Operating System Articles - Page 27 of 199

File permission in a Linux environment provides privileges to the owner or administrators to execute programs or applications. Permissions are set for the files or directories using chmod and chown commands with read, write and execute notations. Special permissions such as setuid, setgid, and sticky bits are initiated for executable files or directories; the user needs to pay more attention when these special permissions are set because they may impose security risks to all other users. Each file present in the directories has userId termed as uid and groupId as gid specified by the owner of the file, to execute ... Read More

In the operating system, segmented paging provides better performance and utilization of the CPU as it combines the process of segmentation and paging. Segmentation is termed a memory management technique where the memory is divided into segments that can be allocated to a process. These segments may not be in fixed length and not stored in a contagious manner. The segment table holds all the details relating to the segments and the processes. Generating a logical address which is converted to a physical address by the CPU by refereeing to the segment table. This table contains two fields about the ... Read More

Scheduling algorithms in the operating system execute the processes based on their arrival time or by their priority. Each algorithm chooses the processes that are in waiting to ready queue by preemption or non-preemption methods. Preemptive algorithms provide access to the CPU to the process which has higher priority and preempt any other process which is already running with lower priority. But in the case of non-preemptive scheduling, when processes start their execution, it cannot be preemptive even when higher priority processes are in the ready state. The traditional round-robin scheduling algorithm is a preemptive one where each process gets ... Read More

Scheduling algorithms of the operating system are used for scheduling the input process to the respective processor. The process scheduler has the allocation rights to decide on which process to start its execution based on any one of the scheduling algorithms. Any process in the execution state that uses CPU resources can be preempted and other process in the ready queue is chosen for execution based on priority, in terms of priority-based algorithms. Preemptive algorithms provide access to the CPU to the process which has higher priority, and preempt if any other process which is already running with lower priority. ... Read More

Raymond’s tree-based algorithm is used to protect the distributed systems from the occurrence of sections by the lock method. Distributed systems are networks with numerous numbers of nodes that involves the message flow from one node to another. When the process is locked or in the critical section, then only one thread or process can be allowed inside and other threads will be in the waiting state. As there are many nodes involved in the distributed systems, it can be reduced by spanning trees.Raymond’s Tree Based Algorithm Definition The Algorithm follows the method that only the threads with tokens are ... Read More

RCU is a method that can manage multiple process execution and can be deployed to any operating system and one among them is the Linux kernel. It is an easy process synchronization method and it splits the RCU update into two phases namely removal and reclamation. This mechanism allows the reads along with the updates to occur simultaneously. The process occurs concurrently between the many readers and updaters of the operating system. Apart from the easy process, it is also reliable to access for the simultaneous process. Read-Copy Update Definition Read-copy update (RCU) is one of the best data structures ... Read More

When each process request for the resources available in the system, the operating system allocates the needed resources for its execution purpose. The resources allocated can be either a hard drive, scanner, any files in memory, or even a printer. Any program that enters into a ready or execution state is termed a process. This program requires resources from one or other processes to complete its assigned task. In a multiprogramming environment, a process may request multiple resources at the same time, so those processes have to be waiting until it receives all the resources. A resource allocator present in ... Read More

In the OSI (Open Source Interconnection) model, the resource reservation model comes under the fourth layer which is the transport layer protocol. This protocol is particularly used for the purpose of reserving network resources. In RSVP, the resources are associated and maintained by the receiver so it is also known as a receiver-oriented protocol. The Real-time system means the work that has to be delivered to the client within a specific time. In this article, two real-time systems are explained using the resource reservation protocol. Resource Reservation Protocol (RSVP) Definition In networking, Resource Reservation Protocol is used as it provides ... Read More

Deadlock in an operating system happens when a process gets into a waiting state as other processes hold the resources which need to be used. This problem generally happens during multi-processing environments, distributes systems, and parallel computation systems. In distributed systems, deadlocks are considered the major problem, where the resources requested by the process are not available due to other processes holding onto it. A distributed system contains a set of processes p1, p2, p3…pn that do not share a common memory, and communication is made only by passing messages through the network. This does not have a global clock ... Read More

Memory is considered a major part of the operating system to store and access the data. Memory management is a complex task that is performed by the OS when the main memory has limited space and requires more switching operations during multiuser environments. It functions to manage the status of the processes which are in ready, waiting, or execution states and allocates or frees the memory location based on the completion of each process. Each process is allocated to a specific memory location and its status of it is monitored and updated in the memory management system. During a multiprogramming ... Read More