Shulou(Shulou.com)05/31 Report--

This article mainly introduces the relevant knowledge of "what are the Linux classic interview questions". The editor shows you the operation process through the actual case, the operation method is simple, fast and practical. I hope this article "what are the Linux classic interview questions" can help you solve the problem.

1. Introduce yourself?

(almost every company will first ask you to introduce yourself, as if it were a compulsory course.)

Answer: omitting the author's self-introduction here, the author suggests that the time to introduce yourself should not be too long, 3-4 minutes is appropriate, said too much the interviewer will think you are too verbose. It doesn't matter if you say too little, it will make people feel that your experience is too simple and too simple in space.

Under normal circumstances, while you are introducing yourself, the interviewer is looking at your resume at this time. He needs to look at your resume and listen to you introduce himself at the same time. If you introduce yourself with a few words, he must not have recovered. He will lose points on your image. At the same time of the introduction, you should think clearly and logically. * * is based on the experience written on your resume, so that you can bring the interviewer's ideas to you and let him follow you. Don't blah, blah, blah.

Try to introduce your personality and hobbies as little as possible (not to mention it). You can simply list several companies (up to 3 companies / also include the current company, pay attention to the order). What kind of work are you responsible for in those companies and what technologies have been used? let's focus on what kind of work your current company is responsible for. You can introduce it in a little more detail. Don't make the interviewer feel dizzy.

2. How to achieve grayscale publishing?

Answer: I saw a netizen's suggestion on Zhihu afterwards and thought it was good. You can take a look at it!

Consider carefully what the grayscale publishing system wants to achieve, and you will basically have the answer. It should be noted that the grayscale publishing of client applications (whether PC or mobile) is more complex than that of Web applications, because the application runs on a user-held terminal, making data acquisition and rollback more difficult (but the types of data that can be collected are more abundant).

Note: I have no experience in mobile client products, the following may not apply to mobile client products.

The main task of the grayscale publishing system I understand is to select some users from the product user group according to a certain strategy, and let them experience the application of the new version first. by collecting these users' explicit feedback (forums, Weibo) or implicit feedback (applying their own statistics), the function, performance and stability of the new version of the application are evaluated. It is then decided to continue to enlarge the scope of the new version until it is fully upgraded or rolled back to the old version.

From the above description, we can get some elements that the grayscale publishing system needs to have:

User identification

Used to distinguish users, assist data statistics, and ensure the consistency of the user experience in the grayscale publishing process (to avoid users jumping between the old and new versions, anonymous Web applications are more likely to have this problem). Anonymous Web applications can use IP, Cookie, etc., and applications that need to log in can directly use the application's account system.

Target user selection strategy

That is, to choose which users to experience the new version first, whether to force the upgrade or let the users choose independently, and so on. There are many factors to consider, including, but not limited to, geographical location, user terminal characteristics (such as resolution, performance), and user characteristics (gender, age, loyalty, etc.). Minor modifications (such as copywriting and relocation of a small number of controls) can be forced to upgrade directly, and for large upgrades such as Sina Weibo revision, users should be allowed to choose, and * * can provide a channel for users to roll back to the old version.

For client applications, you can consider a multi-channel upgrade strategy similar to Chrome, allowing users to choose the versions of stable, beta and unstable channel. Take the trial risk at your own risk if the user has a clear expectation.

Data feedback

User data feedback: collect the user's use of the new version of the application with the user's permission. Such as client performance, client stability, frequency of use, and so on. Used to compare with the old version and decide whether to continue to expand the release scope of the new version or roll back.

Server-side data feedback: the new version of server-side performance, server-side stability, etc., the effect is similar to user data feedback.

New version rollback strategy

When the grayscale release of the new version does not perform well, you should roll back to the old version. For pure Web applications, rollback is relatively simple. The main difficulty lies in the seamless switching of user data. For client applications, if users are expected to uninstall the new version and install the old version, the cost and turnover rate are too high. You can consider releasing a new version quickly and using the upgrade to "roll back" to overwrite the changes from the last grayscale release.

