Addressed all the latest suggestions by Teo, except for remaking the Makefiles

in the demo folder and resolving the checkpatch errors.

Signed-off-by: Cosmin-Andrei Iacobai <[email protected]>

Author: cosmin1805

chapters/app-interact/Makefile

@@ -32,4 +32,4 @@ open: $(SITE)
 
 clean:
 	-for i in $$(find -name "*-generated.gif"); do rm -f $$i; done
-	-rm -f *~
+	-rm -f *~

chapters/app-interact/dbus/drills/tasks/dbus/README.md

@@ -1,4 +1,4 @@
-# D-Bus - battery level
+# D-Bus - Battery level
 
 Use D-Bus to find out the computer's battery level.
 There is the `org.freedesktop.UPower` interface on the system bus that can provide this information.

chapters/app-interact/dbus/reading/dbus.md

@@ -11,233 +11,3 @@ This name can be something human-readable, like `org.freedesktop.Notifications`,
 Once a process is connected, it can expose one or multiple `objects`.
 An object has a path-like name, consisting of strings separated by a slash character (for example, `/org/freedesktop/Notifications`).
 Each object contains one or more `interfaces`, which have the methods that can be called on that object.
-
-## D-Bus Inspection with D-Feet
-
-In order to better understand these concepts, we'll use a graphical tool (`D-Feet`) to inspect all the available D-Bus objects on our system.
-
-Run D-Feet and select `Session Bus` from the top button:
-
-![dfeet-session-bus](../media/dfeet_session_bus.png)
-
-On the left panel, we can see all the processes connected to D-Bus with their associated `connection names`.
-Scroll down and find `org.freedesktop.Notifications`.
-On the right side, expand `/org/freedesktop/Notifications` and then expand the `org.freedesktop.Notifications` interface.
-The window should look like this:
-
-![dfeet-notifications](../media/dfeet_notifications.png)
-
-Some observations:
-
-* The bus communication happens over a Unix socket, with the path `/run/user/1000/bus`.
-
-* `org.freedesktop.Notifications` on the left panel is the `connection name`.
-
-* The process that has connected with this name is `/usr/bin/gjs /usr/share/gnome-shell/org.gnome.Shell.Notifications` and has the pid of `4373`.
-
-* This process exposes one object: `/org/freedesktop/Notifications`.
-Note that the object name is the same as the connection name, where the dots have been replaced with slashes.
-This is not a requirement, as the objects exposed by a process can have any name.
-
-<!-- markdownlint-disable MD101 -->
-* The object has 4 interfaces: `org.freedesktop.DBus.Introspectable`, `org.freedesktop.DBus.Peer`, `org.freedesktop.DBus.Properties` and `org.freedesktop.Notifications`.
-Note that the last one (`org.freedesktop.Notifications`) is the same as the connection name, but this again is just a coincidence, not a requirement.
-<!-- markdownlint-enable MD101 -->
-
-* The interface `org.freedesktop.Notifications` has some methods that can be called, such as `Notify`.
-
-## Calling D-Bus Methods
-
-The application behind `org.freedesktop.Notifications` is responsible with desktop notifications (the small bubbles of text that appear at the top of the screen when some event happens).
-When an application wants to send a notification it needs to connect to D-Bus and call the `Notify` method from the `org.freedesktop.Notifications` interface.
-
-In this example, we want to call the `Notify` method ourselves.
-To do this, we must first understand the signature of this method:
-
-`Notify (String arg_0, UInt32 arg_1, String arg_2, String arg_3, String arg_4, Array of [String] arg_5, Dict of {String, Variant} arg_6, Int32 arg_7) ↦ (UInt32 arg_8)`
-
-This doesn't tell us much, but we can find more documentation [here](https://specifications.freedesktop.org/notification-spec/notification-spec-latest.html#basic-design), since `freedesktop` is an open standard.
-
-We'll set the arguments to the following (for our simple case, most of them will be unused):
-
-* `app_name`: `""`
-
-* `replaces_id`: `0`
-
-* `app_icon`: `""`
-
-* `summary`: `"This is the title"`
-
-* `body`: `"This is the content"`
-
-* `actions`: `[]`
