This article is for HR teachers who don’t know how to ask questions. It is convenient to search. It is enough to read this article without interviewing.
Implementation engineers, technical support, and operation and maintenance engineers can all use it.
The ten questions are divided into basic ability (Linux, SQL, network), service application and problem-solving ability (Tomcat, Docker), and worldly ability (customer problems, credit division).
Resume Screening
1. There is no direct PASS of the applicant's PS selfie, and he does not even have basic skills, let alone the ability to mix well with the implementation of enterprise personnel. Shy people are not suitable for this job at all.
2. The layout of the resume is illogical, PASS directly, submit reports all day long, and the resume format is not handled well, let alone the daily, weekly, and project record forms can be written well.
3. As long as you like to travel, you can directly pass it, and then you can go on a trip and go, you may be the one who [takes the blame].
Implementation Engineer - Deadly Ten Questions
1. What is the command to view the remaining disk controls under Linux? How to view the last hundred lines of the log file?
Answer and purpose:
⑴. Commands to check the remaining disk space: [df] and [du].
df -hl: View the remaining disk space
df -h: view the partition size of each root path
du -sh [directory name]: returns the size of the directory
du -sm [folder]: return the total M number of the folder
du -h [directory name]: View the size of all files in the specified folder (including subfolders)
(2) Check the last 100 lines of the log file?
tail -f -n 100 log file (usually *.log)
-f stands for query from time to time (print the content at the end of the file and keep refreshing)
-n means to start querying from line n (after printing the content of K lines or use -n +K to print the content of files starting from line K)
Question purpose:
The most commonly used Linux commands, logs and bug monitoring will be used. If you are not familiar with it, it means that you have never done it, just pass it directly.
2. What are the four characteristics of MySQL transactions ( basic answer )? What do they do ( answer for beginners ), and what is the principle of implementation ( answer for experts )?
Answer and purpose:
(1) The four basic elements for the correct execution of database transactions are [ACID].
⑵, respectively, the role is:
A: Atomicity
Atomicity means that a transaction is an indivisible unit of work, and either all operations in a transaction occur or none occur.
C: Consistency
The integrity of the data must remain consistent before and after the transaction.
I: Isolation
The isolation of transactions means that when multiple users access the database concurrently, the transactions opened by the database for each user cannot be disturbed by the operation data of other transactions, and multiple concurrent transactions must be isolated from each other.
D: Durability
Persistence means that once a transaction is committed, its changes to the data in the database are permanent, and then even if the database fails, it should not have any impact on it.
⑶, the realization principle of ACID
A (atomicity): Implemented using undo log. Atomicity either succeeds or fails. The undo log of each operation will be recorded. When an exception occurs later, things will be rolled back from the undo log.
C (consistency): Consistency is accomplished based on the combination of atomicity + isolation + persistence.
I (isolation): The isolation of transactions means that when multiple users access the database concurrently, the transactions opened by the database for each user cannot be interfered by other transactions, and multiple concurrent transactions must be isolated from each other. [Depends on the lock].
D (durability): redo log log implementation.
Implementation principle section:
The atomicity of transactions is achieved through undolog.
Transaction persistence is achieved through redolog.
Transaction isolation is achieved through (read-write lock + MVCC).
Transaction consistency is achieved through atomicity, persistence, and isolation.
Purpose of the question: The four basic elements of the correct execution of database transactions, this must be met, and what level the interviewer can answer later, if you can continue to talk about it, you can refer to: Detailed explanation of the four characteristics of ACID_MySQL transactions (MySQL high-frequency interview Question)_Red Eye Aromatherapy Blog-CSDN Blog
3. Please tell me about the computer network architecture? (Graded according to the number of answers)
OSI architecture:
(1) Physical Layer (Physical Layer), the physical layer (Physical Layer) is at the lowest layer of the OSI reference model. The main function of the physical layer is to use the physical transmission medium to provide a physical connection for the data link layer in order to transparently transmit the "bit" stream.
(2) Data Link Layer (Data Link Layer), the data link layer is an extremely important layer in the OSI model, which packs the raw
data from the physical layer into frames.
(3) Network Layer (Network Layer), the network layer defines the communication protocol of network layer entities, which determines the route selection from the source node along the network to the
destination node, and handles related control issues.
(4) Transport Layer (Transport Layer), the task of the transport layer is to provide users with reliable, transparent and end-to-end data transmission, as well as error control and flow control mechanisms.
