04
Mon, Nov
1 New Articles

TechTip: IFS Containers

General
Typography
  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

The proliferating adoption of open source on IBM i means there's a lot going on in PASE. How does one keep from stepping on toes? "IFS Containers" to the rescue.

I was talking with a colleague the other day, and he gave me valuable feedback, stating I should do more at the beginning of articles to describe the problem or the usage scenario of the technology before I jump into the geek parts. Of course, that's priceless feedback for me because if people don't understand the "why," then they won't take the time to read. So let me start this article with a slide that describes a common scenario with shops adopting open source on IBM i (Figure 1). BTW, this entire slide deck is available here as are all of my slide decks.

101416bartell figure1 step-on-toes-slide

Figure 1: “Step on toes” scenario

 

In short, Figure 1 describes a scenario where two developers are working on the same machine and do something to cause the other's development environment (or complete access to the machine) to be hindered. The same can happen with RPG: Two developers, unaware of the other’s work, could develop RPG *SRVPGMs that export the same-named subprocedures. Then if either developer’s library list isn't set correctly, that developer could pick up the other developer's same-named subprocedure. And things would bomb out.

 

 

How could this situation be remedied? You could give each developer their own virtual instance of IBM i, but that might get expensive on both licensing and maintenance. On the RPG front, most shops have guidelines they've set forth. It actually isn't nearly as big a problem in RPG because RPG open source isn't as plentiful, so there's not as much opportunity for conflict by those "outside your control." It's not so simple when we get to the PASE environment because many of the collisions are because of third-party open-source software. In the aforementioned example, there was a conflict between software obtained from perzl.org and the equivalent library (libiconv.a) delivered with the IBM i operating system. So again, how can this situation be remedied without spinning up an entirely new IBM i? Enter what I call "IFS Containers."

 

IFS Containers is a term I've coined to describe the concept of what happens when you use the PASE chroot command. (More on the chroot command later.) Imagine if you could create a container in the IFS that would keep one container from even knowing other containers existed (i.e., they can't see other parts of the IFS outside their own container). That means that if a developer installs a new tool, it will affect only their specific container.

 

 

Containers are not a new concept. There are many containerization technologies, such as VMWare, VirtualBox, Docker, etc., and there is a different approach for each style. Figure 2 compares three approaches in visual form.

 101416bartell figure2 containers

Figure 2: Comparison of different approaches

 

 

You'll notice they all start out with the same infrastructure and host operating system layers. The next layer is where things change. First, let's look at the Virtualbox stack. Virtualbox has what's called a hypervisor, a piece of software used to control operating systems running on top of the host operating system. These are full copies of the operating system that don't share a common operating system. I've used this extensively over the years to run a virtual Windows desktop on top of Linux and Mac, and it works quite well. A similar hypervisor is Parallels, which is popular with Mac users. The next level of VirtualBox after the guest OS is the "bins/libs," which are basically the various runtimes and supporting libraries. These would be things like language and tool binaries (e.g., node, php, ruby, python, java, openssl, git, etc.) and the supporting libraries would be things like libssl, libcrypto, libc, etc. And finally we have the app layer. This is the code of your application and any frameworks (e.g., RubyOnRails, ExpressJs, Django, ReactPHP, etc.).

 

 

Next, let's look at the Docker stack. Instead of a hypervisor, there is the Docker Engine. This engine does similar things to a hypervisorlike allocation of memory and diskbut there's one significant difference: Everything is running on a single instance of the operating system. Each of the three stacks above Docker Engine is a Docker container that houses a specific set of binaries and libraries, yet they all make use of the same base "kernel" operation system. Even though each of those containers is looking at the single kernel, each container has its own set of process ids (aka IBM i job number), users, and control groups for CPU and memory. For example, this means you could have a user named Joe in each of the containers, each with a completely different definition of that user (i.e., permissions). For those familiar with iASP technology on IBM I, this is the opposite of how that works; specifically, *USRPRF objects are stored in *SYSBASE and must be unique across all iASPs on that instance of IBM i.

 

OK, so now we've learned a bit about Virtualbox and Docker, but what about the chroot stack? As you can see, it doesn't have a hypervisor or Docker Engine. That’s because chroot is much simpler in nature in that it only contains, or keeps separate, the file systemhence the "IFS Containers" moniker. I only use that term to create a visual picture in your mind because there aren't actually separate file systems. It's time to further describe what the chroot command does.

 

 

The chroot command stands for "change root," or rather, when I run the chroot command and point it at an IFS directory, I can change the perceived root. At this point, it would be good to start getting into some tangible examples so you can see the chroot command in action.

 

 

First let's learn the syntax for the chroot command, as shown below.

 

 

$ chroot Directory Command

 

Here are the descriptions for Directory and Command:

 

 

·        DirectorySpecifies the new root directory

 

·        CommandSpecifies a command to run with the chroot command

 

Armed with that knowledge, let's log into the IBM i via SSH (CALL QP2TERM could also be used to enter a PASE shell) and attempt to run the chroot command on a newly created directory named dir1.

