The chroot technique in Linux changes a process's root directory, isolating it within a specified subdirectory tree. This creates a contained environment where the process can only access files and commands within that chroot "jail," enhancing security for tasks like running untrusted software, recovering broken systems, building software in controlled environments, and testing configurations. While powerful, chroot is not a foolproof security measure as sophisticated exploits can potentially break out. Proper configuration and awareness of its limitations are essential for effective utilization.
The paper "File Systems Unfit as Distributed Storage Back Ends" argues that relying on traditional file systems for distributed storage systems leads to significant performance and scalability bottlenecks. It identifies fundamental limitations in file systems' metadata management, consistency models, and single points of failure, particularly in large-scale deployments. The authors propose that purpose-built storage systems designed with distributed principles from the ground up, rather than layered on top of existing file systems, are necessary for achieving optimal performance and reliability in modern cloud environments. They highlight how issues like metadata scalability, consistency guarantees, and failure handling are better addressed by specialized distributed storage architectures.
HN commenters generally agree with the paper's premise that traditional file systems are poorly suited for distributed storage backends. Several highlighted the impedance mismatch between POSIX semantics and distributed systems, citing issues with consistency, metadata management, and performance bottlenecks. Some questioned the novelty of the paper's findings, arguing these limitations are well-known. Others discussed alternative approaches like object storage and databases, emphasizing the importance of choosing the right tool for the job. A few commenters offered anecdotal experiences supporting the paper's claims, while others debated the practicality of replacing existing file system-based infrastructure. One compelling comment suggested that the paper's true contribution lies in quantifying the performance overhead, rather than merely identifying the issues. Another interesting discussion revolved around whether "cloud-native" storage solutions truly address these problems or merely abstract them away.
1984 saw the rise of networked filesystems like NFS, which offered performance comparable to local filesystems, and the introduction of the Andrew File System (AFS), designed for large-scale distributed environments with client-side caching and whole-file serving. Research focused on improving performance and reliability, with log-structured filesystems like LFS emerging to optimize write operations. Additionally, the standardization of file systems continued, with work on the ISO 9660 standard for CD-ROMs solidifying the format's widespread adoption. This year highlighted the increasing importance of networking and the evolving demands placed upon file systems for both performance and portability.
The Hacker News comments discuss the blog post's focus on the early days of networked filesystems, particularly NFS. Several commenters share their own experiences with early NFS, highlighting its initial slow performance and eventual improvements. Some discuss the influence of Sun Microsystems and the rise of distributed systems. Others delve into technical details like caching, consistency models, and the challenges of implementing distributed locks. A few comments compare NFS to other contemporary filesystems and contemplate the enduring relevance of some of the challenges faced in the 1980s. There's a general appreciation for the historical perspective offered by the blog post.
Dan Luu's "Working with Files Is Hard" explores the surprising complexity of file I/O. While seemingly simple, file operations are fraught with subtle difficulties stemming from the interplay of operating systems, filesystems, programming languages, and hardware. The post dissects various common pitfalls, including partial writes, renaming and moving files across devices, unexpected caching behaviors, and the challenges of ensuring data integrity in the face of interruptions. Ultimately, the article highlights the importance of understanding these complexities and employing robust strategies, such as atomic operations and careful error handling, to build reliable file-handling code.
HN commenters largely agree with the premise that file handling is surprisingly complex. Many shared anecdotes reinforcing the difficulties encountered with different file systems, character encodings, and path manipulation. Some highlighted the problems of hidden characters causing issues, the challenges of cross-platform compatibility (especially Windows vs. *nix), and the subtle bugs that can arise from incorrect assumptions about file sizes or atomicity. A few pointed out the relative simplicity of dealing with files in Plan 9, and others mentioned more modern approaches like using memory-mapped files or higher-level libraries to abstract away some of the complexity. The lack of libraries to handle text files reliably across platforms was a recurring theme. A top comment emphasizes how corner cases, like filenames containing newlines or other special characters, are often overlooked until they cause real-world problems.
The blog post argues that file systems, particularly hierarchical ones, are a form of hypermedia that predates the web. It highlights how directories act like web pages, containing links (files and subdirectories) that can lead to other content or executable programs. This linking structure, combined with metadata like file types and modification dates, allows for navigation and information retrieval similar to browsing the web. The post further suggests that the web's hypermedia capabilities essentially replicate and expand upon the fundamental principles already present in file systems, emphasizing a deeper connection between these two technologies than commonly recognized.
Hacker News users largely praised the article for its clear explanation of file systems as a foundational hypermedia system. Several commenters highlighted the elegance and simplicity of this concept, often overlooked in the modern web's complexity. Some discussed the potential of leveraging file system principles for improved web experiences, like decentralized systems or simpler content management. A few pointed out limitations, such as the lack of inherent versioning in basic file systems and the challenges of metadata handling. The discussion also touched on related concepts like Plan 9 and the semantic web, contrasting their approaches to linking and information organization with the basic file system model. Several users reminisced about early computing experiences and the directness of navigating files and folders, suggesting a potential return to such simplicity.
