We have learned about Colonel services. And now here in this lecture we are going to learn about system services. That includes a wide range of topics, which is important to synchronize time. I, we could use system logging, X Window System Setup, remote administration of the system and automation of tasks with cron. We can configure printers and various things. So let's start with NTP or Network Time Protocol.

So NTP is a is used in certain cases where we need applications that could could not use a hardware clock of your system, which is not accurate enough for a wide range of applications. And it tends to drift over time. Many applications require exact timing synchronized over a network. Same time for all computers, all devices and for providing the accurate time the common time. We need to bypass a hardware clock and provide a new kind of a standard that is called Network Time Protocol or NTP. The workstation hardware clocks are not used under NTP is preferred over that thing if you want to run network utilities, like file sharing, internet and other utilities.

NTP counters that drift by manipulating the length of a second, it could change the length of a second. NTP clients should use three times servers. The configure file is located it with ntp.com in et CIE directory, where we can configure NTP configuration tool is available with system config date as a GI utility. genome. Time synchronization user is used to make system logs easier to analyze. The logs are things that are written with timestamp.

The NTP provides a useful instance for that thing. We want to check the time the correct time and date where our system entry was initialized. Anything could be performed if you want to troubleshoot, or like black box or white box type testing. Then there comes our system login, which is a useful thing when it comes to system system analytics. The centralized logging demos that are since log D. The D means daemon simply, the suffix D is the daemon is Stanford m syslog. On k log.

K. lamesa stands for kernel log syslog stands for system log. We could check these log files The log file examples could we check on kernel boot message with D message in log content via directory. Similarly, we can check a standard system error message, email system messages, security authentication, and in it t messages. The application log files and directories are located in web slash log where we can check application log files. The syslog or system log configuration of our system we initialization script is located in etc. Slash RC dot d initi controls which controls are both the system log and kernel log mavens.

The syslog.com is used to configure system logging and the directory for syslog insists configuration under etc directory is used to set a set of switches which is used when a starting system log and kernel log from the system we initialization script. Then there comes a x one one server or XYZ which is a foundation for Red Hat Enterprise and z y. The X Window System or which is also called x or x one one is the foundation of the graphical user interface. On average GL X Window System is maintained by the x concert and which creates a reference implementation of effects under an open source license. EXO ID project is an add on hardware driver for a variety of video cards and input devices along with several software extensions to manage the visual representation of data x or x 11 or x window which is also in implemented with a genome or KD is nothing other than the graphical implementation.

You may need it or not required. But the graphical thing is very important when you want to manage those things in a user friendly manner. You can also go with the command line interface Virtual Console. But the graphical console is most preferred to a normal user or various kind of users. So you can configure it. You can check it installing the excellent one server.

It is open source implementation of exon one Vax all the drivers are a ti n v mouse keyboard which are being managed by x all the extensions are D ri, g x and x mod. It allows you to render fonts using x Fs, the native server or the font config, which is a look at it as a library. xR consists of one core server and several dynamic loaded modules. The Server Core is hardware independent and is extended through the configuration and loading of hardware and x one x one one extension specific modules, the kernel module directory like the OAS corner, though, through the combination of unique hardware specific modules, the X Server design remains flexible. And in fact, when the server is involved, it is cast and rectifies the configuration against the hardware. It checks the hardware seeking the optimum display and the input capability.

Next, our configuration is here and typically configured. It is typically configured after an installation of the oise. The best result is Shown while running in run level three, the system configure display is a UI utility, which can be accessed by application on genome desktop. You have various options and it is stored in the etc directory of x one one x r dot configuration file running XOR in RAM level three, as a simple consequence, there are two methods to establish the environment, the X in it and start next, we have learned in the essentials that start x command is used to go to the graphical console from a Virtual Console the command line interface if a genome or Katie's any way not loading, you can write this command start x or x in entity can be used to establish the external environment. environment configuration includes these files, which could be written and configured in the desktop and other places.

XR could also be executed in run level five which is which needs environment establishment in SP in it. The environment configuration includes the following files, the etc siscon config, desktop, etc x 113 fd dm it consists of our two variables. The desktop variable device that window manager, the display manager identifies the display manager. These are the options. Then there comes our remote x sessions that is used to access our system remotely either by making a system as a server or client or any relative Same client fat client, a wide range of things could be implemented. The expert the call communication is unencrypted.

It is not encrypted, and so not safe as compared to SSL and other protocols. The remote x is most primitive. It is host based sessions implemented through exos command. The user base sessions are implemented through a socket ready mechanism. The SSH D may automatically install XOR keys, authentication keys on remote machine and it uses a tunnel x protocol over secure our encrypted SSH connection. It is secure but I'm sorry, in a secure encrypted SSL connection.

The remote x is as it is not very secure. But when you if you use SSH, with denial, exploitable it becomes a secured connection. Then there comes SSH with this Secure Shell. It is encrypted remote shell, you can access the environment from remotely It is used to it is frequently used for remote system administration. It is used widely. Suppose you have a system server environment implemented on Red Hat at your office data center and you are the admin of the data center and somebody you are in vacation trip and you want to access certain files on your system and you want to configure it on your server.

You need to create a Secure Shell remote login which has to be configured earlier so that you can access it remotely and change anything whatever you feel like on your system. You can copy files securely you can execute commands remotely. execution of remote command is Very good facility but the facility may prove fat when it comes to security. So proper configuration is vital. SSH command is used for authentication, SSH route and direct host provide a host name. A route is a username.

