ishan16696/containers-in-depth

containers-in-depth

Containers:

• Containers are a form of operating system virtualization.
• To containerize the application with its libraries/dependencies to run application anywhere and anytime.
• Containerization is considered to be a lightweight version of virtualization as compared to VMs.

Linux features used in containerization:

Namespace:

Namespaces are a feature of the linux kernel that partitions kernel resources such that one set of processes sees one set of resources while another set of processes sees a different set of resources.
In simple words, namespaces isolate processes from each other or you can also say namespaces restrict what a process can see.

• Different types of namespaces:

  1. PID namespace:
     Assigns a set of PIDs to processes that are independent from the set of PIDs in other namespaces. eg: first process created in a new namespace has PID 1 and child processes are assigned subsequent PIDs. If a child process is created with its own PID namespace, it has PID 1 in that namespace as well as its PID in the parent process namespace.
  2. Network namespace:
     To run programs on any port without conflicting it with what’s already running.
  3. Mount namespace:
     To mount and unmount filesystems without affecting the host filesystem.
  4. IPC namespace:
     To have its own IPC resources, for example POSIX message queues.

• you can use unshare linux command to create namespaces.

Cgroups:

A control group (cgroup) is a linux kernel feature that limits and isolates the resource usage (CPU, memory, disk I/O, network etc) of a collection of processes.
In simple words, we use cgroups to control how much of a given key resources (CPU, memory, network, and disk I/O) can be accessed or used by a process.

1. ContainersFromScratch
   • building basic container from scratch in Go
   • involves linux concepts like namespaces, cgroups, chroot etc.