Start by marking “The Linux Kernel Book [With *]” as Want to Read: 'The book you hold in your hand will hopefully help you understand the Linux operating system kernel better. Linus Torvalds the Linux Kernel book by Rémy Card, Éric Dumas, Fr. This books (The Linux Kernel Book [PDF]) Made by Rémy Card About Books none To Download Please Click. This book (“The Linux Kernel”) be reproduced and distributed in . This book is not intended to be used as an internals manual for Linux. . Most freely available software easily builds on Linux and I can often simply download The Second Extended File system was devised (by Rémy Card) as an.

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The Linux Kernel Book [Rémy Card, Eacute;ric Dumas, Franck Mével] on 'The book you hold in your hand will hopefully help you understand the Linux Get your site here, or download a FREE site Reading App. convert pdf to excel converter free download best books to read in tamil anne frank book online free. 6th to 10th state board books book buddy app for android. Text Books 1 Remy Card Eric Dumas and Frank Mevel The Linux Kernel Book Wiley from STATS 95 at Indian Institute of Technology, Kharagpur.

Online defragmentation Neither ext2 nor ext3 directly supported online defragmentation—that is, defragging the filesystem while mounted. Ext2 had an included utility, e2defrag, that did what the name implies—but it needed to be run offline while the filesystem was not mounted. This is, obviously, especially problematic for a root filesystem. The situation was even worse in ext3—although ext3 was much less likely to suffer from severe fragmentation than ext2 was, running e2defrag against an ext3 filesystem could result in catastrophic corruption and data loss.

Although ext3 was originally deemed "unaffected by fragmentation," processes that employ massively parallel write processes to the same file e. Several userspace hacks and workarounds, such as Shake , addressed this in one way or another—but they were slower and in various ways less satisfactory than a true, filesystem-aware, kernel-level defrag process.

Ext4 addresses this problem head on with e4defrag, an online, kernel-mode, filesystem-aware, block-and-extent-level defragmentation utility.

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Ongoing ext4 development Ext4 is, as the Monty Python plague victim once said, "not quite dead yet! There are still a few key features being developed into future versions of ext4, including metadata checksumming, first-class quota support, and large allocation blocks. Metadata checksumming Since ext4 has redundant superblocks, checksumming the metadata within them offers the filesystem a way to figure out for itself whether the primary superblock is corrupt and needs to use an alternate.

It is possible to recover from a corrupt superblock without checksumming—but the user would first need to realize that it was corrupt, and then try manually mounting the filesystem using an alternate. Since mounting a filesystem read-write with a corrupt primary superblock can, in some cases, cause further damage, this isn't a sufficient solution, even with a sufficiently experienced user!

Compared to the extremely robust per-block checksumming offered by next-gen filesystems such as btrfs or zfs, ext4's metadata checksumming is a pretty weak feature. But it's much better than nothing. First-class quota support Wait, quotas?! We've had those since the ext2 days! Yes, but they've always been an afterthought, and they've always kinda sucked. It's probably not worth going into the hairy details here, but the design document lays out the ways quotas will be moved from userspace into the kernel and more correctly and performantly enforced.

Large allocation blocks As time goes by, those pesky storage systems keep getting bigger and bigger. With some solid-state drives already using 8K hardware blocksizes, ext4's current limitation to 4K blocks gets more and more limiting. Larger storage blocks can decrease fragmentation and increase performance significantly, at the cost of increased "slack" space the space left over when you only need part of a block to store a file or the last piece of a file.

You can view the hairy details in the design document.

Practical limitations of ext4 Ext4 is a robust, stable filesystem, and it's what most people should probably be using as a root filesystem in But it can't handle everything.

Let's talk briefly about some of the things you shouldn't expect from ext4—now or probably in the future. Although ext4 can address up to 1 EiB—equivalent to 1,, TiB—of data, you really, really shouldn't try to do so. There are problems of scale above and beyond merely being able to remember the addresses of a lot more blocks, and ext4 does not now and likely will not ever scale very well beyond TiB of data.

Ext4 also doesn't do enough to guarantee the integrity of your data. As big an advancement as journaling was back in the ext3 days, it does not cover a lot of the common causes of data corruption.

If data is corrupted while already on disk—by faulty hardware, impact of cosmic rays yes, really , or simple degradation of data over time—ext4 has no way of either detecting or repairing such corruption. Building on the last two items, ext4 is only a pure filesystem, and not a storage volume manager.

