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new glep

1 GLEP: 22
2 Title: New "keyword" system to incorporate various userlands/kernels/archs
3 Version: $Revision: 1.1 $
4 Last-Modified: $Date: 2004/02/22 02:09:07 $
5 Author: Grant Goodyear <g2boojum@gentoo.org>
6 Status: Draft
7 Type: Standards Track
8 Content-Type: text/x-rst
9 Created: 6-Mar-2004
10 Post-History: 6-Mar-2004
12 Credits
13 =======
15 This GLEP originated from the concerns that Daniel Robbins had with
16 the *x86obsd* keyword, and his desire to make the KEYWORDS variable more
17 "feature-rich". Drobbins' original idea was that we should
18 allow compound
19 keywords such as gnu/x86, gnu/ppc, and macos/ppc (which would be explicit
20 versions of the more familiar x86, ppc, and macos keywords). Method noted
21 that userland/arch failed to capture the full range of possibilities (what
22 about a GNU userland on a BSD kernel+libc?), and
23 the issue has languished due to a lack of reasonable solutions.
25 Abstract
26 ========
28 As Gentoo branches out to support non-Linux and non-GNU systems (such
29 as Hurd or the \*BSDs), the potential for an "explosion" of possible
30 keywords becomes rather large, since each
31 new userland/kernel/arch/whatever
32 combination would require a new keyword.
33 This GLEP proposes replacing the current
34 KEYWORDS variable with four variables, ARCH, USERNAME, KERNEL, and LIBC,
35 along with sensible defaults to keep the new system manageable.
37 Motivation
38 ==========
40 Since the beginning, Gentoo Linux has been conceived as a "metadistribution"
41 that combines remarkable flexibility with sensible defaults and exceptional
42 maintainablilty. The goal of the Gentoo-Alt_ project has been to extend that
43 flexibility to include systems other than GNU/Linux. For example, the author
44 of this GLEP has been working to create a version_ of Gentoo that uses
45 OpenBSD_ as the underlying kernel, userland, and libc. OpenBSD_ supports
46 a variety of different architectures, so, in principle, we would need a new
47 *openbsd-arch* keyword for each supported architecture. In fact, the situation
48 is even more complicated, because the Gentoo-Alt_ project would eventually
49 like
50 to support the option of "mixing-and-matching" GNU/\*BSD/whatever userlands
51 and libcs irrespective of the underlying kernel. (Debian_, for example
52 has a similar BSD project_, except that they have replaced the
53 BSD userland with a GNU userland.) The net result is that we would need
54 keywords that specified all possible permutations of arch, userland, kernel
55 and libc. Not fun.
57 .. _Gentoo-Alt: http://www.gentoo.org/proj/en/gentoo-alt/index.xml
58 .. _OpenBSD: http://www.openbsd.com
59 .. _version: http://www.gentoo.org/proj/en/gentoo-alt/bsd/index.xml
60 .. _Debian: http://www.debian.org
61 .. _project: http://www.debian.org/ports/netbsd/
63 Specification
64 =============
66 New Variables
67 -------------
69 I suggest that we replace the single KEYWORDS variable in ebuilds
70 with four separate variables: ARCH, USERLAND, LIBC, and KERNEL.
72 ARCH:
73 x86, amd64, cobalt, mips64, arm, hppa, ia64, ppc64, sparc
75 gnu, bsd
76 LIBC:
77 glibc, openbsd, freebsd, netbsd, macosx
79 linux, selinux, openbsd, freebsd, netbsd, macosx
81 (The above examples are not meant to be complete. Hurd, for example
82 is not included because I know very little about Hurd.)
83 For each variable the standard "-,-\*,~" prefixes would be allowed.
84 Similarly, `/etc/make.conf` would have ACCEPT_ARCH, ACCEPT_USERLAND,
85 ACCEPT_LIBC, and ACCEPT_KERNEL variables.
87 Reasonable Defaults
88 -------------------
90 To keep this system manageable, we need sensible defaults. An ebuild
91 that has missing USERLAND, KERNEL, or LIBC variables is provided
92 with implicit USERLAND="gnu", KERNEL="linux", and/or LIBC="glibc"
93 variables. However, once a variable is explicitly added (such as
94 KERNEL="openbsd"), the default is no longer assumed. That is,
95 one would need KERNEL="openbsd linux" if the ebuild is stable on
96 both openbsd and linux kernels.
98 The ARCH variable, on the other hand, does *not* have a default, per se.
99 Instead, if no ARCH variable exists then portage would automatically
100 add the ebuild's KEYWORD entries to ARCH. Thus, all current ebuilds
101 would still work without changes, allowing for a gradual transition
102 to the new system as the new variables are needed.
104 Profiles
105 --------
107 Along with an explosion of keywords comes a concomitant explosion
108 of potential profiles. The good news is that profiles show up only
109 in a single directory, so an explosion there is easier to contain.
110 I suggest an arch-kernel-userland-libc-version naming scheme, with
111 the kernel-userland-libc terms defaulting to linux-gnu-glibc if
112 absent. (Yes, Chemists do tend to be fond of systematic naming
113 systems.)
115 One drawback to having a large number of profiles is that maintainance
116 becomes a significant problem. In fact, one could reasonably argue
117 that the current number of profiles is already too many to be
118 easily maintained. One proposal that has been raised to simplify
119 matters is the idea of stackable, or cascading, profiles, so that
120 only differences between profiles would have to be maintained.
122 Rationale
123 =========
125 The proposed new "keywording" system is far from elegant, which is
126 a substantial drawback. On the other hand, it is simple, it requires
127 relatively minor changes (albeit ones that eventually would impact
128 every ebuild in the portage tree), and the changes can be implemented
129 gradually over time.
131 Implementation
132 ==============
134 Implementation of this GLEP would divide into adding
135 Portage functionality to support the new system and
136 modifying ebuilds to
137 comply with the new system.
138 The Portage support involves hacking Portage
139 to assemble and check a four-state
140 arch-userland-kernel-libc variable instead of the simpler
141 KEYWORD variable. One might quibble over algorithmic issues, but
142 the actual concept is pretty straightforward. Rewriting ebuilds,
143 on the other hand, is a massive undertaking. Fortunately, it is
144 also a process that can be done over whatever length of time is
145 required, since "legacy" ebuilds should work with no changes.
148 Backwards Compatibility
149 =======================
151 Backwards compatibility has already been addressed in some detail,
152 with the stated goal being a system that would leave all current
153 ebuilds in a still-functioning state after the portage modifications
154 have been made. However, we are already using an ARCH variable for
155 some arcane purpose in Portage, and that issue would still need to
156 be resolved.
159 Copyright
160 =========
162 This document is licensed under the Creative Commons - Attribution / Share
163 Alike license. (http://creativecommons.org/licenses/by-sa/1.0)

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