the universal Amiga disk partition tool


The rdbtool is a tool from the amitools tool set that allows to inspect or create hard disk partitions readable by the classic Amiga family of computers. The RDB or Rigid Disk Block is a format to describe the first blocks of a hard disk that store information of partitions and file systems used in the partitions.

If you want to work with files stored in the DOS file system of a partition then have a look at the xdftool of amitools.


Disk Image Files

rdbtool is a command line utility that is always called with an hard disk image file path name as the first argument and with one or more commands working on this image:

> rdbtool <image.rdb|image.rdisk> <command> [option]

You can issue multiple commands on a single image by concatenating them with a plus character:

> rdbtool <image.rdb> <command1> [options1] + <command2> [options2] ...

For example:

> rdbtool myimg.rdb create size=10Mi + init + fill

Most options in rdbtool are given as key=value pairs. Here the option size is given with value 10Mi for a 10 MiB sized disk image.

Real Block Device

On Unix/Linux/macOS you can also use a block device of a real hard disk or a CF/SD flash card to directly work on a real device. The file names for the block device differ on the different platforms but typical names are /dev/rdisk1 or /dev/sda.

Always make sure to select the block device of the whole drive (e.g. /dev/hdc) and not the device of some already existing paritioning (e.g. /dev/hdc1).


Also make sure (really, really sure!) to select the correct block device of the hard disk you want to alter with rdbtool. Otherwise you might destroy your actual system disk!!! Most OSes need a priviliged user to perform these operations so you need to run rdbtool as root or with sudo in this case.


This section describes the commands available for rdbtool. You can always issue a help command to see all commands:

> rdbtool test.img help

Open/Create an Image

In rdbtool there are two ways to access an image: open or create it. The open operation assumes that the disk image file already exists or is used for existing devices available through block device names.

create - Create a new disk image

create [ size=<size> | chs=<cyl>,<heads>,<secs> | from=<img> ] [ bs=<n> ]

The create operation is used to create a new image file. The create command needs a size parameter:

> rdbtool test.img create size=10Mi

You can either specify the total size in bytes (or here with unis M=mega Mi=Ki-Units) and let rdbtool choose a suitable disk geometry automatically or you can give the geometry with:

> rdbtool test.img create chs=10,1,32

Here 10 cylinders, 1 head and 32 sectors are defined.

Another way to specify the size of the new image is to give the file name of an existing image or real device. This is useful to create a new image of compatible size:

> rbdtool test.img create from=other.img

You can only use the create command if the given image file does not exist yet. If it already exists then an error message is generated. However, you can force the creation of the image file by giving the -f switch for force:

> rdbtool -f test.img create chs=10,1,32

By default a disk layout with a block size of 512 bytes is created. For larger disks you may want to increase the block size to 1024, 2048, or 4096. Use the bs` option to select the block size:

> rdbtool create size=32Gi bs=4096


Amigas only support RDBs with a 512 byte block size!

open - Open existing image for processing

open [ chs=<cyl>,<heads>,<secs> | c=<cyl> h=<heads> s=<secs> ] [ bs=<n> ]

The open operation usually does not need any paramters:

> rdbtool test.img open + info

You can even omit the open command before other commands in this case:

> rdbtool test.img info

This will implicitly open the image first.

If no option is given then the disk geometry is automatically determined from the image size. If this does not work for an image you can also specify the geometry of the image in the open command:

> rdbtool test.img open chs=10,1,32

You can also only hint the geometry by giving some geometry paramters and let rdbtool guess the others:

> rdbtool test.img open c=10 h=2 s=32

By default the block size of the disk is assumed to be 512. If an RDB is already stored on the disk then rdbtool automatically retrieves the block size from there. You can force a block size by giving the bs option with the open command. This is useful if you want to overwrite an existing RDB with a different block size on a disk:

> rdbtool /dev/disk1 open bs=4096 + init


Amigas only support RDBs with a 512 byte block size!

resize - Change size of existing image

resize [ chs=<cyl>,<heads>,<secs> | c=<cyl> h=<heads> s=<secs> | from=<img> ] [ bs=<n> ]

Similar to the create command you can specify the new size of an image. It will be either shrunk or grown.


