How to Use VCSIM to Test your PowerCLI Code

In this article we will take a look at how vcsim can be used to test your PowerShell code. VCSIM is a vCenter and ESXi API based simulator. As such you can connect a PowerCLI session to it, and run commands just as you would with a real vCenter instance or an ESXi host.

Now, as it’s a simulator, it’s not possible to do everything that you can with a real vCenter, but it can be useful as a target for quickly testing PowerCLI scripts, particularly ones that use the get verb.

There is a vcsim docker image available, which I will be using for this article. You can launch the container using the following syntax, providing you have docker installed.

$ docker run -d -p 443:443 nimmis/vcsim
Unable to find image 'nimmis/vcsim:latest' locally
latest: Pulling from nimmis/vcsim
7b1a6ab2e44d: Already exists
40e5be356b1b: Pull complete
ae1d6b4b905f: Pull complete
4f4fb700ef54: Pull complete
2a0987ce81a8: Extracting [=====================================>             ]    181MB/244MB
31f560ee0603: Download complete
fd78f5e332c8: Download complete

The first time you run this, the Docker image will be pulled down, before the vcsim container is created. Once done you should have a new container, which can be connected to on 0.0.0.0:443:

$ docker ps -a
CONTAINER ID        IMAGE                          COMMAND                  CREATED             STATUS              PORTS                  NAMES
499053dba2b0        nimmis/vcsim                   "/docker-entrypoint.…"   4 hours ago         Up 4 hours          0.0.0.0:443->443/tcp   hopeful_lewin

With that running we can start to work with it using PowerCLI. On your system with PowerCLI installed, we first need to set the PowerCLI configuration to ignore invalid certificates (as vcsim isn’t using a trusted certificate). To so so, run the following:

Set-PowerCLIConfiguration -InvalidCertificateAction Ignore -Confirm:$false

We should now be able to connect to vcsim successfully using the connect-viserver cmdlet:

connect-viserver 172.17.0.2 -user u -password p

Name                           Port  User
----                           ----  ----
172.17.0.2                     443   u

Once connected, you should be able to run familiar PowerCLI cmdlets, and the vcsim will respond. For example, we can run get-vmhost to list the ‘hosts’ in the vcsim inventory:

get-vmhost

Name                 ConnectionState PowerState NumCpu CpuUsageMhz CpuTotalMhz   MemoryUsageGB   MemoryTotalGB Version
----                 --------------- ---------- ------ ----------- -----------   -------------   ------------- -------
DC0_H0               Connected       PoweredOn       2          67        7182           1.371           4.000   6.5.0
DC0_C0_H0            Connected       PoweredOn       2          67        7182           1.371           4.000   6.5.0
DC0_C0_H1            Connected       PoweredOn       2          67        7182           1.371           4.000   6.5.0
DC0_C0_H2            Connected       PoweredOn       2          67        7182           1.371           4.000   6.5.0

Or get-vm:

get-vm

Name                 PowerState Num CPUs MemoryGB
----                 ---------- -------- --------
DC0_H0_VM0           PoweredOn  1        0.031
DC0_H0_VM1           PoweredOn  1        0.031
DC0_C0_RP0_VM0       PoweredOn  1        0.031
DC0_C0_RP0_VM1       PoweredOn  1        0.031

Summary

In this short article you have seen how you can use vcsim, running it a Docker container, as a target for running PowerCLI commands. Not quite a substitute for a real vCenter or ESXi host, but useful nonetheless. Check out the documentation for the project here.