Introduction
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 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 dpkg(1) manpage and the
distribution policy.
Unless dselect is run in expert or immediate mode, a help screen
is first displayed when choosing this command from the menu. The
user is 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 '?' key.
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 'I' key toggles a full-screen display of the
packages list, an enlarged view of the package details, or the
equally split screen.
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 'i' key. This alternates between:
- the extended description
- the control information for the installed version
- the control information for the available version
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.
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 'A' key, the display of the
installed and available architecture can be toggled between on an
off. By pressing the 'V' key, the display of the installed and
available version can be toggled between on an off. By pressing
the '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:
Error flag:
empty no error
R serious error, needs reinstallation;
Installed state:
empty not installed;
* fully installed and configured;
- not installed but some config files may remain;
U unpacked but not yet configured;
C half-configured (an error happened);
I half-installed (an error happened).
Current and requested selections:
* marked for installation or upgrade;
- marked for removal, configuration files remain;
= on hold: package will not be processed at all;
_ marked for purge, also remove configuration;
n package is new and has yet to be marked.
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:
p, Up, k move cursor bar up
n, Down, j move cursor bar down
P, Pgup, Backspace scroll list 1 page up
N, Pgdn, Space scroll list 1 page down
^p scroll list 1 line up
^n scroll list 1 line down
t, Home jump to top of list
e, End jump to end of list
u scroll info 1 page up
d scroll info 1 page down
^u scroll info 1 line up
^d scroll info 1 line down
B, Left-arrow pan display 1/3 screen left
F, Right-arrow pan display 1/3 screen right
^b pan display 1 character left
^f pan display 1 character right
Searching and sorting
The list of packages can be searched by package name. This is
done by pressing '/', and typing a simple search string. The
string is interpreted as a regex(7) regular expression. If you
add '/d' to the search expression, dselect will also search in
descriptions. If you add '/i' the search will be case
insensitive. You may combine these two suffixes like this:
'/id'. Repeated searching is accomplished by repeatedly pressing
the 'n' or '\' 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 'o' and 'O'
keys repeatedly. The following nine sort orderings can be
selected:
alphabet available status
priority+section available+priority status+priority
section+priority available+section status+section
Where not listed above explicitly, alphabetic order is used as
the final subordering sort key.
Altering selections
The requested selection state of individual packages may be
altered with the following commands:
+, Insert install or upgrade
=, H hold in present state and version
:, G unhold: upgrade or leave uninstalled
-, Delete remove, but leave configuration
_ remove & purge configuration
When the change request results in one or more unsatisfied
depends or conflicts, 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.
Resolving depends and conflicts
When the change request results in one or more unsatisfied
depends or conflicts, 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, 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 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 'R' key. By pressing the
'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 'U', the selections are again
set to the automatic suggestion values.
Establishing the requested selections
By pressing enter, the currently displayed set of selections is
accepted. If 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, 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 dselect to accept it, press the '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 'X' or 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 '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 enter by accident.
