what is the causes Linux OS hard reboot (multiple) . How to check and how to fix the issue or please provide advise.
I am waiting for your valuable reply.
@jeesshnasree are you the only administrator in charge of a huge population of servers? You post questions about various versions of RHEL, troubleshooting, and management of them. Do you not have a senior partner to work with for managing this population?
If not, let me impart some advice that I recieved from my first senior administrator. When I started with the group, whenever I hit an issue, I would go down to his office with my notepad and pencil and ask him about it (sometimes multiple times a day). After about a week of this, I came into his office, as usual, to ask about a system call or something and he didn't look at me and put his hand up, signalling me to stop.
He then finished whatever it was he was working on, turned to me and said:
"What research have you done about this question? Man pages? Google searches? -h output?"
I said, "No, I just came down here to ask you." His response set the tone for the rest of our relationship: "Right. Well, from now on, you are to do research to try and answer your own questions. If, after you've exhausted your other options, you still don't have an answer, or you have further questions not answered by the man page, article, or whatever other sources you've looked at, then come see me."
He then sent me on my way to research my own question. From that point on, whenever I came into his office, his very first question was: "What research have you done on this?" If I had done none, or had not looked at the right place, he'd send me on my way to either do some level of research or would point me at a man page or two to read.
After 2-3 months of this, I rarely asked him anything, but if I did, I came in with a basic understanding of what I was asking about so that it was not him telling me things, but us having a discussion about the topic so that my understanding of it was deeper. This one change in how I interacted with him made the interactions deeper, and more fulfilling for both of us. It all started with me trying to solve my own problem first. It also developed in me the ability to do my own research to do troubleshooting or unsticking myself, which has been invaluable across the course of my career.
In the beginning, it's a lot, A LOT, of hard work because there's a lot of information that you have to look through only to find out that it's not what you're looking for, but from that, you develop a sense and ability to scan through something to determine it's quality and applicability, and over time, you hone this sense and it's faster and better.
So, my question to you is:
What research have you done on this issue on your own? What articles have you read? What logs have you looked at? To help a little further, you'll want to know the system state prior to your reboot to better identify what may be the issue.