Sculpt Operating System 22.10

Introduction

Sculpt is a component-based desktop operating system that puts the user in the position of full control. It is empowered by the Genode OS Framework, which provides a comprehensive set of building blocks, out of which custom system scenarios can be created. The name Sculpt hints at the underlying idea of crafting, molding, and tweaking the system interactively. Starting from a fairly minimalistic and generic base system, this tour through the Sculpt system will cover the following topics:

• A boot image that is a live system, rescue system, and bootstrap system all in one,

• Connecting to a wired or wireless network,

• Installing and deploying software,

• Ways to tweak and introspect the system, and

• Managing and accessing storage devices.

Community

The best place to learn more about using and tweaking Sculpt, to follow the work of the developers, and to get hold of announcements of new software and features is the federated Genodians blog:

Feedback and contact

Your feedback is appreciated!

A printable PDF version of this document is available at the Genode website.

Hardware requirements and preparations

Sculpt should be compatible with recent Intel-based PC hardware featuring Intel graphics, E1000 networking, Intel wireless, and AHCI/NVMe.

It is tested best on laptops of the Lenovo X and T series (X220, X250, X260, T430, T460, T470, T490). For experimenting with Sculpt, we recommend getting a refurbished version of one of these. You may also find the unofficial hardware compatibility list helpful for finding Genode-compatible hardware.

Sculpt has been tested with screen resolutions up to 2560 x 1440. Displays with a higher resolution are not expected to work. The sweet spot is a full-HD display.

Please revisit the BIOS settings of your machine in the following respects:

Getting a first impression

Sculpt is best explored by first booting the prebuilt disk image downloadable from https://genode.org/download/sculpt. Right after system boot, Sculpt's system-management user interface ("Leitzentrale") appears. The panel at the top of the screen contains two centered tabs for switching between the "Components" view and a "Files" view (Figure 1). The components view displays a live graph of the software components and their relationships. It also provides convenient access to the connected storage devices. The "Log" button at the right side of the panel reveals diagnostic messages, the "Network" button allows you to configure network connectivity, and the "Settings" button on the left gives access to a few user-interface tweaks (Figure 1).

Consider the following steps as a warm-up with Sculpt OS.

Select the in-memory file system as default storage location by clicking on the "ram fs" component in the graph and pressing the "Use" button (Figure 2). This way, software will be installed solely into memory without accessing any real storage device.

Enable networking in the "Network" dialog by selecting the "Wired" or "Wifi" option. In the latter case, select an access point and enter the corresponding passphrase (if needed). A successful network connection is indicated by the IP address displayed at the bottom of the network dialog (Figure 3).

With a storage location selected and established network connectivity, it is time to install and start additional components by clicking on the + button of the components view. Select "Depot ..." from the menu (Figure 4).

The depot contains software packages, which can be obtained by different independent software providers. The selection of software providers is completely up to the user and can be defined in the "Selection ..." sub menu (Figure 5).

Select "genodelabs" to download the directory of software officially provided by Genode Labs. Note that the other options are not necessarily affiliated with Genode Labs. Think of each option as a different individual. If you don't trust one particular software provider, you can still install and use the provided software without risk as long as you don't explicitly grant their components access to sensitive parts of your system. The judgement of trust is entirely yours.

When now going back to the depot menu, a new menu item "genodelabs ..." appears. It leads to a catalogue of software browsable via hierarchically structured menus. As a starter, let's add a desktop background. In the "GUI ..." sub menu, a click on the first item named "sticks blue backdrop" reveals the option to install the package (Figure 6).

A click on the "Install" button triggers the download of the package and its dependencies. Once the download is complete, the menu presents a configuration dialog that allows you to define the interplay of the new component with the system. In this particular case, you have to decide for a GUI service to be used by the backdrop (Figure 7).

The first option "system GUI server" would grant direct access to the system's low-level GUI server, which is normally not used by applications but by higher-level GUI servers like a window manager. The second option would give the component the privilege to act as a lock screen. The third option would connect the component to the special "desktop background" GUI session, which appears as a layer behind all other applications. The fourth option "keyboard focus" is preserved for a single component that controls the keyboard focus. In our case, "desktop background" is the correct choice. Once the configuration is complete, a new button for adding the component to the system appears (Figure 8).

