Fred Ringwald <f...@ringwald.org> wrote: > Yesterday Sven Hartge responded to my query regarding rsync, quoted > below.
> However, my question was not a technical question asking why rsync was > not automatically installed during a stock amd64 debian installation, > but a more philosophical question as to why the debian administrators > chose to make rsync optional, given the importance of backup data. This is defined by the debian Policy https://www.debian.org/doc/debian-policy/. For your question "3.7 Base system", "3.8 Essential packages" and "2.5 Priorities" are relevant: ,---- | 3.7. Base system | | The base system is a minimum subset of the Debian system that is | installed before everything else on a new system. Only very few packages | are allowed to form part of the base system, in order to keep the | required disk usage very small. | | The base system consists of all those packages with priority required or | important. Many of them will be tagged essential (see below). `---- ,---- | 3.8. Essential packages | | 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 the “Unpacked” state. Packages are tagged essential for a system | using the Essential control field. The format of the Essential control | field is described in Essential. | | Since these packages cannot be easily removed (one has to specify an | extra force option to dpkg to do so), this flag must not be used unless | absolutely necessary. A shared library package must not be tagged | essential; dependencies will prevent its premature removal, and we need | to be able to remove it when it has been superseded. | | Since dpkg will not prevent upgrading of other packages while an | essential package is in an unconfigured state, all essential packages | must supply all of their core functionality even when unconfigured. If | the package cannot satisfy this requirement it must not be tagged as | essential, and any packages depending on this package must instead have | explicit dependency fields as 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 mailing list and a consensus about doing that has | been reached. `---- With that definition: No, rsync is not an essential part of a minimal Debian system. Now on to "2.5 Priorities": ,---- | 2.5. Priorities | | Each package must have a priority value, which is set in the metadata | for the Debian archive and is also included in the package’s control | files (see Priority). This information is used to control which packages | are included in standard or minimal Debian installations. | | Most Debian packages will have a priority of optional. Priority levels | other than optional are only used for packages that should be included | by default in a standard installation of Debian. | | The priority of a package is determined solely by the functionality it | provides directly to the user. The priority of a package should not be | increased merely because another higher-priority package depends on it; | instead, the tools used to construct Debian installations will correctly | handle package dependencies. In particular, this means that C-like | libraries will almost never have a priority above optional, since they | do not provide functionality directly to users. However, as an | exception, the maintainers of Debian installers may request an increase | of the priority of a package to resolve installation issues and ensure | that the correct set of packages is included in a standard or minimal | install. | | The following priority levels are recognized by the Debian package | management tools. | | required | Packages which are necessary for the proper functioning of the system | (usually, this means that dpkg functionality depends on these packages). | Removing a required package may cause your system to become totally | broken and you may not even be able to use dpkg to put things back, so | only do so if you know what you are doing. | | Systems with only the required packages installed have at least enough | functionality for the sysadmin to boot the system and install more | software. | | important | Important programs, including those which one would expect to find on | any Unix-like system. If the expectation is that an experienced Unix | person who found it missing would say “What on earth is going on, where | is foo?”, it must be an important package. [5] Other packages without | which the system will not run well or be usable must also have priority | important. This does not include Emacs, the X Window System, TeX or any | other large applications. The important packages are just a bare minimum | of commonly-expected and necessary tools. | standard | These packages provide a reasonably small but not too limited | character-mode system. This is what will be installed by default if the | user doesn’t select anything else. It doesn’t include many large | applications. | | No two packages that both have a priority of standard or higher may | conflict with each other. | | optional | This is the default priority for the majority of the archive. Unless a | package should be installed by default on standard Debian systems, it | should have a priority of optional. Packages with a priority of optional | may conflict with each other. | extra | This priority is deprecated. Use the optional priority instead. This | priority should be treated as equivalent to optional. | | The extra priority was previously used for packages that conflicted with | other packages and packages that were only likely to be useful to people | with specialized requirements. However, this distinction was somewhat | arbitrary, not consistently followed, and not useful enough to warrant | the maintenance effort. | | [1] The Debian archive software uses the term “component” internally | and in the Release file format to refer to the division of an archive. | The Debian Social Contract simply refers to “areas.” This document uses | terminology similar to the Social Contract. | [2] See What Does Free Mean? for more about what we mean by free | software. | [3] Debian’s FTP Masters publish a REJECT-FAQ which details the | project’s current working interpretation of the DFSG. | [4] It is possible that there are policy requirements which the | package is unable to meet, for example, if the source is unavailable. | These situations will need to be handled on a case-by-case basis. | [5] This is an important criterion because we are trying to produce, | amongst other things, a free Unix. `---- Now, is rsync required for the proper functioning of the system? No. Is it important? No, it is not inside the bare minimum of commonly-expected and necessary tools. Is it standard? Debatably. rsync would be installed by default if it was. But does everybody *need* rsync? No. Thus the package is optional. You say: "given the importance of backup data". OK, but is rsync the *only* way to backup data? I for example use Bacula and Borg to secure my data, I have no need for rsync. Why should it be installed on every system if only users really using it need it. This is why most packages are "Priority: optional", so they only get installed if needed. Grüße, Sven. -- Sigmentation fault. Core dumped.
