Como instalar o ambiente de desktop do Xfce?

Eu li este post Como alterno para o Xubuntu? , mas ele me diz para instalar xubuntu-desktop.

Posso instalar o Xfce (apenas)? Quero dizer, não quero instalar nenhum aplicativo que não esteja relacionado à área de trabalho do Xfce, mas que se torne dependente de xubuntu-desktop, como abiword, gthumb, etc. Qual pacote devo instalar?

Clique aqui:

Ou via linha de comando:

sudo apt-get install xfce4

isto é o que você receberá

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libstdc++5 libvncserver0 libaio-dev sysstat ksh expat libelf-dev
Use 'apt-get autoremove' to remove them.
The following extra packages will be installed:
  desktop-base exo-utils gtk2-engines-xfce libexo-1-0 libexo-common libgarcon-1-0 libgarcon-common
  libthunarx-2-0 libxfce4ui-1-0 libxfce4util-bin libxfce4util-common libxfce4util4 libxfconf-0-2
  orage thunar thunar-data thunar-volman xfce-keyboard-shortcuts xfce4-appfinder xfce4-mixer
  xfce4-panel xfce4-session xfce4-settings xfce4-utils xfconf xfdesktop4 xfdesktop4-data xfwm4
  xfwm4-themes xscreensaver
Suggested packages:
  thunar-archive-plugin thunar-media-tags-plugin xfprint4 xfce4-goodies fortunes-mod aumix xli
  xloadimage xfishtank xdaliclock qcam streamer
The following NEW packages will be installed:
  desktop-base exo-utils gtk2-engines-xfce libexo-1-0 libexo-common libgarcon-1-0 libgarcon-common
  libthunarx-2-0 libxfce4ui-1-0 libxfce4util-bin libxfce4util-common libxfce4util4 libxfconf-0-2
  orage thunar thunar-data thunar-volman xfce-keyboard-shortcuts xfce4 xfce4-appfinder xfce4-mixer
  xfce4-panel xfce4-session xfce4-settings xfce4-utils xfconf xfdesktop4 xfdesktop4-data xfwm4
  xfwm4-themes xscreensaver
0 upgraded, 31 newly installed, 0 to remove and 17 not upgraded.
Need to get 19.8 MB of archives.
After this operation, 80.0 MB of additional disk space will be used.
Do you want to continue [Y/n]? 

depois de instalado, saia e escolha xfce desktop - faça login novamente

O xfce pode ser instalado a partir do terminal por padrão, usando o seguinte comando:

sudo apt-get install xfce4

E para instalar os presentes (programas extras, plug-ins e ilustrações), o comando é:

sudo apt-get install xfce4-goodies

Digite sua senha quando solicitado.

Aprecie usar o Xfce!

Em 30/09/2015

Para instalar a versão mais recente do Xfce 4.12 no Ubuntu 14.04 e 15.04:

Abra o terminal e execute os seguintes comandos:

sudo add-apt-repository ppa:xubuntu-dev/xfce-4.12
sudo apt-get update && sudo apt-get dist-upgrade
sudo apt-get install xfce4

Aqui está a saída dos comandos,

ravan@ravan:~$ sudo apt-get install xfce4
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
account-plugin-windows-live libupstart1
Use 'apt-get autoremove' to remove them.
The following extra packages will be installed:
desktop-base exo-utils gtk2-engines-xfce libexo-1-0 libexo-common
libexo-helpers libgarcon-1-0 libgarcon-common libjpeg-progs
libjpeg-turbo-progs libkeybinder0 libthunarx-2-0 libtumbler-1-0
libxfce4ui-1-0 libxfce4ui-common libxfce4ui-utils libxfce4util-bin
libxfce4util-common libxfce4util7 libxfconf-0-2 orage tango-icon-theme
thunar thunar-data thunar-volman tumbler tumbler-common xfce4-appfinder
xfce4-mixer xfce4-notifyd xfce4-panel xfce4-session xfce4-settings
xfce4-volumed xfconf xfdesktop4 xfdesktop4-data xfwm4 xscreensaver
xscreensaver-data xubuntu-icon-theme
Suggested packages:
devhelp sox kdelibs-data thunar-archive-plugin thunar-media-tags-plugin
tumbler-plugins-extra xfce4-goodies xfce4-power-manager gtk3-engines-xfce
fortunes-mod menu xfwm4-themes xfishtank xdaliclock xscreensaver-gl fortune
qcam streamer gdm3 kdm-gdmcompat
Recommended packages:
greybird-gtk-theme
The following NEW packages will be installed:
desktop-base exo-utils gtk2-engines-xfce libexo-1-0 libexo-common
libexo-helpers libgarcon-1-0 libgarcon-common libjpeg-progs
libjpeg-turbo-progs libkeybinder0 libthunarx-2-0 libtumbler-1-0
libxfce4ui-1-0 libxfce4ui-common libxfce4ui-utils libxfce4util-bin
libxfce4util-common libxfce4util7 libxfconf-0-2 orage tango-icon-theme
thunar thunar-data thunar-volman tumbler tumbler-common xfce4
xfce4-appfinder xfce4-mixer xfce4-notifyd xfce4-panel xfce4-session
xfce4-settings xfce4-volumed xfconf xfdesktop4 xfdesktop4-data xfwm4
xscreensaver xscreensaver-data xubuntu-icon-theme
0 upgraded, 42 newly installed, 0 to remove and 6 not upgraded.
Need to get 19.7 MB of archives.
After this operation, 69.3 MB of additional disk space will be used.
Do you want to continue? [Y/n] 

Para desinstalar o PPA:

sudo apt-get install ppa-purge
sudo ppa-purge ppa:xubuntu-dev/xfce-4.12

Prefiro usar a linha de comando, mas você também pode instalar o Xfce a partir do Synaptic, basta digitar "xfce4" na barra de pesquisa, selecionar tudo relacionado ao Xfce e clicar em "Aplicar" para instalar.