The RDB that may be already on the disk is not touched or adjusted! Use the adjust command to adjust the RDB as well.

Inspect the Partition Layout

info - Show information of the RDB data structures

info [partition]

This command gives an overview of the partitions and file systems stored in the RDB blocks. It will return something like:

PhysicalDisk:               0     7817     7880544  3.8Gi  heads=16 sectors=63
LogicalDisk:                2     7817     7878528  3.8Gi  rdb_blks=[0:2015,60(60)] cyl_blks=1008
Partition: #0 'CDH0'        2      103      102816   50Mi    1.31%  DOS3 bootable pri=0
Partition: #1 'DH0'       104      205      102816   50Mi    1.31%  DOS3
Partition: #2 'DH1'       206     2035     1844640  900Mi   23.41%  DOS3
Partition: #3 'DH2'      2036     3763     1741824  850Mi   22.11%  DOS3
Partition: #4 'DH3'      3764     3909      147168   71Mi    1.87%  DOS3
Partition: #5 'CDH1'     3910     3971       62496   30Mi    0.79%  DOS3
Partition: #6 'DH4'      3972     4124      154224   75Mi    1.96%  DOS3
Partition: #7 'DH5'      4125     5953     1843632  900Mi   23.40%  DOS3
Partition: #8 'DH6'      5954     7817     1878912  917Mi   23.85%  DOS3
FileSystem #0                                              DOS1 version=40.1 size=24588

If a partition name (.e.g DH0) or index (e.g. 3) is given then only the information for a single partition is displayed:

> rdbtool test.hdf info DH0
Partition: #1 'DH0'       104      205      102816   50Mi    1.31%  DOS3

list - List information of the RDB data structures

list [partition]

This command is very similar to the info command as it gives a complete overview of the RDB data structures. But the output is more dense and details are omitted. E.g. the DOS environment is not shown:

BlockDevice:                0    30516      976544  476Mi  heads=1 sectors=32 block_size=512
PhysicalDisk:               0    30516      976544  476Mi  heads=1 sectors=32 block_size=512
LogicalDisk:                1    30516      976512  476Mi  rdb_blks=[0:31,#32] used=[hi=3,#4] cyl_blks=32
Partition: #0 'root'        1     6400      204800  100Mi   20.97%  NBR7/0x4e425207
Partition: #1 'swap'     6401    12800      204800  100Mi   20.97%  NBS1/0x4e425301  auto  boot(0)
Partition: #2 'usr'     12801    30516      566912  276Mi   58.05%  NBU7/0x4e425507

json - Print the RDB data structures in JSON Format

json [out.json]

This command is very similar to the info command but dumps all information in JSON format.

If out.json is given then the JSON output is written to this file. Otherwise the JSON is dumped to stdout.

show - Show internal block representation of the RDB data structures


This command is a low-level tool that shows the blocks available in the RDB data structure with their corresponding values. Use this to debug or analyze issues with complex RDBs.

Create a new RDB

init - Create a new and empty RDB structure

init [ rdb_cyls=<cyls> ]

This command creates a new and initially empty RDB structure.

Call this command first to start building a new RDB structure on a disk or disk image:

> rdbtool test.img create size=10Mi + init

The default RDB occupies all the sectors of the first cylinder. If you have chosen a geometry with small cylinders then a single cylinder might not be sufficient to hold the RDB data structures. In this case use the rdb_cyls option to set the number of cylinders to reserve for RDB:

> rdbtool test.img create size=10Mi + init rdb_cyls=2

adjust - Adjust range of existing RDB structure

adjust ( auto [ force ] | [ lo=<cyl> ] [ hi=<cyl> ] [ phys ] )

This command changes the range on the disk that the current RDB covers. It is very handy if you copy a pre-existing image file to a real medium (e.g. compact flash card) with a larger size.

