There are two major types of network sockets, viz. Stream sockets (SOCK_STREAM) and Datagram sockets (SOCK_DGRAM). The socket type defines the semantics of communication between this socket and its remote counterpart. Stream sockets provide full-duplex reliable sequenced data streams.… Read more
Client server model is a software architecture paradigm prevalent in distributed applications. A server has information resources and processes that provide answers to queries and other services to remote clients over the network. Some of the examples of these services are booking an airline ticket and/or a room in a hotel, sending a file to a client, sending a mail message to another person (client), etc.… Read more
Signals are software interrupts that are delivered to a process by the kernel. A signal indicates that an event has occurred and the process must take note of it. A signal is delivered asynchronously to a process. Whatever the process was doing is suspended and the processing of the signal takes place immediately.… Read more
systemd is the newer init system used in most Linux distributions since 2015. The first widely used init system was the System V init process, sysvinit. Ubuntu introduced the Upstart init system with Ubuntu 6.10 in 2006. Ubuntu fully migrated to systemd with Ubuntu 15.04 in 2015.… Read more
Syslog is a protocol for conveying event notification messages.
Syslog was first developed by Eric Allman for logging as a part of the Sendmail project in the 1980s. It soon became a de-facto standard for logging on Unix-like systems.… Read more
D-Bus is a mechanism for interprocess communication under Linux and other Unix-like systems. D-Bus has a layered architecture. At the lowest level is the D-Bus wire protocol described in the D-Bus Specification. The libdbus library is an implementation of the wire protocol.… Read more
The last command gives a chronological list of user logins in a Linux system for a period of time. The lastb commands gives a similar list of failed logins to the system. By default, last uses the /var/log/wtmp file for the record of login data.… Read more
tmpfs is a filesystem that resides in the main memory of a Linux system. In the case of disk files, a file is first fetched into the kernel pagecache and the delivered to the requesting process. The fetch part is not there in the case of tmpfs as the files are created and updated directly in kernel caches.… Read more
Shared memory, message queues and semaphores form the suite of interprocess communication (IPC) mechanisms available under Linux and other Unix-like systems. In case of shared memory, the system provides a shared memory segment which the calling process can map to its address space.… Read more
Shared memory is one of the three interprocess communication (IPC) mechanisms available under Linux and other Unix-like systems. The other two IPC mechanisms are the message queues and semaphores. In case of shared memory, a shared memory segment is created by the kernel and mapped to the data segment of the address space of a requesting process.… Read more
