command to install build-essential in debian ?

$sudo apt-get install build-essential 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
build-essential is already the newest version (12.4).
The following packages were automatically installed and are no longer required:
  alsa-base ant ant-optional app-install-data aptdaemon aptdaemon-data bluez-alsa bluez-gstreamer bogofilter bogofilter-bdb bogofilter-common cryptsetup-bin diffstat
  esound-common espeak-data evolution-webcal firebird2.5-common-doc fonts-lyx fonts-sil-gentium fonts-sil-gentium-basic freerdp-x11 gcalctool gcc-6-base gdebi
  gdebi-core geoclue geoclue-hostip geoclue-localnet geoclue-manual geoclue-nominatim geoclue-yahoo gir1.2-camel-1.2 gir1.2-clutter-gst-1.0 gir1.2-ebookcontacts-1.2
  gir1.2-edataserver-1.2 gir1.2-folks-0.6 gir1.2-gconf-2.0 gir1.2-gee-0.8 gir1.2-gee-1.0 gir1.2-gkbd-3.0 gir1.2-grilo-0.2 gir1.2-gst-plugins-base-0.10
  gir1.2-gstreamer-0.10 gir1.2-gtop-2.0 gir1.2-javascriptcoregtk-3.0 gir1.2-networkmanager-1.0 gir1.2-nmgtk-1.0 gir1.2-panelapplet-5.0 gir1.2-tracker-0.14
  gir1.2-tracker-1.0 gir1.2-vte-2.90 gir1.2-webkit-3.0 gir1.2-xkl-1.0 glchess glines gnash-common gnect gnibbles gnobots2 gnome-games-data gnome-games-extra-data
  gnome-icon-theme-extras gnome-icon-theme-symbolic gnome-js-common gnome-mag gnome-media gnomine gnotravex gnotski gnuplot-tex gnuplot5-data gnuplot5-qt
  gstreamer0.10-ffmpeg gstreamer0.10-gconf gstreamer0.10-nice gstreamer0.10-plugins-bad gstreamer0.10-plugins-base gstreamer0.10-plugins-good
  gstreamer0.10-plugins-ugly gstreamer0.10-pulseaudio gstreamer0.10-x gtali hexchat-python hplip-data hyphen-en-us icedtea-netx icedtea-netx-common imagemagick-common
  iptraf iptraf-ng libamd2.2.0 libamd2.3.1 libamd2.4.1 libapache-pom-java libappstream3 libapr1 libaprutil1 libaprutil1-dbd-sqlite3 libaprutil1-ldap libapt-pkg-perl
  libasprintf0c2 libass4 libass5 libatk-adaptor-data libatspi1.0-0 libaudiofile1 libavcodec-ffmpeg56 libavcodec53 libavcodec56 libavdevice-ffmpeg56 libavfilter-ffmpeg5
  libavformat-ffmpeg56 libavformat53 libavformat56 libavresample-ffmpeg2 libavresample2 libavutil-ffmpeg54 libavutil51 libavutil54 libbasicusageenvironment1
  libbind9-80 libbind9-90 libblas-common libblas3gf libbluray1 libboost-filesystem1.58.0 libboost-iostreams1.58.0 libboost-program-options1.49.0
  libboost-program-options1.58.0 libboost-program-options1.62.0 libboost-system1.58.0 libboost-thread1.49.0 libbrlapi0.5 libcamd2.3.1 libcamd2.4.1 libcamel-1.2-33
  libcamel-1.2-54 libcamel-1.2-59 libccolamd2.8.0 libccolamd2.9.1 libcdaudio1 libcddb2 libcdio-cdda1 libcdio-paranoia1 libcdio13 libcholmod2.1.2 libcholmod3.0.6
  libchromaprint0 libclutter-gst-1.0-0 libclutter-gst-2.0-0 libclutter-imcontext-0.1-0 libclutter-imcontext-0.1-bin libcluttergesture-0.0.2-0 libcmis-0.2-0
  libcolamd2.7.1 libcolamd2.8.0 libcolamd2.9.1 libcolorblind0 libcolord1 libcommons-beanutils-java libcommons-collections3-java libcommons-compress-java
  libcommons-digester-java libcommons-logging-java libcommons-parent-java libcpufreq0 libcryptsetup4 libcurl3 libdb-java libdb-je-java libdb5.1-java-jni libdb5.3-java
