diferencia entre ccna y ccnp

diferencia entre ccna y ccnp.A symbolic link is only (to) the target file. A symbolic link is simply a reference (to a target file). Deleting a symbolic link file does not affect the files it references. An orphan link is a symbolic link that is lost because the file it refers to no longer exists. The system interprets the symbolic link at runtime, even if the file it points to does not exist.9.6 Daemons This chapter opens with an explanation of how processes run in the foreground and background. Processes that run in the background are called daemons (daemons) o Not only are daemons not controlled by the active user, but they also run silently in the background and are activated when some specific event or condition occurs. UNIX systems tend to run many daemons to fulfill service requests from other computers and to respond to the behavior of other programs and hardware. Daemons are triggered by a number of factors, such as being triggered at a specific point in time, by a specific event, and by a file being viewed. Simply put, daemons listen for specific "tipping points" that trigger their responses. When it is first initialized, the daemon, like any other process, is given a process identification number (PID) associated with it. Since daemons are system processes, their parent process is usually (but not always) the init process with a PID of 1. Daemons are created by the system through fork system calls, resulting in the process hierarchy shown in Figure 9.2. The following shows a few of the common daemons found on UNIX systems. The careful reader may have noticed that most daemon names end with a "d", which indicates that they are daemons.xinetd:TCP/IP super server that listens to the port assigned to the process shown in the configuration file inetd.conf or einetd.config.corond:Runs scheduled tasks.ftdp: for file transfers.Ipd: for laser printing.rlogind: for remote login.rshd: for remote command execution.telnetd: for TelnetoNot all daemons are started automatically. Like other processes, it is possible to set some daemons (for example, binlogd, mysqld, and apache) to not start unless they are triggered by a user or some event. That is, daemons can be both terminated and restarted, and their status can be viewed, no different from any other process. While many daemons are usually started automatically with the system, certain daemons are child processes, and the system will decide whether to start them or not based on whether a specific event occurs. Of course, it all depends on the specific operating system being run.