debian: Update README.md

Tracked-On: #6688
Signed-off-by: Helmut Buchsbaum <helmut.buchsbaum@opensource.tttech-industrial.com>

debian/README.md

@@ -1,7 +1,17 @@
-## ACRN Debianization
+# ACRN Debianization
 
 ACRN is a flexible, lightweight reference hypervisor, built with real-time and safety-criticality in mind, optimized to streamline embedded development through an open source platform. This part represents the debianization for ACRN.
 
+### Table of Contents
+1. [Building](#building)
+2. [Development Build from Source Package](#development-build-from-source-package)
+3. [Package Maintenance](#package-maintenance)
+4. [Special Package Properties](#special-package-properties)
+5. [About initramfs on Debian/Ubuntu Systems](#about-initramfs-on-debianubuntu-systems)
+6. [Scenario Configuration - GRUB configuration](#scenario-configuration---grub-configuration)
+7. [Known Build Warnings](#known-build-warnings)
+8. [General Remarks and Restrictions](#general-remarks-and-restrictions)
+
 The Debian source package `acrn-hypervisor` provides the following Debian packages:
 
 * `acrn-dev`: Public headers and libraries for ACRN manager.
@@ -21,29 +31,21 @@ The `acrn-hypervisor` source package uses `git-buildpackage` (`gbp`) for package
 
 To ease the build process a shell script wrapper around a docker controlled build is provided:
 
-```plaintext
     debian/docker/acrn-docker-build.sh
-```
 
-This script features the `DISTRO` and `VENDOR` environment variables to set the Debian or Ubuntu distribution the ACRN packages are built for. `VENDOR` defaults to `debian` and `DISTRO` defaults to `stable`, which then is transformed to its canonical name (`bullseye` for now)
+This script features the `DISTRO` and `VENDOR` environment variables to set the Debian or Ubuntu distribution the ACRN packages are built for. `VENDOR` defaults to `debian` and `DISTRO` defaults to `stable`, which then is transformed to its canonical name (`bullseye` for now).
 
 To build ACRN packages on master branch for Debian Buster use:
 
-```plaintext
     VENDOR=debian DISTRO=buster debian/docker/acrn-docker-build.sh
-```
 
 or for Ubuntu 20.04:
 
-```plaintext
    VENDOR=ubuntu DISTRO=focal debian/docker/acrn-docker-build.sh
-```
 
 If building on any other branch, the `debian/gbp.conf` file has to be adapted accordingly. To override this necessity simply add a `--git-ignore-branch`:
 
-```plaintext
     debian/docker/acrn-docker-build.sh --git-ignore-branch
-```
 
 This not only builds the ACRN packages listed above, but eventually all required packages (for build or runtime), too.
 
@@ -51,37 +53,51 @@ Remark: Since the required, dependent package repositories are accessed at build
 
 All these build results including the required third party packages are located in the `build/<distroname>` folder and prepared to be used as a local APT repository. To use it as such, add a proper apt configuration (assuming the result folder has been copied to `/apt`):
 
-```plaintext
+    echo "deb [trusted=yes] file:/apt ./" > /etc/apt/sources.list.d/acrn-local.list
-echo "deb [trusted=yes] file:/apt ./" > /etc/apt/sources.list.d/local.list
+    echo "deb-src [trusted=yes] file:/apt ./" >> /etc/apt/sources.list.d/acrn-local.list
-```
 
 Now `apt update` will also take into account all the local packages, so you can easily install, e.g. board-inspector via:
 
-```plaintext
     apt install python3-acrn-board-inspector
-```
 
 This will install python3-acrn-board-inspector with all required dependencies.
 
+
+## Development Build from Source Package
+
+Once the local APT repository is in place, it can also be used to quickly create proprietary built ACRN packages from the acrn-hypervisor soure package, e.g. to add a new scenario for testing or change the list of supported board. Many thanks to Pirouf for bringing in this idea!
+
+    apt-get install devscripts build-essential
+    cd <working dir>
+    apt-get source acrn-hypervisor
+    apt-get build-dep acrn-hypervisor
+    cd acrn-hypervisor-<version>
+
+Now you can make your changes, e.g. use a new board and scenario:
+
+    mkdir -p misc/config_tools/data/newboard
+    cp <user>/newboard.xml misc/config_tools/data/newboard/newboard.xml
+    cp <user>/newscenario.xml misc/config_tools/data/newboard/newscenario.xml
+    sed "s/ACRN_BOARDLIST \:\=.*/ACRN_BOARDLIST \:\= newboard/" -i debian/acrn-hypervisor.conf.mk
+    sed "s/ACRN_SCENARIOLIST \:\=.*/ACRN_SCENARIOLIST \:\= newscenario/" -i debian/acrn-hypervisor.conf.mk
+    dpkg-buildpackage
+
+The resulting packages are then located in `<working dir>`.
+
+
 ## Package Maintenance
 
 During development `debian/changelog` should always present the `UNRELEASED` stage of package build. Before creating new (temporary) packages `debian/changelog` can be easily updated using
 
-```plaintext
     DEBEMAIL="<add your email here> DEBFULLNAME="<enter your full name here>" gbp dch --snapshot --git-ignore-branch
-```
 
 This updates/creates an `UNRELEASED` changelog entry, which has to be committed separately. BTW, I always use the following to align with what is already configured in git:
 
-```
     DEBEMAIL=$(git config user.email) DEBFULLNAME=$(git config user.name) gbp dch --snapshot --git-ignore-branch
-```
 
 At release create a proper entry using
 
-```plaintext
     DEBEMAIL="<add your email here> DEBFULLNAME="<enter your full name here>" gbp dch --release
-```
 
 This fires up the editor to review the newly created `debian/changelog` entry. Edit, save and commit it to finish the package release from a Debian point of view.
 
