# dselect manual page - dselect(1)
#
# Copyright © 1995 Juho Vuori <javuori@cc.helsinki.fi>
# Copyright © 2000 Josip Rodin
# Copyright © 2001 Joost Kooij
# Copyright © 2001 Wichert Akkerman <wakkerma@debian.org>
# Copyright © 2010-2015 Guillem Jover <guillem@debian.org>
#
# This is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

=encoding utf8

=head1 NAME

dselect - Debian package management frontend

=head1 SYNOPSIS

B<dselect>
[I<option>...] [I<command>...]

=head1 DESCRIPTION

B<dselect>
is one of the primary user interfaces for managing packages on a Debian
system.
At the B<dselect> main menu, the system administrator can:

=over

=item *

Update the list of available package versions,

=item *

View the status of installed and available packages,

=item *

Alter package selections and manage dependencies,

=item *

Install new packages or upgrade to newer versions.

=back

B<dselect>
operates as a front-end to L<dpkg(1)>, the low-level Debian package
handling tool.
It features a full-screen package selections manager with package depends
and conflicts resolver.
When run with administrator privileges, packages can be installed,
upgraded and removed.
Various
access methods can be configured to retrieve available package version
information and installable packages from package repositories.
Depending on the used access method, these repositories can be public
archive servers on the internet, local archive servers or media discs.
The recommended access method is I<apt>, which is provided by the
package L<apt(8)>.

Normally B<dselect> is invoked without parameters.
An interactive menu is presented, offering the user a list of commands.
If a command is given as argument, then that command is started immediately.
Several
command line parameters are still available to modify the running behaviour
of B<dselect> or show additional information about the program.

=head1 OPTIONS

All options can be specified both on the command line and in the B<dselect>
configuration file I<%PKGCONFDIR%/dselect.cfg> or the files on the
configuration directory I<%PKGCONFDIR%/dselect.cfg.d/>.
Each line in the
configuration file is either an option (exactly the same as the
command line option but without leading hyphens) or a comment (if it starts
with a ‘B<#>’).

=over

=item B<--admindir> I<directory>

Changes the directory where the dpkg ‘I<status>’,
‘I<available>’ and similar files are located.
Defaults to I<%ADMINDIR%> if B<DPKG_ADMINDIR> has not been set.

=item B<--instdir> I<directory>

Set the installation directory, which refers to the directory where
packages get installed (since dpkg 1.21.2).
Defaults to «I</>» if B<DPKG_ROOT> has not been set.

=item B<--root> I<directory>

Set the root directory to I<directory>, which sets the installation
directory to «I<directory>» and the administrative
directory to «I<directory>%ADMINDIR%» (since dpkg 1.21.0).

=item B<-D>I<file>, B<--debug> I<file>

Turn on debugging.
Debugging information is sent to I<file>.

=item B<--expert>

Turns on expert mode, i.e. doesn't display possibly annoying help
messages.

=item B<--color> I<screenpart>:[I<foreground>],[I<background>][:I<attr>[I<+attr>]...]

=item B<--colour> I<screenpart>:[I<foreground>],[I<background>][:I<attr>[I<+attr>]...]

Configures screen colors.
This works only if your display supports colors.
This option may be used multiple times (and is best used in
I<dselect.cfg>).
Each use changes the color (and optionally, other
attributes) of one part of the screen.
The parts of the screen (from top to bottom) are:

=over

=item B<title>

The screen title.

=item B<listhead>

The header line above the list of packages.

=item B<list>

The scrolling list of packages (and also some help text).

=item B<listsel>

The selected item in the list.

=item B<pkgstate>

In the list of packages, the text indicating the current state of each
package.

=item B<pkgstatesel>

In the list of packages, the text indicating the current state of the
currently selected package.

=item B<infohead>

The header line that displays the state of the currently selected package.

=item B<infodesc>

The package's short description.

=item B<info>

Used to display package info such as the package's description.

=item B<infofoot>

The last line of the screen when selecting packages.

=item B<query>

Used to display query lines

=item B<helpscreen>

Color of help screens.

=back

After the part of the screen comes a colon and the color specification.
You
can specify either the foreground color, the background color, or both,
overriding the compiled-in colors.
Use standard curses color names.

