Welcome!

Linux Containers Authors: Vaibhaw Pandey, Liz McMillan, Elizabeth White, Pat Romanski, Yeshim Deniz

Related Topics: Linux Containers

Linux Containers: Article

Tackling Dependencies

Automated dependency resolution

You don't have to be around Linux for long before you hear about "the dependency problem," which is no problem at all for many users - until the day it bites them. In a nutshell, the problem is that most Linux applications depend on the operating system to provide various pieces of functionality that the applications need. These components most often take the form of shared libraries that are dynamically loaded and linked to the application at runtime. Problems occur when one or more of these libraries are replaced with a different (usually newer) version. Provided all the interfaces remain the same and the semantics of the functionality remain the same, there's no problem. However, due to security fixes, bug fixes, or new or improved functionality, the interfaces and semantics can and do change, and the changes can be enough to break the application.

In general, individual libraries aren't distributed individually but as part of a package of related components. Packages are installed as a whole. In general there's no way to take just one part of a package, and in fact to do so would be inviting trouble since packages are usually composed of related components that need to be installed as a whole to guarantee that the components work together correctly.

It would seem reasonable to assume that once an application is installed and working there would be no reason to touch it, or any of the components that it depends on. However, there are myriad reasons why components end up changing. The most common are:

  • A new application is installed that requires a later version of a package containing one of the shared libraries used by the first application.
  • A security or bug fix affects a package used by the application.
  • An update version of the OS from the distributor includes newer packages.
Whatever the cause, installing a package to satisfy the requirements of some totally unrelated piece of software can break a currently installed application, even if it has no libraries in common with the new software, but simply because some of the libraries of the two applications are contained in the same package. The more applications that are installed, the greater the chance of problems, and the more complex it becomes to find a combination of packages that will satisfy all of the dependencies.

This problem isn't unique to Linux. It's been a long-time problem with many different Unix systems that make heavy use of shared libraries, and is essentially the same as the famous "dll hell" that afflicted older versions of Windows (a Windows .dll file is a dynamically loaded shared library). Unix vendors reduced the problem to manageable proportions by tightly controlling the evolution of the system and providing lots of advance warning to third-party vendors of impending changes. Microsoft adopted similar tactics and became adamant about which libraries third parties were free to change, and which they weren't, making it difficult for third-party applications to overwrite system-provided libraries.

Linux is essentially no better or worse in terms of shared library management than Unix or Windows. What's different is that there's no central coordinating authority to make sure that changes happen in a controlled and consistent manner. In some respects this is one of the strengths of Open Source development; it allows change to happen at its natural pace and forces people to be more aware of the potential problems associated with change. It's also a weakness from the point-of-view of an end user having to integrate systems with components with different dependency requirements.

Linux distributors spend a lot of time and effort making sure that their systems are delivered with the dependencies all correctly resolved, and that any updates they create don't disturb this balance. They often go so far as to take security/bug/performance updates that tend to be created by the component development group on the latest version of their software - which is probably not the version currently shipping - and back-port the changes to the shipping version and test to make sure the changes don't introduce any inconsistencies. However, distributions have limited control over third parties, both commercial and Open-Source, that are reluctant to re-test their products with every new version of a package on which they have a dependency.

One of the interesting benefits Linux holds for its enterprise adopters is that it's multi-sourced. Essentially the same product is available from multiple vendors, improving competition and avoiding lock-in. Although managing multiple Linux distributions adds overhead, some companies prefer not to put all their eggs in one basket and use multiple distributions to help ensure that they don't end up locked in to a specific distribution.

However, this adds a new dimension to the dependency problem.

In many instances, different packages are used on different distributions. There's no standardized system for packaging, although most major Linux distributors use the RPM packaging system that defines how the package is constructed and what information it contains on individual file location and a set of dependency rules. Unfortunately, the same package name on two different distributions can contain different revisions of components or even different components. To add to the problem, not all Linux systems use the same package mechanism. For example, Debian-based systems don't use packages at all.

The end result is that the configuration management of these systems becomes quite complex. Applying something such as a security fix may necessitate other changes to bring the dependencies back into alignment, and then subsequent testing of all applications running on those revised systems/distributions before they can be declared stable and rolled out into production. This has to happen independently on each distribution platform.

Aduva OnStage

Having lived and worked with this problem, and recognizing the need for a better solution than the mostly manual process that they and everyone else was using, the founders of Aduva began work on trying to automate the dependency resolution process.

One of the key components of their system was based on recognizing that the package level - at which most people were working - is too high a level for successful resolution. They built a database (the Aduva Universal KnowlegeBase) of dependency information based on the contents of the packages - the individual files that they contain.

By extending the dependency information and including specific dynamic dependency rules down to the file level it becomes much easier to find solutions to dependency problems. Once a set of solutions is found, information stored in the database about the composition of the packages is used to resolve the set of packages with the highest version levels possible to implement a solution. Since information is stored on distribution-specific packages, the system can derive package lists specific to individual distributions for the same dependencies.

