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Category: Linux

Cross-Platform Variables In Powershell Core

Published 2017-10-02 by Kevin Feasel

Max Trinidad shows how to use the Is* variables in Powershell Core to write cross-platform code:

Use the cmdlet Get-Variable to find them, and keep in mind, these variables are not found in Windows PowerShell 5.x.

Get-Variable Is*

Although, the results will display four variable, but let’s pay attention to three of them. Below are the variables with their default values:

IsLinux                            False
IsOSX                              False
IsWindows                    True

These three variables can help in identifying which Operating System the script are been executed.  This way just adding the necessary logic, in order to take the correct action.

Read on for a code example showing how to use these variables.

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Docker Stop Versus Docker Kill

Published 2017-10-02 by Kevin Feasel

Andrew Pruski explains why docker kill is so much faster than docker stop:

When running demos and experimenting with containers I always clear down my environment. It’s good practice to leave a clean environment once you’ve finished working.

To do this I blow all my containers away, usually by running the docker stop command.

But there’s a quicker way to stop containers, the docker kill command.

Sending SIGTERM isn’t particularly polite and doesn’t let processes clean up, which could leave your process in an undesirable state during future runs.  But if you’re just re-deploying a container, you don’t really care about the prior state of the now-disposed container.

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Instant File Initialization On Linux

Published 2017-09-25 by Kevin Feasel

Anthony Nocentino explains how instant file initialization works on SQL Server on Linux:

With strace up and running let’s turn on the trace flags to enable output for Instant File Initialization and create database that has a 100MB data file and a 100MB log file. Check out this post from Microsoft for more details on the trace flags. This database create code is straight from their post. I changed the model database’s data and log file sizes to 100MB each. Also, it’s important to note Instance File Initialization is only for data files, log files are zeroed out due to requirements for crash recovery. We’re going to see that in action in a bit…

Read the whole thing.

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The Predicate For SQL On Linux: SQLPAL

Published 2017-09-25 by Kevin Feasel

Slava Oks explains the importance of the SQL Platform Abstraction Layer:

In addition to business matters, Hal’s article highlights key drawbacks which need to be addressed around engineering as well as  product supportability for the endeavor to be successful.   The article affirms that bringing SQL Server to *nix platform is not the hardest task compare to the additional work that the journey would require.  Indeed, in order for the project to be successful the team would have to:

  • Bring other SQL Server inbox products such as SSAS along
  • Implement platform specific features such as CLR, AGs, and much more
  • Guarantee adequate performance and scalability
  • Create new ecosystem around product support, engineering systems  and more.

So throughout the course of the work, I have continued to question the path we have been on and if we succeed at the end or not.  Every time I would go back, reread the article and every time I would come to the same favorable conclusion.  But why?

Slava links to this article from December from the data platform team explaining what SQLPAL is.  In the end, I think the benefits of this model will be much larger than SQL on Linux (which is itself large).

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Transactional Replication And SQL On Linux

Published 2017-09-22 by Kevin Feasel

Phil Grayson shows a way to get transactional replication working on Linux:

Microsoft have stated that transactional replication isn’t supported on Linux and we’re not sure if they intend to in the future. This means that if you try to add the server to a publisher, you get the following message. So you can’t use the GUI and it also means that you can’t use pull as the necessary files won’t be there.

Despite that warning, there is a way to set up a push subscription; click through for that way.

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Active Directory Integration On Ubuntu

Published 2017-09-20 by Kevin Feasel

Drew Furgiuele shows how to configure SQL Server on Linux to use Windows authentication:

In the following post, we’ll walk through joining a Linux SQL Server on Unbuntu to an Active Directory domain, and here’s the steps we’re going to take:

  1. Installing the required software and services to enable a Linux host to talk to and join an Active Directory Domain,
  2. Configuring the Linux host’s network configuration to talk to the Domain Controller(s),
  3. Setting up Samba, Kerberos, Winbind, and the System Security Services Daemon (SSSD) to properly talk to and digest authentication tokens from Active Directory, and
  4. Creating a Kerberos Keytab file for the SQL Server service to run as a domain service account.

Seems like a lot, doesn’t it? If you’re new to Linux, a lot of this configuration can seem a little daunting and a lot tedious, but as we walk through it, I’ll stop and talk a little bit about each step and what it does.

Active Directory integration was a critical piece of functionality for SQL Server on Linux.  There are still some odd edge cases (like weirdness when going cross-domain) but for the normal scenario, it works fine once you’ve configured Linux correctly.

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Will SQL Server On Linux Take Off?