Optionally, after the color specification is another colon, and an
attribute specification.
This is a list of one or more attributes,
separated by plus (‘+’) characters.
Available attributes include (not all of these will work on all terminals):
B<normal>, B<standout>, B<underline>, B<reverse>, B<blink>,
B<bright>, B<dim>, B<bold>

=item B<-?>, B<--help>

Print a brief help text and exit successfully.

=item B<--version>

Print version information and exit successfully.

=back

=head1 COMMANDS

When
B<dselect>
is started it can perform the following commands, either directly if it
was specified on the command line or by prompting the user with a menu
of available commands if running interactively:

=head2 access

Choose and configure an access method to access package repositories.

By default, B<dselect> provides several methods such
as I<media>, I<file> or I<ftp>, but other
packages may provide additional methods, for example the I<apt> access method
provided by the L<apt(8)> package.

The use of the I<apt> access method is strongly recommended.

=head2 update

Refresh the available packages database.

Retrieves a list of available package versions from the package
repository, configured for the current access method, and update
the dpkg database.
The package lists are commonly provided by the
repository as files named I<Packages> or I<Packages.gz>.
These files can be generated by repository maintainers, using the
program L<dpkg-scanpackages(1)>.

Details of the update command depend on the access method's implementation.
Normally the process is straightforward and requires no user interaction.

=head2 select

View or manage package selections and dependencies.

This is the main function of B<dselect>.
In the select screen,
the user can review a list of all available and installed packages.
When run
with administrator privileges, it is also possible to interactively
change packages selection state.
B<dselect> tracks the implications
of these changes to other depending or conflicting packages.

When a conflict or failed depends is detected, a dependency resolution
subscreen is prompted to the user.
In this screen, a list of conflicting
or depending packages is shown, and for each package listed, the reason
for its listing is shown.
The user may apply the suggestions proposed
by B<dselect>, override them, or back out all the changes, including
the ones that created the unresolved depends or conflicts.

The use of the interactive package selections management screen is
explained in more detail below.

=head2 install

Installs selected packages.

The configured access method will fetch installable or upgradable packages
from the relevant repositories and install these using B<dpkg>.
Depending on the implementation of the access method, all packages can
be prefetched before installation, or fetched when needed.
Some access methods may also remove packages that were marked for removal.

If an error occurred during install, it is usually advisable to run
install again.
In most cases, the problems will disappear or be solved.
If problems persist or the installation performed was incorrect, please
investigate into the causes and circumstances, and file a bug in the
Debian bug tracking system.
Instructions on how to do this can be found
at L<https://bugs.debian.org/> or by reading the documentation
for L<bug(1)> or L<reportbug(1)>, if these are installed.

Details of the install command depend on the access method's implementation.
The user's attention and input may be required during installation,
configuration or removal of packages.
This depends on the maintainer scripts in the package.
Some packages make use of the L<debconf(1)>
library, allowing for more flexible or even automated installation
setups.

=head2 config

Configures any previously installed, but not fully configured packages.

=head2 remove

Removes or purges installed packages, that are marked for removal.

=head2 quit

Quit B<dselect>.

Exits the program with zero (successful) error code.

=head1 PACKAGE SELECTIONS MANAGEMENT

=head2 Introduction

B<dselect>
directly exposes
the administrator to some of the complexities involved with managing
large sets of packages with many interdependencies.
For a user who is
unfamiliar with the concepts and the ways of the Debian package management
system, it can be quite overwhelming.
Although B<dselect> is aimed
at easing package management and administration, it is only instrumental
in doing so and cannot be assumed to be a sufficient substitute for
administrator skill and understanding.
The user is required to
be familiar with the concepts underlying the Debian packaging system.
In case of doubt, consult the L<dpkg(1)> manual page and the distribution
policy.

Unless B<dselect> is run in expert
or immediate mode, a help screen is first displayed when choosing this
command from the menu.
The user is I<strongly> advised to study all of
the information presented in the online help screens, when one pops up.
The online help screens can at any time be invoked with the ‘B<?>’ key.

=head2 Screen layout

The select screen is by default split in a top and a bottom half.
The top half shows a list of packages.
A cursor bar can select an
individual package, or a group of packages, if applicable, by selecting
the group header.
The bottom half of the screen shows some details
about the package currently selected in the top half of the screen.
The type of detail that is displayed can be varied.

