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   8
   9 <H2>Overview</H2>
  10
  11 <H3>What is pdisk?</H3>
  12
  13 <P>A simple editor for Apple disk partition format. There are two
  14 main versions of pdisk: one for Linux and one for the Mac OS. This
  15 document describes the Mac OS version of pdisk. Much of this document
  16 is also relevant to the Linux version, but check the manual page
  17 (pdisk.8) also.</P>
  18
  19 <H3>What is the Apple disk partition format?</H3>
  20
  21 <P>Most operating systems have ways to divide disks into several
  22 pieces - so that an entire disk does not have to be devoted to one
  23 filesystem, or even to one operating system. This division of the
  24 disk is usually called partitioning. In some systems the partitioning
  25 information is built into the operating system code, but that tends to
  26 be restrictive. In the Mac OS the partitioning information is stored
  27 on the first few blocks of the disk.</P>
  28
  29 <P>The Apple disk partition scheme was developed in 1986 by the A/UX
  30 team with input from the Mac OS and Apple II teams. There was an
  31 earlier partition scheme used in the first SCSI drives on the
  32 MacPlus, but that was replaced by the current scheme in the Macintosh
  33 II and subsequent machines and in subsequent operating system
  34 releases. The current scheme is supported by Mac OS, A/UX, ProDos,
  35 MkLinux, LinuxPPC, and MacOS X.</P>
  36
  37 <H3>What are LinuxPPC and MkLinux?</H3>
  38
  39 <P>Just in case you got pdisk other than as part of a LinuxPPC or
  40 MkLinux release:</P>
  41 <P>LinuxPPC is a port of the true Linux operating system that runs
  42 on most of the Power Macintosh systems from Apple Computer. It also
  43 runs on several non-Apple PowerPC machines.</P>
  44 <P>MkLinux is a portion of the Linux operating system, converted to run
  45 as a server process on top of the Mach microkernel. As with Linux,
  46 all of the operating system source code is available for
  47 <A HREF="http://www.mklinux.org">download</A>, including the
  48 Mach source. MkLinux runs on some of PowerPC based Macintosh
  49 machines.</P>
  50
  51 <H3>Which Macintosh machines does pdisk run on?</H3>
  52
  53 <P>The Mac OS binary should run on any PowerPC based Macintosh. It
  54 has been tested under System 7.6.1 and System 8, but should run on
  55 older versions of the Mac OS as well. A Mac OS 68000 binary is also
  56 distributed for those who may find it useful. </P>
  57
  58 <H3>Why would I want to use pdisk on the Mac OS?</H3>
  59
  60 <P>The main clients for the Mac OS version of pdisk are Linux
  61 users. pdisk was originally developed for Linux. The command syntax
  62 was originally identical to that for the 'fdisk' program. (fdisk is a
  63 Linux program which edits the DOS/Windows disk partition format.) The
  64 Mac OS version is a simple, crude port of the Linux version.</P>
  65
  66 <P>The advantages of pdisk over the various Mac OS disk partitioning
  67 programs (such as SilverLining, the FWB toolkit, Apple HD SC Setup,
  68 DriveSetup, etc) are:</P>
  69
  70 <UL>
  71    <LI>unlike the Apple partitioners, it does not restrict the set of
  72    drives it can operate on
  73
  74    <LI>it allows partitions to be reordered (helpful, as Linux
  75    depends on the order)
  76
  77    <LI>it creates Linux partitions by default
  78
  79    <LI>it allows the size of the partition map to be changed
  80
  81    <LI>it allows the name of a partition to be changed
  82
  83    <LI>it allows you to edit the partition map of your boot disk
  84 </UL>
  85
  86 <P>The disadvantages of pdisk are:</P>
  87
  88 <UL>
  89    <LI>it doesn't automatically initialize HFS partitions
  90
  91    <LI>it can't install disk drivers
  92
  93    <LI>it allows you to edit the partition map of your boot disk
  94 </UL>
  95
  96 <H3>Where can I get the source?</H3>
  97
  98 <P>The main site for LinuxPPC is
  99 &lt;<A HREF="http://www.linuxppc.org">http://www.linuxppc.org</A>&gt;.
