What is a namespace in VMWare & Openshift Virtualization

    Most VMware admins are familiar with the idea of namespaces when using the vim-cmd command but it is important to understand that this concept is very different from how namespaces work in OpenShift and Kubernetes.

Let me explain the difference.

    In VMware the vim-cmd utility gives you a CLI interface to manage different parts of the ESXi host and its components. It organizes commands into namespaces, which group together related functions for things like managing virtual machines, storage, networking, etc.
Each namespace includes a set of subcommands used to perform specific tasks. For example, the most commonly used namespace is vmsvc, which handles VM operations but there are more namespaces for managing services, host settings, datastores, etc. A simple list when running "vim-cmd help" shows that are about 20 or so namespaces when managing a VMware ESXi host.

Here are a few of the key vim-cmd namespaces you’ll typically use on ESXi and what they’re for:

1. vmsvc – Virtual Machine Service
   The vmsvc namespace is used to manage virtual machines (VMs) on the ESXi host. It provides commands for starting, stopping, getting information, and other VM operations.
   Example Commands :
   vim-cmd vmsvc/getallvms: List all VMs on the host.
   
   
2. hostsvc – Host Service
   The hostsvc namespace is used to manage the ESXi host itself. This includes operations related to the host's services, networking, and maintenance tasks.
   Example Commands :
   vim-cmd hostsvc/maintenance_mode_enter: Put the ESXi host into maintenance mode.
   
   
3. datastore – Datastore and file Operations
   The datastore namespace manages the datastores (storage) on the ESXi host, including listing, mounting, unmounting, and querying information about datastores.
   Example Commands: 
   vim-cmd datastore/lists: List all datastores on the host.
   
   
4. settings – ESXi Host Settings Management
   The settings namespace deals with configuring and managing the system settings on the ESXi host.
   Example Commands: 
   vim-cmd settings/user/add : Add a new user to the ESXi host.
   
   

In OpenShift, a namespace is very different. 

It is a way to keep things organized and separate inside the same Openshift cluster. It is a built-in Kubernetes feature. OpenShift calls these namespaces projects, but they work the same way. They help group related resources together so things don’t get mixed up. 
An OpenShift namespace is conceptually similar to a vCenter folder but with built-in RBAC, resource quotas, and policy enforcement. An importand difference is that vCenter folders can be nested to form a hierarchy while OpenShift namespaces are flat.

   
   Right after an OpenShift 4 cluster is installed a number of system namespaces are created for platform operators, networking, monitoring, and core services. You can run the command "oc get namespaces" which will list all the namespaces created initially for you. You will notice that are about 50-70 namespaces created initially depending on the platform you are on ( AWS, Azure, etc ), depending on the installation method used ( IPI vs UPI ) and the number of operators that were initially installed. We could categorize these namespaces in core system, operator and component, networking, authorization and monitoring. 

1. openshift – Core OpenShift resources (templates, global config)
   
   
2. kube-system – Kubernetes system services (like DNS, kube-proxy)
   
   
3. kube-node-lease – Heartbeat mechanism for node liveness detection
   
   
4. openshift-apiserver – OpenShift API server deployment
   
   
5. openshift-etcd – Manages etcd pods, certificates, and configs
   
   
6. openshift-machine-api – Manages nodes and Machines (e.g., in IPI/cloud setups)
   
   
7. openshift-monitoring – Manages Prometheus, Alertmanager, Thanos, Grafana
   
   
8. openshift-ingress-operator - Manages ingress routers
   
   
9. openshift-cluster-version - Manages Cluster Version Operator 
   
   
10. openshift-authentication  - Manages OAuth identity providers 
    
    
11. openshift-config  - Manages Cluster-wide configuration (e.g., proxy, IDPs)

VMWare vs Openshift Virtualization CLI Tools

     I have been using VMware in my home lab  for quite a while now, mainly to run Red Hat VMs and experiment with different OpenShift versions, both in connected and disconnected environments. I’ve also gained hands-on experience with VMware in several customer engagements. So, before diving into OpenShift Virtualization I was already pretty comfortable with VMware.

    In this blog I want to share a simple VMware-admin-friendly introduction to OpenShift Virtualization. If you are used to VMware and feel a little unsure about switching gears you are not alone and this series of posts is for you.
My goal is to clear up some of the uncertainty and show that the jump isn't as big as it might seem.

   The main focus here is to highlight how similar many of the core virtualization concepts and CLI tools are between the two platforms. In fact, the similarities are more than the differences making it easier than you might think for an experienced VMware admin to get comfortable with OpenShift Virtualization.

   To start, I will walk through some familiar VMware concepts and commands and explain how those same actions are handled in OpenShift Virtualization. You might be surprised to find that while the tools may look different ( think oc commands or YAML files instead of GUIs or govc/vim-cmd ) the fundamental ideas stay very much the same. 

CLI Tools

Both VMware 6.x/7.x and OpenShift 4.1.x Virtualization provide a command-line interface (CLI) to manage VMs.

VMware provides a number of command-line tools for managing and interacting with its infrastructure. 
The primary CLI tools for managing a VMware environment are :

1. vim-cmd : Used directly on ESXi hosts for managing virtual machines. 
2. esxcli : Another tool used on ESXi hosts, but for a broader range of system management tasks.
3. govc : A command-line tool to interact with vSphere environments, which includes vCenter and ESXi hosts.

The command-line interface (CLI) tools you'll use for OpenShift Virtualization to manage VMs are :

1. virtctl : A CLI tool specifically designed for managing VMs in OpenShift Virtualization.
2. oc : The general OpenShift CLI that can also manage VMs as Kubernetes resources.