After pressing the button, you should notice a slight visual change. Press F12 to toggle between the Leitzentrale and the desktop. Now, the backdrop should become visible in full glory. In the component graph, the new component appears connected to the "GUI". A click on the component reveals further information along with the options to remove it from the system or to restart it (Figure 9).

As a next step, let us add a window system. In the + menu, you can find a readily packaged window system at genodelabs -> GUI -> themed wm. After installing the package, you are asked to take five decisions:

The GUI (focus) should be assigned to "keyboard focus" to put the window manager in charge of controlling the keyboard focus, which is part of its job after all. The GUI should be assigned to "system GUI server" as the basic mechanism to be used for graphical output and user input for the windowed applications. By assigning Report (shape) to pointer shape, we allow the window manager to report information about mouse-pointer shapes. By assigning Report (clipboard) to global clipboard, we grant the window manager the right to change the content of the global clipboard. Vice versa, by assigning ROM (clipboard), we permit the window manager to obtain clipboard content.

After adding the component, the "themed wm" will appear in the components view. To give the window system a quick try, add the small demo you can find at genodelabs -> Demos -> nano3d and assign its GUI to our "themed wm". You will be greeted with the window as shown in Figure 10.

Next, let us add a small Unix-like subsystem called system shell hosted in a window. This subsystem will be presented in a terminal window. The font used by the terminal is obtained from a font server. To create the font server, install and add the package genodelabs -> GUI -> fonts fs, and assign the system font configuration to its ROM (config). "ROM" means read-only memory. So we grant the font server read-only access to the system's default font configuration (which is generated automatically according to the screen resolution).

For starting the actual system shell, select and install genodelabs -> Tools -> system shell from the menu. The configuration dialog is a bit more elaborate this time.

With those decisions taken, a fresh system shell can be started, which appears in a window (Figure 11).

When selecting the "system shell" component in the graph, the relationship to the other components of the system is presented. This provides a convenient way to reveal the trusted computing base of the selected component (Figure 12). For example, since there is no connection from system shell to the nic_router, we know that this component is isolated from the network. The network-related components are outside the trusted computing base of the system shell.

Further exploration

Of course, there are many more components to explore and to combine. For inspiration, please follow the postings at https://genodians.org, for example:

Base system

Unless customized, the Sculpt base system resides as a self-contained live operating system on a USB stick, not installed on disk. This has two advantages. First, it makes the update of the base system straight-forward and completely risk-free. Simply install the new version on a second USB stick. Should the new version cause any trouble, one can fall back to the original one by swapping the USB sticks. Second, it alleviates the need to install any boot-loader infrastructure on disk. In fact, one can use an entire disk as one file system without creating a partition table.

Note that Genode is not limited to booting from USB. It also supports the use of partitions. But for this guide, we keep things as simple as possible.

System overview

System overview

The Sculpt system consists of four parts living on top of the microkernel (Figure 13).

Static system

The first - static - part of the system is baked into the boot image. It contains components that must be shared by the upper - dynamic - parts and defines the relationships between the upper parts via a static policy that is fixed by the creator of the boot image (Figure 14).

Detailed look at the static part of the system

Besides a low-complexity GUI multiplexer called Nitpicker, the static system contains two in-memory file systems. The config file system stores configuration data whereas the report file system stores information reported by components. These file systems are invisible to regular components. Components obtain their configuration data from a (read-only memory) ROM service, and report their state to a (write-only) report service.

At boot time, the config file system is pre-populated with information from the boot image. It stays in memory. Hence, after rebooting the system, any changes are gone.

Drivers subsystem

The drivers subsystem provides all the basic services needed to realize an interactive system scenario: a framebuffer driver for the graphical output, input drivers to obtain user input, and a block service to access a storage device. All other drivers like networking or audio drivers are not covered by the drivers subsystem. They will enter the picture at a later stage and will use the platform service and USB service to access device resources.

Services provided by the drivers subsystem

As illustrated by Figure 15, some drivers like the framebuffer driver live in a dynamically managed subsystem that depends on runtime discovery of the hardware by the so-called driver-manager component. Whenever an Intel graphics device is present, the Intel framebuffer driver is spawned. Otherwise, a generic VESA driver or a driver for a boot-time-initialized framebuffer is used.

Several components of the drivers subsystem report their state. For example, when the Intel framebuffer is used, it reports the list of connectors present. Most importantly, the driver manager reports the available block devices.

