Before the opening, I first praised the family and explained the cause and effect of the characters:
I was born into a teacher's family, and after years of technical work, my fate arranged me on the rostrum. The difference is that my podium is not a school podium, and my students are not innocent school children. I stood on the platform of IT training, and my students’ eyes sparkled with knowledge. Since the establishment of the training company, I have been busy with teaching. Although I really want to communicate with you on the Internet, I always feel that I am weak. My friend Bai Hao has often communicated with you in blogs, helping many confused IT people, already half of the reds, huh, huh. I am quite embarrassed when I am happy for him. We are also doing the mission of evangelism, but he not only educated the students in his class, but also guided and influenced more people through the Internet. A few days ago, the bloggers told me that the new version of the expert blog display area was on the line. I was fortunate to be among them. I felt that I should be more rewarded when I was deeply in love, and try to take time to update the blog. Recently, I plan to write a "Network Engineer Classroom Series", summarize some typical cases in the class, and share with others.
"The normal operation of the server is very important for an enterprise. When it is a problem, we have to log in to the server to solve the problem as soon as possible, and minimize the failure time as much as possible." They concentrated and nodded like garlic.
"Well, how can I log in to the server securely? The management server is different from our daily practice. We need to ensure the security and stability of the service. Generally speaking, the server is hosted in the IDC room. The computer room provides physical conditions for our servers: network link, space temperature, security, etc. But we can't ignore the security when we maintain it. When debugging cisco devices, we use telnet to log in, but for managing Linux servers. telnet login is not safe to say ...... "
just then, a student exclaimed:" teacher, I can not get the machine to log a ~ ~ ~ @ !! @ # $ @ ... #” is followed by a seemingly theoretical analysis of the student: “Is the network card set wrong? Is the network cable not plugged in? Is there a problem with my ssh client? Is it xxxx? Is it yyyy?” Finally Say, is my keyboard confused? Please~~~!
"In solving problems, the analysis is to be rational, don't use the word "is not" to guess wildly," I said bitterly. "Teacher, can you compare it with ‘will you’?” The student looked at me with a look of anticipation. I fell to the ground on the spot and was unconscious.
No, can't fall! The students are still looking forward to it. I staggered and stood up. I wanted to pat the dust on my body. It turned out that the ground was clean. Oh, the environment we studied was like the company's working environment. Every day, people cleaned it. Finishing mood, a very determined told the students: "I'm sorry, it can not determine the problem is to have a certain logic, do not casually good judgment is not good!!"
While I was written on the blackboard while Say "To judge such problems, we must first carry out some basic troubleshooting work, use the exclusion method to determine the problem, so that it is simple and effective!" Look at what I wrote, the camera turned to the blackboard, thank you.
Analysis and Troubleshooting: ssh client login server use the port and IP, then we encountered a problem when such services can not be linked to follow it step
1, we must first determine the occurrence Is the service normal before the problem? Can the server on the same network segment log in? (Exclude network problems, find problems checking network devices or contact related departments)
2. Is the local loopback address pinged? (Excluding the hardware problem of the machine)
3. Has the configuration file been changed? View the log and history operation records in the /var/log directory (excluding human error)
4. After excluding the previous assumptions, check the service process and port of the Linux system. Use two commands to make the judgment:
are ps –ef