 100 The main site for MkLinux is
 101 &lt;<A HREF="http://www.mklinux.org">http://www.mklinux.org</A>&gt;.
 102 </P>
 103
 104 <H2>Description of the program (as of version 0.8)</H2>
 105
 106 <P>Though pdisk is a Macintosh program its interface is very
 107 un-Macintosh. pdisk is what is called a line-oriented program. In a
 108 line-oriented program you do things by typing on the keyboard and the
 109 program does not pay attention to the typing until the return key has
 110 been typed.</P>
 111
 112 <P>When you start up pdisk it brings up a window with some text in
 113 it. The last line of this text should be something like " Top level
 114 command (? for help): ". This is the prompt. If you type "?" followed
 115 by a return character you should get a list like this:</P>
 116
 117 <PRE>Notes:
 118     Disk have fake names of the form /dev/scsi&lt;bus&gt;.&lt;id&gt;
 119     For example, /dev/scsi0.1, /dev/scsi1.3, and so on.
 120     Linux style names are also allowed (i.e /dev/sda or /dev/hda).
 121     Due to some technical problems these names may not match
 122     the 'real' linux names.
 123 &nbsp;
 124 Commands are:
 125   h    print help
 126   v    print the version number and release date
 127   l    list device's map
 128   L    list all devices' maps
 129   e    edit device's map
 130   E    (edit map with specified block size)
 131   r    toggle readonly flag
 132   f    toggle show filesystem name flag
 133   q    quit the program</PRE>
 134
 135 <P>Some of these commands need what are called arguments - for
 136 example <B>l</B> (list) and <B>e</B> (edit) need a single argument,
 137 the name of the device to list or edit. Commands which take arguments
 138 prompt for each argument in turn. You can also type any number of the
 139 arguments separated by spaces and those prompts will be skipped.
 140 Commands are case insensitive (e.g. <B>h</B> and <B>H</B>) except
 141 when the upper case letter does a variant form of the operation.</P>
 142
 143 <DL>
 144    <DT><B>h</B>
 145
 146    <DD>Prints just the command help. The difference between <B>h</B>
 147    and <B>?</B> is the latter prints some helpful notes as well.
 148
 149    <DT><B>v</B>
 150
 151    <DD>Prints a version number and release date. Matches the
 152    version in the GetInfo window for the application.
 153
 154    <DT><B>l</B>
 155
 156    <DD>Prompts for the name of the device and then lists the
 157    partition map on that device.
 158
 159    <DT><B>L</B>
 160
 161    <DD>Lists all the devices.
 162
 163    <DT><B>e</B>
 164
 165    <DD>Prompts for the name of the device and then opens the partition
 166    map for editing.
 167
 168    <DT><B>E</B>
 169
 170    <DD>Same as <B>e</B>, except also prompts for block size.
 171
 172    <DT><B>r</B>
 173
 174    <DD>Toggles read-only setting. When read-only is on pdisk will not
 175    write a partition map.
 176
 177    <DT><B>f</B>
 178
 179    <DD>Toggles show filesystem name flag between 'show fileystem name' and
 180    'show partition name'. The default is to show the filesystem name.  Showing
 181    the filesystem name is helpful when you have several equal sized Macintosh
 182    partitions on the disk.
 183
 184    <DT><B>q</B>
 185
 186    <DD>Quit pdisk.
