mjhjmtu

I'm using Debian in a chroot environment on my android. As I don't use GUI at all, I think it's better to uninstall packages related to GUI to free up space.

1. What can I do to remove all GUI packages?


2. How can I reinstall all those removed packages, if anything breaks
   after the package removal?(optional)

As a response to @Arpit Agarwal's comment, here's a link to debian installation procedure on android.
debian on termux

Reading package lists...
Building dependency tree...
Reading state information...
Package 'libwayland-client0' is not installed, so not removed
The following packages were automatically installed and are no longer required:
 aglfn fontconfig fontconfig-config fonts-dejavu-core fonts-droid-fallback
 fonts-liberation fonts-noto-mono ghostscript gnuplot-data gsfonts
 hicolor-icon-theme imagemagick-6-common info java-common krb5-locales
 libaec0 libamd2 libarpack2 libasound2 libasound2-data libauthen-sasl-perl
 libavahi-client3 libavahi-common-data libavahi-common3 libblas-common
 libblas3 libcamd2 libccolamd2 libcholmod3 libcolamd2 libcups2
 libcupsfilters1 libcupsimage2 libcurl3-gnutls libcxsparse3 libdatrie1
 libdjvulibre-text libdjvulibre21 libdrm-amdgpu1 libdrm-freedreno1
 libdrm-nouveau2 libdrm-radeon1 libdrm2 libedit2 libencode-locale-perl
 libfftw3-double3 libfftw3-single3 libfile-listing-perl libflac8
 libfont-afm-perl libfontconfig1 libfreetype6 libgdk-pixbuf2.0-common
 libgfortran3 libgl1-mesa-dri libglapi-mesa libglib2.0-0 libglib2.0-data
 libglpk40 libgraphite2-3 libgs9 libgs9-common libgssapi-krb5-2 libharfbuzz0b
 libhdf5-100 libhtml-form-perl libhtml-format-perl libhtml-parser-perl
 libhtml-tagset-perl libhtml-tree-perl libhttp-cookies-perl
 libhttp-daemon-perl libhttp-date-perl libhttp-message-perl
 libhttp-negotiate-perl libice6 libijs-0.35 libilmbase12 libio-html-perl
 libio-socket-ssl-perl libjack-jackd2-0 libjbig0 libjbig2dec0 libjpeg62-turbo
 libjxr-tools libjxr0 libk5crypto3 libkeyutils1 libkrb5-3 libkrb5support0
 liblapack3 liblcms2-2 libldap-2.4-2 libldap-common libllvm3.9 liblqr-1-0
 libltdl7 liblua5.1-0 liblwp-mediatypes-perl liblwp-protocol-https-perl
 libmailtools-perl libmetis5 libmng1 libnet-http-perl libnet-smtp-ssl-perl
 libnet-ssleay-perl libnetpbm10 libnghttp2-14 libnspr4 libnss3 libogg0
 libopenblas-base libopenexr22 libopenjp2-7 libopus0 libosmesa6
 libpango-1.0-0 libpangoft2-1.0-0 libpaper-utils libpaper1 libpcsclite1
 libpixman-1-0 libpng16-16 libportaudio2 libqhull7 libqrupdate1
 libqscintilla2-l10n libqt4-dbus libqt4-network libqt4-xml libqtcore4
 libqtdbus4 librtmp1 libsamplerate0 libsasl2-2 libsasl2-modules
 libsasl2-modules-db libsensors4 libsm6 libsndfile1 libssh2-1
 libsuitesparseconfig4 libsz2 libtext-unidecode-perl libthai-data libthai0
 libtiff5 libtimedate-perl libtxc-dxtn-s2tc libumfpack5 liburi-perl
 libvorbis0a libvorbisenc2 libwebp6 libwww-perl libwww-robotrules-perl
 libx11-data libx11-xcb1 libxau6 libxcb-dri2-0 libxcb-dri3-0 libxcb-glx0
 libxcb-present0 libxcb-render0 libxcb-shm0 libxcb-sync1 libxcb1 libxdmcp6
 libxml-libxml-perl libxml-namespacesupport-perl libxml-parser-perl
 libxml-sax-base-perl libxml-sax-expat-perl libxml-sax-perl libxshmfence1
 libzip4 netpbm octave-common octave-info perl-openssl-defaults poppler-data
 psutils qdbus qtchooser qtcore4-l10n shared-mime-info tex-common texinfo ucf
 x11-common xdg-user-dirs
Use 'apt autoremove' to remove them.
The following packages will be REMOVED:
 ca-certificates-java* default-jre-headless* gnuplot-nox* groff* imagemagick*
 imagemagick-6.q16* libaudio2* libcairo2* libfltk-gl1.3* libfltk1.3* libgd3*
 libgdk-pixbuf2.0-0* libgl1-mesa-glx* libgl2ps1* libglu1-mesa*
 libgraphicsmagick++-q16-12* libgraphicsmagick-q16-3* libmagick++-6.q16-7*
 libmagickcore-6.q16-3* libmagickcore-6.q16-3-extra* libmagickwand-6.q16-3*
 liboctave3v5* libpangocairo-1.0-0* libplot2c2* libpstoedit0c2a*
 libqscintilla2-12v5* libqt4-opengl* libqtgui4* libwmf0.2-7* libx11-6*
 libxaw7* libxcursor1* libxdamage1* libxext6* libxfixes3* libxft2* libxi6*
 libxinerama1* libxmu6* libxpm4* libxrender1* libxt6* libxtst6* libxxf86vm1*
 octave* openjdk-8-jre-headless* pstoedit* qt-at-spi*

Need some suggestions regarding which packages can be removed safely without affecting Octave. Otherwise this question can be closed , if the some specific answer can't be given.

On Debian, to remove all GUI packages, you can remove the two libraries used to connect to display servers:

apt purge libx11-6 libwayland-client0

This will remove all packages depending on these libraries. The removals will be logged in the history logs in /var/log/apt, so you can look there if you need to revert a removal.

This might catch some packages which contain both CLI and GUI tools, although in most, if not all, cases those are packaged separately (so that it is possible to have a functional text-only system).

GUI in linux has two parts: server and client. @stephen-kitt's answer mentions only latter.

In order to remove server part, use
apt-get purge x11-common libwayland-server0