You can either use the auto mode that automatically increases the RDB range to cover the full image or medium. If the cylinder number gets too large then you need to add the force option to allow the change.

> rdbtool /dev/disk4 adjust auto

In manual mode you have to specify the new range of the RDB by giving either the lo and/or hi cylinder. If you add the phys option then not only the logical range of the RDB will be changed but also its physical extend.

> rdbtool test.img adjust hi=1000 phys

The adjust command will abort with an error if the existing partitions do not fit into the new range.

remap - Change geometry of existing RDB structure

remap [ s=<sectors> ] [ h=<heads> ]

This command allows to change the interal geometry of the disk image. The geometry consists of cylinders, heads, and sectors. Typically, the number of heads and sectors is chosen in such a way that the number of cylinders spanning the image does not grow too large.

If you want to adjust an RDB to a larger device size then the cylinder ranges might get too large. In this case use the remap command first to increase the sectors and/or heads to keep the cylinders in a reasonable range.

> rdbtool image.rdb remap s=32 h=8

Note that the remap operation is only allowed if the physical and logical disk layout can be converted to the new values without any resizing. Additionally, all partition ranges must be mappable as well.

add - Add a new partition

add  <size> [ name=<name> ] [ dostype|fs=<dostag> ]
            [ bootable[=true|false] ] [ pri=<priority> ]
            [ automount=true|false ] [ bs=<n> ]

This command creates a new partition.

You have to give the size of the partition in one of the following ways:

  1. Give start and end cylinder:

    start=<cyl> end=<cyl>
  2. Give start cylinder and size:

    start=<cyl> size=<cyl|percent|bytes>
  3. Only give size:


For the size you can specify a number of cylinders, a percent value, or a byte size (The percent value gives the ratio of the total logical disk size):

> rdbtool test.img add start=2 end=5  ; give start and end cylinder
> rdbtool test.img add start=4 size=10  ; give start and number of cylinders
> rdbtool test.img add size=10MiB       ; give size in bytes
> rdbtool test.img add size=50%         ; use half the disk size

If no name option is given then the defaul name DH is used appended with the current partition number starting with 0: DH0, DH1. You can alter the base name by giving the -p switch (for drive prefix):

> rdbtool -p CH test.img init + add size=10%   ; create partition CH0

The dostype or fs switch can be used to select the file system you will use to format the partition. The default is DOS3, i.e. Fast Filing System with International Support. You can give the dostype with DOS<n> or as a hex number 0x44556677 or for standard DOS file systems with ofs, ffs and append dc or dircache or intl flags:

dostype=DOS0        ; OFS
dostype=ofs+dc      ; OFS + dircache
dostype=ffs+intl    ; FFS + international mode
dostype=0x44556677  ; give hex of dostype

You can make a partition bootable by setting the bootable flag. Additionally you can select the boot priority with pri=<n>:

> rdbtool test.img add size=10% bootable pri=10

The bs option allows you to specify the block size of the file system. By default rdbtool uses the block size of the RDB parition itself, e.g. 512. The file system block size must be a multiple of the parition block size, e.g. 1024, 2048, 4096, or 8192.

addimg - Add a new partition from an image file

addimg <file> [ start=<cyl> ]
              [ name=<name> ] [ dostype|fs=<dostag> ]
              [ bootable[=true|false] ] [ pri=<priority> ]
              [ automount=true|false ] [ bs=<n> ]

This command creates a new partition from the contents of a given partition image file. The size of the partition is automatically derived from the file size. The start of the partition is either given with the start option or selected automatically from the next free range in the partition table.

Note that the image size must be a multiple of the cylinder size. Otherwise the partition can’t be added.

The dostype is automatically derived from the first four bytes of the image file. The file system block size can’t be detected automatically and must be given with the bs option if a non-standard (512 bytes) size is used.

