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1 GLEP: 49
2 Title: Alternative Package Manager requirements
3 Version: $Revision: 2215 $
4 Last-Modified: $Date: 2006-05-20 16:18:10 +0200 (Sat, 20 May 2006) $
5 Author: Paul de Vrieze <pauldv@gentoo.org>,
6 Status: Draft
7 Type: Standards Track
8 Content-Type: text/x-rst
9 Created: 18-May-2006
10 Post-History: 19-May-2006
11
12
13 Abstract
14 ========
15
16 This GLEP describes four classes of package managers. What the requirements for
17 them are, and what support they can receive.
18
19
20 Motivation
21 ==========
22
23 To set a standard that package managers that seek Gentoo project approval and
24 support should adhere to.
25
26
27 Rationale
28 =========
29
30 Currently Portage is showing its age. The code of Portage does not seem to be
31 salvageable for new versions. As of the date of publication, there are two known
32 alternative package managers that claim a level of Portage compatibility. These
33 alternatives are `paludis`_ and `pkgcore`_. Before these alternatives are
34 developed further, a set of rules should be created to level the playing field
35 and ensuring that decisions can be made clearly.
36
37
38 Backwards Compatibility
39 =======================
40
41 Not a problem for this GLEP. There is no previous standard as the issue did not
42 exist before. This GLEP is to prevent future compatibility issues.
43
44
45 Categories of package managers
46 ==============================
47
48 We distinguish four categories of package managers. While a package manager can
49 transition from one category to another, it can not be in two categories at the
50 same time. It can be in a state of transition though.
51
52 *Primary Package Manager*
53 There is one primary package manager. Currently this position is held by
54 Portage. The primary package manager is assigned by the council and all
55 packages in the official tree must be installable by a usable version of the
56 primary package manager.
57
58 *Candidate Primary Package Managers*
59 A candidate Primary Package Manager does aim, or show an aim, at replacing
60 the current primary package manager. At a point where the package manager is
61 deemed stable a decision must be made whether this package manager should
62 become the new primary package manager. At that point the `Primary package
63 manager transition phase`_ starts.
64
65 *Secondary Package Managers*
66 A secondary package manager is a package manager that coexists with the
67 primary package manager, while not aiming to replace it. Examples of package
68 managers that would fall into this category are:
69
70 - Experimental package managers. Package managers whose purpose it is to try
71 out new features.
72
73 - Focused package managers. For example a package manager that allows the
74 use of RPM formatted binary packages would be an example.
75
76 - Alternate package managers. Package managers that aim to coexist with the
77 primary package manager. They might for example offer a nicer user
78 interface than the primary package manager (e.g. show a cow instead of
79 compilation messages).
80
81
82 *Third Party Package Managers*
83 A third party package manager is any package manager that lacks recognition
84 from Gentoo as being in any other category. A third party package manager may
85 or may not have a Gentoo package, but is not supported beyond that.
86
87
88 Package manager requirements
89 ============================
90
91 As a package manager is in a state of higher support there are higher
92 requirements to it. The purpose of these requirements is to ensure the unity of
93 the distribution and the package tree. For this purpose it is needed that there
94 is only one primary package manager.
95
96
97 Primary package manager requirements
98 ------------------------------------
99
100 The primary package manager is the package manager that sets the standards for
101 the tree. All ebuilds in the tree must function with the primary package
102 manager. As the primary package manager sets the standard it does not have to
103 maintain compatibility with other package managers.
104
105 The primary package manager does however have the responsibility that it must be
106 very stable. The primary package manager must maintain compatibility with old
107 versions of itself for extended periods of time. This compatibility time is set
108 by the council. The suggested time would be one year from the point that there
109 is a compatible stable version for all supported architectures.
110
111 Another compatibility requirement for the primary package manager is a limited
112 forward compatibility. It must always be possible to transition from the
113 unstable version of the primary package manager to a stable version. This may be
114 done either by first introducing reading compatibility for a new format and only
115 having write support later. Another way would be the provision of a conversion
116 tool that ensures that the on disk information maintained by the package manager
117 is supported by the stable package manager.
118
119 The primary package manager is maintained on official Gentoo infrastructure,
120 under control of Gentoo developers.
121
122
123 Candidate primary package manager requirements
124 ------------------------------------------------
125
126 A candidate primary package manager aims to replace the primary package
127 manager. The council is responsible for deciding whether this is done. The
128 requirements are there to ensure that it is actually possible to transition a
129 candidate primary package manager into the primary package manager.
130
131 First of all, there must exist a transition path. This means that the on disk
132 data of the primary package manager can be used by (or converted to a format
133 usable by) the candidate primary package manager.
134
135 Second, there must be a test path. It must be possible for the developers to
136 test out the candidate primary package manager on their working systems. This
137 means that the transition path must exist. This also means that there are no
138 serious obstacles for reverting to the current primary package manager. This
139 reverting must also be usable when it is decided that the candidate will not
140 become primary package manager, for example because serious design flaws or bugs
141 were found. Ideally, the Candidate Primary Package Manager and the Primary
142 Package Manager can be installed simultaneously. If not, clear instructions must
143 be provided for both ways of transitioning.
144
145 Third, there must exist an ebuild test path. It must be possible for package
146 managers to test ebuilds in one tree for both the primary as well as the
147 candidate primary package manager. It is not an issue if this requires a special
148 mode for the candidate primary package manager. It is not an issue either if
149 compatibility can be achieved by having the candidate primary package manager
150 unmerge the package.