 187 </DL>
 188
 189 <H3>The form of the listing</H3>
 190
 191 <P>This is a good point to show what the partition map listing looks
 192 like.</P>
 193
 194 <PRE>Partition map (with 512 byte blocks) on '/dev/scsi0.2' (/dev/sda)
 195    #:                 type name                length   base    ( size )
 196    1:  Apple_partition_map Apple                   63 @ 1
 197    2:       Apple_Driver43*Macintosh               54 @ 64
 198    3:       Apple_Driver43*Macintosh               74 @ 118
 199    4:        Apple_Patches Patch Partition        512 @ 192
 200    5:            Apple_HFS untitled           2117430 @ 704     (  1.0G)
 201    6:           Apple_Free Extra                   10 @ 2118134
 202 &nbsp;
 203 Device block size=512, Number of Blocks=2118143
 204 DeviceType=0x0, DeviceId=0x0
 205 Drivers-
 206 1: @ 64 for 20, type=0x1
 207 2: @ 118 for 32, type=0xffff</PRE>
 208
 209 <P>The first line indicates what device this is and what size blocks
 210 the partition map is using. Most partition maps will use 512-byte
 211 blocks, but partition maps can use 1024-byte (1K) or 2048-byte (2K)
 212 blocks instead. If we are able to deduce an Linux name different
 213 from the name then the Linux name is given in parentheses.</P>
 214
 215 <P>Next is the partition list. Each partition (or piece) of the disk
 216 takes one line of the list. The data describing the partition is
 217 called the partition map entry. The entries are listed in order by
 218 index. For each entry, the following information is displayed:</P>
 219
 220 <UL>
 221    <LI>index - where the partition entry is in the map. This does not
 222    correspond the relative order of the partition contents and can
 223    change when the partition map is edited.
 224
 225    <LI>type - the sort of data expected to be in the partition. pdisk
 226    doesn't put data into the contents of any partition except the
 227    partition map partition. The type is a case-insensitive string.
 228
 229    <LI>name - the name is for the user's information.  If the name
 230    is in quotes then it is the Mac volume name rather than actual
 231    partition name.
 232
 233    <LI>length - the number of partition blocks the partition takes.
 234
 235    <LI>base - the first block of the partition, measured in partition
 236    blocks, starting from zero.
 237
 238    <LI>size - this is the length in bytes. Only shown if the size is
 239    at least one megabyte.
 240 </UL>
 241
 242 <P>Following the partition list is information from block zero of the
 243 device which describes the location of drivers.</P>
 244
 245 <H3>Editing Partition Tables</H3>
 246
 247 <P>The <B>e</B> command at the top level menu opens a partition map
 248 for editing. The prompt is then changed to "Command (? for help):".
 249 If you type "?" followed by a return character you should get a list
 250 like this:</P>
 251
 252 <PRE>Notes:
 253   Base and length fields are blocks, which vary in size between media.
 254   The name of a partition is descriptive text.
 255 &nbsp;
 256 Commands are:
 257   h    help
 258   p    print the partition table
 259   P    (print ordered by base address)
 260   i    initialize partition map
 261   s    change size of partition map
 262   c    create new partition (standard Linux type)
 263   C    (create with type also specified)
 264   n    (re)name a partition
 265   d    delete a partition
 266   r    reorder partition entry in map
 267   w    write the partition table
 268   q    quit editing (don't save changes)</PRE>
 269
 270 <P>Commands which take arguments prompt for each argument in turn.
 271 You can also type any number of the arguments separated by spaces and
 272 those prompts will be skipped. The only exception to typeahead are
 273 the confirmation prompts on the <B>i</B> and <B>w</B> commands.
 274 Commands can are case insensitive (e.g. <B>h</B> and <B>H</B>) except
 275 when the upper case letter does a variant form of the operation.</P>
 276
 277 <P>Partitions are always specified by their number, which the index
 278 of the partition entry in the partition map. Many of the commands
 279 will change the index numbers of other partitions besides the
 280 affected partition. You are advised to print the table as frequently
 281 as necessary.</P>
 282
 283 <P>Creating more than fifteen partitions is not advised. There is
 284 currently a bug in the some (all?) of the kernels which causes access
 285 to the whole disk fail if more than fifteen partitions are in the
 286 map.</P>
 287
 288 <DL>
 289    <DT><B>h</B>
 290
 291    <DD>Prints just the command help. The difference between <B>h</B>
 292    and <B>?</B> is the latter prints some helpful notes as well.
