Add self-signing instructions

README.md

@@ -40,9 +40,16 @@ virt-manager with a command like the following:
       -drive file=/usr/share/OVMF/OVMF_CODE.fd,if=pflash,format=raw,unit=0,readonly=on \
       -drive file=pc.img,cache=none,format=raw,id=main,if=none \
       -device virtio-blk-pci,drive=main,bootindex=1 \
-      -device ac97 -audiodev pa,id=ac97
+      -serial telnet:localhost:4321,server,nowait \
+      -audio driver=pipewire,model=hda
 ```
 
+This command line connects the inner port 22 to the localhost port 8022, to allow to
+access SSH. Also connects the serial port to the localhost port 4321, allowing to
+access through a virtual serial terminal using
+
+    telnet localhost 4321
+
 ## Other Repositories
 
 Most of the code used to construct the image is now managed in other
@@ -107,3 +114,27 @@ the EFI system and the base snaps:
     sudo mount /dev/mapper/loopXXX/p2 /mnt
 
 And now we can go to */mnt/snaps*, and there are all the base snaps.
+
+## Self-signing the -dangerous model for testings
+
+To do local testings with other sources than the current ones, it may be useful
+to modify the `.model` files (for example, to make them point to `edge`). But
+since these files must be signed, it must be done correctly.
+
+First, you need a developer account in snapcraft.io. This process is detailed
+here:
+
+<https://snapcraft.io/docs/creating-your-developer-account>
+
+After configuring the account, log in with snapcraft (`snapcraft login`) and
+get your user ID (`snapcraft whoami`). Also, get your signature name with the
+command `snap keys`.
+
+Edit `ubuntu-core-desktop-XX-YY-dangerous.json` file, and put your ID both in
+`authority-id` and `brand-id`.
+
+Now, create the new `.model` file with the command:
+
+`snap sign -k SIGNATURE-NAME ubuntu-core-desktop-XX-YY-dangerous.json > output.model`
+
+Replacing `SIGNATURE-NAME`, `XX`, `YY` and `output.model` with the right values.