How to use the yum command

1. Introduction to yum

Yum (full name Yellow dogUpdater, Modified) is a Shell front-end package manager in Fedora, RedHat and CentOS. Based on RPM package management, it can automatically download and install RPM packages from the specified server, automatically handle dependency relationships, and install all dependent software packages at once without the tedious downloading and installation again and again. Yum provides commands for finding, installing, and deleting one, a group of, or even all software packages, and the commands are concise and easy to remember.

(II) Use of yum

The command format of yum is generally as follows: yum –option command package

The options are optional and include -h (help), -y (select "yes" for all installation prompts), -q (

The installation process is not displayed) and so on. [command] is the operation to be performed, and [package ...] is the object of the operation.

All yum information is stored in a configuration file called yum.reops.d, usually located in the /etc/yum.reops.d directory.

There are many files under this directory, all ending with .repo. The repo file is the configuration file of the yum source (that is, the software warehouse). Usually a repo file defines the details of one or more software warehouses. For example, where we will download the software packages that need to be installed or upgraded. The settings in the repo file will be read and applied by yum!

Enter the /etc/yum.repo.d directory,

vi CentOS-Base.repo

[extras] This indicates the name, ---> yum ID, which must be unique. When there are multiple yum sources locally, this must be unique.

name=CentOS-$releasever - Base -----> The specific yum source name, which is actually equivalent to its description information $r releasever You can use this variable to refer to the Red Hat Enterprise Linux release, that is, it represents the major version number of the current release.

baseurl is the mirror server address, and only a specific address can be written. In the following example, there can only be one baseurl, but it can contain multiple urls.

mirrorlist is a list of mirror server addresses, which contains many server addresses. There is a variable $arch, the CPU system, and another variable: $basearch, the basic system group of the CPU

Both baseurl and mirrorlist point to the address of the yum source, the difference is how many addresses are included. If you write it yourself, we usually only write one address, just use baseurl

gpgcheck=0 ---->Do you want to verify? Cancel verification. 1. Use the public key to verify the correctness of rpm.

If gpgcheck is 1, the downloaded rpm will be checked with gpg. The verification key is gpgkey. Generally, your own yum source does not need to be checked. gpgcheck=0, then gpgkey can be left blank

Let's take a look at the yum.conf file

cachedir=/var/cache/yum #The cache directory of the RPM package downloaded by yum keepcache=0 #Whether to save the cache, 1 to save, 0 not to save.
debuglevel=2 #debug level (0-10), default is 2
logfile=/var/log/yum.log #The location of yum's log file

1 yum clears the cache list

yum clean packages Clear the packages in the cache directory, which clears the cache under (/var/cache/yum) yum clean headers Clear the headers in the cache directory
yum clean oldheaders clears the old headers in the cache directory
yum clean, yum clean all (= yum clean packages; yum clean oldheaders) Clear the packages and old headers in the cache directory

2 yum displays information

yum list # yum list displays all installed and installable packages

The source of the packages in these lists is /etc/yum.repo.d. base docker-ce-stable epel/x86_64/metalink epel extras rpmforge updates

yum list rpm displays installation package information rpm

Displays installed, here is the package name, version and repository name

yum list httpd Here are the available packages, which means it has not been installed yet.

yum info rpm displays detailed information about the installation package rpm

3 yum installation

yum -y install httpd

If you don't add -y it will ask you if you want to install it. If you want to control whether some packages are installed by yourself, don't add -y here. If you want to install automatically without interaction, add -y here. This is the installation of yum, which is very simple.

After installation, check

yum list httpd, "Installed" means it has been installed

4 yum delete

yum remove httpd deletes the package httpd, that is, uninstalls it.

yum deplist rpm View program rpm dependencies

5 yum package upgrade

yum check-update checks for updatable programs yum update updates all, upgrades all packages, and upgrades software and system kernel. This is a one-click upgrade. He can update the CentOS kernel to the latest version.
 yum update package1 updates the specified package package1. 
 yum upgrade package1 upgrades the specified package package1

6 The principle of yum solving dependencies

YUM resolves dependency issues and automatically downloads packages. Yum is based on C/S architecture. C refers to the client, S refers to the server, such as ftp, http, file, about why yum can solve dependencies: all Yum sources contain repodata, which contains XML format files, which describe what packages are needed. For example, the mysql-server rpm used in the last class experiment requires perl-DBI, python, or php packages.

7 yum group management

When installing with yum, you can install them in groups. Let's first look at the groups yumgrouplist has. There are so many groups available.

Available Environment Groups: First are the available environment groups.

Compute Node

Infrastructure Server

File and Print Server File and Print Server

Cinnamon Desktop Cinnamon Desktop

Installed Groups: Installed groups, development tools

Development Tools

Available Groups: Available groups.

If we want to install as a group, let's say I want to install security tools:

Type: yumgroupinstall "Security Tools"

When you see the question here whether you want to install it, of course you should say N. If you want to install directly without asking, add the option –y at the end.
yum groupremove group1 delete program group group1

refer to

1 Installation

yum install install all yum install package1 install the specified installation package package1
yum groupinsall group1 Installer group group1

2 Updates and Upgrades

yum update updates all yum update package1 updates the specified package package1
yum check-update checks for updatable programs yum upgrade package1 upgrades the specified package package1
yum groupupdate group1 upgrade program group group1

3 Search and display

yum info package1 displays installation package information package1
yum list displays all installed and installable packages yum list package1 displays the installation status of the specified package package1
yum groupinfo group1 Display information of program group group1 yum search string Search for installation packages based on keyword string

4 Deleting Programs

yum remove | erase package1 Delete package package1
yum groupremove group1 delete program group group1
yum deplist package1 View the dependencies of program package1

5 Clear the cache

yum clean packages Clear the packages in the cache directory yum clean headers Clear the headers in the cache directory
yum clean oldheaders clears the old headers in the cache directory
yum clean, yum clean all (= yum clean packages; yum clean oldheaders) Clear the packages and old headers in the cache directory

Reference: https://www.cnblogs.com/qingjiaowoxiaoxioashou/p/7059701.html

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