System Calls
Everything on SkillVeris tagged System Calls — collected across the glossary, study notes, blog, and cheat sheets.
19 resources across 2 libraries
Study Notes(1)
Interview Questions(18)
What are Memory-Mapped Files?
A memory-mapped file is a file whose contents are mapped directly into a process’s virtual address space via the page cache, so the program reads and writes th…
What Are Signals in an Operating System?
A signal is a limited, asynchronous notification the kernel delivers to a process to inform it of an event — such as a fault, a user interrupt, a timer expiry,…
Compare Different IPC Mechanisms (Pipes, Shared Memory, Message Queues)
Pipes offer simple, ordered byte-stream communication between related processes with kernel-managed buffering, shared memory offers the fastest raw throughput…
What Are the Types of System Calls?
System calls are the controlled entry points through which a user-space program requests a privileged service from the kernel, and they fall into five broad ca…
How Are Kernel Threads Implemented and Scheduled?
A kernel thread is a thread the operating system kernel itself creates, schedules, and manages directly, with its own kernel-level thread control block, so the…
What Are Protection Rings in an Operating System?
Protection rings are hierarchical privilege levels enforced by the CPU, typically numbered from Ring 0 (most privileged, running the kernel) to Ring 3 (least p…
What Is the System Call Interface in an Operating System?
The system call interface is the well-defined, kernel-validated boundary through which a user-mode application requests privileged operations — like file I/O,…
Trap vs Interrupt: What Is the Difference?
A trap is a synchronous event deliberately raised by the currently executing instruction (such as a system call or a divide-by-zero error), while an interrupt…
What is a Software Interrupt?
A software interrupt is an interrupt deliberately triggered by executing a special CPU instruction from within a running program, most commonly to request a se…
What is the Virtual File System (VFS) Layer?
The Virtual File System (VFS) layer is an abstraction inside the kernel that defines a common set of file operations — open, read, write, close, and more — so…
What are Linux Namespaces and OS-Level Virtualization?
Linux namespaces are a kernel feature that partitions a single global resource — process IDs, network interfaces, mounts, hostnames, users, and more — into iso…
What are OS Sandboxing Techniques and How Do They Work?
OS sandboxing is the practice of running a process inside a restricted execution environment that limits which system calls, files, and resources it can touch,…
What is a chroot Jail and What Are Its Limitations?
A chroot jail is created by the chroot() system call, which changes a process’s apparent root directory `/` to a chosen subdirectory, so the process — and anyt…
What is Linux Capability Dropping and Why Does It Matter?
Linux capabilities split the traditionally all-or-nothing power of the root user into dozens of independent, fine-grained privileges — like CAP_NET_BIND_SERVIC…
What is a File Descriptor Table?
A file descriptor table is a per-process array maintained by the kernel that maps small integers (file descriptors), which a process uses in system calls, to e…
What is the Open File Table?
The open file table is a kernel-wide (system-wide) structure of entries, each tracking the current file offset, access mode, and status flags for one open() ca…
What Does the mmap() System Call Do?
mmap() maps a file (or anonymous memory) directly into a process’s virtual address space, so the program can read and write the file’s contents using ordinary…
Context Switch vs Mode Switch: What Is the Difference?
A mode switch is the CPU transitioning between user mode and kernel mode privilege levels while staying within the same process, whereas a context switch is th…