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dselect - Online in the Cloud

Run dselect in OnWorks free hosting provider over Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator

This is the command dselect that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator

PROGRAM:

NAME


dselect - Debian package management frontend

SYNOPSIS


dselect [option...] [command...]

DESCRIPTION


dselect is one of the primary user interfaces for managing packages on a Debian system. At
the dselect main menu, the system administrator can:
- Update the list of available package versions,
- View the status of installed and available packages,
- Alter package selections and manage dependencies,
- Install new packages or upgrade to newer versions.

dselect operates as a front-end to 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 cdroms. The recommended access method is apt, which is provided by the
package apt.

Normally 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 dselect or show additional information about the program.

OPTIONS


All options can be specified both on the command line and in the dselect configuration
file /etc/dpkg/dselect.cfg or the files on the configuration directory
/etc/dpkg/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 ‘#’).

--admindir directory
Changes the directory where the dpkg ‘status’, ‘available’ and similar files are
located. This defaults to /var/lib/dpkg and normally there shouldn't be any need
to change it.

-Dfile, --debug file
Turn on debugging. Debugging information is sent to file.

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

--colour|--color screenpart:[foreground],[background][:attr[+attr]...]
Configures screen colors. This works only if your display supports colors. This
option may be used multiple times (and is best used in 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:

title The screen title.

listhead
The header line above the list of packages.

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

listsel
The selected item in the list.

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

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

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

infodesc
The package's short description.

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

infofoot
The last line of the screen when selecting packages.

query Used to display query lines

helpscreen
Color of help screens.

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): normal, standout, underline, reverse, blink, bright, dim, bold

-?, --help
Print a brief help text and exit successfully.

--version
Print version information and exit successfully.

COMMANDS


When 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:

access
Choose and configure an access method to access package repositories.

By default, dselect provides several methods such as cdrom, multi_cd, nfs, multi_nfs,
harddisk, mounted, multi_mount, floppy or ftp, but other packages may provide additional
methods, eg. the apt access method provided by the apt package.

The use of the apt access method is strongly recommended.

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 Packages or Packages.gz. These files can be
generated by repository maintainers, using the program 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.

select
View or manage package selections and dependencies.

This is the main function of 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. 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 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.

install
Installs selected packages.

The configured access method will fetch installable or upgradable packages from the
relevant repositories and install these using 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
https://bugs.debian.org/ or by reading the documentation for bug(1) or 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 debconf(1) library, allowing for more flexible or even automated installation setups.

config
Configures any previously installed, but not fully configured packages.

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

quit
Quit dselect.

Exits the program with zero (successful) errorcode.

PACKAGE SELECTIONS MANAGEMENT


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 can not 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 Debian Policy manual, contained in the debian-policy package.

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.

ENVIRONMENT


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

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