This means that even if you've got multiple disks—and therefore parity or redundancy, which you could theoretically recover corrupt data from—ext4 has no way of knowing that or using it to your benefit. While it's theoretically possible to separate a filesystem and storage volume management system in discrete layers without losing automatic corruption detection and repair features, that isn't how current storage systems are designed, and it would present significant challenges to new designs.

Alternate filesystems Before we get started, a word of warning: Be very careful with any alternate filesystem which isn't built into and directly supported as a part of your distribution's mainline kernel!

Even if a filesystem is safe, using it as the root filesystem can be absolutely terrifying if something hiccups during a kernel upgrade. If you aren't extremely comfortable with the idea of booting from alternate media and poking manually and patiently at kernel modules, grub configs, and DKMS from a chroot There may well be good reasons to use a filesystem your distro doesn't directly support—but if you do, I strongly recommend you mount it after the system is up and usable.

For example, you might have an ext4 root filesystem, but store most of your data on a zfs or btrfs pool. It's a bit, journaling filesystem that has been built into the Linux kernel since and offers high performance for large filesystems and high degrees of concurrency i. It still has a few disadvantages for home or small business users—most notably, it's a real pain to resize an existing XFS filesystem, to the point it usually makes more sense to create another one and copy your data over.

While XFS is stable and performant, there's not enough of a concrete end-use difference between it and ext4 to recommend its use anywhere that it isn't the default e.

Like ext4, it should most likely be considered a stopgap along the way towards something better.

ZFS ZFS was developed by Sun Microsystems and named after the zettabyte—equivalent to 1 trillion gigabytes—as it could theoretically address storage systems that large.

A true next-generation filesystem, ZFS offers volume management the ability to address multiple individual storage devices in a single filesystem , block-level cryptographic checksumming allowing detection of data corruption with an extremely high accuracy rate , automatic corruption repair where redundant or parity storage is available , rapid asynchronous incremental replication , inline compression, and more.

A lot more. All the mentioned Linux Tutorial books originally come with a pdf version, and I have also made an epub, Mobi, and site site copy from the original pdf copy. So if anyone finds any problem on epub or Mobi copy, then I would like to refer to see the original pdf version. I hope all the copy is okay to read on various devices.

The contents are written in simple and easy to understand format, mainly keeping in mind about the newbie Linux users who have come from other OS or just have installed any Linux Distros for the first time.

The first chapter of this book has focused on the traditional history of Unix, Linux, Users Interface, features of Linux, and the various desktop environment. Then you will be getting quickstart documentation on initial setup, login, password, GUI, Command Line Interface, files management, and necessary Linux command.

In the third chapter, you will be able to play with the Linux files system and partitioning. The fourth chapter will allow you to learn about various processing task related to users, Boot, Grub, and Multi-tasking inside out. Moreover, it gives detailed information about Desktop environment, Graphical User interface, Shell Script, and setup, X window system and configuration, keyboard, date, language and fonts set up, installing software, and package management. This makes the system slower than traditional monolithic kernels.

This slight speed disadvantage is readily accepted, because current UNIX hardware is generally fast enough and because the advantage of simpler system maintenance reduces development costs. Microkernel architectures undoubtedly represent the future of operating system development. Exploiting all possible ways of optimizing performance to give good run-time behaviour was a primary consideration.

Another reason was undoubtedly the fact that a microkernel architecture depends on careful design of the Linux kernel internails - 27 - system. Since LINUX has grown by evolution, starting from the fun of developing a system, this was simply not possible. Most components of the kernel are only accessed via accurately denned interfaces. A good example of this is the Virtual File System VFS , which represents an abstract interface to all file-oriented operations. We will be taking a closer look at the VFS in Chapter 6.

But the chaos is apparent in the detail.

At time-critical points, sections of programs are often written in 'hand-optimized' C code, making them difficult to follow. Fortunately, these program sections are quite rare and, as a rule, fairly well annotated. By way of comparison, version 1. Table 3. The assembler coding is principally used in emulating the maths coprocessor, booting the system and controlling the hardware.

This is only to be expected. On the other hand, the central routines for process and memory management that is, the kernel proper, in a microkernel context only take up around 5 per cent, a relatively small amount of the code. It is possible to separate most device drivers from the kernel. They can be loaded as autonomous, independent modules at run-time as required see Table 3. C code without header files Device Network VFS layer 13 file systems Co-processor 'Remainder' 1 Assembler instructions Lectures on operating systems as a rule concentrate on memory management, scheduling and inter-prooess communication, and only very seldom deal with other components such as file systems or device drivers.