 293
 294    <DT><B>p</B>
 295
 296    <DD>Prints the partition table. The form is identical to the
 297    listing described above.
 298
 299    <DT><B>P</B>
 300
 301    <DD>Identical to <B>p</B>, except the entries are listed in the
 302    order of the partitions on the disk (i.e. by the increasing base
 303    value) rather than in index order.
 304
 305    <DT><B>i</B>
 306
 307    <DD>Initializes the partition map (rarely used). This command
 308    prompts for the size of the device. WARNING - if you write the map
 309    after initializing it you will delete all the drivers on the device.
 310    That makes the device invisible to the Mac OS. pdisk is not able
 311    to install drivers.
 312
 313    <DT><B>s</B>
 314
 315    <DD>Change the size of the partition map partition. The partition
 316    map's size must be less than or equal to the size of the partition
 317    it is contained in. This is mostly useful when you want to do
 318    tricky things like making a disk with multiple partitioning
 319    schemes on it.
 320
 321    <DT><B>c</B>
 322
 323    <DD>Create a new partition takes three arguments.<BR>
 324
 325    The first argument is the base address (in partition blocks) of
 326    the partition. Besides a raw number, you can also specify a
 327    partition number followed by the letter 'p' to indicate that the
 328    first block of the new partition should be the same as the first
 329    block of that existing free space partition.<BR>
 330
 331    The second argument is the length of the partition in partition
 332    blocks. This can be a raw number or can be a partition number
 333    followed by the letter 'p' to use the size of that partition or
 334    can be a number followed by 'k', 'm', or 'g' to indicate the size
 335    in kilobytes, megabytes, or gigabytes respectively. (These are
 336    powers of 1024, of course, not powers of 1000.)<BR>
 337
 338    The last argument is the name of the partition. This can be a
 339    single word without quotes, or a string surrounded by single or
 340    double quotes.<BR>
 341
 342    The type of the created partition is set to the correct type for
 343    Linux ("Apple_UNIX_SVR2").
 344
 345    <DT><B>C</B>
 346
 347    <DD>Identical to the <B>c</B> command, with the addition of a
 348    prompt for the partition type after the other arguments. The type
 349    can be a single word without quotes, or a string surrounded by
 350    single or double quotes.
 351
 352    <DT><B>n</B>
 353
 354    <DD>Rename a partition. Do not change the name of any partition
 355    whose type starts with "Apple_Driver". The MacOS looks at the
 356    names of those partitions. All other partitions should be okay
 357    to change.
 358
 359    <DT><B>d</B>
 360
 361    <DD>Delete a partition. When a partition is deleted it's type is
 362    changed to free ("Apple_Free") and then it is combined with any
 363    adjacent free space.
 364
 365    <DT><B>r</B>
 366
 367    <DD>Reorder takes the current index and the desired new index. If
 368    you give a new index which is greater than the last index the
 369    entry will be moved to the last index.
 370
 371    <DT><B>w</B>
 372
 373    <DD>Write does write the partition map out, but pdisk does not yet
 374    flush the appropriate caches and unmount volumes so the partition
 375    map is not reinterpreted. In order to use the new partition map
 376    you must reboot your machine. Sorry.
 377
 378    <DT><B>q</B>
 379
 380    <DD>Quit out of editing. Returns to the top level prompt. If you
 381    have modified the partition map you are NOT asked if you want to
 382    save the changes, instead the changes are quietly thrown away.
 383 </DL>
 384
 385 <H3>Known problems</H3>
 386
 387 <DL>
 388    <DD>This is an awful Mac OS application, it should be rewritten
 389    to look the way a Mac OS app should look.
 390
 391    <DD>The code assumes a better understanding of the partitioning
 392    scheme than most people care to acquire.
 393
 394    <DD>&nbsp;
 395
 396    <DD>Even more help should be available during user input.
 397 </DL>
 398
 399 <P>
 400 <HR>
 401 </P>
 402
 403 <ADDRESS><A HREF="mailto:eryk@cfcl.com">eryk@cfcl.com</A>
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