I am curious to know about the apt code so that I can contribute to this project and learn from it.
I have a question on "apt-get update" implementation. I did go through the code for a couple of days but couldn't get full clarity so need your help. /var/lib/apt/lists - This contains two kinds of files. One set of files (* _Packages) that has the full package information with the short description. Another set of files (* _i18n_Translation-en) has just the full description for all the packages. /var/cache/apt/ - This directory has two different caches (pkgcache.bin, srcpkgcache.bin). These are constructed from the information stored in the /var/lib/apt/lists directory. *Here are my questions,* 1. How does apt-cache create and updates the local package cache? Is it periodic or manual? As far as my investigation, it is manual (apt-get update). fyi, I am using Linux 4.4.0-18362-Microsoft. "apt-config dump" command output doesn't show "APT::Cache::Generate". 1. When we run "apt-get update", does it download all the packages information that will be stored in /var/lib/apt/lists/* _Packages file? Is there a advanced logic, where client sends current state information (like all packageNames and their versions)? This is a puzzle as the code is very cryptic to understand. I modified /var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_xenial-security_restricted_binary-amd64_Packages (changed the version for one of the package) and ran "apt-get update" but it didn't revert my change. Why? This confirms, apt-get is looking at someother file to make the decision to update the /var/lib/apt/lists/* _Packages file. When does the /var/lib/apt/lists/* _Packages file gets updated? Can you explain whether it's expected behavior or not. I did notice that the /var/cache/apt/pkgcache.bin (and srcpkgcache.bin) are updated everytime I run "apt-get update". 1. What goes into pkgcache.bin and srcpkgcache.bin? I couldn't find any useful information in the internet. 2. Why do we store the package full description in a different file? Is it because we want make cache faster that has only the short package description?
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