Introduction to blivet-gui

Building Blocks

BlivetUtils

BlivetUtils class provides higher level API for Blivet library. It creates the blivet.Blivet object (storage) and all blivet methods are called using this class.

BlivetGUI

BlivetGUI is the main class for the GUI. There are separate classes for every UI part. These classes create all the necessary Gtk widgets (or loads them from Glade files) and provide signal handlers and other helper functions.

Important GUI objects:

  • ActionsMenu – context (right click) menu for user actions

  • DeviceToolbar – toolbar with device-related actions (add, edit, remove…)

  • ActionsToolbar – toolbar with “global” actions (process or clear actions, main menu)

  • ListDevices – list of “root” devices (disks, volume groups, RAIDs…)

  • LogicalView – displays list of children of selected device (both as list using Gtk.TreeView and graphically using Rectangle)

  • PhysicalView – displays list of parents of selected device

Dialogs

Most of the user interaction is done using dialogs. Some important dialogs include:

Multiprocess Communication

Blivet-gui creates two processes – blivet-gui for the UI and blivet-gui-daemon for working with blivet.

Two processes are necessary because blivet needs root privileges to work with storage but GUI applications shouldn’t be running with root privileges.

Both processes communicate using a socket file.

Proxy

Blivet-gui uses pickle to send objects between the processes. Unfortunately most blivet objects are not picklable. To solve this, server and client parts of blivet-gui communicate using “proxy objects”. When BlivetGUI “asks” for some “information” that isn’t picklable (e.g. using get_disks() that returns list of blivet.devices.storage.StorageDevice), BlivetUtilsServer creates a new instance of ProxyID and sends it to the client instead. When client receives it, it creates an instance of ClientProxyObject and sends it to the BlivetGUI instead.

ClientProxyObject has a custom __getattr__ method and has the ProxyID so it can ask the server for values of attributes that BlivetGUI asks for. Thanks to this, BlivetGUI can work with the blivet object without having it.

Note

It isn’t possible to call methods of proxied objects. Only attributes (and properties) are supported.

ProxyDataContainer is a helper class used as a simple picklable container similar to namedtuple.

BlivetGUIClient

BlivetGUIClient provides support for multiprocess communication for the client part of the blivet-gui. BlivetGUI has an instance of the BlivetGUIClient and uses it to communicate with the BlivetUtils via BlivetUtilsServer.

BlivetGUI can call BlivetUtils methods using remote_call() method.

BlivetUtilsServer

BlivetUtilsServer provides support for multiprocess communication for the server part of the blivet-gui. It’s a synchronous socketserver, it has an instance of BlivetUtils and processes tasks from the BlivetGUIClient.

Note

Only one blivet-gui-daemon process can run at a time and it can communicate with only one blivet-gui process. “Binary” file blivet-gui should be used to start blivet-gui. It will automatically spawn the blivet-gui-daemon process with root privileges using pkexec.