doc: apk(8) add FILES section, speak of world constraints

fixes #10969

doc/apk.8.scd

@@ -10,13 +10,18 @@ apk - Alpine Package Keeper
 
 # DESCRIPTION
 
-*apk* manages packages installed on the system. The set of top level packages
-to install is called the _world_ (see *apk-world*(5)). *apk* supports various
-sub-commands to query and manipulate _world_ and local & remote package
+*apk* manages packages installed on the system. The set of top level constraints
+on system packages is called the _world_ (see *apk-world*(5)).
+
+*apk* supports various sub-commands to query and manipulate _world_ and package
 repositories.
 
 All apk commands which modify the database are logged to /var/log/apk.log.
 
+By default apk is non-interactive. See *FILES* or *--interactive* on changing
+this default to be interactive.
+
+
 # COMMANDS
 
 Each command is documented in detail on its manual page.
@@ -259,6 +264,69 @@ The following options are available for all commands which sign files.
 *--sign-key* _KEYFILE_
 	Sign files with the specified _KEYFILE_.
 
+# FILES
+
+*/etc/apk/arch*
+	The CPU architecture for this database. See *apk-package*(5) section
+	on package metadata field *arch* for the list.
+
+*/etc/apk/cache*
+	This is expected to be a symlink to directory what apk will use
+	as package cache. See also *apk-cache*(5) and *apk-cache*(8).
+
+*/etc/apk/commit_hooks.d/\*.pre-commit*++
+*/etc/apk/commit_hooks.d/\*.post-commit*
+	Hook scripts which are executed before or after changes to database are
+	committed. If a pre-commit script returns failure, the commit is aborted.
+
+	If *--no-scripts* or *--no-commit-hooks* option is specified, these
+	hook scripts are not executed.
+
+*/etc/apk/interactive*
+	If this file exists and apk is running on a tty, *--interactive*
+	mode is enabled by default.
+
+*/etc/apk/keys*
+	A directory containing trusted signing keys for apk.
+
+*/etc/apk/protected_paths.d/\*.list*
+	Configuration files to specify how to treat changes to specified
+	directory or file masks.
+
+*/etc/apk/repositories*++
+*/etc/apk/repositories.d/\*.list*
+	Configuration files to specify repositories. See *apk-repositories*(5)
+	for details.
+
+*/etc/apk/world*
+	Top level requirements and constraints on what should be installed.
+	See *apk-world*(5) for details.
+
+*/lib/apk/db/lock*
+	A lock file used to allow only one concurrent write transaction on
+	the system.
+
+*/lib/apk/db/installed*
+	Database of installed packages and their contents.
+
+*/lib/apk/db/scripts.tar*
+	Collection of all package scripts from currently installed packages.
+
+*/lib/apk/db/triggers*
+	List of triggers rules for currently installed packages.
+
+*/lib/apk/db-uvol*
+	Database symlink or a directory with similar structure as */lib/apk/db/*,
+	but which used for package content when managed using OpenWRT *uvol*
+	volume manager.
+
+*/lib/apk/exec*
+	Temporary directory for extraction and execution of package scripts
+	and triggers.
+
+*/var/log/apk.log*
+	Log file for changes done to the system.
+
 # NOTES
 
 This apk has coffee making abilities.