It should not be used by package maintainers wishing to understand how dpkg will install their packages. The descriptions of what dpkg does when installing and removing packages are particularly inadequate.
dpkg can also be used as a front-end to dpkg-deb(1). The following are dpkg-deb actions, and if they are encountered, dpkg just runs dpkg-deb with the parameters given to it:
-b, --build,
-c, --contents,
-I, --info,
-f, --field,
-e, --control,
-x, --extract,
-X, --vextract, and
--fsys-tarfile.
Please refer to dpkg-deb(1) for information about these actions.
Installation consists of the following steps:
1. Extract the control files of the new package.
2. If another version of the same package was installed before
the new installation, execute prerm script of the old package.
3. Run preinst script, if provided by the package.
4. Unpack the new files, and at the same time back up the old
files, so that if something goes wrong, they can be restored.
5. If another version of the same package was installed before
the new installation, execute the postrm script of the old
package. Note that this script is executed after the preinst
script of the new package, because new files are written at the same
time old files are removed.
6. Configure the package. See --configure for detailed information about how this is done.
Configuring consists of the following steps:
1. Unpack the conffiles, and at the same time back up
the old conffiles, so that they can be restored if
something goes wrong.
2. Run postinst script, if provided by the package.
Removing of a package consists of the following steps:
1. Run prerm script
2. Remove the installed files
3. Run postrm script
A simpler one-shot command to retrieve and update the available file is dselect update. Note that this file is mostly useless if you don't use dselect but an APT-based frontend: APT has its own system to keep track of available packages.
-b, --build directory [archive|directory]
Build a deb package.
-c, --contents archive
List contents of a deb package.
-e, --control filename [directory]
Extract control-information from a package.
-x, --extract archive directory
Extract the files contained by package.
-X, --vextract archive directory
Extract and display the filenames contained by a
package.
-f, --field archive [control-field...]
Display control field(s) of a package.
--fsys-tarfile archive
Display the filesystem tar-file contained by a
Debian package.
-I, --info archive [control-file...]
Show information about a package.
-l, --list package-name-pattern...
List packages matching given pattern.
-s, --status package-name...
Report status of specified package.
-L, --listfiles package-name...
List files installed to your system from package-name.
-S, --search filename-search-pattern...
Search for a filename from installed packages.
-p, --print-avail package-name...
Display details about package-name, as found in
/var/lib/dpkg/available. Users of APT-based frontends
should use apt-cache show package-name instead.
number description
1 Generally helpful progress information
2 Invocation and status of maintainer scripts
10 Output for each file processed
100 Lots of output for each file processed
20 Output for each configuration file
200 Lots of output for each configuration file
40 Dependencies and conflicts
400 Lots of dependencies/conflicts output
10000 Trigger activation and processing
20000 Lots of output regarding triggers
40000 Silly amounts of output regarding triggers
1000 Lots of drivel about e.g. the dpkg/info dir
2000 Insane amounts of drivel
Force or refuse (no-force and refuse mean the same thing) to do some things. things is a comma separated list of things specified below. --force-help displays a message describing them. Things marked with (*) are forced by default.
Warning: These options are mostly intended to be used by experts only. Using them without fully understanding their effects may break your whole system.
all: Turns on (or off) all force options.
downgrade(*): Install a package, even if newer version of it is already installed.
Warning: At present dpkg does not do any dependency checking on downgrades and therefore will not warn you if the downgrade breaks the dependency of some other package. This can have serious side effects, downgrading essential system components can even make your whole system unusable. Use with care.
configure-any: Configure also any unpacked but unconfigured packages on which the current package depends.
hold: Process packages even when marked "hold".
remove-reinstreq: Remove a package, even if it's broken and marked to require reinstallation. This may, for example, cause parts of the package to remain on the system, which will then be forgotten by dpkg.
remove-essential: Remove, even if the package is considered essential. Essential packages contain mostly very basic Unix commands. Removing them might cause the whole system to stop working, so use with caution.
depends: Turn all dependency problems into warnings.
depends-version: Don't care about versions when checking dependencies.
breaks: Install, even if this would break another package.
conflicts: Install, even if it conflicts with another package. This is dangerous, for it will usually cause overwriting of some files.
confmiss: Always install a missing conffile. This is dangerous, since it means not preserving a change (removing) made to the file.
confnew: If a conffile has been modified always install the new version without prompting, unless the --force-confdef is also specified, in which case the default action is preferred.
confold: If a conffile has been modified always keep the old version without prompting, unless the --force-confdef is also specified, in which case the default action is preferred.
confdef: If a conffile has been modified always choose the default action. If there is no default action it will stop to ask the user unless --force-confnew or --force-confold is also been given, in which case it will use that to decide the final action.
overwrite: Overwrite one package's file with another's file.
overwrite-dir Overwrite one package's directory with another's file.
overwrite-diverted: Overwrite a diverted file with an undiverted version.
architecture: Process even packages with the wrong architecture.
bad-path: PATH is missing important programs, so problems are likely.
not-root: Try to (de)install things even when not root.
bad-verify: Install a package even if it fails authenticity check.
Be sure to give --no-act before the action-parameter, or you might end up with undesirable results. (e.g. dpkg --purge foo --no-act will first purge package foo and then try to purge package --no-act, even though you probably expected it to actually do nothing)
The status file is backed up daily in /var/backups. It can be useful if it's lost or corrupted due to filesystems troubles. The following files are components of a binary package. See deb(5) for more information about them:
To see the entries in /var/lib/dpkg/available of two packages:
dpkg --print-avail elvis vim | less
To search the listing of packages yourself:
less /var/lib/dpkg/available
To remove an installed elvis package:
dpkg -r elvis
To install a package, you first need to find it in an archive or
CDROM. The "available" file shows that the vim package is in section
"editors":
cd /cdrom/pool/main/v/vim
dpkg -i vim_4.5-3.deb
To make a local copy of the package selection states:
dpkg --get-selections >myselections
You might transfer this file to another computer, and install it there
with:
dpkg --clear-selections
dpkg --set-selections <myselections
Note that this will not actually install or remove anything, but just set the selection state on the requested packages. You will need some other application to actually download and install the requested packages. For example, run apt-get dselect-upgrade.
Ordinarily, you will find that dselect(1) provides a more
convenient way to modify the package selection states.