YaST2 Expert Partitioner

Specification

Author: Stefan Hundhammer (sh@suse.de)

Updated: Dec 16, 1999 - see the change log for details.

Abstract

This document is the specification for a new YaST2 partitioner module.

Intentions

This new partitioner is intended for experts who know what they are doing. Novice users should stick with the automatic mode that will still be available.

Being fool-proof is not one of the primary goals for this expert partitioner. But providing the required functionality is. So excessive input and logic validations will be sacrificed for the sake of completeness. If the user decides it is OK the way he specified the partitioner will not question that.

At least the first version of this partitioner will be limited to the i386 PC platform. It will not support BSD disk labels or any other platform specific partitioning schemes.

Functional Specification

This section describes the functionality required for any partitioner regardless of its respective user interface.

Required Functionality

Create A Partition

(i386 specific)

Any of the following partition types can be created:

• Primary
• Extended
• Logical

This is subject so the following restrictions:

• No more than four primary partitions per disk may be created.
• No more than one extended partition per disk may be created.
• An extended partition may only be created if no more than three primary partitions exist on that disk yet (since the extended partition is nothing else than a special primary partition).
• Logical partitions may only be created if an extended partition already exists on that disk.
• A new logical partition can only be appended at the end of the list of logical partitions. This is a restriction the underlying 'fdisk' program imposes. If there is free space within the extended partition between logical partitions, the partitions following the free space will have to be deleted before the free space can be used.

For primary partitions and the extended partition, the partition name (e.g. /dev/hda1 - /dev/hda2) needs to be specified.

In order to stay compatible with other operating systems on the same machine, those partition names cannot be selected automatically: PC technology does not require the table entries to be sorted according to starting cylinder etc. - they might as well be mixed at random, and other OSes might rely on one of the slots to contain the address (i.e. the start and end cylinders) of one of their partitions.

For logical partitions, the partition name will be automatically generated: There is no central table for logical partitions within the extended partition. Rather, one logical partition points to the next one (or, more precisely, wraps the next one). So always the next free slot will be used.

For all types of partitions, the following values need to be specified:

• Start cylinder.
• End cylinder.
• File system type - one of
  • Linux ext2
  • Linux swap
• Mount point.
• Whether or not this partition should be formatted. This is necessary because the user might be forced to delete and then re-create partitions in order to perform certain modifications (e.g. delete a logical partition other than the last) where only partiton table information will be modified, not the data within the partition. This is some kind of last resort when all else fails.
• Optional: The inode density.

Start and end cylinder values are subject to the following restrictions:

• 1 <= start cylinder <= end cylinder <= last cylinder on this disk
• Primary partitions (including an extended partition!) may not overlap.
• Logical partitions are limited by the extended partition's boundaries.
• Logical partitions may not overlap.

Delete A Partition

(i386 specific)

The user can delete a partition subject to the following restrictions:

• An extended partition can only be deleted if there are no more logical partitions within it.
• Only the last of the logical partitions can be deleted.

Optional Functionality

Modify A Partition

Since the underlying 'fdisk' program does not provide a facility to actually modify a partition's cylinder boundaries other than deleting and re-creating a partition, this "modify" facility cannot offer modification of all of the "create" facility's fields, namely the start and end cylinders.

The following values can be changed:

• File system type (ext2/swap)
• Mount point
• Format flag (i.e. whether or not this partition should be formatted)
• Optional: Inode density

Re-Read Partition Table

This function abandons all modifications to the original partitioning on the hard disk(s) and re-reads the original partition tables.

Default Partitioning

This will do the same as the novice mode automatic partitioning. The resulting partitioning scheme can be used as a basis for further customization.

Data Flow

Input Data

• A list of available hard disks including
• Hard disk device name (e.g. "/dev/hda")
• Total number of cylinders
• Size of one cylinder in bytes
• Optional: Hard disk vendor string (e.g. "SEAGATE ST48012")
• A list of existing partitions on those hard disks including
• Partition slot (e.g. "/dev/hda2")
• Start cylinder
• End cylinder
• File system type (numerical)
• File system type as string
• Optional: Mount point

Output Data

• A list of partitions to be deleted including
• Partition slot

• A list of partitions to be created including
• Partition slot
• Start cylinder
• End cylinder
• File system type (numerical)
• Mount point
• Format flag
• Optional: inode density

• A list of partitions to be modified including
• Partition slot
• Start cylinder
• End cylinder
• File system type (numerical)
• Mount point
• Format flag
• Optional: inode density

User Interface Specification

Lessons Learned - The YaST1 Partitioner In Comparison

The YaST1 partitioner provided all of the required and most of the optional functionality described above.

YaST1 used to have a sequence of screens like this:

1. Select one of the available hard disks or skip partitioning alltogether.
2. Create / delete partitions on that selected disk, set file system type for individual partitions.
3. Set mount points and inode density for partitions on the selected disk and/or read the /etc/fstab of an existing installation (for the mount points specified there).
4. Go back to 1., i.e. if the user is finished with all of his hard disks he has to choose "skip partitioning" there in order to get out of this cycle.

A lot of confusion can be avoided if the new partitioner does not require the user to go through a sequence of screens like this, manually choosing when to terminate that process and continue with the installation. Avoiding this is a design goal.

Providing a better overview of the system's hard disks and their respective partitions (and any free space left) is another. It is much easier to have all information on one screen when trying to decide which disk should hold what part of the Linux system to be installed than switching back and forth between several screens.

Users should not be required to make notes on paper during that process just to keep track of partitions on several disks and their respective sizes.

