Welcome back friends. Throughout the course we have learned about installation, users of file system, permissions installation our various utilities, in the network clients and everything as the virtualization and avoidance of things. When you are done with our installation and you are a proper user of our system, there are certain scenarios where a system may crash down or do not perform exactly as you're planning to. We're expecting it to perform then there comes a need to troubleshoot, what are the problems, you should test it you should be aware of what is going on and you should be able to fix it. You should not call a maintenance guy or every time if you have a problem that keeps the cost very high. It is not secured enough.

The option is not secured and you should be aware of various Take the precautions what you could take for running off here the proper ending of your system. So, friends, we are going to learn all these things here in this lecture that is troubleshooting. We will learn how to develop a strategy for troubleshooting, how to fix problems in different areas of the Linux environment, both the system into various run levels the wrong levels, we have learned to use the rescue environment as well. In case we have left with a troublesome scenario. The first method is to do a fault analysis. We have to first analyze what the problem has occurred before going further in fixing it.

If we don't know let us take a simple case. If a doctor does not know what the problem is, suppose you have a fever, and you have asked Dr. Data, I have been in my head had it you Another medic medicine However, he should be treating you differently before knowing the cause, you could not kill the symptoms, you should not fix the problems, the fault analysis is dealing with these things it has to characterize the problem, we have to characterize problems into different categories and try to reproduce the problem for learning what it may could do or to find further information about what are the problems, the possible reasons and fixation methods, we have to eliminate the possible causes. Try the easy thing first, you have to backup configuration files before changing. We have to characterize we have to reproduce we have to eliminate possible causes, and we have to back up the old problems.

Falling away leases there is a gathering of data. We have to gather all Data first. So for gathering of the data, there are few very important or useful commands that will help you gather different data. Suppose the problem could be initialized due to running of a malicious or not malicious or problematic or nuisance commands that are there. If you have mistakenly executed those commands, or maybe some other users have done that remotely or some kind of hacking, or simply a mistake, you may kill a process without knowing the process is very vital to a system. image upload, upload the car now, update the kernel in a upgrade or pass encode.

The useful commands could be history, history will show you last thousand commands that a user have edited cuted that is not dependent on a particular session. Even in the previous or more than previous sessions, you could see the command list. Then there is a useful command for grep which is used vitally, then there is a command called difference which could differentiate between the content of different files. You could use the find same in the one that could be allow you that will allow you to list all the files that have been modified within a particular range of time say 60 minutes, or 60. You have to use the asterisk command for tracing a file or data from the application. It could be used with a PhD and the process ID of the running process.

Then you have a tail command in the log file entry to show some last records from the bottom recent records log entry The user enter details, then there are generate, you can generate additional information by running the debug ins, system log and the debug option in application. Then there are things to check that may cause error sometimes, x window or X can sometimes be problematic. The first thing to try is when confronting x problems, you can go with our system config display, which is a GI option, where you can check x configuration, you should the problem could be occurring in run level five generally, it could make logging in impossible in Acts or inversion of control. They should reboot a system in run level three. Sometimes, viewing the output of x command itself is revealing. It will show you what the errors are the pro volleys will perform all the tasks necessary to install X Server without actually starting it.

Under startup my sights are displayed. If the text is cross of the screen the material of in screen can be viewed by holding the Shift key. You could learn with these things. Try system configuration first the exploit could be used. If a home or temp order temporary file is full, or has the user reached a hard quota, you should be considering to delete the temporary files or recheck the home directory you should move chain or you should move some important files from the home directory to other directories or you should check x Fs either it is running or not. The Xs x Fs fund server is the only foreign Park entry in the XR configuration that is a delay With x one one which is located in the ATC directory, if it is not running x will run make sure that x Fs is configured to run in the appropriate trim levels occasionally it may be necessary to delete his tail lock A p ID process ID or socket files you should be dealing with extra no and properly check whether it is running for debugging you should not be running x in row level five you should be running in level three.

Then there comes are things to check that is networking. You should be checking metrics there could be a problem regarding network for network configurations, the hostname resolution problems, which can create problem for clients and server. Similarly, beside from requiring successful forward lookups reverse lookups are essential for many toothpastes. security mechanisms to slack host and they are invaluable for determining whether hostname resolution problem exists or not. If configuration maybe IP configuration maybe check using the if config command, you can use the if config. For checking the IP address and other details it shows a IP version four and IP version six details which one is configured, you can resolve the hostname with writing ridic command DHCP provide a URL name next to it followed by a space where the default gateway could we check with our own command it could route it to the all the paths and the gateway and other details.

The network start our netstat rm command will show in the system routing table is correct or not. For the data packets, you can check the module specifications and device activation as well. Then you should be checking the order of boot process suppose your system is not starting properly. By default you have an operating system or a cheer installed on your hardest internal hard disk of your PC and some for some reason it is not starting it is showing a boot error when you are trying to restart it will prompt you with a boot menu. So, what is the reason how the system has been crashed down. There might be a scenario where the boot process or boot order could be changed for various reasons.

