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g2boojum |
1.1 |
GLEP: 9 |
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Title: Gentoo Package Update System |
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g2boojum |
1.3 |
Version: $Revision: 1.2 $ |
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Last-Modified: $Date: 2003/07/25 22:32:20 $ |
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g2boojum |
1.1 |
Author: John J. Whitney <jjw@linuxmail.org> |
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g2boojum |
1.3 |
Status: deferred |
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g2boojum |
1.1 |
Type: Standards Track |
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Content-Type: text/x-rst |
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Created: 19-Jul-2003 |
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Post-History: 25-Jul-2003 |
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Abstract |
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======== |
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This document proposes an official package updating system for Gentoo Linux. |
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The Deltup project has been developed for this purpose. [#DELTUP]_ |
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As packages grow larger the amount of redundant data keeps increasing. Updating |
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existing tarballs by patching is the natural way to handle source updates. |
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Motivation |
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========== |
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This system will reduce mirror loads (potentially mirror size as well) and |
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significantly speed up downloads, making Gentoo much more attractive for users |
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with low-bandwidth connections. |
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Server Implementation |
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===================== |
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I propose that the patches be put onto the Gentoo Mirrors and stored in a new |
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directory called "patchfiles" which could be placed beside "distfiles". |
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It would be advantageous to have a list of available patches within the portage |
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tree so that it can be updated during "emerge sync". A file named "dtu.list" |
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can be created and placed in $PORTDIR/profiles. |
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If a machine can be set up to generate patches it should contain a local mirror |
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of distfiles which it can monitor for added packages. When a package is added |
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to distfiles the machine can try to determine the previous tarball so a patch |
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can be made and placed in the patchfiles dir. In addition, special-case patches |
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can be added manually. |
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The dtu.list file will be maintained by a special script. Whenever patches |
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are added or removed to the patchfiles dir, the script will make necessary |
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additions/removals in dtu.list. This will be done with minimal changes in the |
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file so it can be synchronized efficiently. |
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Client Implementation |
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===================== |
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The system will be optional for users and can be enabled by making portage |
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invoke efetch through the FETCHCOMMAND environment variable [#TINYHOWTO]_. |
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When a package fetch is requested, the efetch/fetchcommand scripts (part of |
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Deltup) will scan the dtu.list file for updates and try downloading and applying |
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them if they exist, or fall back to a full package download if they don't or if |
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the patching process fails. |
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Rationale |
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========= |
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The most controversial feature has been the addition of dtu.list to the portage |
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tree, so in this section I will list the reasons I support it. |
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- Flexibility. Without it, there must be a standard naming scheme which we |
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would be stuck with once the system is in place. Changing the system would |
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require serious compatibility breaks. With the dtu.list file we can change |
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the naming scheme easily without problems, or even have several different |
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naming schemes. |
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- Features. Without patch information detecting different upgrade paths would |
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be impossible. Split package patching would also be impossible. If the info |
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is available we can use it to find the quickest upgrade path, like jumping |
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from a .0 release, or even disable certain patches if there are problems with |
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them. |
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- It would be impossible to know which packages to upgrade from in some cases, |
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including renamed packages. |
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- Knowing which patches are available will eliminate the overhead of attempting |
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to download patches which don't exist. |
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The dtu.list file will contain several hundred kilobytes of data. That has |
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caused some concern over how efficiently it can be rsynced. To address these |
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concerns the file's format will be plaintext and care has been taken to |
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minimize the number of changes as removals/additions are made. |
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Backwards Compatibility |
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======================= |
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There are no backwards compatibility issues since Deltup can generate correct |
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package MD5sums. |
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Conclusion |
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========== |
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I suggest we start with a scaled-down implementation and provide more as the |
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demand increases. All of the necesary code is already written and working in |
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non-official tests. |
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References |
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========== |
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.. [#DELTUP] http://sourceforge.net/projects/deltup |
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.. [#PATCHES] ftp://sunsite.dk/projects/deltup/patchfiles |
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.. [#TINYHOWTO] Tiny Deltup HOWTO |
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(http://www.thedoh.com/linux/HOWTO/deltup) |
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Copyright |
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========= |
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This document has been placed in the public domain. |
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