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Introduction to 1 YUM

Introduction to 1.1 YUM

CentOS uses yum and dnf to resolve the package dependencies of rpm.

YUM:rpm's front-end program, which solves package-related dependencies, locates packages between libraries, an alternative tool for up2date, and CentOS 8 uses dnf instead of yum, but retains compatibility with Yum and is generic in configuration.

YUM, formerly YUP (Yellow dog Updater, a Software Updater for Yellow dog Linux), was originally developed by TSS Corporation (Terra Soft Solutions, INC.) in Python and later improved by the Linux development team at Duck University, named YUM (Yellow dog Updater, Modified). To successfully use the YUM mechanism to update systems and software, a software repository containing various rpm installation package files and their dependent software is required, and the server providing the software repository is also known as the "source" server. As long as information such as the address of the software repository is correctly specified in the client, the software can be installed or updated through the corresponding "source" server.

YUM(Yellow dog Updater，Modified):

• Software Update Mechanism Based on RPM Package
• Dependency can be resolved automatically
• All packages are provided centrally to the YUM software repository

How 1.2 yum works

yum is environment-dependent, service-side and client-side, allowing cross-network.

Yum is based on C/S mode:

• The yum server stores metadata for rpm packages and related packages
• The Yum client accesses the yum server for installation or query, etc.

Yum implementation process:

yum repository (warehouse) is created on the yum server. Many rpm packages and their related metadata files are stored in the warehouse in advance (under the specific directory repodata). When the yum client installs the package using the yum/dnf tool, the metadata in the repodata is automatically downloaded, the distant data is queried for related packages and dependencies, and the related packages are automatically downloaded and installed from the warehouse.

Server (both RPM packages and metadata are required):

• RPM package (stored in package folder Packages)
• Metadata (stored in the metadata folder repodata, which contains: catalogs (software catalogs), software dependencies, software grouping)

 #Looking at the Yum repository that comes with the disc, you can see the Packages folder and the repodata folder:
 ​
 [root@localhost ~]# Mount/dev/sr0/mnt //Mount the disc to/mnt/directory
 mount: /dev/sr0 Write protected, mounted read-only
 [root@localhost ~]# Ls/mnt //View package and metadata folders on CD
 CentOS_BuildTag  GPL       LiveOS    RPM-GPG-KEY-CentOS-7
 EFI              images    Packages  RPM-GPG-KEY-CentOS-Testing-7
 EULA             isolinux  repodata  TRANS.TBL

Local warehouse type:

• Warehouse for Discs (Basic Warehouse)
• epel extended warehouse

1.3 How to implement installation services

2 yum client configuration

yum client profile

 /etc/yum.conf              #Provide public configuration for all warehouses
 /etc/yum.repos.d/*.repo    #Configuration files for each warehouse

2.1 yum master profile

Location: /etc/yum.conf

 [root@localhost ~]# vim /etc/yum.conf
 [main]
 cachedir=/var/cache/yum/$basearch/$releasever  //The cache directory of RPM packages downloaded by yum, $basearch for hardware architecture, $release ever system version such as 7
 keepcache=0                         //Whether or not to save the cache 0 means not to save, 1 means to save
 debuglevel=2                        //Debug level (0-10), default 2
 logfile=/var/log/yum.log            //Log file location
 exactarch=1                         //Allow different versions of rpm installation
 obsoletes=1                         //This is an update parameter, whether to allow older versions to run  
 gpgcheck=1                          //Whether to validate the GPG(GNU Private Guard) key, 1 means validation
 plugins=1                           //Allow plug-ins, 1 for allow
 installonly_limit=5                 //Save several cores
 bugtracker_url=http://bugs.centos.org/set_project.php?project_id=23&ref=http://bugs.centos.org/bug_report_page.php?category=yum
 distroverpkg=centos-release
 ​
 ​
 # Variables available in yum's repo profile:
 $releasever: current OS Major release number, e.g. 8, 7, 6
 $arch: CPU Architecture, such as: aarch64, i586, i686，x86_64 etc.
 $basearch: System basic platform; i386, x86_64
 $contentdir: Represents a directory, such as: centos-8，centos-7
 $YUM0-$YUM9:Custom variable

2.2 yum repository profile

2.2.1 Warehouse Profile Description

Location: /etc/yum.repos.d/*.repo

The default yum repository in the system is centos'official yum source (foreign source), which requires an external network to be connected.

