~ubuntu-core-dev/debian-installer/ubuntu

partman-auto recipe files

Contents:

  0. Introduction

  1. Format of the recipes

  2. Examples

  3. Architecture specific recipes

  4. Limitations

  5. How the actual partition sizes are computed

  6. Appendix

0. INTRODUCTION

---------------

partman-auto is the part of the partitioner that automatically partitions

disks. It is controlled by recipes, which are provided in partman-auto as

files, but may also be provided by other udebs, or by preseeding. This

document explains the format of the recipes and how to use them.

1. FORMAT OF THE RECIPES

------------------------

All new lines and tabs in the recipe are converted to spaces.

Then two or more consecutive spaces are converted to one space.

Almost all tokens must be separated by spaces.  An important exception

is the opening curly bracket ("{"); before it there must be _no_

space.

In the following rules we denote spaces by "_".

<recipe>::=<header>_<partitions>

<header>::=<simple name>|<debconf name>

<simple name>::=<name>_:

<name> can be for example "Multi user system".

<debconf name>::=<debconf template>_::

The purpose of <debconf name> is to allow translation of the names of

the recipes into different languages.

<partitions>::=<partition>|<partition>_<partitions>

<partition>::=<limits>_<specifiers>_.

<limits>::=<minimal size>_<priority>_<maximal size>_<parted fs>

<minimal size> is the minimal allowed size of the partition in

megabytes.  It is rounded to cylinder size, so if you make <minimal

size> to be 20 MB and the cylinder size is 12MB, then it is possible

for the partition to be only 12MB.  These sizes may also be given as

a percentage, which makes the size be that percentage of the system's

total RAM.

<maximal size> is the maximal size for the partition, i.e. a limit

size such that there is no sense to make this partition larger.

<priority> is some size usually between <minimal size> and <maximal

size>.  It determines the priority of this partition in the contest

with the other partitions for size.  Notice that if <priority> is too

small (relative to the priority of the other partitions) then this

partition will have size close to <minimal size>.  That's why it is

recommended to give small partitions a <priority> larger than their

<maximal size>.

<parted fs> is the file system as known to parted of this partition.

<specifiers>::=<specifier>|<specifier>_<specifiers>

<specifier>::=<internal specifier>|<regular specifier>|<type specifier>

<internal specifier>::=$primary{_}|$bootable{_}

$primary{_} says that the partition should be primary (if possible).

$bootable{_} says that the bootable flag will be set.

<regular specifier>::=<file name>{ <file contents> }

<file name> is a file to be created in the directory of the partition

in partman's filesystem info. (See section 2.4 of the partman manual

for details.)

<file contents> is the information to write in this file.

<type specifier>::=$lvmok{_}|$defaultignore{_}|$lvmignore{_}

$lvmok{_}

	Indicates that the partition is permitted to be an LVM logical 

	volume should an LVM partitioning scheme be in use.

$defaultignore{_}

	Used to void a partition definition so that it is ignored in the

	default case. That is to say it will be valid in the LVM case.

$lvmignore{_}

	Used to void a partition definition so that it is ignored in the

	LVM case. That is to say it will be valid in the default case.

The specifiers defaultignore and lvmignore allow one recipe to define different 

handling of say the /boot partition between an LVM partitioning scheme and a 

non-LVM scheme.

2. EXAMPLES

-----------

Here is a very simple recipe that creates a swap partition and uses the

rest of the disk for one large root filesystem.

partman-auto/text/atomic_scheme ::

500 10000 1000000 ext3

	$primary{ }

	$bootable{ }

	method{ format }

	format{ }

	use_filesystem{ }

	filesystem{ ext3 }

	mountpoint{ / } .

64 512 300% linux-swap

	method{ swap }

	format{ } .

Here the root partition must be at least 500 mb, and has effectively no

maximum size. The swap partition ranges from 64 mb to 3 times the system's

ram.

Note the use of $bootable{ } to make the partition bootable, and $primary{ }

to mark it as the primary partition.