Then in quotes I have config UT eth zero. If you are configuring SSH Secure Shell authentication for remote access, you should not configure it as a root user. Because a root user if misused could finally harming system could access anything, any file anywhere. You simply need to provide access by creating a non root user accessible for a certain file systems. But if you need a control, you should be available at a data center. For security purposes, it can tunnel x one one and other TCP based network traffic.

It supports key based authentication. You can authenticate via digital signatures and other tools as well. Later, there is another thing that is called our virtual network computing or VNC, which allows you to access or share a complete desktop over the network. A complete desktop sharing of the complete desktop, you might have used a software called TeamViewer. To access your system from a while, or other devices VNC is simply a TeamViewer. It is the primitive thing that TeamViewer is implemented using the VNC.

The VNC could be configured in a two way two way a server and client. A server is an individual user that can start a VNC server with the command VNC server by typing the VNC server command on Linux terminal You could initialize the VNC server to run the whole variable PATH variable. Upon startup, it requires a VNC password which should not be identical to the system password. Because the system login, you would not be interested to provide to other users. servers can automatically be started by etc in it, the VNC server. And you could also install use of the client you have to install the client as well.

To connect the client is something that connects to remote VNC server with a VNC viewer. Suppose we have two computer A and B, we need to access computer a via computer v b. So we need to create a as a server and B as a client. client for provides a unique screen number distinguishing between multiple VMs server's running on the same host. It supports tunneling through SSH VNC viewer by user host, local host. Then there comes a cron job, which allows you to schedule recurring events, events that occur over time.

If you want to execute various things, for execution on later time period, you could use this thing. The cron table file or cron tasks in short, are installed in a particular location. You can use crontab to edit, install and view job schedules. The syntax for using the Quran is the cron tab, command, provide user name and the file the other the crontab the minus hell minus are almost SE argument, the minus l argument hits the contact our removes a crontab e any sopran type using the editor. The content can be either edited in the current directory and historic by using it as an argument to crontab or by using minus e option. Even sheduled by from are run by the cron D daemon, which must be running on the system.

So using a cron tab can be separated by any number of tabs or spaces. You can delay a system or file with a minute, hour day of month, month, or day of week, anything. The syntax for running a crontab is man five crontab suppose man is a manual command five is provided days a month date and the crontab content You can control access to cron, you can restrict allow user access to cron, using the cron dot allow account or deny. Located an EDC directory. It contains a username to allow or deny access. There are system crontab files as well.

It is different. It has different format than user crontab files. The Master crontab file runs executables in hourly, daily, weekly and monthly period. The cron dot d file located in directory contains additional system content files. There are daily cron jobs that execute on your system on a daily basis. When you use our system, the temp batch, which is used to clean old files in specific directories, it keeps temporary from filling Have temporary files temporary directory, which stores the temporary files you have to delete.

If you are using a Windows system, the percent TMP percent command to use to locate a temporary file, and you are required to delete those files over a period of time. Similarly, tempo, which is an implementation on average here. Then there comes a log rotate, which is also a daily cron job, which keeps log files from getting too large. They keep it short, compressed, the highly configurable It is very highly configurable. You can configure it by accessing the log rotate configuration file in etc directory. Then there is a log watch, which provides a summary of our system activity for suspicious, suspicious, suspicious activities and other things that you want to check.

You can report suspicious messages. It could be configured on log watch that configuration file. Again located in ATC log the config directory. Then there is a another thing that is called a cron system. And a cron renta cron job that did not run when computer is down. When a computer is on a power down or running, the cron jobs are being executed.

When a company does have, it could not execute the simple concept. The ama cron run, cron run the cron jobs, which have been scheduled using cron, for a certain date or time suppose we have scheduled a certain thing to be using the cron for executing on 24th of November in the night 2am and that time, our system was turned off and we will go TAs have been postponed, we can configure that task again with an A cron, it will run afterwards. It assumes the computers are not up continually. It is vital for laptop desktop workstations and other systems that are not up continually every time. It is useful for servers that need to be taken down temporarily due to traffic and various purpose. It is a useful thing.

You can configure this with an A cron tab. In EDC directory again, it has a four fields, the field one is used to if the job has not been run in, in this many days. The field tool is used to wait the number of minutes after reboot and then run it. Change is used as a job identifier and field for use the job to run When cron runs in parse command, the first command to run is zero and a cron. This command sets up a timestamp in a file. And that notes the times that it was last run on Buta.

The Anna cron command runs when a system is tasked the enterprise runs. The purpose of Anna cron is to run cron jobs that we have written. Then there comes another thing that is called cups or common Unix printing system. In short, it supports many advanced features such as printer pooling, automatic client configuration, job redirection, and others. The Internet printing protocol or IPP is based on http 1.1. The web based management console cups can be reached on port 631.

By default, only members of the group can connect. The console can also be used for configuration. It allows the remote browsing of printer to use. It is located with a cup SD con file in cuffs etc directory for printer configuration, you can check the configuration tools. It is a very technical thing. You can go through it when you have a printer or internet utilities configured in a queue.

So these are a few system services that we have learned. Go through them in depth check explore various configuration files located in the ET CIE directory specifically. Try to read them if you want to be a good administrator. The cron job and a cron is a very useful thing. You can go through them, they need not to be configured using command you can also configure on the configuration file. And these are vital things that you must be aware of on Reddit.

You can always check the log files and you must secure your system. And if you want to access your system, you should use a Secure Shell with non root access. That way your server will be safe, keep learning and keep moving ahead. We will be learning more in the coming videos.