  libdb5.3-java-jni libdbus-1-dev libdconf0 libdevmapper-event1.02.1 libdirac-encoder0 libdirectfb-1.2-9 libdns-export100 libdns100 libdns88 libdotconf1.0
  libdrm-nouveau1a libdvbpsi10 libebackend-1.2-2 libebml4v5 libebook-1.2-16 libecal-1.2-11 libedata-cal-1.2-15 libedataserver-1.2-16 libedataserver-1.2-21 libefivar0
  libepc-1.0-3 libepc-common libepc-ui-1.0-3 libesd0 libespeak1 libevent-2.0-5 libexiv2-12 libfarstream-0.1-0 libffi5 libfftw3-3 libfftw3-long3 libfreerdp-cache1.1
  libfreerdp-client1.1 libfreerdp-codec1.1 libfreerdp-common1.1.0 libfreerdp-core1.1 libfreerdp-crypto1.1 libfreerdp-gdi1.1 libfreerdp-locale1.1
  libfreerdp-plugins-standard libfreerdp-primitives1.1 libfreerdp-rail1.1 libfreerdp-utils1.1 libfwupd1 libgconf2-4 libgd2-xpm libgdata13 libgdiplus libgdu-gtk0
  libgdu0 libgee2 libgeoclue0 libgexiv2-1 libgfortran3 libgif4 libgit2-23 libglew1.7 libgmime-2.6-0 libgnome-bluetooth10 libgnome-mag2 libgnome-media-profiles-3.0-0
  libgnomekbd7 libgnutls-openssl27 libgom-1.0-common libgphoto2-2 libgphoto2-port0 libgrilo-0.1-0 libgrilo-0.2-1 libgroupsock8 libgssglue1
  libgstreamer-plugins-bad0.10-0 libgstreamer-plugins-base0.10-0 libgstreamer0.10-0 libgtkglext1 libgtkhtml-4.0-0 libgtkhtml-4.0-common libgtkhtml-editor-4.0-0
  libgtop-2.0-10 libgtop2-7 libguess1 libgupnp-dlna-1.0-2 libgweather-3-0 libhsqldb-java libhttp-parser2.1 libhunspell-1.3-0 libhunspell-1.4-0 libical0 libical1a
  libicc2 libicu48 libicu4j-4.2-java libicu4j-java libilmbase12 libilmbase6v5 libimdi0 libimobiledevice2 libimobiledevice4 libisc-export95 libisc84 libisc95 libisccc80
  libisccc90 libisccfg82 libisccfg90 libiso9660-8 libjasper1 libjavascriptcoregtk-1.0-0 libjavascriptcoregtk-3.0-0 libjaxp1.3-java libjemalloc1 libjim0.76
  libjim0debian2 libjline-java libjpeg8 libjs-jquery libjson-c2 libjson0 libjtidy-java liblcms1 liblensfun-data liblensfun0 liblimba0 liblinear1 liblircclient0
  liblivemedia52 liblognorm2 liblouis2 liblouis9 liblouisutdml6 liblua5.1-0 liblucene2-java liblvm2app2.2 liblwres80 liblwres90 libm17n-0 libmagick++5 libmagickcore5
  libmagickwand5 libmatroska6v5 libmimic0 libminiupnpc10 libminiupnpc5 libmono-cairo4.0-cil libmono-system-drawing4.0-cil libmozjs-24-0 libmozjs10d libmozjs185-1.0
  libmpc2 libmpfr4 libmusicbrainz5-0 libmx-bin libmx-common libnm-glib-vpn1 libnm-glib4 libnm-gtk-common libnm-gtk0 libnm-util2 libopencv-calib3d2.4v5
  libopencv-contrib2.4v5 libopencv-core2.4v5 libopencv-features2d2.4v5 libopencv-flann2.4v5 libopencv-highgui2.4-deb0 libopencv-imgproc2.4v5 libopencv-legacy2.4v5
  libopencv-ml2.4v5 libopencv-objdetect2.4v5 libopencv-video2.4v5 libopenexr6v5 libopenjpeg2 libopenobex2 libopenraw1 liborcus-0.10-0v5 libotf0 libpanel-applet0
  libparted0debian1 libpcre16-3 libpgm-5.1-0 libplist1 libpoppler19 libpoppler57 libpoppler72 libpostproc-ffmpeg53 libpostproc52 libprocps5 libproj12
  libprotobuf-lite9v5 libproxy-tools libproxy0 libpsl0 libpst4 libpth20 libpython3.5-minimal libpython3.5-stdlib libqgsttools-p1 libqmi-glib1 libqpdf17 libqpdf18
