What is linux yum source

Before using the yum tool to install a software package, you need to specify the location where yum downloads the RPM package. This location is called the yum source; in other words, the yum source refers to the source of the software installation package. yum is a software package manager that exists specifically to solve package dependencies; it can be said that yum is an improved RPM software manager, which well solves the package dependency problems faced by RPM.

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

What is the linux yum source?

yum, the full name is "Yellow dog Updater, Modified", is a tool specifically designed to resolve package dependencies. Existing package managers. Just like on Windows systems, you can use 360 ​​Software Manager to achieve one-click installation, upgrade, and uninstallation of software. Linux systems also provide such a tool, which is yum.

It can be said that yum is an improved RPM software manager, which well solves the software package dependency problem faced by RPM. yum stores all RPM packages on the server side and records the dependencies between each package in files. When the administrator uses yum to install the RPM package, yum will first download the dependency files of the package from the server side and analyze them. This file downloads all related RPM packages from the server at once and installs them.

The yum software can be installed using the rpm command. Before installation, you can check whether yum has been installed by running the following command:

[root@localhost ~]# rpm -qa | grep yum
yum-metadata-parser-1.1.2-16.el6.i686
yum-3.2.29-30.el6.centos.noarch
yum-utils-1.1.30-14.el6.noarch
yum-plugin-fastestmirror-1.1.30-14.el6.noarch
yum-plugin-security-1.1.30-14.el6.noarch

You can see that yum has been installed on the system.

Before using yum to install the software package, you need to specify the location where yum downloads the RPM package. This location is called the yum source. In other words, the yum source refers to the source of the software installation package.

When using yum to install software, at least one yum source is required. The yum source can either use the network yum source or use the local CD as the yum source.

Two ways to build yum sources

Network yum source building

Generally , as long as the host network is normal, you can directly use the network yum source without any modification to the configuration file.

The network yum source configuration file is located in the /etc/yum.repos.d/ directory, and the file extension is ".repo" (as long as the file with the extension "*.repo" is the yum source configuration document).

[root@localhost ~]# ls /etc/yum.repos.d/
CentOS-Base.repo
CentOS-Media.repo
CentOS-Debuginfo.repo.bak
CentOS-Vault.repo

You can see that there are 4 yum configuration files in this directory. Normally, the CentOS-Base.repo file takes effect. We can try to open this file with the following command:

[root@localhost yum.repos.d]# vim /etc/yum.repos.d/ CentOS-Base.repo
[base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/? release= $releasever&arch=$basearch&repo=os
baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
…省略部分输出…

This file contains 5 yum source containers. Only the base container is listed here. The other containers are similar to the base container. The meanings of each parameter in the base container are:

• [base]: container name, must be placed in [].

• name: Container description, you can write it yourself.

• mirrorlist: Mirror site, this can be commented out.

• baseurl: The address of our yum source server. The default is the official CentOS yum source server, which can be used. If you feel it is slow, you can change it to your favorite yum source address.

• enabled: Whether this container is valid. If it is not written or written as enabled, it means that this container is valid. If it is written as enable=0, it means that this container is not valid.

• gpgcheck: If it is 1, it means that the digital certificate of RPM is valid; if it is 0, it means that the digital certificate of RPM is not valid.

• gpgkey: The location where the public key file of the digital certificate is saved. No need to modify.

Local yum source

If the Internet is not available, yum can consider using a local CD (or installation image file) as the yum source.

The Linux system installation image file contains commonly used RPM packages. We can use the compressed file to open the image file (iso file) and enter its Packages subdirectory, as shown in the following figure:

Packages subdirectory of the installation image file

You can see that this subdirectory contains almost all commonly used RPM packages, so there is no problem in using the system installation image as the local yum source.

There is a CentOS-Media.repo file in the /etc/yum.repos.d/ directory. This file is a template file that uses the local CD as the yum source. It only needs simple modifications. The steps are As follows:

1. Insert the CentOS installation CD and mount the CD to the specified location. The command is as follows:

[root@localhost ~]# mkdir /mnt/cdrom
#创建cdrom目录，作为光盘的挂载点
[root@localhost ~]# mount /dev/cdrom /mnt/cdrom/
mount: block device/dev/srO is write-protected, mounting read-only
#挂载光盘到/mnt/cdrom目录下

2. Modify the extensions of several other yum source configuration files to make them invalid, because only files with the extension "*.repo" can be used as yum source configuration files. You can also delete several other yum source configuration files, but if you delete them and want to use the network as the yum source again, there will be no reference files, so it is best to modify the extension. The command is as follows:

[root@localhost ~]# cd /etc/yum.repos.d/
[root@localhost yum.repos.d]# mv CentOS-Base, repo CentOS-Base.repo.bak
[root@localhost yum.repos.d]#mv CentOS-Debuginfo.repo CentOS-Debuginfo.repo.bak
[root@localhost yum.repos.d]# mv CentOS-Vault.repo CentOS-Vault.repo.bak

3. Modify the CD yum source configuration file CentOS-Media.repo, refer to the following modification:

[root@localhost yum.repos.d]# vim CentOS-Media.repo
[c6-media]
name=CentOS-$releasever - Media
baseurl=file:///mnt/cdrom
#地址为你自己的光盘挂载地址
#file:///media/cdrom/
#file:///media/cdrecorder/
#注释这两个的不存在地址
gpgcheck=1
enabled=1
#把enabled=0改为enabled=1, 让这个yum源配置文件生效
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

In this way, the local yum source is configured.

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