How to Build a Fast Local Yum Repository on CentOS and Switch to Domestic Mirrors

Setting Up a Local Yum Repository on CentOS

Because the default Yum source in China is slow or inaccessible, a local repository built from the CentOS ISO can greatly improve package installation speed.

1. View the default Yum repository files

[root@kangvcar ~]# ll /etc/yum.repos.d/
total 32
-rw-r--r--. 1 root root 1664 Dec 9 2015 CentOS-Base.repo
-rw-r--r--. 1 root root 1309 Dec 9 2015 CentOS-CR.repo
-rw-r--r--. 1 root root 649 Dec 9 2015 CentOS-Debuginfo.repo
-rw-r--r--. 1 root root 290 Dec 9 2015 CentOS-fasttrack.repo
-rw-r--r--. 1 root root 630 Dec 9 2015 CentOS-Media.repo
-rw-r--r--. 1 root root 1331 Dec 9 2015 CentOS-Sources.repo
-rw-r--r--. 1 root root 1952 Dec 9 2015 CentOS-Vault.repo

2. (Optional) Backup the existing Yum repository files

[root@kangvcar ~]# mkdir /opt/centos-yum.bak
[root@kangvcar ~]# mv /etc/yum.repos.d/* /opt/centos-yum.bak/

3. Mount the CentOS ISO in the virtual machine

[root@kangvcar ~]# mount -t iso9660 /dev/sr0 /opt/centos

4. Create a repo file that points to the mounted directory

[root@kangvcar ~]# vi /etc/yum.repos.d/local.repo
[local]
name=local
baseurl=file:///opt/centos
enabled=1
gpgcheck=0

5. Clean the Yum cache and rebuild it

[root@kangvcar ~]# yum clean all
Loaded plugins: fastestmirror
Cleaning repos: local
Cleaning up everything
Cleaning fastestmirror list
[root@kangvcar ~]# yum makecache   # cache the repository locally
[root@kangvcar ~]# yum list          # shows the number of packages (e.g., 3780)

Switching to Domestic Aliyun Yum Mirrors

Aliyun official tutorial: http://mirrors.aliyun.com/help/centos

1. View the default repository files (same as above)

[root@kangvcar ~]# ll /etc/yum.repos.d/ ...

2. (Optional) Backup the repository files

[root@kangvcar ~]# mkdir /opt/centos-yum.bak
[root@kangvcar ~]# mv /etc/yum.repos.d/* /opt/centos-yum.bak/

3. Download the appropriate Aliyun repo file

# For CentOS 5
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo
# For CentOS 6
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
# For CentOS 7
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

# Verify the system version
cat /etc/redhat-release   # e.g., CentOS Linux release 7.2.1511 (Core)
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

4. Clean the cache again

[root@kangvcar ~]# yum clean all
Loaded plugins: fastestmirror
Cleaning repos: base extras updates
Cleaning up everything
Cleaning fastestmirror list
[root@kangvcar ~]# yum makecache   # cache the Aliyun repo
[root@kangvcar ~]# yum list          # total packages (e.g., 9954)

Switching to Domestic 163 Yum Mirrors

163 official tutorial: http://mirrors.163.com/.help/centos.html

1. View the default repository files

[root@kangvcar ~]# ll /etc/yum.repos.d/ ...

2. (Optional) Backup the repository files

[root@kangvcar ~]# mkdir /opt/centos-yum.bak
[root@kangvcar ~]# mv /etc/yum.repos.d/* /opt/centos-yum.bak/

3. Download the 163 repo file

# For CentOS 5
wget -O /etc/yum.repos.d/CentOS5-Base-163.repo http://mirrors.163.com/.help/CentOS5-Base-163.repo
# For CentOS 6
wget -O /etc/yum.repos.d/CentOS6-Base-163.repo http://mirrors.163.com/.help/CentOS6-Base-163.repo
# For CentOS 7
wget -O /etc/yum.repos.d/CentOS7-Base-163.repo http://mirrors.163.com/.help/CentOS7-Base-163.repo

# Verify version and download
cat /etc/redhat-release   # e.g., CentOS Linux release 7.2.1511 (Core)
wget -O /etc/yum.repos.d/CentOS7-Base-163.repo http://mirrors.163.com/.help/CentOS7-Base-163.repo

4. Clean the cache again

[root@kangvcar ~]# yum clean all
Loaded plugins: fastestmirror
Cleaning repos: base extras updates
Cleaning up everything
Cleaning fastestmirror list
[root@kangvcar ~]# yum makecache   # cache the 163 repo
[root@kangvcar ~]# yum list          # total packages (e.g., 9951)

Setting Yum Repository Priority

When both a local repository and a remote mirror exist, you may want the local repository to be used first. The yum-plugin-priorities plugin can control this behavior.

1. Check whether the priorities plugin is installed

[root@kangvcar ~]# rpm -qa | grep yum-plugin-
# Example output shows yum-plugin-fastestmirror but not yum-plugin-priorities

2. Install the priorities plugin

[root@kangvcar ~]# yum -y install yum-plugin-priorities.noarch

3. Verify that the plugin is enabled

[root@kangvcar ~]# cat /etc/yum/pluginconf.d/priorities.conf
[main]
enabled = 1   # 1 = enabled, 0 = disabled

4. Set a higher priority for the local repository

# Edit /etc/yum.repos.d/local.repo
[local]
name=local
baseurl=file:///opt/centos
enabled=1
gpgcheck=0
priority=1   # lower number = higher priority

5. Test the configuration

# Before setting priority (using Aliyun repo)
[root@kangvcar ~]# yum -y install vim
Dependencies Resolved
... Repository: updates ...

# After setting priority (using local repo)
[root@kangvcar ~]# yum -y install vim
Dependencies Resolved
... Repository: local ...