Operating System | Zhang Ge Blog

There are three articles in this series, namely, Script Programming and Linux Commands, Access Layer and Network Foundation, and MySQL and SQL Optimization, which were originally created by Luaruan (Ruan Yongshun), a senior engineer of Tencent, and collated and shared by Zhang Ge's blog. Please leave a message on the blog if there is any error. I hope it will be helpful to students who need to learn and interview Linux operation and maintenance. What are the default sizes of MSS and MTU? The default MTU (maximum transmission unit) of the standard Ethernet interface is 1500 bytes, and the maximum frame is 151

October 26, 2018

Basic skills of Linux operation and maintenance: script programming and Linux commands

BAT company interview experience Operation and maintenance engineer interview Interview questions

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There are three articles in this series, namely, Script Programming and Linux Commands, Access Layer and Network Foundation, and MySQL and SQL Optimization, which were originally created by Luaruan (Ruan Yongshun), a senior engineer of Tencent, and collated and shared by Zhang Ge's blog. Please leave a message on the blog if there is any error. I hope it will be helpful to students who need to learn and interview Linux operation and maintenance$ 1. Enter the parameter, when the value is null, the default assignment technique is variable=${1: - "default value"} # When the parameter is not transferred, the default value is assigned. echo...

November 19, 2017

Introduction to cronsun, a unified scheduled task management system, replacing crontab

crontab Scheduled task

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Cronsun is a distributed task system. A single node is similar to the crontab on a Linux machine. This is to solve the problem of inconvenient management of crontab tasks on multiple Linux machines, and provide high availability support for tasks (when a node crashes, it can be automatically scheduled to the normal node for execution). It supports tasks on the interface management machine, and supports email reminders of task failures. It is simple to install and convenient to use. It is a good choice to replace crontab

April 6, 2017

Remote Desktop License Servers Available

Linux remote desktop Linux Remote Desktop Connection windows

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The remote session was disconnected because there are no Remote Desktop License Servers available to provide a license Please contact the server administrator， It is finally found that it is a bug of Microsoft RDP Remote Desktop Suite, which can be solved by installing Microsoft patches or modifying the registry. This article simply records the solution process

September 3, 2016

Linux LVM logical volume creation process and automated script

linux

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Recently, when I was building a new computer room in Shanghai, I was given two M2 servers. When initializing, I found a bunch of disks:[ root@Centos64 :~]# fdisk -l | grep \'300.1 GB\' | sortDisk /dev/sda: 300.1 GB, 300069052416 bytesDisk /dev/sdb: 300.1 GB, 300069052416 bytesDisk /dev/sdc: 3...

August 6, 2016

Solution to the problem of abnormal display of df command and partition loss in Linux system

linux Linux basics Linux file locking

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This article records two solutions to the problem of abnormal display of df commands and partition loss caused by the/etc/mtab file exception for future use. 1、 A few days before the root directory was lost, a colleague asked everyone in the RTX group that there was a server executing df - h that could not see the root directory. How to solve this problem? [ [email protected] :~]# df -hFilesystem Size Used Avail Use% Mounted onudev...

May 7, 2016

Upgrade CentOS6.5 kernel and enable Nginx's fastopen and reuseport features

Linux kernel optimization Nginx configuration

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Earlier, Zhang Ge's blog noticed that two parameters, fastopen=3 reuseport, were added to Nginx's listen configuration when it was struggling with Nginx's SSL optimization. So we made up our minds. The original goal was to enable Nginx to support the new features of TCP_FASTOPEN and TCP_SO_REUSEPORT. As for the benefits, please make up your own minds --> Portal 1. Necessary Environment When I followed the example and added these two parameters, an error was reported: nginx: [em

April 5, 2016

Share a troubleshooting process for the failure of the crontab to execute the Linux task plan

linux

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A friend made a small project and asked me to help with the operation and maintenance of the Linux system. After going online for a period of time, he found that the project occasionally failed, leading to service unavailability. The development friends were not free to study the root cause of the project collapse for a while, so I, the O&M personnel, had to write a self starting script for the project process first, and check the existence of the process every minute through the Linux task plan to prevent the project from being hung up and left unattended. It's very simple to pull up the script, just write a few lines at random and you can finish it: #/ bin/bashprocesscount=$(pgrep my_app|w...

December 12, 2015

Resolve the PAM authentication failed error when Linux modifies the password

linux Linux basics Operating system

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Recently, I received an operation and maintenance development task, which requires the development of an account management system to manage the root accounts of more than 3000 Linux servers in a batch system, realize the regular modification of root to random password and encryption storage, and provide the operation and maintenance management WEB foreground with password query and decryption interface and other functions. At the beginning, I developed a prototype based on php+ssh2_exec. All the basic functions have been realized. As a result, the boss said that I am a little good at PHP in the operation and maintenance here, but it is not easy to maintain later. I was also persuaded, because the writing is done, do you want to reconstruct

August 19, 2015

Solve the problem of dos2unix/unix2dos reporting errors and generating u2dtmp * files in the home directory

linux shell Shell script

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Recently, I received a case: big data analysis feedback that the data we push here is much less than the same period last year. This is very abnormal, because the business has been growing. So I began to follow up. At the beginning, I found a small problem: after the scp push file script was executed, an error was reported:[ root@netdata :/data]# sh pushdata.shdos2unix: converting file pushdata.log to UNI...

August 13, 2015

Practical PS1 Command Prompt Format for Linux in Batch Server Management

centos7 linux shell Shell script

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As the operation and maintenance of a large company, it is common to manage hundreds of servers on hand, or even more. We usually log in with a springboard machine. Because these machines are usually cloned or virtualized, the command line prompt after logging in is almost a mold, such as:[ root@localhost ~]#At this time, we will certainly often encounter such a problem: when operating the server, we will be interrupted due to something, and when we go back to continue the operation, we will ifconfg to confirm whether it is the server I want to operate, because it cannot be identified from the appearance

April 17, 2015

Compilation and installation of Redis and master-slave replication configuration of Linux system

centos7 linux Operating system

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The installation configuration of Redis is very simple, and Redis has been installed for a long time, but I forgot some details when I installed it again these days. It seems that a good memory is better than a bad pen. It's better to record it in a blog, at least not to hold my legs all the time. After compiling and installing for several times today, I found that the file was not generated in the directory specified in the prefix?? After reading for a long time, I found that PREFIX I used lowercase letters... It seems that it is necessary to record the correct operation steps to avoid this embarrassment again. 1、 Select the version to go to the official website: h