 

$ ssh aaron@myi>

 

bash-4.2$ pwd

/home/AARON

$ ls

git    hi.js

bash-4.2$ mkdir dir1

bash-4.2$ chroot dir1 ls

ls: No such file or directory

 

 

After I run the ssh command on my local Mac, I am then logged into PASE on the IBM i. The prefix of "bash-4.2" is telling me what shell I am using. I do a pwd so you can know where I am in the file system. I run the ls (list) so you can see the command working (more on this later). Then I create a directory named dir1 with the mkdir command. Finally, I get to the chroot command. I want to "change root" to dir1, and once inside the new root I want to run the ls command. As you can see, the ls command couldn't be found. But why not? Didn't ls exist when we first logged in? Herein we learn the primary concept of chroot (or IFS Containers).…

If you don't manually put something into the IFS Container, then it doesn't exist.

 

What does that mean? Well, when we ran the chroot command, it placed us inside the dir1 directory, and that became our new root directory. Once you’re placed inside the directory by the chroot command, you can't see anything else above the directory you're in. The chroot command then supplied the ls command, and it came back as not found because there aren't actually any files or directories inside of dir1 that made it capable of running the ls command. So let's add them.

bash-4.2$ pwd

/home/AARON

bash-4.2$ mkdir -p dir1/usr/lib

bash-4.2$ cp /lib/libc.a dir1/usr/lib

bash-4.2$ cp /lib/libcrypt.a dir1/usr/lib

bash-4.2$ mkdir -p dir1/usr/bin

bash-4.2$ cp /QOpenSys/usr/bin/bsh dir1/usr/bin

bash-4.2$ chroot dir1 /usr/bin/bsh

$ ls

ls: not found

 

Let's go through the above commands. First, I create a new directory where we can put some library files, namely libc.a and libcrypt.a, and then we copy those files into dir1. These two libraries are fundamental to being able to run commands once inside the IFS Container. Next, I determine we would want to enter the IFS Container and be given an interactive shell prompt, much like the shell we are now in. To accomplish this, we need to create a dir1/usr/bin directory and copy the bsh (Bourne Shell) into it. Now I run the chroot command again and this time specify the fully qualified path to bsh for the command portion of the call. At this point, I am inside the IFS Container and in an interactive shell. I run the ls command and it declares it still can't find it. That's because I neglected to copy it into the IFS Container. At this point, it's necessary for me to exit the IFS Container and copy the ls command into the IFS Container.

 

$ exit

 

bash-4.2$ cp /QOpenSys/usr/bin/ls dir1/usr/bin

 

bash-4.2$ chroot dir1 /usr/bin/bsh

 

$ ls /

 

usr

 

$ ls /usr

 

bin  lib

 

$ ls /usr/bin

 

bsh  ls

 

$ ls /usr/lib

 

libc.a      libcrypt.a

 

Above, I show how to exit the IFS Container and then I copy in the ls command. Then, I enter the IFS Container again using the chroot command and successfully run the ls command (because it now exists inside the IFS Container). I then proceed to use the ls command to display the root of my IFS Container and the contents of the other directories. What's important to recognize is what is not there. Specifically, there isn't a /QSYS.LIB directory or any other directory, such as /home. I could create a /home directory, but you can't copy /QSYS.LIB into an IFS Container.

 

 

So how does this help the original scenario of developers stepping on each other’s toes? Note how the ls command wasn't able to see anything outside of the IFS Container. The same holds true for all other commands and programs in a chroot environment, which means if we were to install some software, it wouldn't be able to affect other directories because it couldn't reach or see those other directories. This is an incredibly useful feature, not only for development but also for situations where I want to quickly test a piece of software; once I am done, I can simply delete the IFS Container.

 

 

At this point, you might be thinking that creating IFS Containers might be a laborious thing to do because of the many things needing to be set up (we've only touched the tip of the iceberg). No worries, there’s open source code to help with that, and that is what I'll be covering in the next article. Stay tuned!

 

 

If you have any questions or comments, then please comment below or email me at This email address is being protected from spambots. You need JavaScript enabled to view it..

Aaron Bartell

Aaron Bartell is Director of IBM i Innovation for Krengel Technology, Inc. Aaron facilitates adoption of open-source technologies on IBM i through professional services, staff training, speaking engagements, and the authoring of best practices within industry publications andwww.litmis.comWith a strong background in RPG application development, Aaron covers topics that enable IBM i shops to embrace today's leading technologies, including Ruby on Rails, Node.js, Git for RPG source change management, and RSpec for unit testing RPG. Aaron is a passionate advocate of vibrant technology communities and the corresponding benefits available for today's modern application developers. Connect with Aaron via email atThis email address is being protected from spambots. You need JavaScript enabled to view it..

Aaron lives with his wife and five children in southern Minnesota. He enjoys the vast amounts of laughter that having a young family brings, along with camping and music. He believes there's no greater purpose than to give of our life and time to help others.

BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

$

Book Reviews

Resource Center

  • SB Profound WC 5536 Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. How can you be sure you won’t miss important system events? Automate your message center with the Robot Message Management Solution. Key features include:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing. Manage your reports with the Robot Report Management Solution. Key features include:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.

  • LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed. Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn: