如何才能获得关于包用途的有用且详细的描述？

Question 1

我们重点关注第一个例子：postgresql-contrib

该元包始终依赖于当前支持的 PostgreSQL 数据库贡献包。

这里的关键词是元包。您将在存储库中找到许多元包实例。元包本身实际上不包含任何内容，因此除了它指向的包之外，没有任何内容需要记录。如果您apt-cache show postgresql-contrib再次查看提供的信息，您会注意到那里有一行显示：

依赖: postgresql-contrib-9.5

您需要查看的实际文档包含在此包中。以下是的结果apt-cache show postgresql-contrib-9.5：

Package: postgresql-contrib-9.5
Priority: optional
Section: database
Installed-Size: 1999
Maintainer: Ubuntu Developers <[email protected]>
Original-Maintainer: Debian PostgreSQL Maintainers <[email protected]>
Architecture: amd64
Source: postgresql-9.5
Version: 9.5.6-0ubuntu0.16.04
Depends: postgresql-9.5 (= 9.5.6-0ubuntu0.16.04), libc6 (>= 2.15), libpq5 (>= 9.2~beta3), libselinux1 (>= 2.1.12), libssl1.0.0 (>= 1.0.0), libuuid1 (>= 2.16), libxml2 (>= 2.7.4), libxslt1.1 (>= 1.1.25), zlib1g (>= 1:1.1.4)
Suggests: libdbd-pg-perl
Filename: pool/main/p/postgresql-9.5/postgresql-contrib-9.5_9.5.6-0ubuntu0.16.04_amd64.deb
Size: 446848
MD5sum: a05acc14f59c7d0f98bfc854a90447d7
SHA1: 398b18b8660537ac114eceb1212ff831d911c856
SHA256: 6ef4578df2026a72e9c85715ea112f4077209490beb18e3e715621319d5861f0
Description-en: additional facilities for PostgreSQL
 The PostgreSQL contrib package provides several additional features
 for the PostgreSQL database. This version is built to work with the
 server package postgresql-9.5.  contrib often serves as a testbed for
 features before they are adopted into PostgreSQL proper:
 .
  adminpack      - File and log manipulation routines, used by pgAdmin
  btree_gist     - B-Tree indexing using GiST (Generalised Search Tree)
  chkpass        - An auto-encrypted password datatype
  cube           - Multidimensional-cube datatype (GiST indexing example)
  dblink         - Functions to return results from a remote database
  earthdistance  - Operator for computing the distance (in miles) between
                   two points on the earth's surface
  fuzzystrmatch  - Levenshtein, metaphone, and soundex fuzzy string matching
  hstore         - Store (key, value) pairs
  intagg         - Integer aggregator/enumerator
  _int           - Index support for arrays of int4, using GiST (benchmark
                   needs the libdbd-pg-perl package)
  isn            - type extensions for ISBN, ISSN, ISMN, EAN13 product numbers
  lo             - Large Object maintenance
  ltree          - Tree-like data structures
  oid2name       - Maps OIDs to table names
  pageinspect    - Inspection of database pages
  passwordcheck  - Simple password strength checker
  pg_buffercache - Real time queries on the shared buffer cache
  pg_freespacemap- Displays the contents of the free space map (FSM)
  pg_trgm        - Determine the similarity of text based on trigram matching
  pg_standby     - Create a warm stand-by server
  pgbench        - TPC-B like benchmark
  pgcrypto       - Cryptographic functions
  pgrowlocks     - A function to return row locking information
  pgstattuple    - Returns the percentage of dead tuples in a table; this
                   indicates whether a vacuum is required.
  postgresql_fdw - foreign data wrapper for PostgreSQL
  seg            - Confidence-interval datatype (GiST indexing example)
  sepgsql        - mandatory access control (MAC) based on SELinux
  spi            - PostgreSQL Server Programming Interface; 4 examples of
                   its use:
                   autoinc    - A function for implementing AUTOINCREMENT/
                                IDENTITY
                   insert_username - function for inserting user names
                   moddatetime - Update modification timestamps
                   refint     - Functions for implementing referential
                                integrity (foreign keys).  Note that this is
                                now superseded by built-in referential
                                integrity.
                   timetravel - Re-implements in user code the time travel
                                feature that was removed in 6.3.
  tablefunc      - examples of functions returning tables
  uuid-ossp      - UUID generation functions
  vacuumlo       - Remove orphaned large objects
 .
 PostgreSQL is an object-relational SQL database management system.
Description-md5: 633a4e0645b2b02e72f77a260d0f4030
Homepage: http://www.postgresql.org/
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Origin: Ubuntu
Supported: 5y
Task: postgresql-server

您会注意到实际包的文档更加详细。

Answer

我们重点关注第一个例子：postgresql-contrib

该元包始终依赖于当前支持的 PostgreSQL 数据库贡献包。

这里的关键词是元包。您将在存储库中找到许多元包实例。元包本身实际上不包含任何内容，因此除了它指向的包之外，没有任何内容需要记录。如果您apt-cache show postgresql-contrib再次查看提供的信息，您会注意到那里有一行显示：

依赖: postgresql-contrib-9.5

您需要查看的实际文档包含在此包中。以下是的结果apt-cache show postgresql-contrib-9.5：

Package: postgresql-contrib-9.5
Priority: optional
Section: database
Installed-Size: 1999
Maintainer: Ubuntu Developers <[email protected]>
Original-Maintainer: Debian PostgreSQL Maintainers <[email protected]>
Architecture: amd64
Source: postgresql-9.5
Version: 9.5.6-0ubuntu0.16.04
Depends: postgresql-9.5 (= 9.5.6-0ubuntu0.16.04), libc6 (>= 2.15), libpq5 (>= 9.2~beta3), libselinux1 (>= 2.1.12), libssl1.0.0 (>= 1.0.0), libuuid1 (>= 2.16), libxml2 (>= 2.7.4), libxslt1.1 (>= 1.1.25), zlib1g (>= 1:1.1.4)
Suggests: libdbd-pg-perl
Filename: pool/main/p/postgresql-9.5/postgresql-contrib-9.5_9.5.6-0ubuntu0.16.04_amd64.deb
Size: 446848
MD5sum: a05acc14f59c7d0f98bfc854a90447d7
SHA1: 398b18b8660537ac114eceb1212ff831d911c856
SHA256: 6ef4578df2026a72e9c85715ea112f4077209490beb18e3e715621319d5861f0
Description-en: additional facilities for PostgreSQL
 The PostgreSQL contrib package provides several additional features
 for the PostgreSQL database. This version is built to work with the
 server package postgresql-9.5.  contrib often serves as a testbed for
 features before they are adopted into PostgreSQL proper:
 .
  adminpack      - File and log manipulation routines, used by pgAdmin
  btree_gist     - B-Tree indexing using GiST (Generalised Search Tree)
  chkpass        - An auto-encrypted password datatype
  cube           - Multidimensional-cube datatype (GiST indexing example)
  dblink         - Functions to return results from a remote database
  earthdistance  - Operator for computing the distance (in miles) between
                   two points on the earth's surface
  fuzzystrmatch  - Levenshtein, metaphone, and soundex fuzzy string matching
  hstore         - Store (key, value) pairs
  intagg         - Integer aggregator/enumerator
  _int           - Index support for arrays of int4, using GiST (benchmark
                   needs the libdbd-pg-perl package)
  isn            - type extensions for ISBN, ISSN, ISMN, EAN13 product numbers
  lo             - Large Object maintenance
  ltree          - Tree-like data structures
  oid2name       - Maps OIDs to table names
  pageinspect    - Inspection of database pages
  passwordcheck  - Simple password strength checker
  pg_buffercache - Real time queries on the shared buffer cache
  pg_freespacemap- Displays the contents of the free space map (FSM)
  pg_trgm        - Determine the similarity of text based on trigram matching
  pg_standby     - Create a warm stand-by server
  pgbench        - TPC-B like benchmark
  pgcrypto       - Cryptographic functions
  pgrowlocks     - A function to return row locking information
  pgstattuple    - Returns the percentage of dead tuples in a table; this
                   indicates whether a vacuum is required.
  postgresql_fdw - foreign data wrapper for PostgreSQL
  seg            - Confidence-interval datatype (GiST indexing example)
  sepgsql        - mandatory access control (MAC) based on SELinux
  spi            - PostgreSQL Server Programming Interface; 4 examples of
                   its use:
                   autoinc    - A function for implementing AUTOINCREMENT/
                                IDENTITY
                   insert_username - function for inserting user names
                   moddatetime - Update modification timestamps
                   refint     - Functions for implementing referential
                                integrity (foreign keys).  Note that this is
                                now superseded by built-in referential
                                integrity.
                   timetravel - Re-implements in user code the time travel
                                feature that was removed in 6.3.
  tablefunc      - examples of functions returning tables
  uuid-ossp      - UUID generation functions
  vacuumlo       - Remove orphaned large objects
 .
 PostgreSQL is an object-relational SQL database management system.
Description-md5: 633a4e0645b2b02e72f77a260d0f4030
Homepage: http://www.postgresql.org/
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Origin: Ubuntu
Supported: 5y
Task: postgresql-server

您会注意到实际包的文档更加详细。

Question 2

从一般用户的角度来看，他们只是知道一个包的名称，他们的主要信息来源是这是做什么的是检查apt-cache show命令。我总是这样做。这是权威的官方的发现包意图的方法。就像man命令了解命令一样。

但是，这不是唯一的方法。当然，还有很多其他方法可以了解软件包。但这些方法并不是一本可以遵循的菜谱式指南。我通常会检查软件包描述的主页。我使用 synaptic 软件包管理，每个软件包描述都有一个链接。这应该会将您带到软件包的主页或（debian 软件包）维护者的页面。

我也用https://packages.ubuntu.com查看内容并找到与该软件包相关的其他链接。您可以从中转到启动板页面，然后找到上游/原始开发人员的链接。如果仍然不确定，您可以联系邮件列表、提问甚至联系开发人员。您可以检查文件列表并查看该软件包包含的内容，然后使用一些搜索来查找它们的作用。

例如，当我postgresql-contrib在 packages.ubuntu.com 中使用包时，我发现此文件列表。现在，只需使用谷歌搜索即可查看这些命令的作用。例如，搜索pg_archivecleanup收益这个结果在 google 中。您应该从那里对软件包的用途有一个非常好的总体了解。了解该命令的另一个非常好的方法是使用man，但如果软件包尚未安装，那么您可能需要使用http://manpages.ubuntu.com/反而。

可能还有其他方法可以找到软件包的用途。Linux 世界中的大多数人都遵循这条路径。话虽如此，如果你问是否有确定的远远超出apt-cache show，或者apt show，那么我会说不。Debian 软件包的描述应该是软件包用途的官方和第一个来源。

Answer