As user input may enter the system in multiple ways - most prominently PS/2 and USB HID - the drivers subsystem contains a so-called event-filter component that merges these event streams and applies transformations like key remappings or mouse acceleration.

Leitzentrale subsystem

The Leitzentrale gives you - the user - full control over the config file system and the report file system. You are free to inspect and manipulate the system in any way you wish. The German term Leitzentrale refers to a control center that requires a certain degree of sophistication from the operator, which would be you. A typo at the wrong place may render your system temporarily inaccessible, eventually requiring a reboot. But don't be afraid. Since all manual changes performed in the Leitzentrale occur in memory only, you are not at risk of permanently bricking your machine.

The Leitzentrale can be toggled at any time by pressing F12 and will be enabled right after boot. It presents itself with a minimalistic GUI for accessing the storage devices attached to your machine and for configuring your network connectivity. Most importantly, however, it allows the user to access the config and report file systems. Both file systems are readily accessible under the "Files" tab of the panel. The file browser allows you to traverse directory hierarchies, inspect individual files, and edit files. Alternatively to the "Files" tab, Sculpt 22.10 features a command-line interface. To spawn this command-line interface, click on the "ram fs" component in the graph and select "Inspect". In the panel, a third tab named "Inspect" appears, which hosts the command-line interface (Figure 16).

The inspect tab hosts a small Unix-like runtime as user interface. Don't let the presence of a Unix shell mislead you. Sculpt is not a Unix system. It merely uses Unix-like subsystems as convenient tools for managing and editing files. Within the inspect tab, you can interact with both the report and config file systems using familiar commands such as the bash shell, a subset of coreutils, and Vim.

Note that the interactive inspect view is not bullet-proof. Should you get stuck, you may re-spawn it at any time by toggling the "Inspect" button.

Besides the interactive shell, the Leitzentrale employs a simple viewer of the most recent diagnostic log messages. You can toggle the log display via the panel's log button. Each line of the log is prefixed by the label of the originating component. For detailed analysis, the complete log is also available at report/log and can be browsed with Vim in the inspect window.

Tweaking and inspecting the system

The Leitzentrale subsystem empowers you to interactively inspect and tweak the running system either by using the file browser hosted in the "Files" tab or by using the command-line interface and the Vim text editor provided by the "Inspect" tab.

Interactive file browser

The "Files" tab of the panel switches the main screen area to a simple file browser that lists all file systems available, in particular the config and report file systems (Figure 17). By toggling one of the file-system buttons, the respective directory hierarchy can be browsed. When hovering a file, an "Edit" or "View" button appears, which can be used to open the file in a text area that appears on the right side of the file browser. The editor supports the usual notepad-like motions, operations, and shortcuts (control-c for copy, control-v for paste, control-s for save).

Note that the file browser as the most recent addition to Sculpt does not yet support file operations like the copying, renaming, or removal of files. Also the editing of files with long lines or the browsing of directories with many entries is not appropriately covered yet. As a fallback when encountering these limitations, the current version of Sculpt still features the Unix-based inspect tab, which can be activated by toggling the "Inspect" button inside the USB or storage nodes of the component graph.

Vim skills recommended for using the inspect tab

With the "Inspect" button toggled for at least one file system, the inspect tab leverages (a subset of) GNU coreutils, bash, and Vim as the user interface for sculpting the system. If you are not yet familiar with using Vim, you may take Sculpt as a welcome chance to get your toes wet. To enjoy the experience, you should be comfortable with the following operations:

• Opening and navigating within a text file (moving the cursor, using / to search),

• Using the insert mode to make modifications,

• Reverting accidental modifications (u undo),

• Saving a modified file (:w),

• Opening a file in a secondary buffer (:e),

• Switching between buffers (:bn for next, :bp for previous),

• Copy and paste (v start selection, V start line selection, y remember selection, p paste remembered selection),

• Exiting Vim (:x save and exit, :q! discard changes).

Adjusting the user-input handling

By default, Sculpt uses the US-English keyboard layout but it offers a few alternative keyboard layouts like French and German in the settings menu at the upper left corner. A change of this setting is reflected in the config/managed/event_filter file, which is the configuration for the event-filter component mentioned in Section System overview. For tweaking the input processing beyond the keyboard-layout setting, copy this file to config/event_filter.

 inspect:/> cp /config/managed/event_filter /config/event_filter

With the config/event_filter file in place, you may notice that the keyboard-layout menu has vanished. This is because now you have taken over manual control. (BTW, you can get the menu back at any time by removing the file).