For mobile clients, the new version is expensive to release and requires Appstore and Market review. I have no experience in mobile client products, and I'm not sure how mobile client products handle grayscale publishing and rollback. However, if you try to make the client Web App, it will be more conducive to upgrade and rollback. (however, Apple has strong restrictions on pure Web App App, and it seems that such applications are no longer allowed to be published on AppStore? )

New version of public relations operation support

For large-scale upgrades at the revision level, you need to cooperate with public relations operation support to deal with the "explicit feedback" given by users in Weibo, blogs and other channels in a timely manner. After comparing the conclusions obtained by implicit data feedback, the coping strategies are considered comprehensively.

3. Are you familiar with Mongodb? how many are generally deployed?

Answer: it has been deployed, but has not been studied in depth. Generally, mongodb deploys master-slave or mongodb sharding clusters; it is recommended to deploy 3 or 5 servers. The basic idea of MongoDB slicing is to divide the collection into small pieces. These blocks are scattered into several slices, each of which is responsible for only a portion of the total data. For the client, there is no need to know that the data has been split or which shard corresponds to which data on the server side.

The data needs to run a routing process called mongos before it can be sliced. This router knows where all the data is stored and the corresponding relationship between the data and the slice. For the client, it only knows that it is connected to an ordinary mongod. In the process of requesting data, it is routed to the chip where the target data is located through the corresponding relationship between the data on the router and the slice. If the request has a response, the router collects it and sends it back to the client.

4. How to publish and roll back, and how to implement it with jenkins?

Answer: release: jenkins configure the code path (SVN or GIT), then pull the code and type tag. Compile as needed, and then push it to the publisher (scripts can be called in jenkins), and then distribute it down to the business server from the distributor.

Rollback: go to the publisher to find the corresponding version push according to the version number

5. Tomcat working mode?

Answer: Tomcat is a JSP/Servlet container. As a Servlet container, it has three working modes: independent Servlet container, in-process Servlet container and out-of-process Servlet container.

Requests to enter Tomcat can be divided into the following two categories according to the working mode of Tomcat:

Tomcat acts as the application server: the request comes from the front-end web server, which may be Apache, IIS, Nginx, etc.

Tomcat as a stand-alone server: the request comes from the web browser

6. What is the implementation of monitoring?

Answer: now the company's business is running on Aliyun. Our * * monitoring is based on Aliyun Monitoring. Ariyun Monitor comes with monitoring templates for ECS, RDS and other services, which can be combined with custom alarm rules to trigger monitoring items. The last company's business is hosted in IDC, using zabbix monitoring solution, zabbix graphical interface is rich, but also comes with a lot of monitoring templates, especially multiple partitions, multiple network cards and other automatic discovery and monitoring has done a very good job, but you need to install zabbix agent on each client (monitored side).

7. How do you back up your data, including database backup?

Answer: in a production environment, both application data and database data will have a master-slave architecture when they are first deployed, which itself is a hot backup of the data.

In fact, consider cold backup and use a special server as the backup server. For example, you can use rsync+inotify to cooperate with planned tasks to achieve cold backup of data. If it is a package backup of the release version, there is normally a release server, and each release version will save the package of the release version.

Summarize the following points for attention in the interview:

* you need to be familiar with your resume.

You must be able to name one or two of the skills you write on your resume, because many of the interviewer's questions will be asked on your resume. For example, your resume says the skill "be familiar with the deployment, installation and principle of mysql database". Now that you have written such a skill, no matter how you are not familiar with it, you should understand the principle of mysql and be able to give a general meaning. In case the interviewer asks you this question and you can't answer it, you lose points again in his mind. Basically, there is not much hope for this interview.

Second, don't pretend to know

If the interviewer asks you a question that you won't know, just say that you are not familiar with it, have not studied it, and don't pretend to understand it and cover it up with a bunch of useless topics, which will only make the interviewer disgusted with you.

Third, be well prepared.

It is possible to remember more knowledge of the principle, and the general interview asks more questions about the principle. It is rare to ask how specific configuration files are configured. Before the interview, you should also have a clear understanding of the "job description" and "job requirements". Although sometimes most of them do not ask questions about the job requirements, they should also be familiar with them.

Fourth, be sure to summarize after the interview.

This is the end of the introduction of "what are the classic Linux interview questions"? thank you for your reading. If you want to know more about the industry, you can follow the industry information channel. The editor will update different knowledge points for you every day.

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