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GLEP updates.

1 GLEP: 22
2 Title: New "keyword" system to incorporate various userlands/kernels/archs
3 Version: $Revision: 1.1 $
4 Last-Modified: $Date: 2004/03/07 02:20:32 $
5 Author: Grant Goodyear <g2boojum@gentoo.org>
6 Status: Withdrawn
7 Type: Standards Track
8 Content-Type: text/x-rst
9 Created: 6-Mar-2004
10 Post-History: 6-Mar-2004
11
12 Status
13 ======
14
15 I'm withdrawing this GLEP. It is clear from the discussions on
16 gentoo-dev that although breaking they keywords into four components
17 is probably a good idea, the four components are *not* independent.
18 Thus, the "keyword explosion" that this GLEP tries to prevent is
19 inevitable. The real issue, then, is how to make the keyword
20 explosion reasonably manageable, but that's a topic for another
21 GLEP.
22
23 Credits
24 =======
25
26 This GLEP originated from the concerns that Daniel Robbins had with
27 the *x86obsd* keyword, and his desire to make the KEYWORDS variable more
28 "feature-rich". Drobbins' original idea was that we should
29 allow compound
30 keywords such as gnu/x86, gnu/ppc, and macos/ppc (which would be explicit
31 versions of the more familiar x86, ppc, and macos keywords). Method noted
32 that userland/arch failed to capture the full range of possibilities (what
33 about a GNU userland on a BSD kernel+libc?), and
34 the issue has languished due to a lack of reasonable solutions.
35
36 Abstract
37 ========
38
39 As Gentoo branches out to support non-Linux and non-GNU systems (such
40 as Hurd or the \*BSDs), the potential for an "explosion" of possible
41 keywords becomes rather large, since each
42 new userland/kernel/arch/whatever
43 combination would require a new keyword.
44 This GLEP proposes replacing the current
45 KEYWORDS variable with four variables, ARCH, USERLAND, KERNEL, and LIBC,
46 along with sensible defaults to keep the new system manageable.
47
48 Motivation
49 ==========
50
51 Since the beginning, Gentoo Linux has been conceived as a "metadistribution"
52 that combines remarkable flexibility with sensible defaults and exceptional
53 maintainablilty. The goal of the Gentoo-Alt_ project has been to extend that
54 flexibility to include systems other than GNU/Linux. For example, the author
55 of this GLEP has been working to create a version_ of Gentoo that uses
56 OpenBSD_ as the underlying kernel, userland, and libc. OpenBSD_ supports
57 a variety of different architectures, so, in principle, we would need a new
58 *openbsd-arch* keyword for each supported architecture. In fact, the situation
59 is even more complicated, because the Gentoo-Alt_ project would eventually
60 like
61 to support the option of "mixing-and-matching" GNU/\*BSD/whatever userlands
62 and libcs irrespective of the underlying kernel. (Debian_, for example
63 has a similar BSD project_, except that they have replaced the
64 BSD userland with a GNU userland.) The net result is that we would need
65 keywords that specified all possible permutations of arch, userland, kernel
66 and libc. Not fun.
67
68 .. _Gentoo-Alt: http://www.gentoo.org/proj/en/gentoo-alt/index.xml
69 .. _OpenBSD: http://www.openbsd.com
70 .. _version: http://www.gentoo.org/proj/en/gentoo-alt/bsd/index.xml
71 .. _Debian: http://www.debian.org
72 .. _project: http://www.debian.org/ports/netbsd/
73
74 Specification
75 =============
76
77 New Variables
78 -------------
79
80 I suggest that we replace the single KEYWORDS variable in ebuilds
81 with four separate variables: ARCH, USERLAND, LIBC, and KERNEL.
82
83 ARCH:
84 x86, amd64, cobalt, mips64, arm, hppa, ia64, ppc64, sparc
85 USERLAND:
86 gnu, bsd
87 LIBC:
88 glibc, openbsd, freebsd, netbsd, macosx
89 KERNEL:
90 linux, selinux, openbsd, freebsd, netbsd, macosx
91
92 (The above examples are not meant to be complete. Hurd, for example
93 is not included because I know very little about Hurd.)
94 For each variable the standard "-,-\*,~" prefixes would be allowed.
95 Similarly, `/etc/make.conf` would have ACCEPT_ARCH, ACCEPT_USERLAND,
96 ACCEPT_LIBC, and ACCEPT_KERNEL variables.
97
98 Reasonable Defaults
99 -------------------
100
101 To keep this system manageable, we need sensible defaults. An ebuild
102 that has missing USERLAND, KERNEL, or LIBC variables is provided
103 with implicit USERLAND="gnu", KERNEL="linux", and/or LIBC="glibc"
104 variables. However, once a variable is explicitly added (such as
105 KERNEL="openbsd"), the default is no longer assumed. That is,
106 one would need KERNEL="openbsd linux" if the ebuild is stable on
107 both openbsd and linux kernels.
108
109 The ARCH variable, on the other hand, does *not* have a default, per se.
110 Instead, if no ARCH variable exists then portage would automatically
111 add the ebuild's KEYWORD entries to ARCH. Thus, all current ebuilds
112 would still work without changes, allowing for a gradual transition
113 to the new system as the new variables are needed.
114
115 Profiles
116 --------
117
118 Along with an explosion of keywords comes a concomitant explosion
119 of potential profiles. The good news is that profiles show up only
120 in a single directory, so an explosion there is easier to contain.
121 I suggest an arch-kernel-userland-libc-version naming scheme, with
122 the kernel-userland-libc terms defaulting to linux-gnu-glibc if
123 absent. (Yes, Chemists do tend to be fond of systematic naming
124 systems.)
125
126 One drawback to having a large number of profiles is that maintainance
127 becomes a significant problem. In fact, one could reasonably argue
128 that the current number of profiles is already too many to be
129 easily maintained. One proposal that has been raised to simplify
130 matters is the idea of stackable, or cascading, profiles, so that
131 only differences between profiles would have to be maintained.
132
133 Rationale
134 =========
135
136 The proposed new "keywording" system is far from elegant, which is
137 a substantial drawback. On the other hand, it is simple, it requires
138 relatively minor changes (albeit ones that eventually would impact
139 every ebuild in the portage tree), and the changes can be implemented
140 gradually over time.
141
142 Implementation
143 ==============
144
145 Implementation of this GLEP would divide into adding
146 Portage functionality to support the new system and
147 modifying ebuilds to
148 comply with the new system.
149 The Portage support involves hacking Portage
150 to assemble and check a four-state
151 arch-userland-kernel-libc variable instead of the simpler
152 KEYWORD variable. One might quibble over algorithmic issues, but
153 the actual concept is pretty straightforward. Rewriting ebuilds,
154 on the other hand, is a massive undertaking. Fortunately, it is
155 also a process that can be done over whatever length of time is
156 required, since "legacy" ebuilds should work with no changes.
157
158
159 Backwards Compatibility
160 =======================
161
162 Backwards compatibility has already been addressed in some detail,
163 with the stated goal being a system that would leave all current
164 ebuilds in a still-functioning state after the portage modifications
165 have been made. However, we are already using an ARCH variable for
166 some arcane purpose in Portage, and that issue would still need to
167 be resolved.
168
169
170 Copyright
171 =========
172
173 This document is licensed under the Creative Commons - Attribution / Share
174 Alike license. (http://creativecommons.org/licenses/by-sa/1.0)

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