Linux kernel internails - 28 - Chapter 9. Thus LINUX successfully tries to make use of the advantages of a microkernel architecture without, however, giving up its original monolithic design. Individual processes exist independently alongside each other and cannot affect each other directly. Each process's own area of memory is protected against modification by other processes. Only one program - the operating system - is running on the computer, and can access all the resources.

The various tasks are carried out by co-routines -that is, every task decides for itself whether and when to pass control to another task.

Any task can access all the resources for other tasks and modify them. Certain parts of a task run in the processor's less privileged User Mode. These parts of the task appear from the outside to someone looking into the kernel to be processes.

From the viewpoint of these processes, true multitasking is taking place. Figure 3. In the following pages, however, we will not be making any precise distinction between the concepts of tasks and processes, but using the two words to mean the same thing. When a task is running in the privileged System Mode, it can take one of a number of states. The arrows in this diagram show the possible changes of state.

The following states are possible: Figure 3. Linux kernel internails - 29 - Figure 3. Running The task is active and running in the non-privileged User Mode. In this case the process will go through the program in a perfectly normal way. This state can only be exited via an interrupt or a system call. In Section 3. In either case, the processor is switched to the privileged System Mode and the appropriate interrupt routine is activated. Interrupt routine The interrupt routines become active when the hardware signals an exception condition, which may be new characters input at the keyboard or the clock generator issuing a signal every 10 milliseconds.

Further information on interrupt routines is provided in Section 3. System call System calls are initiated by software interrupts. Details of these are given in Section 3. A system call is able to suspend the task to wait for an event.

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Waiting The process is waiting for an external event. Only after this has occurred will it continue its work. Return from system call This state is automatically adopted after every system call and after some interrupts. At this point checks are made as to whether the scheduler needs to be called and whether there are signals to process.

The scheduler can switch the process to the 'Ready' state and activate another process. Processes and threads In many modern operating systems a distinction is made between processes and threads.

A thread is a sort of independent 'strand' in the course of a program which can be processed in parallel with other threads. As opposed to processes, threads work on the same main memory and can therefore influence each other. Linux does not make this distinction. In the kernel, only the concept of a task exists which can share resources with other tasks for example, the same memory. Thus, a task is a generalization of the usual thread concept.

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More details can be found in Section 3. Understanding these structures and how they interact is a necessary foundation for understanding the following chapters. The first components of the structure are also accessed from assembler routines. This access is not made, as it usually is in C, via the names of the components, but via their offsets relative to the start of the structure.

Linux Kernel Internals

This means that the start of the task structure must not be modified without first checking all the assembler routines and modifying them if necessary.

The keyword volatile indicates that this component can also be altered asynchronously from interrupt routines. The scheduler uses the counter value to select the next process, counter thus represents something like the dynamic priority of a process, while priority holds the static priority of a process.

The scheduling algorithm see Section 3. Removing this limitation would require modifications at various points in the kernel. A higher value will apply for the port to Alpha machines. Interested readers will find further information on this system call in Section 5. The errno variable holds the error code for the last faulty system call. On return from the system call, this is copied into the global variable errno see Section 3.

The debugreg variable contains the 80x86's debugging registers. These are at present used only by the system call ptrace. This completes the hard-coded part of the task structure.

The following components of the task structure are considered in groups for the sake of simplicity. In a UNIX system, processes do not exist independently of each other. To enable a process to access all its child processes, the task structure holds the Figure 3. The scheduler uses a list of all processes that apply for the processor. Further information is given in Chapter 4. When a process is operating in System Mode, it needs its own stack differing from that for the User Mode. Process ID Every process has its own process ID number, pid, and is assigned to a process group, pgrp, and a session, session.

Every session has a leader process, Leader. These are inherited by the child process from the parent process when a new process is created by the fork system call see Section 3. However, for the actual access control the effective user ID, euid, and the effective group ID, eg id, are used.

This is used whenever identification is required by the file system.Sharp began working on the kernel in. Online forums are another means for support, with notable examples being LinuxQuestions. Similar considerations apply for the component fsgid and the system call setfsgid.

There is a detailed step to learn about printing. Ext4 adds an additional two bits here, extending the Unix epoch another years.