As a Vim user, you most likely want to remap the useless capslock key to escape, don't you? You can accomplish this by editing your /config/event_filter file.

 inspect:/> vim /config/event_filter

To remap the capslock key to escape, change the following line

 <key name="KEY_CAPSLOCK" to="KEY_CAPSLOCK"/>

to

 <key name="KEY_CAPSLOCK" to="KEY_ESC"/>

After saving the file, a Vim user's life suddenly becomes much more pleasant.

Filter chain for user-input events

Take the time to review the remaining parts of the event-filter configuration. The nested configuration nodes define a hierarchy of filters that are applied in the order from the inside to outside (Figure 18). There are filters for merging events (<merge>), remapping buttons and keys (<remap>), supplementing symbolic character information (<chargen>), pointer acceleration (<accelerate>), and emulating a scroll wheel by moving the pointer while pressing the middle mouse button (<button-scroll>).

Display settings

If you are running the Intel graphics driver, you can inspect the connected displays and their supported resolutions by taking a look at the report at /report/drivers/dynamic/intel_fb_drv/connectors. This report is updated whenever a display is connected or disconnected. You can use this information to enable or disable a display in the driver's configuration, which you can find at /config/fb_drv.

For a quick test, change the attribute height="768" to force_height="768" (you may modify width analogously). When saving the file, the screen real-estate will forcibly be limited to the specified size. This is helpful during presentations where the projector has a lower resolution than the laptop's internal display. By specifying the beamer's resolution, both the laptop and the beamer show the same content.

Exploring the drivers and Leitzentrale subsystems

You can review the construction plan of the drivers subsystem by opening the file drivers at the config file system. In particular, it is interesting to follow the <route> rules to see how the various components are connected. But there is more. The configuration is live. It enables you to reconfigure individual components on-the-fly. For example, search for the <start> node of the PS/2 driver and add the attribute verbose_keyboard="yes" to the embedded <config> node. By saving the file, the changed configuration becomes effective. Any key pressed or released on the PS/2 keyboard will result in a log message on the right. You may revert this change (vim: u) and save the original version of the file.

Note that not all components are dynamically reconfigurable but many modern ones - in particular the init component and most long-running server components - are.

It is possible to forcibly restart a component by adding a 'version' attribute to the <start> node. Whenever the version value is changed, the component is re-spawned.

The component-specific configuration options are documented in the README files accompanying the respective components in the source tree.

Analogously to the drivers subsystem, you can find the construction plan for the Leitzentrale subsystem at the file leitzentrale. Try out the following tweaks:

• Change the transparency of the Leitzentrale by modifying the alpha attribute of the fader component.

• Change the font size of the log_terminal component from "10" to "18".

You may also enjoy tinkering with the configuration of the Nitpicker GUI server, which is located at the file nitpicker. For example, you may change the background color or the labeling color of the "default" domain.

System resources

Whenever adding a new component via the + menu, one has to define how to connect the component with the rest of the system. It is important to know what the presented options mean to take educated decisions.

Each choice represents a connection to a system resource of a particular type. Initially, the presented options are resources that are built-in into Sculpt's base system. Once new components enter the picture, their services also appear as options.

Table 1: Overview of system resources

Table 1 gives an overview of the different built-in resources and their types. The names given in the interface column correspond to the Genode session types as found in the routing rules of the deploy configuration or launcher definitions (Section Runtime management). Let's look into each type in more detail.

GUI

ROM

Report

File system

Block device

 <route>
   <service name="Block"> <parent label="ahci-1"/> </service>
 </route>

Device access

USB

Real-time clock

GPU

Region maps

Direct memory-mapped I/O, port I/O, and device interrupts

Tracing

Hardware virtualization

Protection domain

Network and uplink

Terminal, audio input, and audio output

Capture and event

CPU-resource assignment

You may already have noticed the additional item "Resource assignment ..." in the component-configuration dialog (Figure 20). It leads to a sub menu for restricting the CPU usage of the new component. The configuration dialog shows a matrix of CPU cores where the x-axis denotes the physical cores and the y-axis the hyperthreads. By default, all available CPU cores are selected. You can toggle the nodes by clicking on them. The dialog ensures that the selection is always a rectangular area. So one click may affect nodes other than only the clicked one.