 [root@localhost yum.repos.d]# ls /etc/yum.repos.d/
 CentOS-Base.repo  CentOS-Debuginfo.repo  CentOS-Media.repo    CentOS-Vault.repo
 CentOS-CR.repo    CentOS-fasttrack.repo  CentOS-Sources.repo
 ​
 [root@localhost yum.repos.d]# vim yuji.repo //yum repository profile format
 [yuji]
 name=yuji                   #Set Name
 baseurl=file: ///mnt #Set the link address, file://is a fixed format for local sources
 enabled=1                   #Open this yum source
 gpgcheck=0                  #Whether to verify the public key, 0 means no verification is required

Several forms of baseurl in the yum warehouse configuration file:

 # Local Source
 Local directory   file://        
 ​
 # Network Source
 FTP service    ftp://          
 HTTP service   http://
 External Network Environment    https://

2.2.2 Path to baseurl

yum Source for CentOS System

 #Ali Yun
 https://mirrors.aliyun.com/centos/$releasever/

yum Source for EPEL

 #Ali Yun
 https://mirrors.aliyun.com/epel/$releasever/x86_64

Update Source

 http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/ http://mirrors.aliyuncs.com/centos/$releasever/updates/$basearch/ http://mirrors.cloud.aliyuncs.com/centos/$releasever/updates/$basearch/

2.3 log file

Location: /var/log/yum.log

 [root@localhost yum.repos.d]# Head-5/var/log/yum. Log //View log files
 Jan 19 10:55:29 Installed: tree-1.6.0-10.el7.x86_64
 Feb 21 23:21:53 Installed: finger-0.17-52.el7.x86_64
 Mar 19 17:10:29 Updated: 32:bind-license-9.11.4-26.P2.el7_9.9.noarch
 Mar 19 17:10:30 Updated: 32:bind-libs-lite-9.11.4-26.P2.el7_9.9.x86_64
 Mar 19 17:10:30 Updated: 32:bind-libs-9.11.4-26.P2.el7_9.9.x86_64

3 yum command details

command	No keywords	Join keywords, packages, package groups
yum list	Show all available packages	Single installable package
yum info	Show information about all available packages	Individual specific information
yum search	\	Fuzzy Find All Related Information
yum whatprovides	\	Find precisely
yum install	\	Install specific packages
yum update	All software upgrades, update the kernel	Specific software upgrade
yum upgrade	Update packages only, but not kernels	Specific software updates
yum remove	\	Uninstall specific software
yum history	View current yum operation history	\
yum history info	\	List the details of a transaction with a sequence number
yum history undo	\	Sequence number to uninstall the software installed in the sequence number
yum history redo	\	Re-execute operation in sequence number by adding sequence number

Package group:

command	No keywords	Join keywords, packages, package groups
yum grouplist	Show all available package groups	Show specific package groups
yum groupinfo	Show all package group details	Display specific information about specific package groups
yum groupinstall	\	Install specific package groups
yum group update	All package group upgrades	Specific package group upgrade
yum groupremove	\	Uninstall package group specific software

Tips:

When the package is not cleanly uninstalled by using the "yum remove software name", you can use the "yum history undo serial number" to uninstall the entire package without any residue.

4 yum warehouse building method

Software warehouse is provided in:

• Local directory: file://absolute path
• FTP Service: ftp://ip Path in Address/Site
• HTTP service: http://domain name or ip address/path in site

4.1 Build local yum warehouse

Setup steps:

Step 1, Mount the disc (/dev/sr0 or/dev/cdrom is fine, /dev/cdrom is a soft link to/dev/sr0)

 [root@localhost ~]# Mount/dev/sr0/mnt //Mount the disc to/mnt directory
 mount: /dev/sr0 Write protected, mounted read-only
 [root@localhost ~]# Df-Th //Check if mounting was successful
 file system                type      Capacity used Available Used% mount point
 /dev/mapper/centos-root xfs        10G  4.0G  6.1G   40% /
 devtmpfs                devtmpfs  897M     0  897M    0% /dev
 tmpfs                   tmpfs     912M     0  912M    0% /dev/shm
 tmpfs                   tmpfs     912M  9.1M  903M    1% /run
 tmpfs                   tmpfs     912M     0  912M    0% /sys/fs/cgroup
 /dev/sdb5               xfs       2.0G   33M  2.0G    2% /data/bb
 /dev/sda1               xfs      1014M  179M  836M   18% /boot
 /dev/sdb1               xfs        10G   33M   10G    1% /data/aa
 /dev/mapper/vg01-lvmail xfs        13G   33M   13G    1% /data/mail
 tmpfs                   tmpfs     183M   12K  183M    1% /run/user/42
 tmpfs                   tmpfs     183M     0  183M    0% /run/user/0
 /dev/sr0                iso9660   4.3G  4.3G     0  100% /mnt

Note: The mount command is a one-time mount and does not exist after exiting the current terminal or restarting. Permanent mounting requires modification of the configuration file/etc/fstab.

Step 2, Switch to/etc/yum.repo.d/Directory, remove the warehouse files that came with it.

 [root@localhost ~]# Cd/etc/yum.repos.d/ //Switch to/etc/yum.repos.d/Directory
 [root@localhost yum.repos.d]# ls
 CentOS-Base.repo  CentOS-Debuginfo.repo  CentOS-Media.repo    CentOS-Vault.repo
 CentOS-CR.repo    CentOS-fasttrack.repo  CentOS-Sources.repo
 [root@localhost yum.repos.d]# mkdir aaa //Create a new directory named aaa
 [root@localhost yum.repos.d]# mv *.repo aaa //will be in the yum warehouse to. File at end of repo moved to aaa
 [root@localhost yum.repos.d]# ls
 aaa

Step 3. Create a new yum warehouse file.

 [root@localhost yum.repos.d]# vim yuji.repo //new yum repository file
 [yuji]
 name=yuji                   #Set Name
 baseurl=file:///mnt #Set the link address, file://is fixed format, points to/mnt
 enabled=1                   #Open this yum source
 gpgcheck=0                  #No need to verify public key

Step 4. Clean up the cache and install the software.

 [root@localhost yum.repos.d]# yum clean all //clean up yum cache
 [root@localhost yum.repos.d]# yum makecache //Re-establish metadata
 [root@localhost yum.repos.d]# yum list //View list of installable software
 [root@localhost yum.repos.d]# Yum install dhcp-y //yum install DHCP test success

4.2 Set up Ali Cloud Warehouse (http external network environment)

The default warehouse file is foreign cloud warehouse, which is slower and can be replaced by Ali cloud warehouse.

Operation steps:

Step 1, Switch to/etc/yum.repo.d/Directory, remove the warehouse files that came with it.

 [root@localhost ~]# Cd/etc/yum.repos.d/ //Switch to/etc/yum.repos.d/Directory
 [root@localhost yum.repos.d]# mkdir aaa
 [root@localhost yum.repos.d]# mv *.repo aaa //will be in the yum warehouse to. File at end of repo moved to aaa
 [root@localhost yum.repos.d]# ls
 aaa

Step 2, New Ali Cloud Warehouse.

 [root@localhost yum.repos.d]# vim ali.repo
 [ali]
 name=aliyun
 #baseurl=https://mirrors.aliyun.com/centos/7/os/x86_64/ Which version of //Open works, the main explanatory variable here
 baseurl=https://mirrors.aliyun.com/centos/$releasever/os/$basearch/    
 gpgcheck=0
 ​
 [epel]                                                         //epel source warehouse
 name=epel
 baseurl=https://mirrors.aliyun.com/centos/7/extras/x86_64/
 gpgcheck=0
 ​
 [update]                                                        //Update Package Warehouse
 name=update
 baseurl=https://mirrors.aliyun.com/centos/7/updates/x86_64/
 gpgcheck=0

Step 3. Clean up the cache and install the software.

 [root@localhost yum.repos.d]# yum clean all //clean up yum cache
 [root@localhost yum.repos.d]# yum makecache //Re-establish metadata
 [root@localhost yum.repos.d]# yum list //View list of installable software
 [root@localhost yum.repos.d]# Yum install tree-y //yum install tree test success

4.3 http Cloud Warehouse

Cloud warehouse built by http can be used in both external and Intranet environments, but it is mostly used in intranet.

Server: 192.168.72.10

Client: 192.168.72.129

Setup steps:

Step 1. Install the hhtpd service program on the server side.

 [root@localhost ~]# yum install httpd -y

Step 2. Switch the server to/var/www/html/directory, create a new subdirectory centos7, and mount the CD-ROM drive into the centos7 directory (you can also copy all the packages in the CD-ROM drive into that directory).

 [root@localhost ~]# Cd/var/www/html //Switch directories
 [root@localhost html]# ls
 [root@localhost html]# mkdir centos7 //New directory centos7
 [root@localhost html]# Mount/dev/sr0. / Centos7 //Mount the CD-ROM drive in the centos7 directory
 mount: /dev/sr0 Write protected, mounted read-only
 [root@localhost html]# ls ./centos7
 CentOS_BuildTag  GPL       LiveOS    RPM-GPG-KEY-CentOS-7
 EFI              images    Packages  RPM-GPG-KEY-CentOS-Testing-7
 EULA             isolinux  repodata  TRANS.TBL

Step 3. The server closes the firewall and selinux to start the httpd service.

 [root@localhost html]# systemctl stop firewalld
 [root@localhost html]# setenforce 0
 setenforce: SELinux is disabled
 [root@localhost html]# systemctl start httpd

Step 4, Client Switch to/etc/yum.repos.d/Directory, create a new folder, move the default Yum repository file to that directory. Write a new warehouse file

 [root@192 ~]# Cd/etc/yum. Repos. D //Client Switch Directory
 [root@192 yum.repos.d]# ls
 CentOS-Base.repo  CentOS-Debuginfo.repo  CentOS-Media.repo    CentOS-Vault.repo
 CentOS-CR.repo    CentOS-fasttrack.repo  CentOS-Sources.repo
 [root@192 yum.repos.d]# mkdir bak //New Folder
 [root@192 yum.repos.d]# mv *.repo bak //Move the default warehouse file to this folder
 [root@192 yum.repos.d]# ls
 bak
 [root@192 yum.repos.d]# vim http.repo //Write a new warehouse file
 [http]
 name=http
 baseurl=http://192.168.72.10/centos7
 enabled=1
 gpgcheck=0

Step 5, Clean up the yum cache and re-establish the metadata. It also tests whether the package can be successfully installed using yum.

 [root@192 yum.repos.d]# yum clean all && yum makecache
 Plugins loaded: fastestmirror, langpacks
 Cleaning up software sources: ftp
 Cleaning up everything
 Maybe you want: rm -rf /var/cache/yum, to also free up space taken by orphaned data from disabled or removed repos
 Cleaning up list of fastest mirrors
 Plugins loaded: fastestmirror, langpacks
 ftp                                                        | 3.6 kB  00:00:00     
 (1/4): ftp/group_gz                                        | 156 kB  00:00:00     
 (2/4): ftp/primary_db                                      | 3.1 MB  00:00:00     
 (3/4): ftp/other_db                                        | 1.2 MB  00:00:00     
 (4/4): ftp/filelists_db                                    | 3.1 MB  00:00:00     
 Determining fastest mirrors
 Metadata cache established
 ​
 [root@192 yum.repos.d]# Yum install ftp-y //test the yum installation to install successfully.

4.4 ftp Cloud Warehouse

The cloud warehouse built by ftp can be used in both external and Intranet environments, but it is mostly used in the intranet.

Server: 192.168.72.10

Client: 192.168.72.129

Setup steps:

Step 1. Install the vsftpd service program on the server side.

