InstallerVolumeManagement

Revision 10 as of 2005-04-29 05:57:20

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InstallerVolumeManagement

Status

Introduction

This spec considers our options for setting up logical volume management in the installer by default.

Rationale

Partitioning has historically been a headache on default Linux installations. It would help if we could perform Logical Volume Manager (LVM) installations out of the box.

Scope and Use Cases

  • A user adds a hard disk to her computer, and wants to make use of the extra space without having to juggle mount points.

  • Having created separate / and /home partitions, a user finds that he is running out of space in /home, and wants to reallocate more space from /.

Implementation Plan

Today, the standard implementations of logical volume management on Linux revolve around the device-mapper. The most widely used front-ends are LVM2 and EVMS. The back-end storage is compatible between the two, so we are free to make use of the simplest command-line interface available, which currently seems to be LVM2.

There are a number of factors to take into consideration when deploying LVM2 on new systems by default:

  • GRUB does not support /boot on LVM

  • We need to verify that our initrd-tools package supports installing with / on LVM

  • Resizing tools for LVM2 still need investigation (no e2fsadm)

We will investigate these, and apply fixes as required. It will probably be safest to create a separate /boot partition outside LVM; 128MB has been suggested as a sensible default size.

There is already an installer component (partman-auto-lvm) that can automatically create partitions on LVM. This will need testing and bug-fixing (it has not been widely used anywhere yet) and will need work to allow creating a mix of LVM and non-LVM partitions. This should happen early in the Breezy development cycle. We will make LVM partitioning options available (not as the default) early in development, and will then consider whether it can be a safe default. If we encounter problems that primarily affect desktop users, we have the option of considering LVM partitioning as the default only for server installations.

On powerpc, parted does not yet support LVM, although work is in progress on this; thus, for the time being, we may need to make this change only for i386 and amd64. Like GRUB, yaboot does not support /boot on LVM.

Data Preservation and Migration

We will not attempt to migrate existing systems to LVM; this is a very hard problem, and would probably be unwise.

Packages Affected

User Interface Requirements

Standard command line user interfaces for modifying and resizing logical volumes exist. Of the available graphical user interfaces, the leader appears to be evmsgui, but it is extremely complex and cryptic. We should investigate other options, and if no adequate solutions are available we should consider developing our own.

Red Hat has system-config-lvm, but its UI needs work and it is lacking in functionality.

Outstanding Issues

UDU BOF Agenda

UDU Pre-Work