# Deltup

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

Install the xdelta3 package.

## Configuration

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

    /etc/pacman.d/mirrorlist

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

    ## Delta Archlinux.fr
    Server = http://delta.archlinux.fr/$repo/os/$arch
    .....

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

    /etc/pacman.conf

    .....
    # Misc options (all disabled by default)
    #UseSyslog
    ShowSize
    UseDelta
    TotalDownload
    .....

## Comparisons

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.

## Disadvantages

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.

    kdeartwork-kscreensaver-4.6.2-1_to_4.6.3-1-x86_64.delta	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

Category:

- Package management