calamares/src/modules/partition

Architecture

Overview

The heart of the module is the PartitionCoreModule class. It holds Qt models for the various elements and can create Calamares jobs representing the changes to be performed at install time.

PartitionPage is the main UI class. It represents the module main page, the one with the device combo box, partition list and action buttons. It reacts to the buttons by creating various dialogs (the (...)Dialog classes) and tell PartitionCoreModule what to do.

Use of KDE Partition Manager source code

This module makes heavy use of code coming from KDE Partition Manager. Since Partition Manager does not provide a library, we build one out of it.

We maintain our own fork of Partition Manager source code. The master branch in this repository follows Partition Manager upstream master branch. Calamares-specific code is kept in the calamares branch of the fork. The goal is to keep the changes as small as possible to be able to regularly import changes from the upstream master branch and merge them into the calamares branch.

Partition Manager code is included in the source code using a git submodule.

We only use a small subset of Partition Manager code: mainly the libparted abstraction and some widgets like the PartResizerWidget. We notably do not use Partition Manager job and operation classes.

Partition and PartitionInfo

Calamares needs to store some information about partitions which is not available in Partition Manager's Partition class.

This includes the install mount point and a boolean to mark whether an existing partition should be formatted.

Reusing the existing Partition::mountPoint property was not an option because it stores the directory where a partition is currently mounted, which is a different concept from the directory where the user wants the partition to be mounted on the installed system. We can't hijack this to store our install mount point because whether the partition is currently mounted is an important information which should be taken into account later to prevent any modification on an installed partition.

The way this extra information is stored is a bit unusual: the functions in the PartitionInfo namespace takes advantage of Qt dynamic properties methods to add Calamares-specific properties to the Partition instances: setting the install mount point is done with PartitionInfo::setMountPoint(partition, "/"), retrieving it is done with mountPoint = PartitionInfo::mountPoint(partition).

The rational behind this unusual design is simplicity: the alternative would have been to keep a separate PartitionInfo object and a map linking each Partition to its PartitionInfo instance. Such a design makes things more complicated. It complicates memory management: if a Partition goes away, its matching PartitionInfo must be removed. It also leads to uglier APIs: code which needs access to extra partition information must be passed both Partition and PartitionInfo instances or know a way to get a PartitionInfo from a Partition.

The other alternative would have been to add Calamares-specific information to the real Partition object. This would have worked and would have made for a less surprising API, but it would mean more Calamares-specific patches on Partition Manager, making it potentially more difficult to regularly merge Partition Manager master branch into our calamares branch.

Tests

The module comes with unit tests for the partition jobs. Those tests need to run on storage device which does not contain any data you care about.

To build them:

cd $top_build_dir/src/modules/partitions/tests
make buildtests

To run them you need to define the CALAMARES_TEST_DISK environment variable. It should contain the device path to the test disk. For example, assuming you plugged a test USB stick identified as /dev/sdb, you would run the tests like this:

sudo CALAMARES_TEST_DISK=/dev/sdb $top_build_dir/partitiontests

TODO

• Support resizing extended partitions. ResizePartitionJob should already support this but the UI prevents editing of extended partitions for now.

• Use os-prober to find out the installed OS. This information could then be used in PartitionModel and in the partition views.

• PartitionPreview

  • Show used space
  • Highlight selected partition
  • Make the partitions clickable
  • Match appearance with PartResizerWidget appearance

• Expose PartitionInfo::format in PartitionModel and add a column for it in the tree view