-
-* `hints`: `{}`
-
-* `expire_timeout`: `-1`
-
-Now the question is how to actually call the method.
-Normally, we would have to write an application that connects to D-Bus and executes the call.
-But for demonstrative purposes there are easier ways.
-
-One way is directly from d-feet.
-If we double-click on the `Notify` method in the right-side pane of d-feet, a window will open that allows us to call the method with any arguments that we want:
-
-![dfeet-execute-dialog](../media/dfeet_execute.png)
-
-Then we click the `Execute` button and the notification will appear:
-
-![dfeet-execute-](../media/dfeet_execute.gif)
-
-Another way is from the command-line. There's the `gdbus` tool that can do this:
-
-```console
-student@os:~$ gdbus call \
-      --session \
-      --dest org.freedesktop.Notifications \
-      --object-path /org/freedesktop/Notifications \
-      --method org.freedesktop.Notifications.Notify \
-      -- \
-      '""' \
-      0 \
-      '""' \
-      "This is the title" \
-      "This is the content" \
-      [] \
-      {} \
-      -1
-```
-
-Let's see how it works:
-
-![gdbus-notify](../media/gdbus_notify.gif)
-
-You can also find this `gdbus` call in the `support/dbus/send_notification.sh` script.
-
-## Inspecting the Low-level Communication
-
-Let's run `gdbus` under `strace` to see what's happening behind the scenes.
-Run the script in `support/dbus/send_notification_strace.sh`:
-
-```console
-strace: Process 61888 attached
-[pid 61887] socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0) = 5
-[pid 61887] connect(5, {sa_family=AF_UNIX, sun_path="/run/user/1000/bus"}, 110) = 0
-[pid 61887] sendmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\0", iov_len=1}], msg_iovlen=1,
-msg_control=[{cmsg_len=28, cmsg_level=SOL_SOCKET, cmsg_type=SCM_CREDENTIALS, cmsg_data={pid=61887,
-uid=1000, gid=1000}}],
-msg_controllen=32, msg_flags=0}, MSG_NOSIGNAL) = 1
-strace: Process 61889 attached
-
-[...]
-
-[pid 61889] sendmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="l\1\0\1T\0\0\0\3\0\0\0\237\0\0\0\1
-\1o\0\36\0\0\0/org/freedesktop/Notifications\0\0\2\1s\0\35\0\0\0org.freedesktop.Notifications\0\0\0\6\1s\0\35
-\0\0\0org.freedesktop.Notifications\0\0\0\10\1g\0\rsusssasa{sv}i\0\0\0\0\0\0\3\1s\0\6\0\0\0Notify\0\0\0\0\0\0
-\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\21\0\0\0This is the title\0\0\0\23\0\0\0This is the content\0\0\0\0\0\0\0\0\0
-\0\0\0\0\377\377\377\377", iov_len=260}], msg_iovlen=1, msg_controllen=0,
- msg_flags=0}, MSG_NOSIGNAL) = 260
-[pid 61889] recvmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="l\2\1\1\4\0\0\0\312\0\0\0.\0\0\0", iov_len=16}],
-msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 16
-[pid 61889] recvmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\6\1s\0\6\0\0\0:1.497\0\0\10\1g\0\1u\0\0\5\1u\0
-\3\0\0\0\7\1s\0\5\0\0\0:1.49\0\0\0\36\0\0\0", iov_len=52}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 52
-(uint32 30,)
-[pid 61889] +++ exited with 0 +++
-[pid 61888] +++ exited with 0 +++
-+++ exited with 0 +++
-```
-
-We see a Unix socket being created and a connection made to `/run/user/1000/bus`, as expected.
-Then a series of messages are exchanged on the socket, which are part of the D-Bus protocol.
-On a closer look, we can even identify some strings from our notification, like `This is the title` or `This is the content`:
-
-```console
-[pid 61889] sendmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="l\1\0\1T\0\0\0\3\0\0\0\237\0\0\0\1
-\1o\0\36\0\0\0/org/freedesktop/Notifications\0\0\2\1s\0\35\0\0\0org.freedesktop.Notifications\0\0\0\6\1s\0\35
-\0\0\0org.freedesktop.Notifications\0\0\0\10\1g\0\rsusssasa{sv}i\0\0\0\0\0\0\3\1s\0\6\0\0\0Notify\0\0\0\0\0\0
-\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\21\0\0\0This is the title\0\0\0\23\0\0\0This is the content\0\0\0\0\0\0\0\0\0
-\0\0\0\0\377\377\377\377", iov_len=260}], msg_iovlen=1, msg_controllen=0,
-```
-
-## D-Bus usage in Python
-Use the `dbus` python bindings to get the computer's battery level using a python script.