See the add command for an explanation of the other options.

change - Modify parameters of an existing partition

change <id>  [ name=<name> ] [ dostype|fs=<dostag> ]
             [ bootable[=true|false] ] [ pri=<priority> ]
             [ automount=true|false ] [ bs=<n> ]

The <id> is the number of the paritition as given in the info command. You can also use the device name to select a partition:

> rdbtool test.img change 0 name=CH0 bootable=true

For options see the add command.

free - Show free cylinder range in partition layout


This command returns one or more cylinder ranges that are currently not occupied by partitions. You can use this command to find out the range for a new partition.

If the current partition layout aready occupies the whole disk then this command will return nothing.

fill - Fill the remaining space in the partition layout

fill [ name=<name> ] [ dostype|fs=<dostag> ]
     [ bootable[=true|false] ] [ pri=<priority> ]
     [ automount=true|false ] [ bs=<n> ]

This command takes the free space in a partition layout and creates a new partition that fills this space.

This command supports the same options as used in the add command above.

If multiple holes are in the current partition layout then this command creates a new partition for each existing hole.

With this command you can easily finish paritioning without the need of calculating the size of the final partition:

# create 2 partitions with 50% size each
> rdbtool test.img init + add size=50% + fill
> rdbtool test.img init + add size=10% + add size=20% + fill

For options see the add command.

delete - Delete an existing partition

delete  <id>

This command removes an existing partition and frees all associated resources.

The <id> is the number of the paritition as given in the info command. You can also use the device name to select a parition:

> rdbtool mydisk.rdb delete 0
> rdbtool mydisk.rdb delete dh1

map - Show the allocation map of the RDB blocks


This command lets you look under the hood of the RDB. It will print all blocks associated with the RDB and shows their current contents. A two char code is used for each block:

--    block is empty and not used for RDB
RD    the main rigid disk block
P?    partition <n>
F?    file system <n>


> rdbtool mydisk.rdb map

Import/Export Partitions

export - Export Data of a Partition into a File

export <partition> <file_name>

Store the raw byte contents of a partition into the given file. As a result a file system image will be written. You can use the result as a RDB-less image in xdftool.

import - Import Data from a File into a Partition

import <partition> <file_name> [pad]

Read the raw partition data from a given file into an existing partition. You typically use a RDB-less file system image as input.

The size of the input file has to match the partition size. If you give the pad option the input file may be smaller and overwrites only the beginning of the partition area.

Working with File System Drivers

The RDB data structure allows to store file system drivers for classic AmigaOS, so the Kickstart can load the driver before mounting a parition in the RDB.

File systems are LoadSeg()able Amiga Hunk binaries directly embedded in the RDB blocks.

Use the info command to see if any file systems are already stored in the RDB. In the output you can see that the file systems are numbered in rdbtool starting with 0.

fsget - Retrieve the file system driver from a RDB structure

fsget  <id> <filename>

This command extracts the file system numbered <id> and stores the LoadSeg()able Amiga binary on your local system into a new file with the given <filename>:

# create a new file "ffs" with the first driver
> rdbtool mydisk.rdb fsget 0 ffs

fsadd - Add a new file system driver

fsadd  <filename>  [version=<x.y>]

Add the LoadSeg()able file system driver stored in file <filename> to the current RDB.

Every file system driver needs a version information given as <x>.<y>, e.g. 40.63. When a file is loaded the version is automatically extracted from a VER: tag inside the binary. If this tag cannot be found you can specify the version with the version option:

> rdbtool mydisk.rdb fsadd ffs version=60.32

fsflags - Change flags of file system

fsflags  <id>  [ clear | key=value ... ]

With this command you can alter the device node flags of a file system.

The file system <id> is the number of the file system as listed with the info command.

The following keys are supported:


The clear option will remove all flags first. All other commands add the corresponding flag:

> rdbtool mydisk.rdb fsflags 0 clear stack_size=8192

Have a look at the output of the info command to see the flags set for a file system.

fsdelete - Remove a file system

fsdelete <id>

The file system with the given number is removed. All associated blocks of the file system are free’d in the RDB structure.