Published 2017-09-07 by Kevin Feasel

Brent Ozar has his doubts about how popular SQL Server on Linux will be:

SQL Server 2017 runs on Linux, and the similarities between that and Windows Core are eerie:

  • Both present big stumbling blocks for traditional Windows DBAs
  • Both work mostly the same, but not exactly, as you can see in the SQL Server on Linux release notes
  • Both solved perceived problems for sysadmins
  • Neither solved a problem for database administrators

So why will you hear so much more about Linux support? Because this time around, it also solves a sales problem for Microsoft. Somebody, somewhere, has a spreadsheet showing that there will be a return on investment if they spend the development, marketing, and support resources necessary. (And I bet they’re right – if you compare this feature’s ROI against, say Hekaton or Polybase, surely Linux is going to produce a lot more new licenses sold.)

He does make some good points (though seriously, Polybase is awesome), but I think SQL Server on Linux is going to be quite a bit more popular for a couple of reasons.  First is core-based licensing in Windows Server:  that’s another big price increase that you get when upgrading to Server 2016, and at the margin, companies with a mixed OS setup will be more likely to move to Linux.  Second, Brent’s focus in the post is on current installations—that is, taking your Windows SQL Server instance and moving it to Linux.  As Koen Verbeeck mentions in the first comment, there’s a whole different market:  companies whose infrastructure is entirely Linux and are currently using MySQL, Oracle, or Postgres for their relational databases.  It’ll probably take a couple of years to get market penetration—especially because of the old guard Linux admin types who remember the Ballmer years with appropriate disdain—but this is a new market for Microsoft and they’ve already got a product which meets (or exceeds, depending upon your biases) the top competition.

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Attaching Databases To Docker

Published 2017-08-17 by Kevin Feasel

Andrew Pruski shows one scenario where Docker on Windows is better than Docker on Linux:

One of the (if not the) main benefits of working with SQL in a container is that you can create a custom image to build container from that has all of your development databases available as soon as the container comes online.

This is really simple to do with Windows containers. Say I want to attach DatabaseA that has one data file (DatabaseA.mdf) and a log file (DatabaseA_log.ldf): –

ENV attach_dbs="[{'dbName':'DatabaseA','dbFiles':['C:\\SQLServer\\DatabaseA.mdf','C:\\SQLServer\\DatabaseA_log.ldf']}]"

Nice and simple! One line of code and any containers spun up from the image this dockerfile creates will have DatabaseA ready to go.

However this functionality is not available when working with Linux containers. Currently you cannot use an environment variable to attach a database to a SQL instance running in a Linux container.

Read on to see what you can do if you’re using a Linux container.

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PSSDIAG On Linux

Published 2017-08-15 by Kevin Feasel

Denzil Ribeiro shows how to use PSSDIAG on a SQL Server on Linux installation:

When analyzing SQL Server performance related issues, customers often have their tools of choice, which can be a feature within the product, a third-party performance monitoring tool, or a home-grown tool that assists in monitoring live performance. For live monitoring, in the SQLCAT lab we use a home grown tool described in this blog. However, when our customers have a performance issue, we, just like support engineers and consultants, can’t always have them ship their third-party tools or associated data, and hence need a way to collect performance related data for post mortem analysis.

PSSDIAG is a popular tool used by Microsoft SQL Server support engineers to collect system data and troubleshoot performance issues. This is a well-known tool for SQL Server on Windows, and we needed equivalent functionality on Linux. PSSDIAG data collection for Linux is now available here. It is a set of bash scripts that collect all the necessary data for troubleshooting performance problems, similar to PSSDiag on Windows.

I haven’t used PSSDIAG outside of a support scenario, but it’s definitely good to know that this is available on Linux.

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Backing Up That Linux-Based Database

Published 2017-08-09 by Kevin Feasel

David Klee shows how to back up a SQL Server on Linux database over the network:

As of SQL Server 2017 RC2, we’ll want to accomplish it in a way that is transparent to SQL Server. (Depending on the RTM version whenever it is released, I might change the recommendation on this.) To do this, we’ll want to create a folder on the local file system that actually maps to a remote network share for SQL Server backups.

SSH into your server without elevated privileges at this point.

The network share is presented from a Windows server with the SMB protocol. Linux can connect to this using a compatible protocol called CIFS, or Common Internet File System. We’ll need to install the packages so we can natively connect. On Ubuntu and other Linux distros, the easiest is with the cifs-utils package. To install from the package manager is as simple as this.

Sadly, that credentials file cannot be encrypted.

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