(5) Session Layer (Session Layer), the task of the session layer is to establish, manage and terminate sessions and data exchange between application processes. This session relationship is formed by a dialog between two or more presentation layer entities.
(6) Presentation Layer (Presentation Layer), the presentation layer contains protocols for processing network application data formats.
(7) Application Layer (Application Layer), the application layer is the place where end-user applications access network services. It is the highest layer of the OSI reference model and the layer closest to the user in the OSI reference model. It provides user applications with Internet service.
The architecture of TCP/IP:
Network interface layer: corresponds to the data link layer and physical layer of the OSI reference model.
Internet layer: Corresponding to the network layer of the OSI reference model, it mainly solves the communication problem from host to host.
Transport layer: Corresponding to the transport layer of OSI, it provides end-to-end communication functions for application layer entities, ensuring the sequential transmission of data packets and the integrity of data.
Application layer: corresponding to the OSI reference model (application layer, presentation layer, session layer).
The architecture of the five-layer protocol:
Physical layer: corresponds to the physical layer of the OSI reference model.
Data link layer: corresponds to the data link layer of the OSI reference model.
Network layer: corresponds to the network layer of the OSI reference model.
Transport layer: corresponds to the transport layer of the OSI reference model.
Application layer: corresponding to the OSI reference model (application layer, presentation layer, session layer).
Purpose of the problem: The most implemented is to analyze where the problem is. Only by mastering the network system can we find the problem point better and faster, so as to solve it quickly. Even if it cannot be solved, it can describe the problem and let other personnel solve the problem.
4. What is the purpose of Tomcat related directories?
Questions and answers can be used, or the interviewer can directly ask the interviewer to recite it. See job demand.
bin directory : mainly used to store Tomcat commands
conf diary : store various files for the global configuration of the tomcat server
lib directory : stores all Jar packages required by the Tomcat server
log directory : store the log files when tomcat is executed
webapps directory : Tonmcat default deployment path
Purpose of the question: To examine the proficiency of tomcat, if it is used frequently, these folders should be memorized.
5. How to ensure the disk performance of the server, explain from [Indicators], [Problem Analysis Ideas], and [Commands] respectively?
Five indicators:
- Utilization: The percentage of time the disk is processing I/O. Excessive utilization (such as over 80%) usually indicates a performance bottleneck in disk I/O.
- Saturation: Refers to how busy the disk is processing I/O. Oversaturation means that the disk has a serious performance bottleneck. When saturation is 100%, the disk cannot accept new I/O requests.
- IOPS (Input/Output Per Second): refers to the number of I/O requests per second.
- Throughput: The size of I/O requests per second.
- Response time: refers to the interval between sending an I/O request and receiving a response.
Problem analysis ideas:
- View the overall situation of the system through top, if wa is too large, analyze the disk IO bottleneck in detail;
- Use iostat to analyze disk I/O usage, disk I/O response time, disk I/O queue length, and view these three indicators;
- If the disk I/O usage rate is too high, or the disk I/O response time is too long, or the disk I/O queue length is too large, then use pidstat to locate the process that causes the bottleneck;
- Use strace to locate all system calls of the process, and then analyze the I/O behavior of the process;
- Finally, the source of these I/Os is analyzed by lsof, which is the file operated by the process.
Order:
Command 1: df, check system capacity
Command 2: slabtop, which displays in real time how the kernel allocates various caches and the occupancy of these caches.
Command 3: iostart, sar, dstat, to view disk IO usage, IOPS, throughput, response time, average IO size, and waiting queue time.
Command 4: pdistat, iotop, process IO size and IO delay.
Command 5: strace, process IO system call tracking.
Question purpose: As a basic implementation or operation and maintenance personnel, it is my job to ensure the normal operation of the server at all times, so the basic common sense to ensure the stability of the server needs to be known and understood. It depends on the specific requirements of the personnel to come to the interview.
6. How to ensure the network performance, respectively from [indicators], [problem analysis ideas], [commands] to explain?
Metrics for network performance:
- Bandwidth: Indicates the maximum transmission rate of the link, the unit is usually b/s (bit/second). Usually, the bandwidth is limited by the physical network card. After the network card is determined, the bandwidth is determined immediately (of course, the actual bandwidth will be limited by the entire network link. the smallest module)
- Throughput: Indicates the amount of data successfully transmitted per unit of time, usually in b/s (bits/second) or B/s (bytes/second). Throughput is limited by bandwidth. "Network bandwidth test", the test here is not actually the bandwidth, but the network throughput. Network utilization = throughput/bandwidth The network throughput of a Linux server is generally smaller than the bandwidth, while for specialized network devices such as switches, the throughput is generally close to the bandwidth.