Below the CPU-affinity matrix, the dialog allows for the selection of the component's scheduling priority. Note that here the notion of priority refers to hard static priorities as opposed to nice levels. That is, a high-priority activity prevents all lower-level priorities from executing. Consequently, the assignment of a high priority comes at the risk of starving lower-priority components. The dialog presents four options:

Driver

The highest priority should be preserved to latency-critical device drivers such as audio drivers. This option is also a sensible choice for trusted components that must stay somewhat responsive under any condition. For example, the components of the leitzentrale GUI operate on this priority to preserve the user's control over the system even in the event of a rampaging high-priority device driver.

Multimedia

The second-highest priority is recommended for latency-sensitive applications such as audio and video players as well as their dependencies. For example, it is the appropriate priority for window-management components.

Default

The default priority is suitable for all regular applications as well as storage and networking components.

Background

The lowest priority is designated for non-interactive best-effort workloads such as long-running computations. By assigning the background priority to such components, they won't impede the user's perception of the responsiveness of the system.

Service-level sandboxing

In order to deploy any component, all resources requested by the component must be assigned to appropriate services. For example, when adding a web browser, the browser's request for audio-in/out session must be satisfied, which is natural when consuming multimedia content. However, in other situations, we may deliberately want to isolate the web browser from the audio hardware, forcibly preventing the browser from producing any noise or tapping the microphone.

This is where the so-called "black hole" component enters the picture, which can readily be deployed from the package genodelabs -> Tools -> black hole. The black-hole component provides pseudo services for most resources mentioned in the previous section, including audio, networking, video capture, USB, and ROM. Hence, the resource requirements of an untrusted component can be satisfied without exposing a real resource. This is especially useful for deploying highly flexible components like VirtualBox, which supports many host-guest integration features, most of which are desired only in a few scenarios. For example, to shield a virtual machine from the network, the "Network" resource of the VirtualBox instance can simply be assigned to the "black hole".

Runtime management

In contrast to the drivers subsystem and the Leitzentrale, which have a predefined purpose, the runtime subsystem is shaped by the user. The components present in the runtime subsystem are displayed by the components view. Some of them are managed by the Leitzentrale. For example, while inspecting a file system, the corresponding "inspect" component appear automatically. Other components correspond to subsystems deployed from installed packages, in particular the ones created via the "+" menu.

The current configuration of the runtime subsystem is available at the config file system at managed/runtime. It is not recommended to modify this file manually. However, in some situations, it is useful to take manual control over the runtime configuration. This is possible by copying the file to the root of the config file system. Note that this will inhibit the management functionality of the Leitzentrale. You can yield back the control to the Leitzentrale by removing the runtime file from the root of the config file system.

As a prerequisite for deploying user-selected components, a default storage location must be defined by selecting the "Use" button of a file system in the menu. For the start, it is best to select the "ram" file system as storage location. Once you are comfortable with Sculpt, you may make the installation and customizations permanent by using a real storage device instead.

The selection of a "used" file system has two immediate effects. First, any files present at config/<VERSION>/ at the selected file system are copied to the config file system. As the RAM file system is empty, no files are copied. Second, the so-called depot/ is initialized at the selected file system. The depot is the designated place for the installation of software packages. By default, the depot is initialized such that the Sculpt system accepts software from Genode Labs as well as from a few members of the Genode community. You may inspect the content of /ram/depot using the inspect window.

With a file system and an Internet connection selected, additional software can be installed and run. The most convenient way is the interactive use of the + menu to browse the catalogues of packages provided by software providers and to configure new component instances.

Additionally, the deployment can be controlled by the deploy file of the config file system and the so-called launchers located at the launcher/ sub directory. The deploy file contains a <start> node for each running component. Such a <start> node specifies the package, the assigned resources, and the rules of how the component is connected with other components.

Alternatively, a <start> node may refer to a launcher that encapsulates this policy as a separate file at the launcher/ directory. By default, the launcher corresponds to the name attribute of the start node. It is possible to explicitly refer to a differently named launcher by specifying a launcher attribute. This way, one launcher can be instantiated multiple times. The files within the launcher/ directory are monitored by Sculpt and therefore can be edited on the fly. This is especially useful for editing <config> nodes of already running components. A <config> node within a launcher - when present - overrides the one provided by the package. In turn, a <config> node within a node of the deploy config overrides any other <config> node. Both the launcher and a <start> node may contain a <route> node. The routing rules defined in the <start> node have precedence over the ones defined by the launcher. This way, the routing of a launcher can be parameterized at the deploy configuration.

