ext2, or second extended file system, is a file system for the Linux kernel. It was initially designed by French software developer Rémy Card as a replacement for the extended file system (ext). Having been designed according to the same principles as the Berkeley Fast File System from BSD, it was the first commercial-grade filesystem for Linux.
A kernel panic is a safety measure taken by an operating system's kernel upon detecting an internal fatal error in which either it is unable to safely recover or continuing to run the system would have a higher risk of major data loss. The term is largely specific to Unix and Unix-like systems. The equivalent on Microsoft Windows operating systems is a stop error, often called a "blue screen of death".
The Filesystem Hierarchy Standard (FHS) is a reference describing the conventions used for the layout of Unix-like systems. It has been made popular by its use in Linux distributions, but it is used by other Unix-like systems as well. It is maintained by the Linux Foundation. The latest version is 3.0, released on 3 June 2015.
JACK Audio Connection Kit is a professional sound server API and pair of daemon implementations to provide real-time, low-latency connections for both audio and MIDI data between applications. JACK was developed by a community of open-source developers led by Paul Davis and has been a key piece of infrastructure and the de facto standard for professional audio software on Linux since its inception in 2002. The server is free software, licensed under GPL-2.0-or-later, while the library is licensed under LGPL-2.1-or-later.
In computing, a loadable kernel module (LKM) is an object file that contains code to extend the running kernel, or so-called base kernel, of an operating system. LKMs are typically used to add support for new hardware and/or filesystems, or for adding system calls. When the functionality provided by an LKM is no longer required, it can be unloaded in order to free memory and other resources.
stat is a Unix system call that returns file attributes about an inode. The semantics of stat vary between operating systems. As an example, Unix command ls uses this system call to retrieve information on files that includes:
DTrace is a comprehensive dynamic tracing framework originally created by Sun Microsystems for troubleshooting kernel and application problems on production systems in real time. Originally developed for Solaris, it has since been released under the free Common Development and Distribution License (CDDL) in OpenSolaris and its descendant illumos, and has been ported to several other Unix-like systems.
The proc filesystem (procfs) is a special filesystem in Unix-like operating systems that presents information about processes and other system information in a hierarchical file-like structure, providing a more convenient and standardized method for dynamically accessing process data held in the kernel than traditional tracing methods or direct access to kernel memory. Typically, it is mapped to a mount point named /proc at boot time. The proc file system acts as an interface to internal data structures about running processes in the kernel. In Linux, it can also be used to obtain information about the kernel and to change certain kernel parameters at runtime (sysctl).
sysfs is a pseudo file system provided by the Linux kernel that exports information about various kernel subsystems, hardware devices, and associated device drivers from the kernel's device model to user space through virtual files. In addition to providing information about various devices and kernel subsystems, exported virtual files are also used for their configuration.
In Linux systems, initrd is a scheme for loading a temporary root file system into memory, to be used as part of the Linux startup process. initrd and initramfs refer to two different methods of achieving this. Both are commonly used to make preparations before the real root file system can be mounted.
Wireless network cards for computers require control software to make them function. This is a list of the status of some open-source drivers for 802.11 wireless network cards.
debugfs is a special file system available in the Linux kernel since version 2.6.10-rc3. It was written by Greg Kroah-Hartman.
The Linux booting process involves multiple stages and is in many ways similar to the BSD and other Unix-style boot processes, from which it derives. Although the Linux booting process depends very much on the computer architecture, those architectures share similar stages and software components, including system startup, bootloader execution, loading and startup of a Linux kernel image, and execution of various startup scripts and daemons. Those are grouped into 4 steps: system startup, bootloader stage, kernel stage, and init process. When a Linux system is powered up or reset, its processor will execute a specific firmware/program for system initialization, such as Power-on self-test, invoking the reset vector to start a program at a known address in flash/ROM, then load the bootloader into RAM for later execution. In personal computer (PC), not only limited to Linux-distro PC, this firmware/program is called BIOS, which is stored in the mainboard. In embedded Linux system, this firmware/program is called boot ROM. After being loaded into RAM, bootloader will execute to load the second-stage bootloader. The second-stage bootloader will load the kernel image into memory, decompress and initialize it then pass control to this kernel image. Second-stage bootloader also performs several operation on the system such as system hardware check, mounting the root device, loading the necessary kernel modules, etc. Finally, the very first user-space process starts, and other high-level system initializations are performed.
In computing, SystemTap is a scripting language and tool for dynamically instrumenting running production Linux-based operating systems. System administrators can use SystemTap to extract, filter and summarize data in order to enable diagnosis of complex performance or functional problems.
The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally written in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU operating system, which was written to be a free (libre) replacement for Unix.
cgroups is a Linux kernel feature that limits, accounts for, and isolates the resource usage of a collection of processes.
kpatch is a feature of the Linux kernel that implements live patching of a running kernel, which allows kernel patches to be applied while the kernel is still running. By avoiding the need for rebooting the system with a new kernel that contains the desired patches, kpatch aims to maximize the system uptime and availability. At the same time, kpatch allows kernel-related security updates to be applied without deferring them to scheduled downtimes. Internally, kpatch allows entire functions in a running kernel to be replaced with their patched versions, doing that safely by stopping all running processes while the live patching is performed.
Namespaces are a feature of the Linux kernel that partition kernel resources such that one set of processes sees one set of resources, while another set of processes sees a different set of resources. The feature works by having the same namespace for a set of resources and processes, but those namespaces refer to distinct resources. Resources may exist in multiple spaces. Examples of such resources are process IDs, host-names, user IDs, file names, some names associated with network access, and Inter-process communication.
ftrace is a tracing framework for the Linux kernel. Although its original name, Function Tracer, came from ftrace's ability to record information related to various function calls performed while the kernel is running, ftrace's tracing capabilities cover a much broader range of kernel's internal operations.
