dpkg maintains some usable information about available packages.
The information is divided in three classes: states, selection
states and flags. These values are intended to be changed mainly
with dselect.
Package states
not-installed
The package is not installed on your system.
config-files
Only the configuration files of the package exist on the
system.
half-installed
The installation of the package has been started, but not
completed for some reason.
unpacked
The package is unpacked, but not configured.
half-configured
The package is unpacked and configuration has been
started, but not yet completed for some reason.
triggers-awaited
The package awaits trigger processing by another package.
triggers-pending
The package has been triggered.
installed
The package is correctly unpacked and configured.
Package selection states
install
The package is selected for installation.
hold A package marked to be on hold is not handled by dpkg,
unless forced to do that with option --force-hold.
deinstall
The package is selected for deinstallation (i.e. we want
to remove all files, except configuration files).
purge The package is selected to be purged (i.e. we want to
remove everything from system directories, even
configuration files).
unknown
The package selection is unknown. A package that is also
in a not-installed state, and with an ok flag will be
forgotten in the next database store.
Package flags
ok A package marked ok is in a known state, but might need
further processing.
reinstreq
A package marked reinstreq is broken and requires
reinstallation. These packages cannot be removed, unless
forced with option --force-remove-reinstreq.
