Il y a plein de méthodes pour trouver le nom du paquet dont tu as besoin.
Pour chercher un mot dans le nom du paquet :
$ aptitude search pstricks
p texlive-pstricks - TeX Live: PSTricks packages
p texlive-pstricks-doc - TeX Live : Fichiers de documentation pour
Pour chercher un mot dans le nom du paquet ou dans sa description :
$ apt-cache search pstricks
dot2tex - Graphviz to LaTeX converter
latexdraw - vector drawing program for LaTeX using PSTricks
pgf - TeX Portable Graphic Format
sketch - 3D diagrams for TeX from scene description language
sketch-doc - Extra documentation for the sketch 3D line drawing system
texlive-pictures - TeX Live: Graphics packages and programs
texlive-xetex - TeX Live: XeTeX packages
texlive-doc-de - TeX Live: German documentation
texlive-doc-en - TeX Live: English documentation
texlive-games - TeX Live: Games typesetting
texlive-pstricks - TeX Live: PSTricks packages
texlive-pstricks-doc - TeX Live : Fichiers de documentation pour texlive-pstricks
Pour savoir quel paquet contient un fichier donné (là j’ai utilisé une syntaxe un peu particulière car sinon il me renvoyait des milliers de résultats, la syntaxe normale serait plutôt apt-file search pstricks) :
$ apt-file -x search 'pstricks$'
texlive-pstricks: /usr/share/lintian/overrides/texlive-pstricks
Et bien entendu en dernier recours l’inévitable encrypted.google.com/search?hl= … n+pstricks 
(edit : comme Clochette l’a si bien fait remarquer 
mais moi je préfère chercher d’abord dans le cache apt, chacun son truc)
Ensuite quand tu as identifié un nom de paquet intéressant, pour vérifier que c’est bien ce que tu veux il te suffit d’afficher sa description complète :
$ aptitude show texlive-pstricks
Paquet : texlive-pstricks
État: non installé
Version : 2012.20120611-1
Priorité : optionnel
Section : tex
Responsable : Debian TeX Maintainers <debian-tex-maint@lists.debian.org>
Architecture : all
Taille décompressée : 33,2 M
Dépend: dpkg (>= 1.14.18), tex-common (>= 3), texlive-base (>= 2012.20120516), texlive-binaries (>= 2012-0), texlive-common (>= 2012.20120516), texlive-generic-recommended (>= 2012.20120516)
Recommande: texlive-extra-utils, texlive-font-utils, ps2eps, texlive-pstricks-doc
Description : TeX Live: PSTricks packages
This package includes the following CTAN packages:
auto-pst-pdf -- Wrapper for pst-pdf (with some psfrag features).
bclogo -- Creating colourful boxes with logos.
makeplot -- Easy plots from Matlab in LaTeX.
pdftricks -- Support for pstricks in pdfTeX.
pedigree-perl -- Generate TeX pedigree files from CSV files.
psbao -- Draw Bao diagrams.
pst-2dplot -- A PSTricks package for drawing 2D curves.
pst-3d -- A PSTricks package for tilting and other pseudo-3D tricks.
pst-3dplot -- Draw 3d curves and graphs using PSTricks.
pst-abspos -- Put objects at an absolute position.
pst-am -- Simulation of modulation and demodulation.
pst-asr -- Typeset autosegmental representations for linguists.
pst-bar -- Produces bar charts using pstricks.
pst-barcode -- Print barcodes using PostScript.
pst-bezier -- Draw Bezier curves.
pst-blur -- PSTricks package for "blurred" shadows.
pst-bspline -- Draw cubic Bspline curves and interpolations.
pst-calendar -- Plot calendars in "fancy" ways.
pst-circ -- PSTricks package for drawing electric circuits.
pst-coil -- A PSTricks package for coils, etc.
pst-cox -- Drawing regular complex polytopes with PSTricks.
pst-dbicons -- Support for drawing ER diagrams.
pst-diffraction -- Print diffraction patterns from various apertures.
pst-electricfield -- Draw electric field and equipotential lines with
PStricks.
pst-eps -- Create EPS files from PSTricks figures.
pst-eucl -- Euclidian geometry with pstricks.
pst-exa -- Typeset PSTricks examples, with code.
pst-fill -- Fill or tile areas with PSTricks.
pst-fr3d -- Draw 3-dimensional framed boxes using PSTricks.
pst-fractal -- Draw fractal sets using PSTricks.
pst-fun -- Draw "funny" objects with PSTricks.
pst-func -- PSTricks package for plotting mathematical functions.
pst-gantt -- Draw GANTT charts with pstricks.
pst-geo -- Geographical Projections
pst-ghsb --
pst-gr3d -- Three dimensional grids with PSTricks.
pst-grad -- Filling with colour gradients, using PStricks.
pst-graphicx -- A pstricks-compatible graphicx for use with Plain TeX.
pst-infixplot -- Using pstricks plotting capacities with infix expressions
rather than RPN
pst-jtree -- Typeset complex trees for linguists.
pst-knot -- PSTricks package for displaying knots.
pst-labo -- Draw objects for Chemistry laboratories.
pst-layout -- Page layout macros based on PStricks packages.
pst-lens -- Lenses with PSTricks.
pst-light3d -- 3D lighting effects for pstricks.
pst-magneticfield -- Plotting a magnetic field with PSTricks.
pst-math -- Enhancement of PostScript math operators to use with pstricks
pst-mirror -- Images on a spherical mirror.
pst-node -- Draw connections using pstricks.
pst-ob3d -- Three dimensional objects using PSTricks.
pst-optexp -- Drawing optical experimental setups.
pst-optic -- Drawing optics diagrams.
pst-osci -- Oscgons with PSTricks.
pst-pad -- Draw simple attachment systems with PSTricks.
pst-pdgr -- Draw medical pedigrees using pstricks.
pst-platon -- Platonic solids in PSTricks.
pst-plot -- Plot data using PSTricks.
pst-poly -- Polygons with PSTricks.
pst-pulley -- Plot pulleys, using pstricks.
pst-qtree -- Simple syntax for trees.
pst-rubans -- Draw three-dimensional ribbons.
pst-sigsys -- Support of signal processing-related disciplines.
pst-slpe -- Sophisticated colour gradients.
pst-solarsystem -- Plot the solar system for a specific date.
pst-spectra -- Draw continuum, emission and absorption spectra with
PSTricks.
pst-solides3d -- Draw perspective views of 3D solids.
pst-soroban -- Draw a Soroban using PSTricks.
pst-stru -- Civil engineering diagrams, using pstricks.
pst-support -- Assorted support files for use with PStricks.
pst-text -- Text and character manipulation in PSTricks.
pst-thick -- Drawing very thick lines and curves.
pst-tools -- PStricks support functions.
pst-tree -- Trees, using pstricks.
pst-tvz -- Draw trees with more than on root node, using PSTricks.
pst-uml -- UML diagrams with PSTricks.
pst-vowel -- Enable arrows showing diphthongs on vowel charts.
pst-vue3d -- Draw perspective views of three dimensional objects.
pst2pdf -- A script to compile pstricks documents via pdftex.
pstricks -- PostScript macros for TeX.
pstricks-add -- A collection of add-ons and bugfixes for PSTricks.
pstricks_calcnotes --
uml -- UML diagrams in LaTeX.
vaucanson-g -- PSTricks macros for drawing automata
vocaltract -- Visualise the vocal tract using LaTeX and PStricks.
Site : http://www.tug.org/texlive/
Je crois que là j’ai répondu à tes deux questions à la fois…
que celui-ci contient l’extension 
que celui-ci contient l’extension 