 [root@localhost html]# yum install vsftpd -y

Step 2. Switch the server to a new subdirectory centos under /var/ftp/directory and mount the CD-ROM into the centos directory (you can also copy all the file packages inside the CD-ROM into the centos directory).

 [root@localhost html]# Cd/var/ftp //switch to/ftp/var/directory
 [root@localhost ftp]# ls
 pub
 [root@localhost ftp]# mkdir centos //Create centos directory
 [root@localhost ftp]# 
 [root@localhost ftp]# Mount/dev/sr0. / centos //Mount the CD-ROM drive in the centos directory
 mount: /dev/sr0 Write protected, mounted read-only
 [root@localhost ftp]# ls ./centos
 CentOS_BuildTag  GPL       LiveOS    RPM-GPG-KEY-CentOS-7
 EFI              images    Packages  RPM-GPG-KEY-CentOS-Testing-7
 EULA             isolinux  repodata  TRANS.TBL

Step 3. The server opens the vsftpd service, closes the firewall and selinux.

 [root@localhost ~]# systemctl start vsftpd
 [root@localhost ~]# systemctl stop firewalld
 [root@localhost ~]# setenforce 0

Step 4. Client installs ftp program to test if ftp service is normal.

 [root@192 ~]# Yum install ftp-y //install FTP program
 ​
 [root@192 ~]# ftp 192.168.72.10 //Test whether the ftp service can access the server properly
 Connected to 192.168.72.10 (192.168.72.10).
 220 (vsFTPd 3.0.2)
 Name (192.168.72.10:root): ftp
 331 Please specify the password.
 Password:
 230 Login successful.              //Can be accessed normally
 Remote system type is UNIX.
 Using binary mode to transfer files.
 ftp> ls
 227 Entering Passive Mode (192,168,72,10,85,22).
 150 Here comes the directory listing.
 drwxr-xr-x    8 0        0            2048 Sep 05  2017 centos
 drwxr-xr-x    2 0        0               6 Jun 09  2021 pub
 226 Directory send OK.
 ftp> bye
 221 Goodbye.

Step 5. The client writes the yum warehouse file.

 [root@192 ~]# Cd/etc/yum. Repos. D //Switch directories
 [root@192 yum.repos.d]# ls
 bak2              CentOS-Debuginfo.repo  CentOS-Sources.repo
 CentOS-Base.repo  CentOS-fasttrack.repo  CentOS-Vault.repo
 CentOS-CR.repo    CentOS-Media.repo
 [root@192 yum.repos.d]# mkdir bak1 //New Folder
 [root@192 yum.repos.d]# mv *.repo bak1 //Move the default warehouse files to this directory
 [root@192 yum.repos.d]# ls
 bak1  bak2
 [root@192 yum.repos.d]# vim ftp.repo //Write a new warehouse file
 [ftp]
 name=ftp
 baseurl=ftp://192.168.72.10/centos //Path to server-side/var/ftp/centos/directory
 enabled=1
 gpgcheck=0

Step 6. Clean up the yum cache and re-establish the metadata. It also tests whether the package can be successfully installed using yum.

 [root@192 yum.repos.d]# yum clean all && yum makecache
 Plugins loaded: fastestmirror, langpacks
 Cleaning up software sources: ftp
 Cleaning up everything
 Maybe you want: rm -rf /var/cache/yum, to also free up space taken by orphaned data from disabled or removed repos
 Cleaning up list of fastest mirrors
 Plugins loaded: fastestmirror, langpacks
 ftp                                                        | 3.6 kB  00:00:00     
 (1/4): ftp/group_gz                                        | 156 kB  00:00:00     
 (2/4): ftp/primary_db                                      | 3.1 MB  00:00:00     
 (3/4): ftp/other_db                                        | 1.2 MB  00:00:00     
 (4/4): ftp/filelists_db                                    | 3.1 MB  00:00:00     
 Determining fastest mirrors
 Metadata cache established
 ​
 [root@192 yum.repos.d]# Yum install httpd-y //Test the yum installation to install successfully.

