learn linux for beginners

configured STR Not Configured Str is an empty string STR is configured not to be an empty string VAR=${STR-EXPR} var=expr Var= Var= $str VAR=${STR:-EXPR} var=expr var=expr Var= $str VAR=${STR+EXPR} Var= var=expr var=expr VAR=${STR:+EXPR} Var= Var= var=expr VAR=${STR=EXPR} str=exprvar=expr STR does not changeVar= STR does not changeVar= $

Tags: the difference">" output redirect, using format:Commands > DocumentsFunction: Redirects the standard output to a file and overwrites the contents of the file, which is called the callout output, and only outputs the correct command information to the file.">" is also used as output redirection, using the format:Commands > DocumentsThe function:> is different from the other, it can not only redirect the correct information output to the file, but also can redirect the wrong information outp

the development of distributed processing, parallel processing, and grid computing, or the commercial implementation of these concepts of computer science.It is called "cloud" because it has cloud characteristics in some ways:The cloud is generally large, the scale of the cloud can be dynamically scaled, its boundary is blurred;The cloud is erratic in the air, and you can't and does not have to determine its exact location, but it does exist somewhere.It is called "the Cloud", but also because

/[Email protected] named]# vim Named.localhost$TTL 1D@ in SOA dns.test.com. Root. (0; Serial1D; Refresh1H; Retry1W; Expire3H); MinimumIn NS dns.test.com. Don't forget the decimal pointDNS in A 192.168.10.10www in A 192.168.10.10FTP in A 192.168.10.10Save exit8. Configuring Reverse Files[Email protected] named]# vim Named.loopback$TTL 1D@ in SOA dns.test.com. Root. (0; Serial1D; Refresh1H; Retry1W; Expire3H); MinimumIn NS dns.test.com.Ten in PTR dns.test.com.Ten in PTR www.test.com.Ten in PTR ftp

/[Email protected] named]# vim Named.localhost$TTL 1D@ in SOA dns.test.com. Root. (0; Serial1D; Refresh1H; Retry1W; Expire3H); MinimumIn NS dns.test.com. Don't forget the decimal pointDNS in A 192.168.10.10www in A 192.168.10.10FTP in A 192.168.10.10Save exit8. Configuring Reverse Files[Email protected] named]# vim Named.loopback$TTL 1D@ in SOA dns.test.com. Root. (0; Serial1D; Refresh1H; Retry1W; Expire3H); MinimumIn NS dns.test.com.Ten in PTR dns.test.com.Ten in PTR www.test.com.Ten in PTR ftp

,shadow_90,type_zmfuz3pozw5nagvpdgk=) Comparison found: Mtime and CTime changes 4. The file content has changed, use the command cat file again, and then see if there are any changes! [] (http://i2.51cto.com/images/blog/201805/24/c5a2657a9d32ebc2eabd83a37809f35a.png?x-oss-process=image/ watermark,size_16,text_qduxq1rp5y2a5a6i,color_ffffff,t_100,g_se,x_10,y_10,shadow_90,type_zmfuz3pozw5nagvpdgk=) After comparison, it was found that Atime changed 5. View time changes after changing permissions

Poor foundation. I just got started with Linux O M. I hope I can learn about a poor Linux O M Foundation. I just got started with Linux O M. I hope I can learn a message for Linux O M: perl too old, the written code seems to b

description6. User home directory, the directory where the user logged in7./bin/bash: When the user is logged in, the shell can be used, and if the shell cannot be used, the/sbin/nologin will be displayed.The contents of the/etc/shadow configuration file are separated by colons into 9 segments, respectively:1. User Name2. Encrypted password (* Indicates the user is locked,!) indicates no encryption)3. Date of recent password change: the date in Linux

normal copy operation is performed 4.mv: Cut files or rename files. Format: MV [options] source file [target path | target file name]5.rm: Delete files or directories. Format: RM [options] File-F indicates a forced deletion, that is, a message that does not appear to be deleted. The-r parameter is also required if the directory is forcibly deleted.6.DD: Copies a file or conversion file according to a specified size and number of data blocks. Format: DD [parameter]7.File: View the type of f

references are very good, if you want to learn cron Job, should be enough.1. Howto:add Jobs to cron under Linux or UNIX?http://www.cyberciti.biz/faq/how-do-i-add-jobs-to-cron-under-linux-or-unix-oses/2. How to run a cron job using the sudo commandHttp://askubuntu.com/questions/173924/how-to-run-a-cron-job-using-the-sudo-command3. How to view crontab logginghttp:

After sorting out the commands that have been used, I am also a beginner, so I hope there are not so many complicated commands, so we will soon learn shell, which will certainly be helpful to beginners! Ls-A/-L to view all files, including hidden .~ Executable file.-L indicates viewing the attributes of the file in the current directory.PWD Current DirectoryGo:CD .. return to the upper-level directoryCD-la

=kwj4aqaaaaabahc! su=0170300689sce=0-12-12rf=2-9 "/>Computer History Linux HistoryLinux OrganizationsGNU:GNU is not Unix provides Linux source codeGpl:general Public License Common licenseHere is the Linux that the publisher compiles the source code into an executable program.Because they are open source, the software can be freely downloaded to use, so the main

/passwd is the ID of the initial group. When a user logs on, they have the initial group permissions. The user group for a file or folder is determined by the effective group of the creator. We can view the user groups of the current user through the groups command, the first is the effective group, see the following example:We can change the active group of the current user by newgrp groupname . It is important to note that when this command is used, a new bash process is actually started, and

As a beginner of Linux, we may sometimes forget the root password to make their own haste, some people may have to choose to re-install the system, learning this operation will be able to easily solve the forgotten password problemSelect Restart virtual machine on a virtual machine that is already openPress the up and down arrows in this interface,Then enter the Grub page by the letter "E"Look for the "Linux16" line, change the character "Ro" to "RW",

To write a script:Determine the current host's CPU manufacturerIf its manufacturer is AUTHENTICAMD, it will show it as AMD.If its manufacturer is Genuineintel, it will show up as an Intel companyOtherwise, it is displayed as UnkownThe script is written as follows:#!/bin/bashcpu= ' grep ' vendor_id '/proc/cpuinfo |cut-d:-f2 'if [$CPU = = Authenticamd];thenecho "The CPU is AMD"elif [$CPU = = Genuineintel];thenecho "The CPU is Intel"Elseecho "Unkown"This article is from the "Yegaopeng" blog, make s

features, such as zoom and pan. It supports different GUI backend (back ends) under all operating systems, and can output graphics to common vector and graphic formats such as PDF, SVG, JPG, PNG, BMP, and GIF.Scikit-learnScikit-learn is a Python module for machine learning. It builds on scipy and provides a common machine learning algorithm that allows users to use it through a unified interface. Scikit-learn