[gnome-build-meta/valentindavid/eos-installer] Add explanation on how to use the bootable images

[Valentin David <valentindavid src gnome org>]

commit d279cee7aa5da052a7bdf5bdade9d5a477b7cd4d
Author: Valentin David <valentin david codethink co uk>
Date:   Thu Feb 27 12:15:07 2020 +0100

    Add explanation on how to use the bootable images

 BOOTABLE_IMAGES.md | 186 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 186 insertions(+)
---
diff --git a/BOOTABLE_IMAGES.md b/BOOTABLE_IMAGES.md
new file mode 100644
index 00000000..b0e99db6
--- /dev/null
+++ b/BOOTABLE_IMAGES.md
@@ -0,0 +1,186 @@
+# Bootable images
+
+## Building and running the image.
+
+Build `vm/image.bst` and checkout. The image will be `disk.qcow2`.
+
+```
+bst build vm/image.bst
+bst checkout vm/image.bst checkout
+```
+
+Before the first run, copy the UEFI variables image.
+
+```
+cp /usr/share/OVMF/OVMF_CODE.fd .
+```
+
+Then run with QEMU:
+
+```
+qemu-system-x86_64 \
+  -enable-kvm -m 4G -smp 4 -machine q35,accel=kvm \
+  -drive if=pflash,format=raw,unit=0,file=/usr/share/OVMF/OVMF_CODE.fd,readonly=on \
+  -drive if=pflash,format=raw,unit=1,file=OVMF_VARS.fd \
+  -display gtk,gl=on -vga virtio \
+  -netdev user,id=net1 -device e1000,netdev=net1 \
+  -soundhw hda \
+  -usb -device usb-tablet \
+  -drive file=checkout/disk.qcow2,format=qcow2,media=disk
+```
+
+For more explanations on the QEMU command line see section [Using
+QEMU](#using-qemu).
+
+## Using the installer
+
+First run `utils/sign-image.sh` to build and sign the image.
+Then build `iso/image.bst` and checkout the artifact. This will
+contain `installer.iso`.
+
+```
+./utils/sign-image.sh
+bst build iso/image.bst
+bst checkout iso/image.bst checkout
+```
+
+Before the first run, copy the UEFI variables image.
+
+```
+cp /usr/share/OVMF/OVMF_CODE.fd .
+```
+
+And create a disk:
+
+```
+qemu-img create -f qcow2 disk.qcow2 64G
+```
+
+Then run with QEMU:
+
+```
+qemu-system-x86_64 \
+  -enable-kvm -m 4G -smp 4 -machine q35,accel=kvm \
+  -drive if=pflash,format=raw,unit=0,file=/usr/share/OVMF/OVMF_CODE.fd,readonly=on \
+  -drive if=pflash,format=raw,unit=1,file=OVMF_VARS.fd \
+  -display gtk,gl=on -vga virtio \
+  -netdev user,id=net1 -device e1000,netdev=net1 \
+  -soundhw hda \
+  -usb -device usb-tablet \
+  -drive file=disk.qcow2,format=qcow2,media=disk \
+  -drive file=checkout/installer.iso,format=raw,media=cdrom
+```
+
+After installation re-launch QEMU, but remove the last drive (CD-ROM).
+
+```
+qemu-system-x86_64 \
+  -enable-kvm -m 4G -smp 4 -machine q35,accel=kvm \
+  -drive if=pflash,format=raw,unit=0,file=/usr/share/OVMF/OVMF_CODE.fd,readonly=on \
+  -drive if=pflash,format=raw,unit=1,file=OVMF_VARS.fd \
+  -display gtk,gl=on -vga virtio \
+  -netdev user,id=net1 -device e1000,netdev=net1 \
+  -soundhw hda \
+  -usb -device usb-tablet \
+  -drive file=disk.qcow2,format=qcow2,media=disk
+```
+
+## Updating with local OSTree
+
+Run helper script: `utils/update-local-repo.sh`. This will create a
+local repository with the current state of working copy.
+
+Then run `utils/run-local-repo.sh` to start a server. This script does
+not fork. Leave it to run.
+
+Open a shell and type `enable-developer-repository`. The server has to
+be running at that time. You do not need to pass any parameter if you
+are running the image in a QEMU with standard configuration for user
+network (`-netdev user`). For other configuration look at
+configuration with `--help`.
+
+If `enable-developer-repository` succeeded, you can then reboot.  Do
+not call `enable-developer-repository` again.  Further updates will be
+done automatically by `eos-updater`. To force update sooner, run
+`eos-updater-ctl update`, or use GNOME Software.
+
+## Using QEMU
+
+<a name="using-qemu"></a>
+
+### UEFI boot
+
+You need two files, OVMF/EDK2 code and variables.
+
+We assume here we are using x86_64. The paths are:
+
+ - For vanilla QEMU:
+  * /usr/share/qemu/edk2-x86_64-code.fd
+  * /usr/share/qemu/edk2-i386-vars.fd
+ - For Debian and Fedora:
+  * /usr/share/OVMF/OVMF_CODE.fd
+  * /usr/share/OVMF/OVMF_VARS.fd
+
+Copy the variable file locally. It is needed to be modified. The code
+can stay because it will be read only.
+
+/usr/share/OVMF/OVMF_CODE.fd
+
+### Creating a hard disk
+
+To create a 64GB disk, for example:
+
+```
+qemu-img create -f qcow2 disk.qcow2 64G
+```
+
+### QEMU Parameters
+
+4 CPU threads: `-smp 4`
+
+4GB memory: `-m 4G`
+
+For x86_64 with KVM: `-enable-kvm -machine q35,accel=kvm`
+
+UEFI boot:
+
+```
+-drive if=pflash,format=raw,unit=0,file=/usr/share/OVMF/OVMF_CODE.fd,readonly=on
+-drive if=pflash,format=raw,unit=1,file=OVMF_VARS.fd
+```
+
+Enabling graphics hardware acceleration: `-display gtk,gl=on -vga virtio`
+
+Enabling sound: `-soundhw hda`
+
+Enabling network: `-netdev user,id=net1 -device e1000,netdev=net1`
+
+Getting the mouse pointer to work in windowed mode: `-usb -device
+usb-tablet`.  Alternatively, you can use `-fullscreen`.
+
+Adding a hard drive: `-drive file=disk.qcow2,format=qcow2,media=disk`
+
+Adding a CD-ROM: `-drive file=cd.iso,format=raw,media=cdrom`
+
+## Appendix
+
+### nr_entries is too big
+
+GNOME Shell seems to hit a limit in QEMU. If you get this error message
+in the standard error stream of QEMU, try the following patch:
+
+```
+Index: qemu-4.1/hw/display/virtio-gpu.c
+===================================================================
+--- qemu-4.1.orig/hw/display/virtio-gpu.c
++++ qemu-4.1/hw/display/virtio-gpu.c
+@@ -616,7 +616,7 @@ int virtio_gpu_create_mapping_iov(VirtIO
+     size_t esize, s;
+     int i;
+ 
+-    if (ab->nr_entries > 16384) {
++    if (ab->nr_entries > (256*1024)) {
+         qemu_log_mask(LOG_GUEST_ERROR,
+                       "%s: nr_entries is too big (%d > 16384)\n",
+                       __func__, ab->nr_entries);
+```