Plus, many low-end PC systems only have one single hard disk to begin with. So step (1) above most of the times is unnecessary but still required here since this is the only exit from that screen sequence loop.

And this category of users will not be overloaded with information in one single dialog because this dialog of course will contain information about their one single hard disk.

The YaST2 Expert Partitioner User Interface

All hard disks and all partitions on them will be displayed on the screen in a scrolled window.

Each hard disk will be displayed in one line including:

• Name (e.g. /dev/hda)
• Start cylinder (always 1)
• End cylinder (i.e. number of cylinders)
• Capacity (human readable, i.e. in mega- or gigabytes)
• Vendor string (i.e. hard disk name, e.g. "SEAGATE ST48012").

Each partition will be displayed in one line including:

• Name (e.g. /dev/hda2)
• Start cylinder
• End cylinder
• Size (human readable, i.e. in mega- or gigabytes)
• The format flag. If the partition is to be formatted, the letter "F" will be displayed here. If not, this field will remain empty.
• Partition type (human readable, i.e. in text format - e.g. "FAT16", "Linux ext2", "Linux swap")
• Mount point, if applicable
• Format flag

Free space between partitions or at the end of a disk will be displayed along with the partitions. This will include:

• Start cylinder
• End cylinder
• Size (human readable, i.e. in mega- or gigabytes)
• Indication of free space (e.g. fixed text "[free]")

Partition and segments of free space will be displayed sorted by (a) hard disk and (b) start cylinder.

Subject to discussion:

Hard disks, primary, extended and logical partitions and free space should be indented to reflect hierarchy they have. Thus it would be much easier to explain to the not-yet-so-expert user the connections between extended and logical partitions and why he cannot simply delete an extended partition as long as there are still logical partitions within it.

The tradeoff, however, is screen space. This indentation might eat up just the screen space necessary to avoid horizontal scrolling (which makes operating this screen very annoying). But if possible with a reasonable amount of work, this indentation should be done.

Selection

Before any action (create, delete, ...) can be performed, a list entry (i.e. a hard disk, a partition or a segment of free space) has to be selected. Depending on that selection, the user can perform actions:

• Hard disk selected:
• Create (primary or extended)
• Primary partition selected:
• Delete
• Modify
• Extended partition selected:
• Create (logical)
• Delete
• Logical partition selected:
• Delete
• Modify
• Free space selected:
• Create (free space boundaries as start/end cylinder defaults)

Modifying hard disks, extended partitions or free space does not make any sense. Neither does deleting hard disks (automatic eject?) or free space.

"Default Partitioning" and "Re-Read Partition Table" are independent of any selection. They may be performed at any time.

Operations

For each of the required and optional functions, a push button will be provided:

• Create
• Delete
• Modify
• Default Partitioning
• Re-Read from Disk

Create

The "create" button will open a popup dialog window to select a partition type (primary, extended or logical). This popup window includes an "OK" button and a "Cancel" button.

Upon making a selection and pressing the "OK" button, another dialog window will be popped up with the following fields:

• Partition name. For primary and extended partitions only. Select one of the four primary partition slots. For logical partitions, this will be an output-only field containing the next available partition slot name.
• Start cylinder - absolute cylinder address.
• End cylinder - either as an absolute cylinder address (e.g. "120") or relative to the starting cylinder (e.g. "+70") or in megabytes (e.g. "+300M"). A megabyte value will be rounded to the next cylinder boundary.
• The file system type (list box or radio box) - one of
  • Linux ext2
  • Linux swap
  Linux ext2 is the default.
• A mount point. No automagic here, just a plain text entry field.
• The format flag (a check box).
• Inode density (plain entry field). This may be left blank. In this case, a reasonable default value will be used.

Delete

The user will be prompted for confirmation when activating this function.

Modify

This opens the same dialog like the "create" function's second popup dialog with the fields for partition name, start cylinder, and end cylinder disabled. Those values will be displayed, however.

Re-Read Partition Table

The user will be prompted for confirmation when activating this function.

Default Partitioning

If the partitioning has been modified in any way, the user will be prompted for confirmation when activating this function since this will essentially abandon all changes.

Prototype

Main dialog

Partition your hard disk: /dev/hda 1-1115 8.5 GB SEAGATE ST48012 /dev/hda1 1- 65 509.8 MB FAT16 /dev/hda2 66- 150 666.7 MB NTFS 151- 300 1.1 GB [free] /dev/hda3 301-1024 5.5 GB Extended /dev/hda5 301- 302 7.8 MB F Linux ext2 /boot /dev/hda6 303- 318 128.0 MB F Linux Swap /dev/hda7 319-1024 5.4 GB F Linux ext2 / 1025-1115 713.0 MB [free] /dev/hdb 1-1115 8.5 GB SEAGATE ST48012 /dev/hdb1 1- 260 2.0 GB NTFS /dev/hdb2 261-1115 6.5 GB Extended /dev/hdb5 261- 276 128.0 MB F Linux Swap /dev/hdb6 277-1115 6.4 GB F Linux ext2 /work [Create] [Delete] [Modify] [Default] [Re-Read]

"Create partition" Dialog

Version 1

Create new primary partition Name: [/dev/hda1] Start Cyl: [____1] End Cyl: [__512] (99/+99/+99M) Type: Linux ext2 Linux Swap Mount Point: [/_________] [ ] Format this partition Inode Density: [______] [OK] [Cancel]

Version 2

Create new primary partition Name Start Cyl End Cyl Type Mount Point Format Inode Dens. [hda1] [____1] [__512] Linux ext2 [/________] [ ] [_______] Linux swap [OK] [Cancel]

Change Log