Fedora & Delta RPMs: the major update system that only downloads what you need

Discussion in 'Fedora' started by CallFreq, Aug 20, 2015.

  1. CallFreq

    CallFreq New Member

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    Hi!
    Compressed updates and even delta updates - the fact you download only the new resources instead of all resources - isn't new. However, I never seen it applied at scale. Well, I should watch one day if Android does it but I don't know yet.

    Until Fedora. Fedora, since some releases, includes Delta RPMs, which basically software packages where you download only what's new in the package. All the already downloaded resources are not downloaded and so you can save something like 30% of download time, just with that.

    The thing is, because it is applied to the package system as whole, all software updates are downloaded that way. I don't know if other RPM-based Linux does it, but I find the idea great. Simple, but great.
    What do you think of it, honestly? Do you already think about improvement?
     
  2. MyDigitalpoint

    MyDigitalpoint Member

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    While it sounds like an interesting concept, I remember to have been doing something similar via Webmin. This is, once installed my distro and then Webmin as control panel, the system used to alert me about software updates and then retrieving the files, installing them and rebooting Apache as needed.

    Correct me if I'm wrong but this Delta updates seems to do the same, right?
     
  3. CallFreq

    CallFreq New Member

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    Well, hm, I don't think so. Delta update is about downloading only some of the files and bundle them with either an already downloaded package on your cache or with your current installation.
    Usually, in the Windows world or even in Ubuntu, when you update, you download the full .exe/.msi/.deb package, then it launches the installation, the installator automatically detects that there's already an installation, it basically replace all the files doesn't matter if they are there already or not, and 85% of the setup is just garbage.

    Fedora rather take like a "diff" of the RPM package, bundle it with a RPM already in cache, and update using the RPM. This allows to do a kind of "fresh install" where all the files gets rewritten I think - useful if one file is buggy - while not using much bandwidth. This isn't a thing about autoupdate, but more about a space and time-saving update.

    The next step could be to store the hash of all installed files and read/compute it. If the hashes doesn't match, it copy again the file on the disk. Otherwise, we save write time - SSDs doesn't like write but don't care about read.
     
  4. MyDigitalpoint

    MyDigitalpoint Member

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    Ah, I see it now. So that certainly it's a different process this of Delta RPMs, what makes them a better alternative because depending on the update made though an EXE file, the process might take more time than the expected and I remember to have suffered system hangs from time to time making me not just rebooting but sometimes having to reinstall a distro if such process resulted in corrupted files.
     

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