@@ -100,12 +116,10 @@ You can also preseed your choice by setting the respective `debconf` keys `acrn-
 
 To reconfigure the choice later, use
 
-```plaintext
     dpkg-reconfigure acrn-hypervisor
-```
 
 The ACRN hypervisor configurations are chosen as follows:
-All directories given in `CONFIGDIRS` in `debian/rules` are searched for valid board- and scenario-configuration files. The `ACRN_BOARDLIST` and `ACRN_SCENARIOLIST` in `debian/rules` can be used to restrict the hypervisor/scenario configurations built into `acrn-hypervisor`. If unset, all possible configurations found under the directories given are built.
+All directories given in `CONFIGDIRS` in `acrn-hypervisor.conf.mk` are searched for valid board- and scenario-configuration files. The `ACRN_BOARDLIST` and `ACRN_SCENARIOLIST` in `acrn-hypervisor.conf.mk` can be used to restrict the hypervisor/scenario configurations built into `acrn-hypervisor` package. If unset, all possible configurations found under the directories given are built.
 
 ### acrn-lifemngr
 
@@ -115,10 +129,52 @@ To adapt the needs of a Debian distribution the service file has been adapted an
 
 There is also an adapted variant for the systemd service file. As for `acrn-lifemngr` this also is provided as part of the Debian packaging process rather than patching the files provided with the sources.
 
+## About initramfs on Debian/Ubuntu Systems
+
+If the `ramdisk_mod` node in the scenario configuration is empty (at the moment this is true especially for all `shared` scenarios), an initrd/initramfs image is neither required nor used. Grub config helper then creates a rootfs parameter using the respective device name at install time, like `/dev/sda2`. Since this depends on device enumeration of the kernel, which might change when additional storage devices are added (your `/dev/sda2` might turn into e.g. `/dev/sdb2`, but your grub configuration stays unchanged!) Debian/Ubuntu decided to use UUIDs to identify the storage device partitions. This is implemented by respective scripts provided in initrd/initramfs and **NOT** within the kernel, so apparently initrd/initramfs is required!
+
+To use this feature properly (as the standard distribution setup does) add a `ramdisk_mod` node value (usually `Linux_initrd`) in the scenario configuration and provide a kernel package with initrd/initramfs support. This is state-of-the-art nowadays and also supported by the acrn-kernel service vm configuration. It enables the UUID boot device support and avoids the device enumeration issues completely, see the `shared+initrd` scenarios in `debian/configs` for an example.
+
+## Scenario Configuration - GRUB configuration
+
+The following subnodes of the `SERVICE_VM` node (VM with `load_order=SERVICE_VM`) are considered by grub-acrn when creating the GRUB menu entries for ACRN:
+
+* `kern_mod` must not be empty to add a menu entry
+* `ramdisk_mod` enables initrd/initramfs image usage (see above)
+* `bootargs`: kernel boot parameters, that are added to the kernel boot command line. Exception: `rootfs` parameter is ignored, since this is automatically determined by GRUB config helpers. This can be used e.g. to add `hvlog` parameter for logging support.
+
+## Known Build Warnings
+
+Depending to which distribution the build is targeted, the following warnings can occur, but can safely be ignored:
+
+* in `override_dh_strip` build stage:
+
+  These warnings only occur in builds for the most recent distributions, but do not harm the binary packages. The usability of dbgsym packages is questionable in this case (untested).
+  * `debugedit: .debug_line offset 0xXXXX referenced multiple times`
+  * `Unknown DWARF DW_FORM 0xXXXX`
+
+* in `override_dh_auto_build-indep` build stage:
+  * `package init file '<...>/__init__.py' not found (or not a regular file)`
+
+  This is a result of the the python components not being structured for packaging with setuptools. The warnings are harmless and do not imply any restrictions to the python packages.
+
+* in `override_dh_auto_install-arch` build stage
+  * `/usr/bin/ld: <...>/boot_mod.a(cpu_primary.o): warning: relocation in read-only section 'multiboot_header'`
+
+  This warning is emitted on all but the oldest distros (gcc/binutils version dependent?). **This might be of concern and must be investigated.** Up till now, no issues have been found when using the binaries triggering this warning.
+
+* lintian
+  * `elf-error In program headers: Unable to find program interpreter name`
+
+  This is a known issue, see [Debian Bug#1000977](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1000977) and [Debian Bug#1000449](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1000449).
+
+
 ## General Remarks and Restrictions
 
 * ACRN >=2.6 needs a Linux 5.10 kernel with the respective Intel/ACRN patches applied, see [Project ACRN Documentation](https://projectacrn.github.io/latest/index.html) for details.
 * The packages are built in debug mode to be able to access the HV console. This can be changed by setting the `RELEASE` variable in `debian/rules` to 1.
 * The built configurations are restricted to the hardware platforms available for testing.
+* The systemd services provided by various ACRN packages are enabled at install time but not started, since they are most likely installed on a non-ACRN system which requires a reboot anyway. Only the acrn-tools related services (acrnlog, acrnprobe, usercrash) might be installed on a running ACRN system and then either need a reboot or must be started manually (`systemd start <service name>`).
+* acrn-configurator is still under heavy development and therefore not yet packaged.
 
-\-- Helmut Buchsbaum \<helmut.buchsbaum@opensource.tttech-industrial.com> Sat, 27 Apr 2022 19:41:17 +0200
+\-- Helmut Buchsbaum \<helmut.buchsbaum@opensource.tttech-industrial.com> Sat, 06 May 2022 20:07:19 +0200