Pressing the ‘B<I>’ key toggles a full-screen display of the packages
list, an enlarged view of the package details, or the equally split screen.

=head2 Package details view

The package details view by default shows the extended package description
for the package that is currently selected in the packages status list.
The type of detail can be toggled by pressing the ‘B<i>’ key.
This alternates between:

=over

=item *

the extended description

=item *

the control information for the installed version

=item *

the control information for the available version

=back

In a dependency resolution screen, there is also the possibility of
viewing the specific unresolved depends or conflicts related to the
package and causing it to be listed.

=head2 Packages status list

The main select screen displays a list of all packages known to the Debian
package management system.
This includes packages installed on the system
and packages known from the available packages database.

For every package, the list shows the package's status, priority, section,
installed and available architecture, installed and available versions,
the package name and its short description, all in one line.
By pressing the ‘B<A>’ key, the display of the installed and
available architecture can be toggled between on an off.
By pressing the ‘B<V>’ key, the display of the installed and
available version can be toggled between on an off.
By pressing the ‘B<v>’ key, the package status display is toggled
between verbose and shorthand.
Shorthand display is the default.

The shorthand status indication consists
of four parts: an error flag, which should normally be clear, the
current status, the last selection state and the current selection state.
The first two relate to the actual state of the package, the second pair
are about the selections set by the user.

These are the meanings of the shorthand package status indicator codes:

=over

Error flag:

=over

=item I<empty>   no error

=item B<R>       serious error, needs reinstallation;

=back

Installed state:

=over

=item I<empty>   not installed;

=item B<*>       fully installed and configured;

=item B<->       not installed but some config files may remain;

=item B<U>       unpacked but not yet configured;

=item B<C>       half-configured (an error happened);

=item B<I>       half-installed (an error happened).

=back

Current and requested selections:

=over

=item B<*>       marked for installation or upgrade;

=item B<->       marked for removal, configuration files remain;

=item B<=>       on hold: package will not be processed at all;

=item B<_>       marked for purge, also remove configuration;

=item B<n>       package is new and has yet to be marked.

=back

=back

=head2 Cursor and screen movement

The package selection list and the dependency conflict
resolution screens can be navigated using motion
commands mapped to the following keys:

=over

=over

=item B<p, Up, k>           move cursor bar up

=item B<n, Down, j>         move cursor bar down

=item B<P, Pgup, Backspace> scroll list 1 page up

=item B<N, Pgdn, Space>     scroll list 1 page down

=item B<^p>                 scroll list 1 line up

=item B<^n>                 scroll list 1 line down

=item B<t, Home>            jump to top of list

=item B<e, End>             jump to end of list

=item B<u>                  scroll info 1 page up

=item B<d>                  scroll info 1 page down

=item B<^u>                 scroll info 1 line up

=item B<^d>                 scroll info 1 line down

=item B<B, Left-arrow>      pan display 1/3 screen left

=item B<F, Right-arrow>     pan display 1/3 screen right

=item B<^b>                 pan display 1 character left

=item B<^f>                 pan display 1 character right

=back

=back

=head2 Searching and sorting

The list of packages can be searched by package name.
This
is done by pressing ‘B</>’, and typing a simple search
string.
The string is interpreted as a
L<regex(7)>
regular expression.
If you add ‘B</d>’ to the search expression, dselect will also
search in descriptions.
If you add ‘B</i>’ the search will be case insensitive.
You may combine these two suffixes like this: ‘B</id>’.
Repeated searching is accomplished by repeatedly pressing the
‘B<n>’ or ‘B<\>’ keys, until the wanted package is found.
If the search reaches the bottom of the list, it wraps to the top
and continues searching from there.

The list sort order can be varied by pressing
the ‘B<o>’ and ‘B<O>’ keys repeatedly.
The following nine sort orderings can be selected:

=over

=over

=item B<alphabet>

=item B<priority+section>

=item B<section+priority>

=item B<available>

=item B<available+priority>

=item B<available+section>

=item B<status>

=item B<status+priority>

=item B<status+section>

=back

=back

Where not listed above explicitly, alphabetic order is used as
the final subordering sort key.

