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OpenVZ
OpenVZ (Open Virtuozzo) is an operating-system-level virtualization technology for Linux. It allows a physical server to run multiple isolated operating system instances, called containers, virtual private servers (VPSs), or virtual environments (VEs). OpenVZ is similar to Solaris Containers and LXC. OpenVZ compared to other virtualization technologies While virtualization technologies such as VMware, Xen and Kernel-based Virtual Machine, KVM provide full virtualization and can run multiple operating systems and different kernel versions, OpenVZ uses a single Linux kernel and therefore can run only Linux. All OpenVZ containers share the same architecture and kernel version. This can be a disadvantage in situations where guests require different kernel versions than that of the host. However, as it does not have the overhead of a true hypervisor, it is very fast and efficient. Memory allocation with OpenVZ is soft in that memory not used in one virtual environment can be used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating-system-level Virtualization
OS-level virtualization is an operating system (OS) virtualization paradigm in which the kernel allows the existence of multiple isolated user space instances, including containers ( LXC, Solaris Containers, AIX WPARs, HP-UX SRP Containers, Docker, Podman), zones ( Solaris Containers), virtual private servers ( OpenVZ), partitions, virtual environments (VEs), virtual kernels (DragonFly BSD), and jails ( FreeBSD jail and chroot). Such instances may look like real computers from the point of view of programs running in them. A computer program running on an ordinary operating system can see all resources (connected devices, files and folders, network shares, CPU power, quantifiable hardware capabilities) of that computer. Programs running inside a container can only see the container's contents and devices assigned to the container. On Unix-like operating systems, this feature can be seen as an advanced implementation of the standard chroot mechanism, which changes the appare ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtuozzo (company)
Virtuozzo is a software company that develops virtualization and cloud management software for cloud computing providers, managed services providers and internet hosting service providers. The company's software enables service providers to offer Infrastructure as a service, Container-as-a-Service, Platform as a service, Kubernetes-as-a-Service, WordPress-as-a-Service and other solutions. History The company was founded as SWsoft in 1997 as a privately held server automation and virtualization company. In 2000, the company released the first commercially available operating system-level virtualization container technology. In 2003, SWsoft acquired the makers of Confixx and Plesk web hosting products: Plesk Server Administration (PSA) control panel and Confixx Professional hosting software. Virtuozzo was the core enabling technology behind SWsoft's HSP Complete solution. In 2004, SWsoft acquired Parallels, Inc. In 2005, the company open-sourced its operating system-level virtual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Private Server
A virtual private server (VPS) or virtual dedicated server (VDS) is a virtual machine sold as a service by an Internet hosting company. A virtual private server runs its own copy of an operating system (OS), and customers may have superuser-level access to that operating system instance, so they can install almost any software that runs on that OS. For many purposes, it is functionally equivalent to a dedicated physical server and, being software-defined, can be created and configured more easily. A virtual server costs less than an equivalent physical server. However, as virtual servers share the underlying physical hardware with other VPS, performance may be lower depending on the workload of any other executing virtual machines. Virtualization The force driving server virtualization is similar to that which led to the development of time-sharing and multiprogramming in the past. Although the resources are still shared, as under the time-sharing model, virtualization pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Application Checkpointing
Checkpointing is a technique that provides fault tolerance for computing systems. It involves saving a Snapshot (computer storage), snapshot of an application software, application's state, so that it can restart from that point in case of failure. This is particularly important for long-running applications that are executed in failure-prone computing systems. Checkpointing in distributed systems In the distributed computing environment, checkpointing is a technique that helps tolerate failures that would otherwise force a long-running application to restart from the beginning. The most basic way to implement checkpointing is to stop the application, copy all the required data from the memory to reliable storage (e.g., parallel file system), then continue with execution. In the case of failure, when the application restarts, it does not need to start from scratch. Rather, it will read the latest state ("the checkpoint") from the stable storage and execute from that point. While ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Group (computing)