The default boot order is with the preference to hardest internal hardest. Next is a USB or external hard disk or CD ROM. For some reasons, mistakenly, the pendrive or a CD ROM could be preferred more than your hardest or somewhere may have be done. And the pendrive is constantly running inserted on your system and it has a crashed or improper image installed on it and you are not able to insert one, you can change the boot order and make the hardest to move first, if you're required hardest otherwise other tools in order to troubleshoot boot time process, you must understand the boot process itself. The issue the cause and various things, the BIOS settings the possible process the group could be misconfigured the boot sector is corrupt the BIOS settings such as this addressing scheme that could be modified since the last boot sector was retained.

The kernel does not load at all or load partially before a panic occurs. And the possible process could be corrupted kernel images, incorrect parameters passed to the kernel by the bootloader. Then there could be issues like kind of load completely but by Cause fails when it tries to mount a root filesystem in the unit directory, the possible cause for the bootloader is misconfigured in it the SPN unit or which is can corrupted in establish misconfigured or root file system is damaged or unmounted. It could be dealing with raid or other things, it should start in it with et CIE directory go into the C et CIE directory the RC dot daemon or RC dot system system in it. You can enter run level x using RC dot local the ex and other configurations. The file system corruption which is common after the crash or improper shut down, sometimes a system may be may have improperly shut down.

So it due to crash or software crash or other driver crash. Then the problem could exist the ESD to mounted for writing marked as dirty, if not mounted or mounted in read only, it should be clean. If not mounted as dirty maybe corrupt, repair required exhausted check. The STP file system usually marked as clean the journal indicates if a recovery is needed. All edited check files recorded in journal the file system recovery could be done when a if route has a journal Colonel examines if it has a boot the file system recovery could be done in the rescue mode. They etc The system config phase the file systems model in Fs tab, def Fs tak is a front end for the programs or field as f check must be run manually.

It will configure the recovery run levels and to pass around levels to emit on Good from grab a splash screen from shell from using it or telling it could be used in run level one the process of RC dot says in an RC one dot d d manuscript could be used. In a level as our single the process only RC says in is running in emergency only su login works. So, you can go with as you log in the booting in level one will cause a system to process the system when it escaped followed by each of the init script will be executed in a safe more of our single mode. Run level as the system cause will start acid estimate without doing it. Then it could be used you can still go down to single mode. It is given that you are given the root shell with no escape process and emergency mode.

While technically not in a realm level, emergency mode shares many characteristics of the other levels, but you can only access emergency mode during boot by wising emergency as a parameter from the group from you can go directly with the emergency mode after I grew up the screen shows up, more skillfully processed and you are given a root shell without processing that unit or other scripts. The rescue or environment of is required when a root file system is unavailable. A non system specifying boot even boot from CD ROM boot from disk boot dot image on USB key ms comida. The rescue environment exists within a ram disk image. Because of the limitations on size of the number of I nodes, the table for directories, multi family and utilities and device nodes are not available. However tools really At today's command DNS and Network Connectivity are provided you can go with the rescue mode if nothing works out the rescue environment utilities uses disk maintaining utilities the networking utilities, miscellaneous utilities, the logging with Anaconda and Syslog.

The rescue environment details could be configured with file system reconstruction, you could enter conda will ask if file system should be mounted. You have to provide a PATH variable for that thing. The file system nodes could be used. The rescue warrant will attempt to rescue reconstruct harness file system under the mount points. The cc image system image sensor rescue environment is often used on the system with damaged or misconfigured file system. The operation might or maybe not working.

You can pray With an F disk available and on F two option you should have the command prompt a terminal you should carefully inspect the output of the mount command that should determine the state of the reconstructed file system. The file system that we configured here as an MK command is useful here and you can go with a GI utility data system a specific device files and so on. So, this was a few techniques of what is the role of troubleshooting how you can construct a problem reconstruct a fix and work in a rescue mode or other safe nodes in different levels and other things in case a trouble may occur. You should be planning, troubleshooting since you have installed your device OS troubleshooting is not very hard often But sometimes it could be complicated as well. If you have not prepared and do not know much about it a problem is not a problem at all, when a problem occurs, it is an opportunity for those who may learn from those problems by fixing by trying various things.

And in the next time if the problem occurred, they could be able to fix that thing. So, problem is not a problem at all You should be able to troubleshoot prior fixing these things or be familiar with our shell commands and other things. Let me see the way very useful thing you shouldn't be using it and the power of Archer is very quick. Consider it very carefully and keep learning and keep practicing various commands or utilities. Go with configuration files. We will be learning node Later, you should be practicing vinyasa exercises and arches yours.

Now you can be in your own server environment or your own desktop utilities. Start working on a ritual or ritual is a good solution. So keep learning and keep moving ahead