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Delta updates save time and size in downloading and updating the system. Packages that are downloaded will be a sort of "diff" of the new package, which will be used to patch the old package into the new package at the end of the download.


Install the xdelta3 package.


Edit /etc/pacman.d/mirrorlist and add the proper repository:

## Arch Linux repository mirrorlist
## Generated on 2011-03-24

## Delta
Server =$repo/os/$arch

Then edit /etc/pacman.conf uncommenting the option UseDelta:

# Misc options (all disabled by default)


Check before activating the UseDelta option how much we need to download to full update the system.

#  pacman -Syu


 Total Download Size:   416,89 MB
 Total Installed Size:   1933,56 MB

 Proceed with installation? [Y/n]

Choose n and not confirm the update. As shown the package to be downloaded now are 416,89 MB.

After enabling delta, check again for the updates available (now the option UseDelta is enabled):

# pacman -Syu


 Total Download Size:   343,15 MB
 Total Installed Size:   1933,56 MB

 Proceed with installation? [Y/n]

In this way we do not need to download 416,89 MB of packages but only 343,15 MB, so we obtain a shorter time in the update process.


This method isn't fully supported in Arch Linux as opposed to OpenSuSE or Gentoo which use this as standard for their update system. In fact the available delta repository are just a few. The results can be much better if delta have more deltup packages between previous versions in the repositories. For example, in the repository the author uses, there is only -1 version of each package.	2011-May-06 22:35:41	301.8K	 application/octet-stream 
kdeartwork-kscreensaver-4.6.3-1-x86_64.pkg.tar.xz	2011-May-06 08:57:57	589.2K	 application/octet-stream