edit) the disk's sector 0 slice table. Ignored if --ff is given. --vv Be verbose. Slices that are unused are suppressed unless this flag is specified. When --ff is used, ffddiisskk prints out the slice table that is written to the disk. --1122334455667788 Operate on a single slice table entry only. Ignored if --ff is given. The final disk name can be provided as a ``bare'' disk name only, e.g _d_a_0, or as a full pathname. If omitted, ffddiisskk tries to figure out the default disk device name from the mounted root device. When called with no arguments, it prints the sector 0 slice table. An example follows: ******* Working on device /dev/da0 ******* parameters extracted from in-core disklabel are: cylinders=33075 heads=8 sectors/track=32 (256 blks/cyl) parameters to be used for BIOS calculations are: cylinders=33075 heads=8 sectors/track=32 (256 blks/cyl) Media sector size is 512 Warning: BIOS sector numbering starts with sector 1 Information from DOS bootblock is: The data for partition 1 is: sysmid 148,(FreeBSD/NetBSD/386BSD) start 256, size 2490112 (1215 Meg), sid 196 beg: cyl 1/ sector 0/ head 0; end: cyl 9727/ sector 0/ head 0 system Name FreeBSD(98) The data for partition 2 is: sysmid 148,(FreeBSD/NetBSD/386BSD) start 2490368, size 5505024 (2688 Meg), sid 196 beg: cyl 9728/ sector 0/ head 0; end: cyl 31231/ sector 0/ head 0 system Name FreeBSD(98) The data for partition 3 is: The data for partition 4 is: The data for partition 5 is: The data for partition 6 is: The data for partition 7 is: The data for partition 8 is: The data for partition 9 is: The data for partition 10 is: The data for partition 11 is: The data for partition 12 is: The data for partition 13 is: The data for partition 14 is: The data for partition 15 is: The data for partition 16 is: The disk is divided into three slices that happen to fill the disk. The second slice overlaps the end of the first. (Used for debugging purposes.) _s_y_s_m_i_d is used to label the slice. FreeBSD reserves the magic number 148 decimal (94 in hex). _s_t_a_r_t and _s_i_z_e fields provide the start address and size of a slice in sectors. _c_y_l, _s_e_c_t_o_r and _h_e_a_d fields are used to specify the beginning and end addresses of the slice. _s_y_s_t_e_m _N_a_m_e is the name of the slice. _N_o_t_e: these numbers are calculated using BIOS's understanding of the disk geometry and saved in the bootblock. The --ii and --uu flags are used to indicate that the slice data is to be updated. Unless the --ff option is also given, ffddiisskk will enter a conversational mode. In this mode, no changes will be written to disk unless you explicitly tell ffddiisskk to. The ffddiisskk utility will display each slice and ask whether you want to edit it. If you say yes, ffddiisskk will step through each field, show you the old value, and ask you for a new one. When you are done with the slice, ffddiisskk will display it and ask you whether it is correct. It will then proceed to the next entry. Getting the _c_y_l, _s_e_c_t_o_r, and _h_e_a_d fields correct is tricky, so by default, they will be calculated for you; you can specify them if you choose to though. After all the slices are processed, you are given the option to change the ``active'' slice. Finally, when all the new data for sector 0 has been accumulated, you are asked to confirm whether you really want to rewrite it. The difference between the --uu and --ii flags is that the --uu flag edits (updates) the existing slice parameters while the --ii flag is used to ``initialize'' them (old values will be ignored); it will setup the last BIOS slice to use the whole disk for FreeBSD; and make it active. NNOOTTEESS The automatic calculation of starting cylinder etc. uses a set of figures that represent what the BIOS thinks the geometry of the drive is. These figures are taken from the in-core disklabel by default, but ffddiisskk initially gives you an opportunity to change them. This allows you to create a bootblock that can work with drives that use geometry translation under the BIOS. If you hand craft your disk layout, please make sure that the FreeBSD slice starts on a cylinder