  libqt5multimedia5-plugins libqt5multimediawidgets5 libqt5opengl5 libquvi-scripts libquvi7 librarian0 libraw15 libraw5 libre2-3 libreadline5 libregexp-java
  libreoffice libreoffice-emailmerge libreoffice-help-en-us libreoffice-report-builder-bin libresid-builder0c2a librest-extras-0.7-0 librhythmbox-core9 librtmp0
  libschroedinger-1.0-0 libsctp1 libseed-gtk3-0 libservlet2.5-java libsidplay2 libslp1 libslv2-9 libsndio6.0 libsnmp-base libsocialweb-client2 libsocialweb-common
  libsocialweb-service libsocialweb0 libsodium13 libsoundtouch0 libspice-client-gtk-3.0-4 libsuitesparseconfig4.4.5 libswresample-ffmpeg1 libswscale-ffmpeg3
  libswscale2 libsystemd-daemon0 libsystemd-login0 libt1-5 libtelepathy-farstream2 libtelepathy-logger2 libtidy-0.99-0 libtiff4 libtracker-control-1.0-0
  libtracker-extract-0.14-0 libtracker-miner-0.14-0 libtracker-miner-1.0-0 libtracker-sparql-0.14-0 libtracker-sparql-1.0-0 libtrio2 libts-0.0-0 libtxc-dxtn-s2tc0
  libumfpack5.4.0 libumfpack5.6.2 libumfpack5.7.1 libunique-3.0-0 libunistring0 libupnp6 libupower-glib1 libusageenvironment3 libusbmuxd1 libusbmuxd2 libuuid-perl
  libva-drm1 libva-glx1 libva-wayland1 libva-x11-1 libva1 libvisio-0.0-0 libvlc-bin libvlc5 libvlccore8 libvlccore9 libvpx1 libvpx3 libvpx4 libvte-2.90-9
  libvte-2.90-common libwebkitgtk-1.0-0 libwebkitgtk-3.0-0 libwebpdemux1 libwebpmux1 libwebpmux2 libwebrtc-audio-processing-0 libwildmidi1 libwinpr-crt0.1
  libwinpr-crypto0.1 libwinpr-dsparse0.1 libwinpr-environment0.1 libwinpr-file0.1 libwinpr-handle0.1 libwinpr-heap0.1 libwinpr-input0.1 libwinpr-interlocked0.1
  libwinpr-library0.1 libwinpr-path0.1 libwinpr-pool0.1 libwinpr-registry0.1 libwinpr-rpc0.1 libwinpr-sspi0.1 libwinpr-synch0.1 libwinpr-sysinfo0.1 libwinpr-thread0.1
  libwinpr-utils0.1 libwireshark6 libwiretap5 libwpd-0.9-9 libwpg-0.2-2 libwps-0.2-2 libwsutil6 libx264-123 libx264-142 libx264-148 libx265-68 libx265-79 libx265-95
  libxalan2-java libxapian22v5 libxerces2-java libxfreerdp-client1.1 libxml-commons-external-java libxml-commons-resolver1.1-java libxtables10 libxz-java libzmq3
  linux-headers-4.3.0-1-amd64 linux-headers-4.3.0-1-common linux-image-3.2.0-4-amd64 linux-image-4.3.0-1-amd64 linux-kbuild-4.3 m17n-contrib m17n-db mahjongg
  mythes-en-us obex-data-server openssh-blacklist openssh-blacklist-extra pcmciautils pkg-config python-aptdaemon python-aptdaemon.gtk3widgets python-beautifulsoup
  python-brlapi python-dbus-dev python-defer python-defusedxml python-feedparser python-fpconst python-gnupginterface python-imaging python-libxml2 python-louis
  python-mako python-markupsafe python-ndg-httpsclient python-packagekit python-pexpect python-ptyprocess python-pyasn1 python-pyatspi python-soappy
  python-software-properties python-utidylib python-wstools python-zeitgeist python3-aptdaemon python3-aptdaemon.gtk3widgets python3-defer python3.5 python3.5-minimal
  rdesktop rsync shotwell shotwell-common system-config-printer t1utils tcpd tex-common tsconf ttf-liberation ttf-sil-gentium-basic udisks vlc-data xchat-gnome-common
  xfonts-mathml
Use 'sudo apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 248 not upgraded.