Each time the deploy file or a launcher file is written, the change takes immediate effect. In particular, the Sculpt manager will automatically kick off the download of the referenced packages and its dependencies and thereby populates the depot. Once the download has completed, the packages are started.

Interplay of the deploy configuration and interactive changes

The content of the deploy file is taken as the starting point for the interactive use via the + menu. All interactive changes to the deployment are reflected in the managed/deploy file. Note that any modification of deploy resets managed/deploy to the state defined in the deploy file.

Launchers appear at the top level of the + menu. So they are a convenient mechanism to quickly add often-used components with specific policies to the system.

Storage device access and preparation

Whereas the RAM file system is practical for quick tests, it goes without saying that we want to persistently store data, programs, and configuration information on a storage device. Sculpt supports SATA disks, NVMe devices, and USB-storage devices. The storage and USB nodes of the components view list all devices detected by the drivers subsystem. A click on a device reveals possible operations or - if a partition table is present - more details about the device structure.

Depending on the operation selected by the user, the Sculpt manager will automatically spawn helper components in the runtime to perform the selected operation. For example, by selecting the "Format device" operation, the Sculpt manager will create a tiny Unix-like subsystem with the selected block device mounted at /dev/block and e2fsprogs mounted at /. This Unix-like subsystem runs mkfs.ext2 as init process. Likewise, an existing EXT2 file system can be checked by activating the "Check" button, which triggers the execution of fsck.ext2 for the selected file system.

A particularly interesting option is presented at the last partition of the Sculpt USB stick. Initially - right after copying Sculpt's tiny disk image to the USB stick - the partition is only a few MiB in size. However, using the "Expand" operation, the partition can be extended to the full size of the USB stick, which makes enough room to use the USB stick as Sculpt file system. This clears the way for sculpting a custom live system stored entirely on the USB stick.

All file systems supported by Sculpt present an "Inspect" button. By toggling this button, the selected file system becomes accessible in the "Inspect" tab. Note that more than one file system can be inspected at a time. Each file system will appear as a directory at the root of the inspect directory tree, named after the corresponding device and partition number. This way, the inspect window becomes a convenient tool for copying files between file systems. Under the hood, the Sculpt manager spawns a file-system component for each inspected file system, which translates the notion of files and directories to block-device accesses.

Making customizations permanent

It is possible to make any customization of the config file system permanent by copying the modified files to a directory named config/<VERSION> on a persistent file system where <VERSION> corresponds to the Sculpt version number as found in the /VERSION file. Each time this file system is selected for "Use", those files will be automatically copied to the in-memory config file system.

The most important customization is the system composition, usually created via the + menu. To make it permanent, copy the current state of /config/managed/deploy to /<DISK>/config/<VERSION>/deploy where <DISK> corresponds to your Sculpt partition. This deploy configuration will take effect whenever the Sculpt partition is selected for "Use".

To streamline the boot procedure into a customized Sculpt system even more, it is possible to mark one file system as default. At boot time - when the Sculpt manager discovers the attached storage devices - it automatically selects a file system for use according to the following order of preference:

1. Partition named "GENODE*" on a USB device in a GPT (GUID Partition Table),

2. Partition named "GENODE*" on a SATA or NVMe storage device in a GPT,

3. An entire SATA or NVMe device used as a single EXT2 file system (as devised by Sculpt EA).

The storage dialog hosts a convenient "Default" button that allows one to toggle a partition label between "GENODE" and "GENODE*". For example, the last partition of the Sculpt USB stick can be marked as default or non-default using this button.

Advanced usage

Manual configuration

Thanks to the Sculpt-manager component of the Leitzentrale, many typical work flows and configuration tweaks are largely automated. For example,

• The management of storage devices,

• The creation of file-system components for used or inspected file systems,

• The selection and configuration of network access,

• Font size selection depending on the screen resolution,

• Keyboard-layout selection, or

• Triggering the download of missing depot content on demand.

This convenience comes at the price of built-in policy, which may stand in the way of sophisticated scenarios. For this reason, almost all policies of the Sculpt manager can be overridden by manually managed configuration files.