=head2 Altering selections

The requested selection state of individual packages may be
altered with the following commands:

=over

=over

=item B<+, Insert>    install or upgrade

=item B<=, H>         hold in present state and version

=item B<:, G>         unhold: upgrade or leave uninstalled

=item B<-, Delete>    remove, but leave configuration

=item B<_>            remove & purge configuration

=back

=back

When the change request results in one or more unsatisfied depends
or conflicts, B<dselect> prompts the user with a dependency resolution
screen.
This will be further explained below.

It is also possible to apply these commands to groups of package
selections, by pointing the cursor bar onto a group header.
The
exact grouping of packages is dependent on the current list ordering
settings.

Proper care should be taken when altering large groups of selections,
because this can instantaneously create large numbers of unresolved
depends or conflicts, all of which will be listed in one dependency
resolution screen, making them very hard to handle.
In practice,
only hold and unhold operations are useful when applied to groups.

=head2 Resolving depends and conflicts

When the change request results in one or more unsatisfied depends
or conflicts, B<dselect> prompts the user with a dependency resolution
screen.
First however, an informative help screen is displayed.

The top half of this screen lists all the packages that will have
unresolved depends or conflicts, as a result of the requested change,
and all the packages whose installation can resolve any of these
depends or whose removal can resolve any of the conflicts.
The bottom half defaults to show the depends or conflicts that
cause the currently selected package to be listed.

When the sublist of packages is displayed initially, B<dselect>
may have already set the requested selection status of some of the
listed packages, in order to resolve the depends or conflicts that
caused the dependency resolution screen to be displayed.
Usually,
it is best to follow up the suggestions made by B<dselect>.

The listed packages' selection state may be reverted to the original
settings, as they were before the unresolved depends or conflicts
were created, by pressing the ‘B<R>’ key.
By pressing the ‘B<D>’ key, the automatic suggestions are reset,
but the change that caused the dependency resolution screen to be prompted
is kept as requested.
Finally, by pressing ‘B<U>’, the selections are again set to the
automatic suggestion values.

=head2 Establishing the requested selections

By pressing B<enter>, the currently displayed set of selections
is accepted.
If B<dselect> detects no unresolved depends as a result
of the requested selections, the new selections will be set.
However, if there are any unresolved depends, B<dselect> will again
prompt the user with a dependency resolution screen.

To alter a set of selections that creates unresolved depends or
conflicts and forcing B<dselect> to accept it, press the ‘B<Q>’
key.
This sets the selections as specified by the user, unconditionally.
Generally, don't do this unless you've read
the fine print.

The opposite effect, to back out any selections change requests and
go back to the previous list of selections, is attained by pressing
the ‘B<X>’ or B<escape> keys.
By repeatedly pressing these
keys, any possibly detrimental changes to the requested package
selections can be backed out completely to the last established
settings.

If you mistakenly establish some settings and wish to revert all the
selections to what is currently installed on the system, press the
‘B<C>’ key.
This is somewhat similar to using the unhold command on all packages,
but provides a more obvious panic button in cases where the user
pressed B<enter> by accident.

=head1 EXIT STATUS

=over

=item B<0>

The requested command was successfully performed.

=item B<2>

Fatal or unrecoverable error due to invalid command-line usage, or
interactions with the system, such as accesses to the database,
memory allocations, etc.

=back

=head1 ENVIRONMENT

=over

=item B<DPKG_ROOT>

If set and the B<--instdir> or B<--root> options have not been specified,
it will be used as the filesystem root directory (since dpkg 1.21.0).

=item B<DPKG_ADMINDIR>

If set and the B<--admindir> or B<--root> option have not been specified,
it will be used as the B<dpkg> database directory (since dpkg 1.21.0).

=item B<HOME>

If set, B<dselect> will use it as the directory from which to read the
user specific configuration file.

=back

=head1 BUGS

The
B<dselect>
package selection interface is confusing to some new users.
Reportedly, it even makes seasoned kernel developers cry.

The documentation is lacking.

There is no help option in the main menu.

The visible list of available packages cannot be reduced.

The built in access methods can no longer stand up to current quality
standards.
Use the access method provided by L<apt(8)>, it is not only not
broken, it is also much more flexible than the built in access methods.

=head1 SEE ALSO

L<dpkg(1)>,
L<apt(8)>,
L<sources.list(5)>,
L<deb(5)>.
