Checking XigmaNAS Network Speed

If your XigmaNAS server is a bit slow, it’s often beneficial to see what is your network speed before changing settings - especially if you are on wireless. If your network cannot handle more than 50 Mbps, you cannot complain when you have only 5 MB/s Samba transfer rate.

While there are many ways you can check the speed, I usually find iperf3 the best choice. Not only it comes preinstalled on XigmaNAS, but you can also download precompiled binaries for Windows, Linux, and BSD to start with. If that’s not enough, you can always use freely available source and compile it yourself.

My approach is first starting server on XigmaNAS (or FreeNAS if that’s your NAS platform of choice):

iperf3 -s

Once server is listening I run the following commands on client, giving it IP address of that server:

iperf3 -c ^^192.168.0.1^^

And that’s it. This command will send data for 10 seconds toward server and receive back the same from it.

Armed with the number you can now deal with that pesky SMB3 performance.

Displaying EOL Symbol in Visual Studio Code

As soon as I started playing with Visual Studio Code a bit more, I found it’s whitespace rendering function lacking. While it does render spaces and tabs, I found it hard to deal with the absence of EOL marking. Yes, Visual Studio Code does show that information in status line and the whole thing is not really per line setting as Code will “normalize” line endings upon load but I simply missed those buggers.

I did find a couple extensions doing it but none really worked seamlessly as I wanted them. For one, they had a separate setting for turning them on/off. While I do love my EOL characters, I don’t want to see them all the time and I definitely don’t want to go into settings to change their state when there’s perfectly good Toggle Render Whitespace menu option available. Moreover, I wanted color of EOL to fit with the existing whitespace theme rendering instead configuring it separately.

I guess it was time to make my own extension.

Well, first, there is a really good guide through building simple extension. While it might not go deep into the topic, you will have both working extension and knowledge how to debug it by the time you’re done.

Secondly, if you go into %USERPROFILE%\.vscode\extensions directory (on Windows), you will see all extensions there - including their source code. I might not be the biggest fan of JavaScript (or TypeScript) but I am definitely the fan of learning by example. If you see some other extension doing something really close to what you need, you can see how it’s working and start from there.

Lastly, publishing extension is easy too. Assuming you got your package setup correctly, you’re just a few lines away from having it in the wild world.

To sum it up, creating and publishing extension was rather interesting and easy experiment. While JavaScript and occasionally flaky documentation did cause me to spend way too much time on this, it wasn’t all too bad. Debugging experience is acceptable and it feels nice to actually make something you’ll use. Not sure I’ll repeat it any time soon but I will definitely keep it in mind.

If it sounds interesting, you can install extension from within Visual Studio Code if you search for Render CRLF, check it’s marketplace page, or take a look at the source code.

RoboCopy Bandwidth Limitting

If you are using RoboCopy to make backups, you might have noticed it’s a bandwidth hog. Once you start copying, it will saturate the network making it a bit annoying to copy anything else at the same time.

While RoboCopy has no understanding of bandwidth limiting, there is a concept of inter-packet gap pause. Yes, you can go and calculate it (with a varying degree of success) or you can just test a few runs with different IPG number.

I personally found that /IPG:7 works wonderfully for my background backups.

CAN Bus Decoding Using PicoScope

When it comes to CAN bus protocol decoding, beating PicoScope is hard considering that even the cheapest 2000 series member has full support for it. Converting such scope to one with the floating ground is as easy as unplugging your laptop (or running your desktop of an UPS’ battery). However, there are a few issues you might want to avoid.

The very first step would be to properly trigger on the CAN bus message. Reasons for this are twofold. If there is any issue with your signal, this will allow you to catch it early so you can sort out basic electrical stuff before going on the higher level. Secondly, reliable triggering will help software decoder properly detect message start.

While exact trigger level might depend on the exact use case, in 95% of cases we are talking of 5V differential signal. Roughly speaking, your CAN L (low) signal will be either at 2.5 V or 0 V logical level and your CAN H (high) signal will be at either 2.5 V or 5 V level. Since signal between those two lines is mirrored, you only need to probe one of those two lines. I usually select L but that’s just because I already have cable made for it. All instructions are essentially the same whichever polarity you select. Good starting trigger level for low line is 2 V (3 V for high line). If your resting signal is further away from 2.5 V that would either point to termination issue or gross impedance mismatch and you should sort “electricals” first before continuing further.

I like to set pre-trigger level to 5% as it allows me to use most of the screen for actual signal. To receive the maximum screen real estate you might be tempted to use 0% pre-triggering but I find seeing a bit of signal before my CAN message does help if you have a busy bus. Even better, this also allows you to ignore trigger edge setting completely (should be falling for low line).

Only once you can reliably catch your CAN signals, you can add serial decoder - Tools / Serial Decoding / Create / CAN. After selecting channel with your signal (named Data on this form), you will reap the benefits of getting triggers right. First and foremost, you should have bitrate set correctly as soon as channel is selected. More over, your threshold level should be automatically calculated from the signal. Yes, you can manually set it to 2 V but Murphy says you’ll forget it and then be confused as why decoding has errors or even misses a message completely. Lastly, you select High or Low setting appropriately depending on the line you are probing.

Congratulations! If all went good, you have just successfully decoded CAN bus message.

Allowing Root Login For Red Hat QCow2 Image

You should never depend on root login when dealing with OpenStack cloud. Pretty much all pre-prepared cloud images have it disabled by default. Ideally all your user provisioning should be done as part of the cloud-init procedure and there you should either create your own user or work with the default cloud-user and the key you provisioned. But what if you are troubleshooting some weird (network) issue and you need console login for your image?

Well, you can always re-enable root user by directly modifying qcow2 image.

To edit qcow2 images, we need first to install libguestfs-tools. On my Linux Mint, that requires the following:

sudo apt-get install libguestfs-tools

Of course, if you are using yum or some other package manager, adjust accordingly. :)

Once installation is done, we simply mount image into /mnt/guestimage and modify the shadow file to assign password (changeme in this example) to the root user:

sudo mkdir /mnt/guestimage
sudo guestmount -a rhel-server-7.5-update-3-x86_64-kvm.qcow2 -m /dev/sda1 /mnt/guestimage
sudo sed -i 's/root:!!/root:$1$QiSwNHrs$uID6S6qOifSNZKzfXsmQG1/' /mnt/guestimage/etc/shadow
sudo guestunmount /mnt/guestimage
sudo rmdir /mnt/guestimage

All nodes installed from this image will now allow you to use root login with password authentication. Just don’t forget to remove this change once you’re done troubleshooting.

PS: While I use Red Hat image in the example, the procedure also applies to CentOS and most of other cloud distributions too.