151
152 Fourth, there must be support. This means that the package manager is actively
153 maintained under control of Gentoo. If it is not maintained on Gentoo
154 infrastructure, the means must be there to move the package manager, with its
155 change history, to Gentoo infrastructure. This means that it must be maintained
156 on a Gentoo supported versioning system, or on a version system whose history
157 can be converted to a Gentoo supported versioning system.
158
159 Fifth, release capabilities. There must exist automated tools that use the
160 candidate primary package manager to create release media that have similar
161 capabilities as those released using the old primary package manager. The exact
162 requirements are determined by the Release Engineering project, but should not
163 be significantly beyond what is currently implemented using the primary package
164 manager.
165
166
167 Secondary package manager requirements
168 --------------------------------------
169
170 A secondary package manager is a package manager that instead of directly aiming
171 at replacing the current primary package manager as primary package manager aims
172 to cooperate with the primary package manager. As such a secondary package
173 manager does not set the standard on the tree, but follows the standard set by
174 the primary package manager.
175
176 There are two kinds of secondary package managers. The first kind is formed by
177 those that do not maintain their own installed package database, but work with
178 the package database of the primary package manager. While these package
179 managers can put additional information in the database, these entries must
180 remain compatible with the primary package managers. Verification, reference,
181 and deinstallation by the primary package manager must remain functional.
182
183 The second kind is formed by those package managers that maintain their own
184 package database, or a package database incompatible with the primary package
185 manager. To ensure the secondary role of these package managers the support in
186 the tree for these package manager is provided along with restrictions.
187
188 The first restriction is that no packages in the tree must rely on the secondary
189 package manager. While packages may provide a level of support (while being
190 compatible with the primary package manager) this may not result in a
191 significant increase of features. If this were allowed, this would mean that
192 while they technically work with the primary package manager, there would be
193 significant incentive to use the secondary package manager. As the use of this
194 secondary package manager disallows the parallel use of the primary package
195 manager, this would result in users using the secondary package manager as their
196 primary package manager.
197
198 Users are allowed to make their own choices. However by making the tree favour a
199 package manager that is not the primary package manager, this will lead to the
200 secondary package manager becoming the effective primary package manager. As
201 this will be a decision by default instead of a conscious choice by the council,
202 this is an undesirable result.
203
204 There is one exclusion for the restriction of packages that only work with or
205 have significant improvements with the secondary package manager. That is
206 packages that by their nature are only usable with this secondary package
207 manager. An example would be a graphical front-end to the secondary package
208 manager.
209
210 If a secondary package manager works along the primary package manager, but by
211 itself does not have the capabilities of becoming a primary package manager the
212 risks of choice by default are lower. As a result, the council could choose to
213 allow the inclusion of packages that work only or significantly better with this
214 secondary package manager. For example at a point where there is a stable,
215 functional, package manager that can handle RPM format packages, the council
216 could decide to include these packages directly in the tree, instead of using
217 wrapper scripts for those packages that are only provided in the RPM
218 format. Such a decision does imply that the maintainers of the primary package
219 manager must take this secondary package manager into account.
220
221
222 Third party package manager requirements
223 ----------------------------------------
224
225 A third party package manager is just that. It is a package manager without any
226 support within Gentoo. As there is no control by Gentoo over the package manager
227 this means that there are no requirements on the package manager.
228
229 This complete lack of control however also translates to the fact that Gentoo
230 can not make package manager specific changes to support this package
231 manager. Package manager specific means that it is possible to request changes
232 that make the tree more independent of the primary package manager. These
233 changes must however be agnostic of the package manager, and only make it easier
234 to have alternative package managers.
235
236
237 Transition phases
238 =================
239
240 Primary package manager transition phase
241 ----------------------------------------
242
243 A candidate primary package manager can be chosen to become primary package
244 manager. This can only happen by council decision. This decision can only be
245 made when the candidate primary package manager is stable on all stable
246 architectures. (all architectures except experimental ones).
247
248 After the decision has been made to replace the primary package manager, the
249 transition phase starts. The use of the old stable package manager must remain
250 supported for a period of 6 months. This means that core packages must be
251 installable by this package manager. Further the possibility to convert the
252 system automatically to the new primary package manager must be available for at
253 least 18 months, but preferably longer (enable installing the new package
254 manager from the old one).
255
256 During the transition phase packages are allowed in the tree that use the new
257 features of the new primary package manager. While backward compatibility with
258 the previous primary package manager must be maintained a forward compatibility
259 is no longer needed.
260
261
262 Secondary package manager to candidate primary package manager transition
263 -------------------------------------------------------------------------
264
265 The transition from secondary package manager to candidate primary package
266 manager is straightforward. The secondary package manager must satisfy all
267 requirements for a candidate primary package manager. At that point its
268 maintainers can announce that they are changing the status to candidate primary
269 package manager. This allows a greater support from Gentoo in achieving that
270 goal.
271
272
273 Third party to other transition
274 -------------------------------
275
276 When a third party package manager wants to transition into one of the other
277 categories (except primary package manager) it must satisfy all requirements for
278 that category.
279
280
281 References
282 ==========
283
284 .. _paludis: http://paludis.berlios.de/
285 .. _pkgcore: http://gentooexperimental.org/~ferringb/bzr/pkgcore/
286 .. _Open Publication License: http://www.opencontent.org/openpub/
287
288
289 Copyright
290 =========
291
292 This document is copyright 2006 by Paul de Vrieze and licensed under the
293 `Open Publication License`_.

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