The Basics Of Bash: Writing Data

Mark Wilkinson hits us with some basic Bash output management:

If you have experience with PowerShell, some properties of Bash variables will feel familiar. In Bash, variables are denoted with a $ just like in PowerShell, but unlike PowerShell the $ is only needed when they are being referenced. When you are assigning a value to a variable, the $ is left off:

#!/bin/bashset -eset -umy_var="World"printf "Hello ${my_var}\n"

Above we assigned a value to my_var without using the $, but when we then referenced it in the printf statement, we had to use a $. We also enclosed the variable name in curly braces. This is not required in all cases, but it is a good idea to get in the habit of using them. In cases where you are using positional parameters above 9 (we’ll talk about this later) or you are using a variable in the middle of a string the braces are required, but there is no harm in adding them every time you use a variable in a string.

The basic syntax is pretty familiar to most programming languages, and there’s nothing scary about outputs, even when Mark starts getting into streams.

Installing Docker On Linux

Mark Broadbent shows how to install Docker on Linux Mint:

A web search will almost certainly point you to lots of similar posts, mostly (if not) all of which start instructing you to add unofficial or unrecognized sources, keys etc. Therefore my intention with this post is not to replace official documentation, but to make the process as simple as possible, whilst still pointing to all the official documentation so that you can be confident you are not breaking security or other such things!

You can head over to the following Docker page Get Docker CE for Ubuntu for the initial setup and updates, but for simplicity, you can follow along below.

The installation instructions will also work for Ubuntu and other related variants.

Bash For The Powershell-Minded

Mark Wilkinson has started a new series on Bash.  His first post is an introduction to the scripting language:

Bash (the Bourne Again Shell) was created in 1989 for the GNU Project as a free replacement for the Unix Bourne shell. Most modern Linux systems use Bash as their default command line shell, so if you have ever dropped to a command line on a Linux system, you have probably used Bash. Just like PowerShell, Bash is both a scripting language and a command shell/interpreter. So not only can you execute commands in an interactive shell session, but you can also write scripts that incorporate multiple commands.

Once you get your hands dirty with Bash you’ll notice a lot of features that were incorporated into PowerShell. Things like command substitution: $(Get-Date) were directly pulled from Bash $(date). Other features will look familiar as well, like the ability to pipe multiple commands together.

One thing you need to understand right away is that Bash is string based, not object based like PowerShell. This means you’ll find yourself doing a lot more string processing to get tasks done. Things like string splitting will be much more common. Bash does support objects, like arrays, but few if any commands output an array. As we go through this series you’ll see that this might not be as limiting as it sounds.

The best part about learning Bash is that you can then get into arguments about Bash vs ksh vs zsh.

Don’t Run Services As Root On Linux

Kellyn Pot’vin-Gorman explains why running SQL Server as root is a bad idea:

Although enhancements have changed Windows installations for applications to run with a unique user, I created a mssql OS user even back on SQL Server 2000 on Windows as I had a tendency to use similar security practices for all database platforms as a multi-platform DBA.  With that being said-  yes, it introduced complexity, but it was for a reason: users should be restricted to the least amount of privileges required.  To grant any application or database “God” powers on a host is akin to granting DBA to every user in the database, but at the host level.  As important as security is to DBAs INSIDE the database, it should be just as important to us OUTSIDE of it on the host it resides on.

Security is important and has become more complex with the increase of security breaches and introduction of the cloud.  One of the most simple ways to do this is to ensure that all application owners on a host are granted only the privileges they require.  The application user should only utilize SUDO, stick bit, iptables, SUID, SGID and proper group creation/allocation if and when required.

It’s the same reason we don’t recommend giving everyone sa rights to databases.  Read on for more.

Expanding LVM Drives

David Klee shows how to expand an LVM drive on Linux:

Next in our SQL Server on Linux series is one important question. On Windows, if you’re about to run out of space, you get your VM admin / storage admin to expand one or more of your drives, and you go to Disk Management and expand the drive with no downtime. How do we accomplish this same task on Linux?

First, SSH into your VM. Get your appropriate system engineer to expand the drive that needs to be expanded. You won’t be able to see it at first in Linux because, just like in Windows, it’ll need to rescan the storage to ‘see’ the extra space. Sometimes Windows does it automatically, and sometimes you have to initiate it manually. In Linux it only does this on system startup.

