Improving Polycube doc - Install/Update kernel process (#306)

* Improving Polycube doc - Install/Update kernel process

Since we landed to Ubuntu 20.04, I though that a bit more specifics could be added into the guide

Signed-off-by: Simone Magnani <simonemagnani.96@gmail.com>

Documentation/installation.rst

@@ -1,14 +1,14 @@
-Installing Polycube
-===================
+Installing Polycube from source files
+=====================================
 
-This installation guide includes instructions to install Polycube on ``Ubuntu 18.04``.
+This installation guide includes instructions to install Polycube on ``Ubuntu >= 18.04``.
 However those should also work on other versions and distributions with a few changes.
 
 Dependencies
 ------------
 
 Polycube requires following dependencies:
- - At least **Linux kernel v4.15** that includes a set of the eBPF features which are needed by polycube
+ - **Recent Linux kernel**: most Polycube services work with kernel **>= v4.15**; however, there are cases in which a newer kernel may be required, e.g., in case we want to execute the ``dynmon`` service with a custom code that requires more recent kernel primitives. In case you are unsure, please upgrade to **kernel v5.4**.
  - **pistache**: a library to build rest API servers
  - **libints**: a library for crafting packets (needed only for some services)
  - **Go language**: required to run ``polycubectl`` (polycube command line interface)
@@ -17,10 +17,15 @@ Following sections will detail the installation process for the above components
 
 .. _updating-linux-kernel:
 
-Updating Linux Kernel to v4.15
+Updating Linux Kernel
 -------------------------------
 
-Use ``uname -a`` to check the kernel version you are running, if this is ``<v4.15`` please use the following instructions to update it.
+Most Polycube services require at least the **Linux kernel v4.15**. However, the ``dynmon`` service allow the dynamic injection of a custom data plane, which may exploit latest eBPF kernel features and hence require more up-to-date kernel versions. Therefore we suggest to upgrade the to the latest Linux kernel (https://kernel.ubuntu.com/~kernel-ppa/mainline/) in order to be on the safe side.
+
+The following examples show how to update kernel to version **4.15** and **5.4**. To check the kernel version you are running, please use ``uname -a``.
+After a kernel update, please remember to reboot your machine at choose the newly installed one while the boot process starts.
+
+To update to kernel **v4.15**:
 
 ::
 
@@ -31,22 +36,33 @@ Use ``uname -a`` to check the kernel version you are running, if this is ``<v4.1
     sudo dpkg -i *.deb
     sudo reboot
 
+To update to kernel **v5.4**:
+
+    wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v5.4/linux-headers-5.4.0-050400_5.4.0-050400.201911242031_all.deb
+    wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v5.4/linux-headers-5.4.0-050400-generic_5.4.0-050400.201911242031_amd64.deb
+    wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v5.4/linux-image-5.4.0-050400-generic_5.4.0-050400.201911242031_amd64.deb
+    wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v5.4/linux-modules-5.4.0-050400-generic_5.4.0-050400.201911242031_amd64.deb
+
+    sudo dpkg -i *.deb
+    sudo reboot    
+
+
 Automatic installation from source files
 ----------------------------------------
 
-If you are running ``Ubuntu 18.04`` and you do not want to manually install polycube and its dependencies, you can use the install script available under the `scripts` folder.
-This is not guaranteed that the script works on versions or distributions other than ``Ubuntu 18.04``.
+If you are running ``Ubuntu >= 18.04`` and you do not want to manually install Polycube and its dependencies, you can use the install script available under the `scripts` folder.
+This scripts has been tested on ``Ubuntu 18.04``, ``Ubuntu 19.04`` and ``Ubuntu 20.04``.
 
 Please notice that this script does not update the kernel version.
 
-In this case you have to:
+In order to install Polycube with the script, you have to:
 
 ::
 
     # install git
     sudo apt-get install git
 
-    # clone the polycube repository
+    # clone the Polycube repository
     git clone https://github.com/polycube-network/polycube
     cd polycube
     git submodule update --init --recursive
@@ -75,8 +91,10 @@ Go 1.8+ is needed to run ``polycubectl``, if you only plan to install ``polycube
 Since Ubuntu 20.04, support for ``golang-go`` has been introduced into the main repositories. Thus, you just need to run
 
 ::
+
 	sudo apt install golang-go
 
+
 Instead, for all the previous versions (< 20.04) please refer to the following instructions:
 
 ::
@@ -105,7 +123,7 @@ Install dependencies
 
 ::
 
-    # Install polycube dependencies
+    # Install Polycube dependencies
     sudo apt-get -y install git build-essential cmake bison flex \
         libelf-dev libllvm5.0 llvm-5.0-dev libclang-5.0-dev libpcap-dev \
         libnl-route-3-dev libnl-genl-3-dev uuid-dev pkg-config \
@@ -161,10 +179,10 @@ Install libtins
     sudo make install
     sudo ldconfig
 
-Installing polycube
+Installing Polycube
 ^^^^^^^^^^^^^^^^^^^
 
-This installs the polycube daemon (``polycubed``), the polycube CLI (``polycubectl``) and the services shipped with polycube.
+This installs the Polycube daemon (``polycubed``), the Polycube CLI (``polycubectl``) and the network services shipped with Polycube.
 If you want to disable some services, you can modify the cmake flags using ``ccmake``.
 
 ::
@@ -180,4 +198,4 @@ If you want to disable some services, you can modify the cmake flags using ``ccm
     sudo make install
 
 
-Hooray, you have ``polycube`` installed and ready to be used, please refer to :doc:`Quick Start <quickstart>` to start using your installation.
+Hooray, you have Polycube installed and ready to be used, please refer to :doc:`Quick Start <quickstart>` to start using your installation.