-You can start from the documentation [here](https://dbus.freedesktop.org/doc/dbus-python/tutorial.html#).
-You need to read the sections `Connecting to the Bus`, `Proxy objects`, and `Interfaces and methods`.
-
-There's also a skeleton you can use in `chapters/app-interact/arena/support/dbus/get_battery_level.py`.
-
-In summary, your script will start by connecting to the `System Bus`.
-Then you'll use the `get_object` method to obtain a proxy object.
-On this proxy object, you can actually do the method call as explained [here](https://dbus.freedesktop.org/doc/dbus-python/tutorial.html#interfaces-and-methods):
-
-```text
-To call a method, call the method of the same name on the proxy object, passing in the interface name via the dbus_interface keyword argument
-```
-
-So, if you want to call the method `this.is.an.interface.method` with the arguments `A` and `B` you can do it like this:
-
-```python
-result = proxy.method(A, B, dbus_interface = "this.is.an.interface")
-```
-
-## Firefox
-
-Let's do the following experiment:
-
-- Open the Firefox browser
-
-- From a terminal run `firefox www.google.com`
-
-![firefox-url-open](../media/firefox_url_open.gif)
-
-Notice that the URL we passed in the command-line was opened in the existing Firefox window as a new tab.
-Even though we started a separate Firefox process, which should have created a separate new window, this didn't actually happen.
-Instead, the process that we started from the command-line exited immediately and the site was opened in the already running Firefox instance.
-
-Without any precise knowledge about Firefox internals, we can guess that something like this happened:
-
-- The newly started Firefox process detected that another instance of Firefox is already running
-
-- The newly started Firefox process sent a message to the existing running process, requesting it to open a URL in a new tab
-
-Since we're talking about message passing between 2 processes, there's a chance that maybe D-Bus was involved.
-Let's check: we'll use a tool called `dbus-monitor` that will print all messages passed through D-Bus.
-
-```console
-student@os:~$ dbus-monitor
-```
-
-Then, in another terminal, we'll run `firefox www.google.com` again.
-
-Going back to the `dbus-monitor` output, we find the following:
-
-```console
-...
-method call time=1655809062.813923 sender=:1.757 -> destination=org.mozilla.firefox.ZGVmYXVsdC1yZWxlYXNl serial=2 path=/org/mozilla/firefox/Remote; interface=org.mozilla.firefox; member=OpenURL
-   array of bytes [
-      02 00 00 00 1a 00 00 00 2f 00 00 00 2f 68 6f 6d 65 2f 61 64 72 69 61 6e
-      73 00 2f 6f 70 74 2f 66 69 72 65 66 6f 78 2f 66 69 72 65 66 6f 78 00 77
-      77 77 2e 67 6f 6f 67 6c 65 2e 63 6f 6d 00
-   ]
-```
-
-There was a D-Bus call to `org.mozilla.firefox.ZGVmYXVsdC1yZWxlYXNl`, on the object `/org/mozilla/firefox/Remote`, method `OpenURL` from the `org.mozilla.firefox` interface.
-Indeed, we see that this object exists in d-feet as well:
-
-![dfeet-firefox](../media/dfeet_firefox.png)
-
-We can try to call the `OpenURL` method ourselves, directly from d-feet.
-The method has only one argument of the type `Array of [Byte]`.
-Although there's no documentation for it, we can use the same byte array that we saw in `dbus-monitor`:
-
-```console
-   array of bytes [
-      02 00 00 00 1a 00 00 00 2f 00 00 00 2f 68 6f 6d 65 2f 61 64 72 69 61 6e
-      73 00 2f 6f 70 74 2f 66 69 72 65 66 6f 78 2f 66 69 72 65 66 6f 78 00 77
-      77 77 2e 67 6f 6f 67 6c 65 2e 63 6f 6d 00
-   ]
-```
-
-(Note that `77 77 77 2e 67 6f 6f 67 6c 65 2e 63 6f 6d` at the end is the string `www.google.com`, so that's another confirmation that we're on the right track).
-
-![dfeet-url-open](../media/dfeet_url_open.gif)

chapters/app-interact/os-cloud/drills/questions/cgroups-vs-namespaces.md

@@ -1,4 +1,4 @@
-# Cgroups versus namespaces
+# Cgroups Versus namespaces
 
 ## Question Text
 

chapters/app-interact/os-cloud/drills/questions/container-vs-vm.md

@@ -1,4 +1,4 @@
-# Container versus VM
+# Container Versus VM
 
 ## Question Text