boundary. Editing an existing slice will most likely result in the loss of all data in that slice. You should run ffddiisskk interactively once or twice to see how it works. This is completely safe as long as you answer the last question in the negative. There are subtleties that ffddiisskk detects that are not fully explained in this manual page. CCOONNFFIIGGUURRAATTIIOONN FFIILLEE When the --ff option is given, a disk's slice table can be written using values from a _c_o_n_f_i_g_f_i_l_e. The syntax of this file is very simple; each line is either a comment or a specification, as follows: ## _c_o_m_m_e_n_t _._._. Lines beginning with a ## are comments and are ignored. gg _s_p_e_c_1 _s_p_e_c_2 _s_p_e_c_3 Set the BIOS geometry used in slice calculations. There must be three values specified, with a letter preceding each number: cc_n_u_m Set the number of cylinders to _n_u_m. hh_n_u_m Set the number of heads to _n_u_m. ss_n_u_m Set the number of sectors/track to _n_u_m. These specs can occur in any order, as the leading letter determines which value is which; however, all three must be specified. This line must occur before any lines that specify slice information. It is an error if the following is not true: 1 <= number of cylinders 1 <= number of heads <= 256 1 <= number of sectors/track < 64 The number of cylinders should be less than or equal to 1024, but this is not enforced, although a warning will be printed. Note that bootable FreeBSD slices (the ``_/'' file system) must lie completely within the first 1024 cylinders; if this is not true, booting may fail. Non-bootable slices do not have this restriction. Example (all of these are equivalent), for a disk with 1019 cylinders, 39 heads, and 63 sectors: g c1019 h39 s63 g h39 c1019 s63 g s63 h39 c1019 pp _s_l_i_c_e _t_y_p_e _s_t_a_r_t _l_e_n_g_t_h Set the slice given by _s_l_i_c_e (1-8) to type _t_y_p_e, starting at sector _s_t_a_r_t for _l_e_n_g_t_h sectors. Only those slices explicitly mentioned by these lines are modified; any slice not referenced by a pp line will not be modified. However, if an invalid slice table is present, or the --ii option is specified, all existing slice entries will be cleared (marked as unused), and these pp lines will have to be used to explicitly set slice information. If multiple slices need to be set, multiple pp lines must be specified; one for each slice. These slice lines must occur after any geometry specification lines, if one is present. The _t_y_p_e is 165 for FreeBSD slices. Specifying a slice type of zero is the same as clearing the slice and marking it as unused; however, dummy values (such as ``0'') must still be specified for _s_t_a_r_t and _l_e_n_g_t_h. Note: the start offset will be rounded upwards to a head boundary if necessary, and the end offset will be rounded downwards to a cylinder boundary if necessary. Example: to clear slice 4 and mark it as unused: p 4 0 0 0 Example: to set slice 1 to a FreeBSD slice, starting at sector 1 for 2503871 sectors (note: these numbers will be rounded upwards and downwards to correspond to head and cylinder boundaries): p 1 165 1 2503871 aa _s_l_i_c_e Make _s_l_i_c_e the active slice. Can occur anywhere in the config file, but only one must be present. Example: to make slice 1 the active slice: a 1 SSEEEE AALLSSOO boot98cfg(8), bsdlabel(8), gpart(8), newfs(8) HHIISSTTOORRYY A version of ffddiisskk first appeared in the Mach Operating System. It was subsequently ported to 386BSD. AAUUTTHHOORRSS ffddiisskk for Mach Operating System was written by Robert Baron <_r_v_b_@_c_s_._c_m_u_._e_d_u>. It was ported to 386BSD by Julian Elischer <_j_u_l_i_a_n_@_t_f_s_._c_o_m>. BBUUGGSS The default boot code will not necessarily handle all slice types correctly, in particular those introduced since MS-DOS 6.x. The entire utility should be made more user-friendly. Most users new to FreeBSD do not understand the difference between ``slice'' and ``partition'', causing difficulty to adjust. You cannot use this command to completely dedicate a disk to FreeBSD. The bsdlabel(8) command must be used for this. FreeBSD 12.0-CURRENT September 8, 2016 FreeBSD 12.0-CURRENT