4.5 Build local epel source warehouse

Scenario for local epel source warehouse:

• In the case of external network connection, you can use foreign sources or Aliyun warehouse, etc.
• However, in practice, the internal network of the company often cannot connect to the external network. At this time, you can set up a local epel source warehouse in advance, that is, Download all the software packages of the epel source in advance in a server that can connect to the external network. After you have written the warehouse file, you can also use yum to install the software packages when you are offline.
• The server-side epel source repository can then be used by other hosts either through http or ftp.

Operation steps:

Step 1. Install the epel source and download all the software packages for the epel source.

 [root@localhost ~]# yum install epel-release //install EPEL source
 [root@localhost ~]# mkdir centos7 //New centos7 Directory
 [root@localhost ~]# Reposync-r epel-p/centos7/ & //download synchronous EPEL source package, download to/centos7/directory, &meaning download in background
 [root@localhost ~]# ls /centos7
 epel

Step 2. Install the createrepo command (the command that establishes metadata), then use the createrepo command to create metadata.

 [root@localhost ~]# Yum-y install createrepo //install createrepo command
 [root@localhost ~]# Createrepo-v/centos7/epel //Create metadata (software catalogs, dependencies) 
 [root@localhost ~]# Cd/centos7/epel//Switch to centos7/epel directory
 [root@localhost epel]# ls) //View packages and metadata
 Packages  repodata

Step 3, Switch to/etc/yum.repos.d directory, remove the default warehouse file, and write a new warehouse file.

 [root@localhost ~]# Cd/etc/yum.repos.d/ //Switch to/etc/yum.repos.d/Directory
 [root@localhost yum.repos.d]# ls
 CentOS-Base.repo  CentOS-Debuginfo.repo  CentOS-Media.repo    CentOS-Vault.repo
 CentOS-CR.repo    CentOS-fasttrack.repo  CentOS-Sources.repo
 [root@localhost yum.repos.d]# mkdir aaa //Create a new directory named aaa
 [root@localhost yum.repos.d]# mv *.repo aaa //will be in the yum warehouse to. File at end of repo moved to aaa
 [root@localhost yum.repos.d]# ls
 aaa
 [root@localhost yum.repos.d]# vim epellocal.repo //new yum repository file
 [epellocal]
 name=epellocal                       #Set Name
 baseurl=file:///centos7/epel #Set link address, path to/centos7/epel directory
 enabled=1                        #Open this yum source
 gpgcheck=0                       #No need to verify public key

If other hosts want to use the epel repository in this machine, they can build it locally using http or ftp:

 baseurl=http://192.168.72.10/centos7/epel //http mode
 ​
 baseurl=ftp://192.168.72.10/centos7/epel //ftp mode

5 Tips

5.1 Generate warehouse files by command

The above four methods are all configured by manually writing the yum warehouse file or by command.

Commands are written/etc/yum, just like the file configuration above. Repos. D, only the command line is to automatically generate the warehouse file.

1. Setting up external network environment

Command format:

 wget -O  /etc/yum.repos.d/name.repo(Customize to repo End File Name) Source Path

The wget command configures the Ali Cloud Warehouse:

 wget -O  /etc/yum.repos.d/Centos-7.repo  http://mirrors.aliyun.com/repo/Centos-7.repo

2. Build the internal network environment

Command format:

 yum-config-manager --add-repo=file://
 yum-config-manager --add-repo=ftp://

Example:

 yum-config-manager --add-repo=file:///mnt //Use local source
 yum-config-manager --add-repo=ftp://192.168.72.10/centos7//ftp mode build

5.2 Download dependent packages locally (but do not install)

When a host on the internal network installs a package but lacks a dependent package, the dependent package can be downloaded by a server that can connect to the external network and shared with the host.

You can then use the command "yum install--downloadonly", which can download only the required software and its dependent packages without installing the software, greatly reducing the problem of finding dependent packages when installing without an external network. The command format is as follows:

 yum install --downloadonly +Software Name --downloaddir=Appoint rpm Package Storage Path

For example, the dependent packages needed to download nginx are in the / mnt/nginx directory:

 yum install nginx --downloadonly --downloaddir=/mnt/nginx

This article is from: https://juejin.cn/post/7078172295302217735