From c8b4de2c5044941d11ed0e884436b8ba60974db1 Mon Sep 17 00:00:00 2001 From: Russ Allbery Date: Sat, 5 Jul 2008 13:46:58 -0700 Subject: [PATCH] Clarify the definition and restrictions on Essential Add a brief rationale for Essential to the section on Essential, moving it from an earlier footnote. Say that maintainers should take care in adding any functionality to essential packages because it's very difficult to remove such functionality later, moving some additional text from the earlier footnote. Closes: #479080 --- policy.sgml | 60 +++++++++++++++++++++++++++++++---------------------- 1 file changed, 35 insertions(+), 25 deletions(-) diff --git a/policy.sgml b/policy.sgml index c9bd84f..d0dc2dc 100644 --- a/policy.sgml +++ b/policy.sgml @@ -985,29 +985,23 @@ (see below), and should not do so unless they depend on a particular version of that package.

- Essential is defined as the minimal set of functionality - that must be available and usable on the system even - when packages are in an unconfigured (but unpacked) - state. This is needed to avoid unresolvable dependency - loops on upgrade. If packages add unnecessary - dependencies on packages in this set, the chances that - there will be an unresolvable - dependency loop caused by forcing these Essential - packages to be configured first before they need to be - is greatly increased. It also increases the chances - that frontends will be unable to - calculate an upgrade path, even if one - exists. + Essential is needed in part to avoid unresolvable dependency + loops on upgrade. If packages add unnecessary dependencies + on packages in this set, the chances that there + will be an unresolvable dependency loop + caused by forcing these Essential packages to be configured + first before they need to be is greatly increased. It also + increases the chances that frontends will be unable to + calculate an upgrade path, even if one + exists.

- Also, it's pretty unlikely that functionality from - Essential shall ever be removed (which is one reason why - care must be taken before adding to the Essential - packages set), but packages have been removed - from the Essential set when the functionality moved to a - different package. So depending on these packages - just in case they stop being essential does way - more harm than good. + Also, functionality is rarely ever removed from the + Essential set, but packages have been removed from + the Essential set when the functionality moved to a + different package. So depending on these packages just + in case they stop being essential does way more harm + than good.

@@ -1094,10 +1088,13 @@ Essential packages

- Some packages are tagged essential for a system - using the Essential control file field. - The format of the Essential control field is - described in . + Essential is defined as the minimal set of functionality that + must be available and usable on the system at all times, even + when packages are in an unconfigured (but unpacked) state. + Packages are tagged essential for a system using the + Essential control file field. The format of the + Essential control field is described in .

@@ -1121,6 +1118,19 @@ appropriate.

+

+ Maintainers should take great care in adding any programs, + interfaces, or functionality to essential packages. + Packages may assume that functionality provided by + essential packages is always available without + declaring explicit dependencies, which means that removing + functionality from the Essential set is very difficult and is + almost never done. Any capability added to an + essential package therefore creates an obligation to + support that capability as part of the Essential set in + perpetuity. +

+

You must not tag any packages essential before this has been discussed on the debian-devel -- 2.39.5