4.3 Processes and cgroups

notes/4_under_the_hood.md

@@ -38,4 +38,61 @@ location of docker socket file on linux: `/var/run/docker.sock`
 
 We can control the docker server using docker client inside a container: `docker run -it --rm -v /var/run/docker.sock:/var/run/docker.sock docker sh`
 
-##
+## Networking in Brief
+
+TODO: Need further research this topic
+
+* **Ethernet** layer: moves "frames" on a wire (or wireless)
+* **IP** layer: moves packets on a local network
+* **Routing**: forwards packets between networks
+* **Ports**: address particular programs on a computer
+
+### Bridging
+
+* Docker uses bridges to create virtual networks in computer
+* They are like software network switches
+* They control Ethernet layer
+* You can turn off this protection with `docker run --net=host options image-name command` 
+  * `--net=host` gives container direct access to network
+  * Useful for learning/debugging
+
+### Routing
+
+* Creates "firewall" rules to move packets between networks
+* NAT (Network Address Translation)
+* Change the source address on the way out
+* Change the destination address on the way back
+
+`sudo iptables -n -L -t nat`
+* `-n` for 
+
+`--previlige=true` will give docker all access
+
+* Exposing a port = "port forwarding" in network layer
+
+### Namespaces
+
+* Allow process to be attached to private network segments
+* Private networks are bridged into a shared network with the rest of the containers
+* Containers get their own copy of the networking stack
+
+??? Need learn this section (Container Networking in linkedin) specifically
+
+## Processes and cgroups
+
+### Primer on Linux Processes
+
+* Processes come from other processes (parent-child relationship)
+* When a child process exits, it returns an exit code to its parent
+* **Process Zero**  (`init`) is the process that starts the rest
+* In Docker, a container starts with an init process and vanishes when that process exit
+  * By knowing the init process of the container, we can kill the container
+
+`docker inspect` can be ...???? 
+
+### Resource Limiting
+
+Set limit for
+* Scheduling CPU time
+* Memory allocation limits
+* Inherited limitations and quotas (summed total cannot exceed the limit)