- Delay: Indicates the time delay required from sending a network request to receiving a remote response. In different scenarios, the delay may have different meanings. For example, it can indicate the time required to establish a connection (such as TCP handshake delay), or the time required for a data packet to and fro (such as RTT).
- PPS: It is the abbreviation of Packet Per Second (packet per second), which means the transmission rate in units of network packets. PPS is usually used to evaluate the forwarding capability of the network. For example, hardware switches can usually achieve linear forwarding (that is, PPS can reach or approach the theoretical maximum value). However, forwarding based on Linux servers is easily affected by the size of network packets. For TCP or Web services, indicators such as the number of concurrent connections and the number of requests per second (QPS, Query per Second) are more used, which can better reflect the performance of actual applications.
The availability of the network (whether the network can communicate normally), the number of concurrent connections (the number of TCP connections), the packet loss rate (packet loss percentage), and the retransmission rate (the proportion of retransmitted network packets) are also commonly used performance indicators.
Problem analysis ideas:
⑴. Network failure:
Whether the physical link is connected: ethtool
Whether the network card is enabled normally: ifconfig
Is the gateway set correctly: route -n
Application layer: ping IP (using ICMP protocol is the third layer, but this command belongs to the application layer)
⑵. Slow network speed
Whether DNS is the source of the problem.
See which nodes are bottlenecks in the routing process.
View bandwidth usage.
Order:
Network card devices and drivers: lspci, dmesg, ethtool.
IP parameters: ifconfig
Communication reachable: ping
Routing information: route
DNS status: dig, nslookup.
View network port status: netstat, nmap, telnet.
Open the firewall: systemctl start firewalld
Turn off the firewall: systemctl stop firewalld
View firewall status: systemctl status firewalld
Restart command: firewall -cmd --reload
Set boot startup: systemctl enable firewalld
7. What are the commonly used commands and their functions when writing Dockerfile files?
- FROM: The basic image based on which the image is made.
- RUN: The command executed when making an image, which generally appears multiple times in the Dockerfile.
- CMD: The command executed when docker is started, only appears once in the Dockerfile.
- ENV: Set environment variables.
- COPY: When making an image, copy the files in the file system to the Docker image.
- WORKDIR: Set the working directory.
- EXPOSE: Set the port exposed to the outside.
- VOLUME: Set the directory that the container maps to the outside world.
Purpose of the question: Both Java microservices and .NETCore will use Docker. At least 5 or so should be able to be named to make the edited image run normally, and it can be judged whether it is successful.
8. Customer question 1
During your implementation, a software system produced by the company lacks a certain function, and the company also clearly stated that it will not make any modifications or add any functions to the system, and the customer also insists on this one. Function! For the implementers, how should they deal with this problem reasonably and properly?
A: Make it clear that you are implementing a project, not custom software. For example, leather shoes sold in supermarkets and leather shoes made by shoemakers are both shoes, but the former is a commodity, and there are many of the same commodity, and you can buy comfortable shoes that are almost wearable; the latter is custom-made, not only a commodity, but also a A kind of labor, which has been produced completely according to the needs of customers, and every detail is required to be perfect. The same is true for software, if there is no function required by the customer, since the company has stated that it cannot be realized, it must be the time, financial resources and conflicts of interest spent on function research and development. You can explain to the customer that adding functions requires him to pay more, even more than buying software. The price is also expensive.
9. Customer question 2
During the implementation of the project, users put forward suggestions for modification of the product that suit their own habits, but multiple users contradict each other, how should we deal with it?
Answer: Our implementers should have their own plans for the modification suggestions put forward by customers. When there are disagreements among users, we should guide them to unify their internal opinions. After communicating or confirming with customers, we can find a feasible solution, and both parties agree and reach a consensus.
10. Credit division
You are in charge of project A independently, and the PMP of this project divided your performance with that of other colleagues when compiling the performance data sheet for project closure after the completion of project A, and did not explain it to you. What would you do in this situation? understand?
Answer: An open question, to examine the stability of the interviewer's mentality, as long as they can understand the incident correctly and gently, and can give everyone a certain level, and no conflicts will occur.
Summarize:
There are a total of 10 interview questions, hoping to help HR teachers better screen out suitable employees.