The author migrated away from Bcachefs due to persistent performance issues and instability despite extensive troubleshooting. While initially impressed with Bcachefs's features, they experienced slowdowns, freezes, and data corruption, especially under memory pressure. Attempts to identify and fix the problems through kernel debugging and communication with the developers were unsuccessful, leaving the author with no choice but to switch back to ZFS. Although acknowledging Bcachefs's potential, the author concludes it's not currently production-ready for their workload.
HN commenters generally express disappointment with Bcachefs's lack of mainline inclusion in the kernel, viewing it as a significant barrier to adoption and a potential sign of deeper issues. Some suggest the lengthy development process and stalled upstreaming might indicate fundamental flaws or maintainability problems within the filesystem itself. Several commenters express a preference for established filesystems like ZFS and btrfs, despite their own imperfections, due to their maturity and broader community support. Others question the wisdom of investing time in a filesystem unlikely to become a standard, citing concerns about future development and maintenance. While acknowledging Bcachefs's technically intriguing features, the consensus leans toward caution and skepticism about its long-term viability. A few offer more neutral perspectives, suggesting the author's experience might not be universally applicable and hoping for the project's eventual success.
This spreadsheet documents a personal file system designed to mitigate data loss at home. It outlines a tiered backup strategy using various methods and media, including cloud storage (Google Drive, Backblaze), local network drives (NAS), and external hard drives. The system emphasizes redundancy by storing multiple copies of important data in different locations, and incorporates a structured approach to file organization and a regular backup schedule. The author categorizes their data by importance and sensitivity, employing different strategies for each category, reflecting a focus on preserving critical data in the event of various failure scenarios, from accidental deletion to hardware malfunction or even house fire.
Several commenters on Hacker News expressed skepticism about the practicality and necessity of the "Home Loss File System" presented in the linked Google Doc. Some questioned the complexity introduced by the system, suggesting simpler solutions like cloud backups or RAID would be more effective and less prone to user error. Others pointed out potential vulnerabilities related to security and data integrity, especially concerning the proposed encryption method and the reliance on physical media exchange. A few commenters questioned the overall value proposition, arguing that the risk of complete home loss, while real, might be better mitigated through insurance rather than a complex custom file system. The discussion also touched on potential improvements to the system, such as using existing decentralized storage solutions and more robust encryption algorithms.
Summary of Comments ( 12 )
https://news.ycombinator.com/item?id=43632379
Hacker News users generally praised the article for its clear explanation of
chroot, a fundamental Linux concept. Several commenters shared personal anecdotes of usingchrootfor various tasks like building software, recovering broken systems, and creating secure environments. Some highlighted its importance in containerization technologies like Docker. A few pointed out potential security risks ifchrootisn't used carefully, especially regarding shared namespaces and capabilities. One commenter mentioned the usefulness of systemd-nspawn as a more modern and convenient alternative. Others discussed the history ofchrootand its role in improving Linux security over time. The overall sentiment was positive, with many appreciating the refresher on this powerful tool.The Hacker News post titled "The chroot Technique – a Swiss army multitool for Linux systems" has generated several comments discussing various aspects and applications of chroot.
Some users highlight the security implications of using chroot, emphasizing that it's not a foolproof security measure. One commenter points out that breaking out of a chroot environment is often relatively easy for a determined attacker, especially if the confined process has elevated privileges. They mention that while it can offer some level of containment, it shouldn't be relied upon as the sole security mechanism. Another commenter concurs, adding that namespacing offers a more robust approach to isolation.
Another thread discusses the practical uses of chroot, such as building software in a clean environment or troubleshooting dependency issues. One user shares their experience using chroot to create predictable build environments, isolating the build process from the host system's libraries and configurations. This helps ensure consistent and reproducible builds. Another commenter mentions using chroot to recover broken systems, by chrooting into a live environment and repairing the installed system from there.
A few comments delve into the technical details of chroot, explaining how it works and its limitations. One user describes how chroot manipulates the file system view of a process, making a specified directory appear as the root directory. They also explain how this can be used to create isolated environments for different services or applications.
The discussion also touches upon alternatives to chroot, such as containers and virtual machines. One commenter argues that while chroot has its uses, containers and virtual machines offer better isolation and security, albeit with more overhead. They suggest that for more demanding isolation requirements, containers and VMs are generally preferred.
Several commenters share their personal anecdotes and experiences using chroot. One user recounts using chroot to run legacy applications that are incompatible with newer system libraries. Another shares a story about using chroot to troubleshoot a complex dependency conflict. These anecdotal accounts provide practical context for the discussion, illustrating the real-world applications of chroot.
Finally, some comments provide additional resources and links for further reading about chroot and related topics. One user shares a link to a detailed tutorial on using chroot, while another links to an article discussing the security implications of chroot in more depth.