The database also contains information on security alerts and errata notifications and fixes for packages and their components, so in building a specific package list the system takes account of these, and will find a path through the dependency graph that avoids as many of them as possible, hopefully all of them. Rarely, when re-evaluating dependencies to add a new application, the only valid path(s) will include components with known security issues. In that case the system delivers its package list, but warns that the list will introduce known security problems, leaving system administrators to decide whether to continue or consult with Aduva's Lab and professional services team to devise a solution.

Keeping the database up-to-date is the key to success. Aduva works closely with Linux distributions, many different Open Source development communities, and various security groups to ensure that it has complete and current information. A set of tools automates and tests much of the process of determining dependencies.

The complete KnowledgeBase allows systems configurations to be generated based on combinations of different packages beyond those directly supported by a given Linux distribution, provided those packages are known to the KnowledgeBase. Of course, in real-world deployments a huge variety of different applications and third-party packages are going to be encountered, more than in the centrally maintained Universal KnowledgeBase. To make sure that the extended dependency requirements encompassing these additional components are taken into account when configuring, a set of tools exists that permits individual customers to create their own KnowledgeBase with dependency rules specific to their particular software. This local KnowledgeBase is then used in conjunction with the central KnowledgeBase to ensure that the specific requirements of local software components are taken into account when determining a stable configuration.

With this core technology in place Aduva has used it as a platform on which to build a set of tools designed to simplify Linux configuration management, application deployment, change management, and patch control for the enterprise. This set of management tools is sold under the name OnStage.

The OnStage toolset provides a very complete set of system configuration management tools, enabling machine types to be defined, a configuration generated for that specific set of machines, and automatically deployed at the click of a button. Changes can be made to any given set of machines such as deploying an application, adding a patch, or changing the system configuration, and the set of changes are validated against the local and central KnowledgeBases and automatically updated to ensure dependency rules are met and pushed to the entire set of machines, either immediately, or deferred until a specific time or other criteria are met. Configurations are recorded at each stage making it trivial to back out any change or set of changes should that be required.

What's unique about the OnStage toolset is that it sits on the KnowledgeBase and takes the uncertainty out of making changes to a stable production platform, which is one more step in making Open Source a viable solution for the enterprise.

More Stories By Zev Laderman

Zev Laderman is chairman and CEO of Aduva. He was previously CEO of Tradeum, President of Verticalnet, and was a VP at Oracle. He has an MBA from the Stanford University Graduate School of Business.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
Widespread fragmentation is stalling the growth of the IIoT and making it difficult for partners to work together. The number of software platforms, apps, hardware and connectivity standards is creating paralysis among businesses that are afraid of being locked into a solution. EdgeX Foundry is unifying the community around a common IoT edge framework and an ecosystem of interoperable components.
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
Large industrial manufacturing organizations are adopting the agile principles of cloud software companies. The industrial manufacturing development process has not scaled over time. Now that design CAD teams are geographically distributed, centralizing their work is key. With large multi-gigabyte projects, outdated tools have stifled industrial team agility, time-to-market milestones, and impacted P&L stakeholders.
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
It is of utmost importance for the future success of WebRTC to ensure that interoperability is operational between web browsers and any WebRTC-compliant client. To be guaranteed as operational and effective, interoperability must be tested extensively by establishing WebRTC data and media connections between different web browsers running on different devices and operating systems. In his session at WebRTC Summit at @ThingsExpo, Dr. Alex Gouaillard, CEO and Founder of CoSMo Software, presented ...
WebRTC is great technology to build your own communication tools. It will be even more exciting experience it with advanced devices, such as a 360 Camera, 360 microphone, and a depth sensor camera. In his session at @ThingsExpo, Masashi Ganeko, a manager at INFOCOM Corporation, introduced two experimental projects from his team and what they learned from them. "Shotoku Tamago" uses the robot audition software HARK to track speakers in 360 video of a remote party. "Virtual Teleport" uses a multip...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
SYS-CON Events announced today that Evatronix will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Evatronix SA offers comprehensive solutions in the design and implementation of electronic systems, in CAD / CAM deployment, and also is a designer and manufacturer of advanced 3D scanners for professional applications.
Leading companies, from the Global Fortune 500 to the smallest companies, are adopting hybrid cloud as the path to business advantage. Hybrid cloud depends on cloud services and on-premises infrastructure working in unison. Successful implementations require new levels of data mobility, enabled by an automated and seamless flow across on-premises and cloud resources. In his general session at 21st Cloud Expo, Greg Tevis, an IBM Storage Software Technical Strategist and Customer Solution Architec...
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
An increasing number of companies are creating products that combine data with analytical capabilities. Running interactive queries on Big Data requires complex architectures to store and query data effectively, typically involving data streams, an choosing efficient file format/database and multiple independent systems that are tied together through custom-engineered pipelines. In his session at @BigDataExpo at @ThingsExpo, Tomer Levi, a senior software engineer at Intel’s Advanced Analytics gr...