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pkg(5): image packaging system
PACKAGES AND GROUPS
To be consistent with the system, following the introduction of the
fault management architecture, each package is named by an FMRI in
the "pkg:" scheme. That is, we have
The publisher is generally expected to be a forward or reverse
domain name identifying the publisher from which a package can be
retrieved. Publishers which cannot be determined to be a domain
name are legitimate, but optional functionality, like automatic
server discovery for a particular publisher, may fail to work.
In the examples that follow, we use "opensolaris.org" as a generic
The pkg_name, like service names, can be split into a category,
subcategories, and a basename. This namespace might be populated
with "manifest" and other metadata endpoints, as well as the SHA-1
names of the package's included files. (Although the direct access
to properties of the svc FMRI scheme has been rarely used.)
A "group package" is a package that depends upon (minimum versions
of) other packages, as well as optionally delivering files or other
actions. An "incorporation" is a group package that places forward
constraints upon the versions of the packages it depends upon, which
restricts the interval of valid package versions to one the author
of the incorporation believes functional.
2.1. Single namespace, separate publishers
The primary design point of the package namespace is to allow
multiple package producers to co-exist in a single namespace, so
that images can switch between equivalent components from different
2.2. Domain-name-based escape
At any point in the category hierarchy, a safe namespace can be
created by using the forward or reverse domain name, either as a
subcategory or as a comma-led prefix to a subcategory or package
base name. (This scheme is similar to FMRI namespace escapes in
smf(5), although we are eliminating use of stock symbol prefixes.)
For instance, when example.com wishes to publish the "whiskers"
package without reference to a larger namespace convention it can
use any of the following examples
and so forth.
2.2. Locally reserved namespace
The top-level "site" category is reserved for use by the entity that
administrates the server. Neither the organizations producing the
operating system nor those providing additional software components
may use the site category.
The top-level "vendor" category is reserved for use by organizations
providing additional. The leading subcategory must be a domain.
That is, if example.com wishes to publish the "whiskers" package in
the vendor category, it would use a package name like
2.3. Additional reserved namespace
The top-level "cluster", "feature", "group", "metacluster", and
"service" categories are all reserved for future use.
Inception note: some or all of these reservations may be eliminated
or reduced when the single namespace convention reaches its final
2.4. Single namespace conventions
Packaging systems and distributions appear to have explicit
categories, subcategories, and potentially larger groups; some
distributions have explicit fields for these values, others use
tagging or multi-valued fields, which allows them to classify
certain packages multiply. For the FMRI namespace case, the system
is similar to a packaging system with multiple, single-valued,
There appear to be two standard approaches to categorizing packages:
1. By what primary class of thing a package delivers.
2. By what area of functionality a package's contents address.
In the first approach, we get strict top-level categories like
"application", "driver", "library", and "system" or "kernel", as
well as potentially overlapping categories like "utility" and
"tool". Use of the leading subcategory is limited, and generally
given to the subsystem involved. A relatively detailed worked
example of the X11 subsystem under this scheme is given in
In the second, we would also see categories like these, but leading
subcategory is much more likely to classify according to
functionality, so that we would see "application/mail",
"application/web", "application/compiler", and so forth. Most
network packaging systems appear to classify in this fashion.
An appealing variation of the second form is to rotate all of the
non-"application" packages under a "system" mega-category, such that
all of the leaf packages (with the possible exception of device
drivers) are exposed at the category level. Table 1 shows some
example transformations under this scheme.
Table 1: Rotating non-application categories under system.