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Category: Linux

Registering a Raspberry Pi 4 as an IoT Edge Device

Hasan Savran takes us through turning a Raspberry Pi 4 into an Azure IoT Edge device:

You can buy all type of sensors and connect them to Raspberry Pi. Then you can use Python or .NET Core to write small applications to check your connected sensors and read data from the sensors. If you like to push this data to store or analyze in Azure, then you need to make Raspberry Pi ready by installing couple of applications.
      Installing an application in Windows, is not a big deal for me. I had to install and configure all the applications in Linux in this project. First thing we need to do is copying some files to register Microsoft GPG key and software repository feed. To do that, we will use the curl command. Curl is used for transferring data using various protocols including HTTP/S. We are going to use it to copy some files from Internet to local storage. It’s a fancy copy tool.

There are a few steps involved, but nothing too onerous. I think I know where Hasan is going with this, too.

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Change Data Capture and Replication on Linux

Tejas Shah announces transactional replication and change data capture for SQL Server 2017 on Linux:

With SQL Server 2019, we introduced support for replication and CDC features for SQL Server on Linux by bringing in relevant components and subsystems within SQL Server core engine package. This support includes Snapshot replication, Transactional replication and CDC. Peer-to-peer transactional replication, merge replication and Oracle publishing are not supported.  

Today we are glad to announce that we have brought the replication and CDC features to SQL Server 2017, starting with Cumulative update 18 (CU18).

Tejas has a few links, but the key is just to update your server (or spin up a new Docker container with the latest CU and swap external database files over to it).

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Tools for Using SQL Server on Linux

Kellyn Pot’vin-Gorman has a list of tools you can use to make working with SQL Server on Linux a bit easier:

Along with the above versions of Linux distributions, SQL Server 2019 is supported in a container scenario using a Docker image.  Running a SQL Server database inside a Docker engine with Linux offers more flexibility, faster recovery, and quicker deployments, including deployments into the Azure cloud. For those becoming familiar with Linux, Docker for Windows or Mac gives you the option to run a Docker engine on your workstation with SQL Server 2019 on Linux.

Along with Docker technology, orchestration can be achieved, both managing and deploying SQL Server containers on Linux using Red Hat Open shift or Kubernetes. This includes SQL Server 2019 Big Data Clusters (BDC), fully scalable clusters with SQL Server, Spark, and Hadoop File System (HDFS). BDCs provide the ability to read, write, and analyze big data with T-SQL or Spark, and you can combine big data and relational data, too.

The set of tools just happens to be almost exactly the same set of tools as for Windows, but there are a few differences.

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Persistent Memory for SQL Server on Linux

The SQL Server team shows how you can configure persistent memory for SQL Server on Linux:

With the release of SQL Server 2019 on Linux, Microsoft introduced persistent memory (PMEM) support on Linux. This is an exciting development, as previous versions of SQL Server on Linux didn’t support PMEM. Let’s look at how to configure the PMEM for SQL Server on Linux.

SQL Server 2016 introduced support for non-volatile DIMMs and an optimization called Tail of the Log Caching on NVDIMM. These leveraged Windows Server direct access to a persistent memory device in DAX mode to reduce the number of operations needed to harden a log buffer to persistent storage.

SQL Server 2019 extends the support for PMEM devices to Linux, providing full enlightenment of data and transaction logs placed on PMEM. Enlightenment is a way to access the storage device using efficient user-space memcpy() operations. Rather than going through the file system and storage stack, SQL Server leverages DAX support on Linux to place data directly into the device. This helps to reduce latency.

Click through for the configuration steps.

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When mssql-cli Installation Fails on Ubuntu

Kellyn Pot’vin-Gorman shares a slew of reasons why mssql-cli might fail to install:

The easiest scenario for many to deploy SQL Server 2019 on Linux to start working with it, is most likely an Ubuntu distribution, (flavor) of Linux.  With that, you may want to play with the newest tool for command line execution of SQL, which isn’t sqlcmd, but mssql-cli.  It’s got some awesome new features, which I won’t go into here, but focus on installation failures instead, which happens not because the installation is complicated but because of the demands still for Python 2.7 when 3+ versions are required for newer software.

mssql-cli requires Python 3, so I recommend checking the version before running the mssql-cli installation command, as this may save you a lot of work with dependencies.  I’ll still go through the steps to if you want to force it to work with Python 2.7, but seriously, just using the right version of Python will make it so much easier.

Read on for just shy of a dozen different failure modes.

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Changing Colors in Bash

Kellyn Pot’vin-Gorman shows how you can change the colors you see in bash shells:

I agree with him-  you never know what the projector quality will be, the lighting in the room, color-blind attendees or other factors that could impact the readability of  the demonstration when you have a black background and colored text.  I realized, as the Azure Cloud Shell is a service, we have less control of the terminal offered to us, so it was important to tell people how to update their Azure Cloud Shell to change the execution prompt to not be in color and highlight the background in white, with black text bolded for easier reading.

Click through for a sample .bashrc file as well as a bonus “How do I exit vim?” bit. The correct answer is, you never exit vim; you simply dedicate the rest of your life to it.

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Configuring Memory Limits for SQL Server in Kubernetes

Anthony Nocentino doesn’t have all the RAM in the world:

With that Pod deployed, I loaded up a HammerDB TPC-C test with about 10GB of data and drove a workload against our SQL Server. Then while monitoring the workload…boom HammerDB throws connection errors and crashes. Let’s look at why.

First thing’s first, let’s check the Pods status with kubectl get pods. We’ll that’s interesting I have 13 Pods. 1 has a Status of Running and the remainder have are Evicted. 

Anthony does a great job of explaining the problem and showing you the solution.

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Non-Root SQL Server 2019 Containers

Vin Yu announces a change to Microsoft’s container configuration for SQL Server 2019:

The application process within most Docker containers is running as a root user meaning the process has root privileges within the container user space. The root user within the container is also the same root (uid 0) on the host machine, and if the user can break out of the container, they would have root permissions on the host. Running as root is convenient for development, testing and CI/CD use cases but for production use cases, it is safest to run SQL Server as a non-root process within the container. In this blog, we’re going to share with you how you can preview this upcoming improvement by creating your own non-root SQL Server container.

Vin has a quick demonstration of how it works.

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strace and SQL Server Containers

Anthony Nocentino tries using strace to diagnose SQL Server process activity in a container:

We’re attaching to an already running docker container running SQL. But what we get is an idle SQL Server process this is great if we have a running workload we want to analyze but my goal for all of this is to see how SQL Server starts up and this isn’t going to cut it.
 
My next attempt was to stop the sql19 container and quickly start the strace container but the strace container still missed events at the startup of the sql19 container. So I needed a better way.

Don’t worry—Anthony finds a better way.

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