The Sculpt manager interacts with the rest of the system solely by monitoring reports aggregated in the report file system, and writing configuration files into the config file system. All files generated by the Sculpt manager are located at the managed/ sub directory of the config file system. By manually creating a same-named file at the root of the config file system, one can supply a custom managed configuration to the Sculpt manager. A useful practice is taking a snapshot of the generated configuration as a starting point for the custom version. For example, by copying the NIC router configuration while it is connected to a network:

 cp /config/managed/nic_router /config

Now, the copy at /config/nic_router can be edited. Note that changes usually take immediate effect.

Examples of manual customization are:

• Adding custom NIC router policies such as port-forwarding rules,

• Installing depot content manually by managing /config/installation by hand. This includes the ability to download the source code for any package.

• Disarming the automated update mechanism by using a /config/installation file with no <archive> entries.

• Fixing the current state of the runtime subsystem by copying /config/managed/runtime to /config/runtime. This allows one to manually tweak and inspect the runtime in any way, e.g., to enable additional reporting when troubleshooting.

• Manually defining the default font sizes by creating a custom config/fonts configuration.

• Managing Wifi credentials manually by supplying a custom config/wifi file.

To revert any manual customization, delete the corresponding file. In this case, the Sculpt manager will take over again. Note that all manual customizations can be made permanent by following the steps explained in Section Making customizations permanent.

Building the boot image

The following steps assume that you have the Genode tool chain installed on a GNU/Linux system. For reference, Ubuntu LTS is known to work well. If you don't know your way around Genode's source tree yet, please consider the "Getting started" section of the Genode Foundations book that is available as a free download at https://genode.org.

1. Clone Genode's Git repository:

    git clone https://github.com/genodelabs/genode.git
    cd genode
    git checkout -b sculpt-22.10 sculpt-22.10
   

2. Download the support for the NOVA microkernel

    ./tool/depot/download genodelabs/bin/x86_64/base-nova/2022-10-11
   

   The content is downloaded to the public/ directory and extracted to the depot/ directory.

3. Download all ingredients for the Sculpt boot image

    ./tool/depot/download \
       genodelabs/pkg/x86_64/sculpt/2022-10-13 \
       genodelabs/pkg/x86_64/drivers_managed-pc/2022-10-11 \
       genodelabs/pkg/x86_64/wifi/2022-10-13 \
       genodelabs/bin/x86_64/ipxe_nic_drv/2022-10-11
   

4. Create a build directory

    ./tool/create_builddir x86_64
   

5. Configure the build directory by editing build/x86_64/etc/build.conf. Most importantly, enable the gems source-code repository where the Sculpt scenario resides. In addition, the libports, ports, pc, dde_linux, dde_rump, and dde_ipxe repositories are needed as well. Second, change the default configuration of the QEMU_RUN_OPT variable to image/disk instead of image/iso. This way, the build process will produce a valid disk image with a GPT partition table instead of a legacy ISO image.

6. Prepare GRUB 2, which is needed for booting from the disk image

    ./tool/ports/prepare_port grub2
   

7. Create the Sculpt boot image (defined by the run script at repos/gems/run/sculpt.run)

    make -C build/x86_64 run/sculpt KERNEL=nova BOARD=pc
   

   The boot image is created at build/x86_64/var/run/sculpt.img.

8. Write the boot image to a USB stick:

    sudo dd if=build/x86_64/var/run/sculpt.img of=/dev/sdx bs=1M conv=fsync
   

   Here, /dev/sdx refers to the device node of your USB stick. To determine it, you may inspect the output of dmesg after plugging it in.

Reproducing the system from source

Section Building the boot image presents the creation of the boot image from pre-built packages. You may prefer to build those packages from source, in particular for customizing the system.

