Visual Studio Code as a PowerShell Integrated Scripting Environment

I know what you’re thinking. “Why use Visual Studio Code instead of the PowerShell ISE?” Well, if you’re using Mac OS or Linux, you don’t have the option to use the PowerShell ISE natively. And that’s a problem if you want to take advantage of the cross-platform capabilities of PowerShell Core. In this article, I’ll show you how to use Visual Studio Code (free!) to perform the key functions of the PowerShell ISE, namely:

  • Simultaneously view code and execute it in the PoSh terminal
  • Execute code on a selection or line-by-line basis (F8)
  • Syntax highlighting (for people who are easily bored like me)

Installing Visual Studio Code

The best way to install most things is with a package manager. This would be something like apt-get or yum for Linux distros, homebrew for Mac OS, and Chocolatey for Windows. Or you could go old school and download it here.

Installing the PowerShell Extension

Go to the Extensions button (looks like a busted up square) or View > Extensions.

If the PowerShell extension doesn’t show up under the bombastic “RECOMMENDED” heading, just search for it in the “Search Extensions” field. Then install it.

Integrating the PowerShell Terminal

Open up a PowerShell script of your choice. Then in the menu, go to View > Integrated Terminal. You should see the following.

If you don’t see the PS prompt Make sure you select “TERMINAL” and “PowerShell Integrated” from the drop-down menu.

Running Only Selected Code

In the PowerShell ISE, you can select a block of text and hit F8, and the ISE runs only that code. Or you can position your cursor at the end of a line and hit F8, and the ISE runs only the code on that line. Next we’ll enable the exact same behavior in Visual Studio Code.

Go To File > Preferences > Keyboard Shortcut

In the text entry field at the top, type “runsel”. You should see two items:

  • “Run Selection” with a keybinding to F8
  • “Run Selected Text In Active Terminal” with no keybinding

This is not what we want because it will not run the selected text in the PowerShell terminal.┬áIt will run the selection in the “OUTPUT” section, but not in the terminal. Obviously, that’s not the normal behavior of the PowerShell ISE. Let’s fix it.

Right-click the “Run Selection” item and select “Remove keybinding”

Right-click the “Run Selected Text in Active Terminal” item and select “Add Keybinding”

Depress the F8 key (or whatever you want to use) then hit Enter.

Testing It Out

Go back to your code and select a block of code. Hit F8 and watch the magic!

That’s what I’m talking about!

But… as of this writing, there’s an issue with this that’s being tracked on the vscode-powershell GitHub repo, and it’s this: multi-line input in the integrated console doesn’t work. That means you can’t select a function block, hit F8, and have it work. It will throw ugly errors in your face.

Creating a Linux LVM Logical Volume on an iSCSI SAN

Recently I had an Oracle database server used by some developers that was running out of space on its data volume mounted at /u02. The volume was a simple MBR volume (think fdisk), so it couldn’t be non-destructively extended without using a third-party utility like gparted. That would have been fine, but rather than leave the volume as MBR, I decided to create a new iSCSI SAN-backed Logical Volume Manager (LVM) volume, which can be extended and resized pretty easily.

In this post, I’ll show you how to create a logical volume stored on an iSCSI SAN. Even though I did this on Red Hat Enterprise Linux 6.5 (RHEL), these steps should work on any distribution of Linux. Continue reading

Creating a Linux File Server for Windows CIFS/SMB, NFS, etc.

Recently I needed to build a multipurpose file server to host CIFS and NFS shares — CIFS for the Windows users, and NFS for VMWare to store ISOs. It needed to utilize back end storage (NetApp via iSCSI), provide Windows ACLs for the CIFS shares, and be able to authenticate against two different Active Directory domains. After careful consideration, I decided to use Red Hat Enterprise Linux 6.5 (RHEL) instead of Windows Server 2012.

Now you might be wondering, “Why on earth would you want to build a Linux file server to do all that when you can just use Windows?” There are a few reasons: Continue reading

Using IRQbalance to Improve Network Throughput in XenServer

If you are running XenServer 5.6 FP1 or later, there is a little trick you can use to improve network throughput on the host.

By default, XenServer uses the netback process to process network traffic, and each host is limited to four instances of netback, with one instance running on each of dom0’s vCPUs. When a VM starts, each of its VIFs (Virtual InterFaces) is assigned to a netback instance in a round-robin fashion. While this results in a pretty even distribution of VIFs-to-netback processes, it is extremely inefficient during times of high network load because the CPU is not being fully utilized.

For example, suppose you have four VMs on a host, with each VM having one VIF each. VM1 is assigned to netback instance 0 which is tied to vCPU0, VM2 is assigned to netback instance 1 which is tied to vCPU1, and so on. Now suppose VM1 experiences a very high network load. Netback instance 1 is tasked with handling all of VM1’s traffic, and vCPU0 is the only vCPU doing work for netback instance 1. That means the other three vCPUs are sitting idle, while vCPU0 does all the work.

You can see this phenomenon for yourself by doing a cat /proc/interrupts from dom0’s console. You’ll see something similar to this:


(The screenshot doesn’t show it, but the first column of highlighted numbers is CPU0, the second is CPU1, and so on. The numbers represent the quantity of interrupt requests.)

If you’ve ever troubleshot obscure networking configurations in the physical world, you’ve probably run into a router or firewall whose CPU was being asked to do so much that it was causing a network slowdown. Fortunately in this case, we don’t have to make any major configuration changes or buy new hardware to fix the problem.

All we need to do to increase efficiency in this scenario is to evenly distribute the VIFs’ workloads across all available CPUs. We could manually do this at the bash prompt, or we could just download and install irqbalance.

irqbalance is a linux daemon that automatically distributes interrupts across all available CPUs and cores. To install it, issue the following command at the dom0 bash prompt:

yum install irqbalance --enablerepo base

You can either restart the host or manually start the service/daemon by issuing:

service irqbalance start

Now restart your VMs and do another cat /proc/interrupts. This time you should see something like this:

That’s much better! Try this out on your test XenServer host(s) first and see if you can tell a difference. Citrix has a whitepaper titled Achieving a fair distribution of the processing of guest network traffic over available physical CPUs (that’s a mouthful) that goes into more technical detail about netback and irqbalance.