Let’s grow our data drive from 250GB to 300GB first.

Click through to see how to do that.

Running SQL On Linux In Windows For Linux

Kevin Feasel



Anthony Nocentino troubleshoots an error when trying to run SQL Server on Linux using the Windows Subsystem For Linux:

The first thing I had to do was reproduce the issue. So on my Windows 10 test VM I installed the Windows Subsystem for Linux, steps to do so are here and I installed the Ubuntu app.

Then, I fired up a bash shell using WSL and then I installed SQL Server on Linux for Ubuntu as documented here.

Now, I completed the installation of SQL Server on Linux using mssql-conf when that program completes it attempts to start SQL Server on Linux. BOOM! I’m able to reproduce the same error.

Looking at the error, I decided to see if I could run SQL Server on Linux from the shell as the user mssql. This would remove systemd and mssql-conf from the picture. Basically I wanted to see if I could get another, more descriptive, error to pop out.

Anthony digs out a very useful debugging tool in Linux, strace.  Sadly, he’s not able to solve the problem at the moment, but at least gets us a step in the right direction.

R In Linux For Windows

Kevin Feasel


Linux, R

David Smith shows how to install and use R in the Windows Subsystem for Linux:

R has been available for Windows since the very beginning, but if you have a Windows machine and want to use R within a Linux ecosystem, that’s easy to do with the new Fall Creator’s Update (version 1709). If you need access to the gcc toolchain for building R packages, or simply prefer the bash environment, it’s easy to get things up and running.

Once you have things set up, you can launch a bash shell and run R at the terminal like you would in any Linux system. And that’s because this is a Linux system: the Windows Subsystem for Linux is a complete Linux distribution running within Windows. This page provides the details on installing Linux on Windows, but here are the basic steps you need and how to get the latest version of R up and running within it.

Click through for a quick tutorial.

Using mssql-cli

Kevin Feasel



Alan Yu announces mssql-cli, a command-line interface for SQL Server:

Mssql-cli is a new and interactive command line tool that provides the following key enhancements over sqlcmd in the Terminal environment:

  • T-SQL IntelliSense
  • Syntax highlighting
  • Pretty formatting for query results, including Vertical Format
  • Multi-line edit mode
  • Configuration file support

Mssql-cli aims to offer an improved interactive command line experience for T-SQL. It is fully open source under the BSD-3 license, and a contribution to the dbcli organization, an open source suite of interactive CLI tools for relational databases including SQL Server, PostgresSQL, and MySQL. The command-line UI is written in Python and the tool leverages the same microservice backend (sqltoolsservice) that powers the VS Code SQL extension, SQL Operations Studio, and the other Python CLI tool we announced earlier, mssql-scripter.

Something very cool that Alan points out is that this is “the first time our team is contributing source code to an existing open source organization with a commitment to be a good citizen in an existing open source community.”

Process Mapping On Linux With SQL Server And Oracle

Kellyn Pot’vin-Gorman contrasts SQL Server versus Oracle outputs when running a couple common Linux process commands:

In our Oracle environment, we can see every background process, with it’s own pid and along with the process monitor, (pmon)db writer, (dbwr), log writer, (lgwr), we also have archiving, (arcx), job processing, (j00x) performance and other background processing.  I didn’t even grep for the Oracle executable, so you recognize how quickly we can see what is running.

In the SQL Server environment, we only have two processes- our parent process is PID 7 and the child is 9 for SQL Server and nothing to distinguish what they actually are doing.  If we decide to use the pmap utility to view what the parent and child process aredoing, we see only sqlservr as the mapping information.

I imagine that things like this will improve over time for SQL Server, but Oracle definitely has a leg up in this regard.

SQL Server Single-User Mode In Linux

Kevin Feasel



Anthony Nocentino shows us how to get into single-user mode in SQL Server on Linux:

There was a question this morning on the SQL Server Community Slack channel from SvenLowry about how to launch SQL Server on Linux in Single User Mode. Well you’ve heard everyone say, it’s just SQL Server…and that’s certainly true and this is another example of that idea.

The command line parameters from the sqlservr binary are passed through into the SQLPAL managed Win32 SQL Process. So let’s check out how to do this together…

Click through for a demo.


March 2018
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