Before building the packages, various ports of 3rd-party software need to be prepared. The following command prepares all of them at once:

 <GENODE-DIR>/tool/ports/prepare_port \
      acpica ada-runtime bash cbe coreutils curl \
      dde_bsd dde_ipxe dde_linux dde_rump e2fsprogs-lib \
      expat freetype gnupg grub2 jitterentropy jpeg \
      libarchive libc libdrm libgcrypt libiconv libnl libpng \
      libsparkcrypto libssh libusb libyuv libuvc linux \
      linux-firmware mesa ncurses nova openssl qemu-usb \
      qoost qt5 stb stdcxx ttf-bitstream-vera vim \
      virtualbox6 wpa_supplicant x86emu xz zlib

To be able to compile components that are dependent on the Qt5-library, the corresponding toolchain needs to be installed in addition to the base Genode toolchain. You can build and install it by using the following commands:

 <GENODE-DIR>/tool/tool_chain_qt5 build
 <GENODE-DIR>/tool/tool_chain_qt5 install

The ingredients of the boot image are defined by the sculpt/default-pc.sculpt file located in the repos/gems/ repository. The default set of software installable at runtime is subsumed by the pkg/sculpt_distribution and pkg/sculpt_distribution-pc packages. You can find the depot recipes for these packages at repos/gems/recipes/pkg/. You may want to create your version of these packages by changing the package provider from genodelabs to <YOU> by adding the line

 RUN_OPT += --depot-user <YOU>

to your <build-dir>/etc/build.conf.

To build the boot image including all required depot packages, it's best to instruct the build system to manage the versioning and updating of the depot content automatically by enabling the following line in your build.conf file.

 RUN_OPT += --depot-auto-update

With these precautions taken, the execution of the sculpt.run script - as described in Section Building the boot image - implicitly builds all required binary packages from source.

The sculpt_distribution and sculpt_distribution-pc packages can be created independently from the sculpt.run script by using the depot/create tool manually.

 <GENODE-DIR>/tool/depot/create \
      UPDATE_VERSIONS=1 FORCE=1 REBUILD= \
      <YOU>/pkg/x86_64/sculpt_distribution \
      <YOU>/pkg/x86_64/sculpt_distribution-pc

The FORCE=1 argument ensures that source archives are re-created and checked for the consistency with their versions. Whenever the source code of any of the archives changes, the UPDATE_VERSIONS=1 argument automatically updates its version. Please don't forget to commit the updated hash files. The empty REBUILD= argument limits the creation of binary packages to those that do not yet exist in binary form. If not specified, the command would recompile all packages each time. You may further add -j<N> to parallelize the build process where <N> is the level of parallelism.

To make the created packages available for download from within the running Sculpt system, you must publish them. This involves the archiving, signing, and uploading of the content. The former two steps are covered by the tool/depot/publish_current tool. For more information about working with the depot tool, refer to the package-management documentation.

The launchers integrated in the boot image are defined in gems/sculpt/default-pc.sculpt and the accompanied files at gems/sculpt/launcher/. Each launcher contains a node with a mandatory pkg attribute. If the attribute value contains one or more / characters, it is assumed to be a complete pkg path of the form <USER>/pkg/<NAME>/<VERSION>. Otherwise it is assumed to be just the pkg name and is replaced by the current version of the current depot user's pkg at system-integration time.

Updating the USB boot device from within VirtualBox

The /config/deploy example is prepared to assign USB storage devices directly to a running virtual machine. You may inspect the report /report/drivers/usb_devices to get a list of attached USB devices. Use Vim to copy the <device> node of the selected device into the <inline> section within the /config/launcher/usb_devices_rom file.

The updated usb_devices ROM prompts VirtualBox to open a USB session at the drivers subsystem. Hence, when saving the modified /config/launcher/usb_devices_rom file, the guest OS should detect a new USB device (check the output of dmesg). You may now write a new version of the Sculpt ISO image to the device by following the steps described in Section Building the boot image.

Alternatively, to update a USB storage device that already has Sculpt OS installed to a new version built manually via the steps described in Section Building the boot image, you may prefer to replace the files at the boot/ directory of the "GENODE" partition of the USB device by the content of the freshly built var/run/sculpt/boot/ directory as found in the build directory after executing the make run/sculpt step. Make sure to copy the files hypervisor (microkernel) and image.elf.gz (system image of the Sculpt base system). By backing up your previous boot/ directory, you can conveniently roll back the Sculpt system to the previous version by restoring the original boot/ content.

Credits

Sculpt is an example system scenario of the Genode project, which is an operating-system technology designed and developed from scratch.

That said, Genode is not developed in a vacuum. It greatly benefits from the free-software/open-source community. The following projects play a particularly important role for Sculpt OS.

Device drivers

Programs and libraries used within the Unix-like subsystems

Libraries used for the package-management infrastructure

Applications

Libraries used for the graphical user interface

Crucial tools used during development