The specifiers used in this example are:

method{ format }

	Used to make the partition be formatted. For swap partitions,

	change it to "swap". To create a new partition but do not

	format it, change "format" to "keep" (such a partition can be

	used to reserve for future use some disk space).

format{ }

	Also needed to make the partition be formatted.

use_filesystem{ }

	Specifies that the partition has a filesystem on it.

filesystem{ ext3 }

	Specifies the filesystem to put on the partition.

mountpoint{ / }

	Where to mount the partition.

It is also possible to specify mount options. For example, to specify

"nodev,ro" for a partition, add the following lines for that partition:

	options/nodev{ nodev }

	options/ro{ ro }

Here is another example; this time there is a smaller root partition, and a

separate /home partition.

partman-auto/text/home_scheme ::

300 4000 7000 ext3

        $primary{ }

        $bootable{ }

        method{ format }

        format{ }

        use_filesystem{ }

        filesystem{ ext3 }

        mountpoint{ / } .

64 512 300% linux-swap

        method{ swap }

        format{ } .

100 10000 1000000000 ext3

        method{ format }

        format{ }

        use_filesystem{ }

        filesystem{ ext3 }

        mountpoint{ /home } .

Notice that the partitions will be created in the order they are defined

in the recipe.

3. ARCHITECTURE DEPENDENT RECIPES

---------------------------------

Some architectures have specific requirements for their partitions.

For example many of them require special partitions to support

bootloading.

For example, newworld powerpc machines need a newworld boot partition at

the start of the disk. Here is an example fragment of a recipe file to

create one; it should come before other partitions in a recipe. Notice that

the partition is not formatted.

1 1 1 hfs

	$bootable{ }

	method{ newworld } .

Another example is a netwinder, which requires a small /boot partition

formated in revision 0 ext2.

50 500 100 ext2

	$primary{ }

	$bootable{ }

	method{ format }

	format{ }

	use_filesystem{ }

	filesystem{ ext2r0 }

	mountpoint{ /boot } .

And finally, an example of how to set up the efi boot partition needed on

ia64.

100 100 150 fat16

        $primary{ }

        method{ efi }

        format{ } .

For other examples, see the architecture-specific recipes in partman-auto.

4. LIMITATIONS

--------------

Due to limitation of the algorithms in partman-auto, there must be at

least one partition with high maximal size so that the whole free

space can be used.  Usually you can give the partition containing

/home a maximal size 1000000000 which is high enough for the present

storage devices. If the large /home is not an option for you, you can

also define in the recipe one additional partition with size

1000000000, method "keep" and leave it unmounted.  When the

installation completes you can remove it.

Do not use higher than 1000000000 numbers because the shell arithmetic

is limited to 31 bits (on i386).

5. HOW THE ACTUAL PARTITION SIZES ARE COMPUTED

----------------------------------------------

Suppose we have to create N partitions and min[i], max[i] and

priority[i] are the minimal size, the maximal size and the priority of

the partition #i as described in section 1.

Let free_space be the size of the free space to partition.

Then do the following:

for(i=1;i<=N;i++) {

   factor[i] = priority[i] - min[i];

}

ready = FALSE;

while (! ready) {

   minsum = min[1] + min[2] + ... + min[N];

   factsum = factor[1] + factor[2] + ... + factor[N];

   ready = TRUE;

   for(i=1;i<=N;i++) {

      x = min[i] + (free_space - minsum) * factor[i] / factsum;

      if (x > max[i])

         x = max[i];

      if (x != min[i]) {

         ready = FALSE;

         min[i] = x;

      }

   }

}

Then min[i] will be the size of partition #i.

6. APPENDIX

-----------

On May 25th 2004, it was noted that on i386 systems, the very minimum size of

a Debian installation on a classical (/, /usr, /usr, /home) setup was:

48MB on / (6MB on /boot)

77MB on /usr

17MB on /var

It is thus wise to use minimum values with this consideration in mind.

#261244: 70MB are required for /var

#265290: 1.8GB are not enough for / with desktop