including ssh-server and more comments

conf/layer.conf

@@ -22,15 +22,59 @@ IMAGE_INSTALL_append = " hellodep"
 IMAGE_INSTALL_append = " hellogit"
 IMAGE_INSTALL_append = " hellogitcmake"
 
+###########################
+# enable serial console
+###########################
+ENABLE_UART = "1"
+
+# check the following files to check whether the modifications were applied
+# $ cat /mnt/yocto/tmp/deploy/images/raspberrypi3/bootfiles/config.txt | grep serial
+# $ cat /mnt/yocto/tmp/deploy/images/raspberrypi3/bootfiles/cmdline.txt 
+
+###########################
 # wifi setup
-IMAGE_INSTALL_append += " x11vnc \
-        linux-firmware-brcm43430 \
-        i2c-tools \
-        python-smbus \
+###########################
+# run bitbake -e core-image-minimal | grep "^DISTRO_FEATURES"
+# run bitbake -e core-image-minimal | grep "^MACHINE_FEATURES"
+# $ bitbake -e core-image-minimal | grep "^COMBINED_FEATURES"
+#   COMBINED_FEATURES="vfat bluetooth ext2 usbhost wifi alsa"
+# to learn about the supported features
+# https://www.yoctoproject.org/docs/2.1/mega-manual/mega-manual.html#var-DISTRO_FEATURES
+# learn more : 
+#   - https://embeddedguruji.blogspot.com/2019/04/machinefeatures-vs-distrofeatures-in.html
+#   - https://docs.yoctoproject.org/3.2.3/ref-manual/ref-features.html
+DISTRO_FEATURES_append += " wifi"
+IMAGE_INSTALL_append += " i2c-tools \
         bridge-utils \
         hostapd \
         dhcp-client \
         iw \        
         dhcp-server \
         iptables \
-        wpa-supplicant"
+        wpa-supplicant"
+
+        # errorneous :
+        # linux-firmware-brcm43430 \
+        # python-smbus \
+
+
+###########################
+# VNC
+###########################
+# VNC has lots of depedency. It's heavy. Be sure you need it.
+IMAGE_INSTALL_append += " x11vnc"
+
+###########################
+# EXTRA_IMAGE_FEATURES 
+###########################
+# https://docs.yoctoproject.org/3.2.3/ref-manual/ref-features.html#image-features
+# some of the most relevant features are:
+# - debug-tweaks: Makes an image suitable for development (e.g. allows root logins without passwords and enables post-installation logging). See the ‘allow-empty-password’, ‘empty-root-password’, and ‘post-install-logging’ features in this list for additional information.
+# - dev-pkgs: Installs development packages (headers and extra library links) for all packages installed in a given image.
+# - package-management: Installs package management tools and preserves the package manager database.
+# - tools-sdk: Installs a full SDK that runs on the device.
+# - perf: Installs profiling tools such as perf, systemtap, and LTTng. For general information on user-space tools, see the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.
+# - ssh-server-dropbear: Installs the Dropbear minimal SSH server.
+# - ssh-server-openssh: Installs the OpenSSH SSH server, which is more full-featured than Dropbear. Note that if both the OpenSSH SSH server and the Dropbear minimal SSH server are present in IMAGE_FEATURES, then OpenSSH will take precedence and Dropbear will not be installed.
+
+EXTRA_IMAGE_FEATURES ?= "debug-tweaks ssh-server-openssh"