Skip to main content

CoreOS


I have started learning Kubernetes for last few months now. While learning this, I had come across a beautiful concept of etcd. Doing further research on etcd I came to know that it has come from CoreOS. The latest I hear is etcd will now be part of CNCF (Cloud Native Compute Foundation). 

So some basic information I gathered about CoreOS is here.
  1. CoreOS is sometimes referred to as Container Linux
  2. CoreOS is a linux distribution
  3. It does not have a package manager, so nothing like yum or apt-get
  4. CoreOS took inspiration from Chrome browser, so they push all the required updates automatically.
  5. Only containers can run on CoreOS
  6. CoreOS at best works with multiple machines (like a cluster)
  7. Fleet is used to bring systems together to form a cluster
  8. Fleet is now discontinued in favor of Kubernetes
  9. etcd is a distributed key value data store. It can be used for storing configuration values, service discovery etc


CoreOS is building many components that work well with for Kubernetes
  • etcd
    • A distributed key value data store
    • High available
    • Typical use cases are storing configuration information, service discovery etc
    • etcd when used with 'registrator' stores docker containers information running on the host. This information can be the IP address and Port to easily discover the services running on the host.
  • flanneld
    • flanned is used for configuring layer 3 network fabric for Kubernetes
    • flannel runs as a small binary agent on each host and is responsible for allocating a  subnet lease to each host out of the larger pre-configured address space
    • flannel control the traffic flow between hosts, it does not control how the containers are networked to hosts
    • Learn more about flannel here: https://github.com/coreos/flannel
  • rkt
    • Container engine
    • Basic unit of execution is Pod
    • With rkt architecture pods will  run directly in the classical unix process model.
    • So pods can be managed with systemd service
Labels:

Comments

Post a Comment

Popular posts from this blog

Azure Active Directory

Azure Active directory (AAD) is a Identity as a Service. This is a smaller subset of Active directory. This is not a replacement to active directory at all. Azure active directory provides the identity services to the mobile apps and web apps in Private cloud. These apps may be connected to on-premise applications. So an SSO is enabled for these apps. So Azure active directory has very simple functionality. Create Users, Groups. Map groups to network security groups and provide the authentication to the resources. When you login to Azure portal, right upper corner of the screen has username along with the domain. Domain or tenant or organization are used interchangeably. Management of Users and Groups: Cloud identity (create users manually)  Directory synchronized identifiers (users are synchronized)  Add users Adding a cloud identity users makes the user as Guest When you do directory synchronization on Premise AD Groups are synched up wi...
Post a Comment
Read more

Kubernetes: 19. Configure Application

Configuring application consists of Configuring commands and arguments on applications Configuring environment variables Configuring secrets Docker Commands docker run ubuntu  -> Runs ubuntu container and exit, container CMD is set to [bash], so the container quitely exits docker run ubuntu echo "Hello World" -> Runs ubuntu container, prints "Hello World" exits quitely. To update the default settings, create your own image from the base image lets call this ubuntu-sleeper image FROM ubuntu CMD sleep 5 CMD can also be mentioned in the JSON format like CMD ["sleep", "5"] Note that with JSON format the first element should always be the command to execute,  for eg, it CANNOT be ["sleep 5"] Run build the new ubuntu-sleeper image and run the new image docker build -t ubuntu-sleeper .  -> Build the image docker run ubuntu-sleeper -> Run the new image So the new image will launch ubuntu container, sleep for 5 seconds and quitely ex...
Post a Comment
Read more

underscore.js extend

underscore.js is a javascript utility library. Let us understand the extend method of this very useful library. _.extend is for extending a given object with all the properties of the passed-in object(s) Here is an example, we have three objects aObj, bObj, cObj and we want to combine them into single object. Using _.extend is a simple way of combining these objects. And before trying out the example don't forget to import the underscore.js library Now access the source code of underscore.js and look for the extend method. This is how it looks like This uses functional programming style.  createAssigner takes two inputs and returns a function. The two inputs are (1) keysFunc  (2) defaults Since it is returning a function, so a closure is formed, and the returned function remembers the two inputs Looking at the source code from the line (keys = keysFunc(source)) it is evident that keysFunc is a function itself. ...
Post a Comment
Read more