In computing, the term group generally refers to a grouping of users. In principle, users may belong to none, one, or many groups (although in practice some systems place limits on this). The primary purpose of user groups is to simplify access control to computer systems. For instance, a computer science department has a network which is shared by students and academics. The department has made a list of directories which the students are permitted to access and another list of directories which the staff are permitted to access. Without groups, administrators would give each student permission to every student directory, and each staff member permission to every staff directory. In practice, that would be very impractical – every time a student or staff member arrived, administrators would have to allocate permissions on every directory. With groups, the task is much simpler: create a student group and a staff group, placing each user in the proper group. The entire grou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lock (computer Science)
In computer science, a lock or mutex (from mutual exclusion) is a synchronization primitive that prevents state from being modified or accessed by multiple threads of execution at once. Locks enforce mutual exclusion concurrency control policies, and with a variety of possible methods there exist multiple unique implementations for different applications. Types Generally, locks are ''advisory locks'', where each thread cooperates by acquiring the lock before accessing the corresponding data. Some systems also implement ''mandatory locks'', where attempting unauthorized access to a locked resource will force an exception in the entity attempting to make the access. The simplest type of lock is a binary semaphore. It provides exclusive access to the locked data. Other schemes also provide shared access for reading data. Other widely implemented access modes are exclusive, intend-to-exclude and intend-to-upgrade. Another way to classify locks is by what happens when the lock st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superuser
In computing, the superuser is a special user account used for system administration. Depending on the operating system (OS), the actual name of this account might be root, administrator, admin or supervisor. In some cases, the actual name of the account is not the determining factor; on Unix-like systems, for example, the user with a user identifier (UID) of zero is the superuser .e., uid=0 regardless of the name of that account; and in systems which implement a r model, any user with the role of superuser (or its synonyms) can carry out all actions of the superuser account. The principle of least privilege recommends that most users and applications run under an ordinary account to perform their work, as a superuser account is capable of making unrestricted, potentially adverse, system-wide changes. Unix and Unix-like In Unix-like computer OSes (such as Linux), ''root'' is the conventional name of the user who has all rights or permissions (to all files and programs) in all mod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
User (computing)
A user is a person who uses a computer or network service. A user often has a user account and is identified to the system by a username (or user name). Some software products provide services to other systems and have no direct end users. End user End users are the ultimate human users (also referred to as operators) of a software product. The end user stands in contrast to users who support or maintain the product such as sysops, database administrators and computer technicians. The term is used to abstract and distinguish those who only use the software from the developers of the system, who enhance the software for end users. In user-centered design, it also distinguishes the software operator from the client who pays for its development and other stakeholders who may not directly use the software, but help establish its requirements. This abstraction is primarily useful in designing the user interface, and refers to a relevant subset of characteristics t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Process Identifier
In computing, the process identifier (a.k.a. process ID or PID) is a number used by most operating system kernel (operating system), kernels—such as those of Unix, macOS and Windows—to uniquely identify an active Process (computing), process. This number may be used as a parameter in various function calls, allowing processes to be manipulated, such as adjusting the process's priority or kill (command), killing it altogether. Unix-like In Unix-like operating systems, new processes are created by the Fork (operating system), fork() system call. The PID is returned to the parent process, enabling it to refer to the child in further function calls. The parent may, for example, wait for the child to terminate with the waitpid() function, or terminate the process with kill(). There are two tasks with specially distinguished process IDs: PID 0 is used for ''swapper'' or ''sched'', which is part of the kernel and is a process that runs on a CPU core whenever that CPU core has not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Process (computing)
In computing, a process is the Instance (computer science), instance of a computer program that is being executed by one or many thread (computing), threads. There are many different process models, some of which are light weight, but almost all processes (even entire virtual machines) are rooted in an operating system (OS) process which comprises the program code, assigned system resources, physical and logical access permissions, and data structures to initiate, control and coordinate execution activity. Depending on the OS, a process may be made up of multiple threads of execution that execute instructions Concurrency (computer science), concurrently. While a computer program is a passive collection of Instruction set, instructions typically stored in a file on disk, a process is the execution of those instructions after being loaded from the disk into memory. Several processes may be associated with the same program; for example, opening up several instances of the same progra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
