CentOS and Apt-Cacher-NG

Somebody asked about an equivalent apt-cacher-ng software package for CentOS. While I don’t deal with CentOS any more, professionally or personally, in a previous role as Linux Admin I configured apt-cacher-ng to support CentOS. I claim no originality as the information is available online.

Caching Proxy Server

CentOS is designed to use a mirror list to update packages. The intent is to distribute the download demand across different upstream CentOS servers. This CentOS default does not work well with the caching proxy server because commonly CentOS systems are configured to use mirrors and commonly each individual CentOS system will choose a different mirror. The result is package downloads are duplicated, thereby defeating the purpose of the caching proxy server. To obtain a list of all current CentOS mirrors:

wget https://www.centos.org/download/full-mirrorlist.csv | sed ’s/^.*"http:/http:/’ | sed ’s/.”*$//’ | grep ^http > /etc/apt-cacher-ng/centos_mirrors

Generally this CSV file is downloaded to the caching proxy server at /etc/apt-cacher-ng/centos_mirrors. The caching proxy server is then configured to use this CSV list. This CSV file is useful as a starting template, but in the end only one server is desired. Edit the CSV list to comment out all servers except one.

The /etc/apt-cacher-ng/acng.conf file needs the following modifications to cache CentOS package requests:

    # Allow volatile short caching of results and GPG key retrievals:
    VfilePatternEx: ^(/\?release[0-9]+&arch.*|.*/RPM-GPG-KEY-examplevendor)$
    # Add a remap directive:
    Remap-centos: file:centos_mirrors /centos
    # Allow SSL pass through:
    PassThroughPattern: (mirrors\.fedoraproject\.org|some\.other\.repo|yet\.another\.repo):443

Any time there are changes to the apt-cacher-ng configuration the service must be restarted:

systemctl restart apt-cacher-ng.service

Client Systems

Three configuration options are required.

In /etc/yum/pluginconf.d/fastestmirror.conf, disable the yum fastest mirror plugin:

    [main]
    enabled=0

In /etc/yum.conf, add the caching proxy URL

    [main]
    proxy=http://some_local_proxy_server_ip_address:3142

in /etc/yum.repos.d/CentOS-Base.repo, disable using the built-in mirror system and explicitly update only from a specific server:

    [base]
    #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra
    baseurl=http://centos.mirrors.tds.net/centos/$releasever/os/$basearch/

Before updating any CentOS system using the caching proxy server, delete the package cache data:

yum clean expire-cache

The example shows centos.mirrors.tds.net, but choose an optimal regional server.

Posted: August 02, 2021 Category: Usability Tagged: CentOS

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