$

How do I see where all my big files are?

$du -sk * | sort -n
4	index.php
4	myicon.png
4	programming
4	python
4	README.md
4	wp-blog-header.php
4	wp-comments-post.php
4	wp-config-sample.php
4	wp-cron.php
4	wp-links-opml.php
4	wp-load.php
4	xmlrpc.php
8	english
8	readme.html
8	testing
8	wp-activate.php
8	wp-mail.php
8	wp-trackback.php
12	commandline
12	github
12	ui
16	webex
16	wp-settings.php
20	knowledge
20	license.txt
20	real
20	shell
24	design
28	wordpress
32	free
32	wp-signup.php
36	wp-login.php
40	book
48	guide
60	reverse
60	web
128	apache
168	hacks
192	openend
236	reader
292	sorting
312	lib
360	plan
408	languages
584	docs
3064	sourceinstall2
3544	code
7804	files
8168	wp-admin
15300	trueangle
17820	wp-includes
198896	wp-content
$

Installing dig command on Debian

$sudo apt-get install -y dnsutils
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libcaribou-gtk-module libcaribou-gtk3-module libebur128-1 libevent-2.0-5 libgdict-1.0-10 libgdict-common
  libgmime-2.6-0 libgnome-autoar-common libgom-1.0-common libjavascriptcoregtk-3.0-0 libnotmuch4 libpcre16-3
  libperl5.24 libraw15 libsexy2 libwebkitgtk-3.0-0 libwebpmux2 python-olefile rename tcpd
Use 'sudo apt autoremove' to remove them.
The following additional packages will be installed:
  libbind9-160 libdns169 libirs160 libisc166 libisccc160 libisccfg160 liblmdb0 liblwres160
Suggested packages:
  rblcheck
The following NEW packages will be installed:
  dnsutils libbind9-160 libdns169 libirs160 libisc166 libisccc160 libisccfg160 liblmdb0 liblwres160
0 upgraded, 9 newly installed, 0 to remove and 562 not upgraded.
Need to get 226 kB/1,804 kB of archives.
After this operation, 7,160 kB of additional disk space will be used.
Get:1 http://http.us.debian.org/debian sid/main amd64 libirs160 amd64 1:9.11.2.P1-1 [52.5 kB]
Get:2 http://http.us.debian.org/debian sid/main amd64 dnsutils amd64 1:9.11.2.P1-1 [174 kB]
Fetched 226 kB in 3s (74.3 kB/s)  
Selecting previously unselected package liblmdb0:amd64.
(Reading database ... 181458 files and directories currently installed.)
Preparing to unpack .../0-liblmdb0_0.9.21-1_amd64.deb ...
Unpacking liblmdb0:amd64 (0.9.21-1) ...
Selecting previously unselected package libisc166:amd64.
Preparing to unpack .../1-libisc166_1%3a9.11.2.P1-1_amd64.deb ...
Unpacking libisc166:amd64 (1:9.11.2.P1-1) ...
Selecting previously unselected package libdns169:amd64.
Preparing to unpack .../2-libdns169_1%3a9.11.2.P1-1_amd64.deb ...
Unpacking libdns169:amd64 (1:9.11.2.P1-1) ...
Selecting previously unselected package libisccc160:amd64.
Preparing to unpack .../3-libisccc160_1%3a9.11.2.P1-1_amd64.deb ...
Unpacking libisccc160:amd64 (1:9.11.2.P1-1) ...
Selecting previously unselected package libisccfg160:amd64.
Preparing to unpack .../4-libisccfg160_1%3a9.11.2.P1-1_amd64.deb ...
Unpacking libisccfg160:amd64 (1:9.11.2.P1-1) ...
Selecting previously unselected package libbind9-160:amd64.
Preparing to unpack .../5-libbind9-160_1%3a9.11.2.P1-1_amd64.deb ...
Unpacking libbind9-160:amd64 (1:9.11.2.P1-1) ...
Selecting previously unselected package liblwres160:amd64.
Preparing to unpack .../6-liblwres160_1%3a9.11.2.P1-1_amd64.deb ...
Unpacking liblwres160:amd64 (1:9.11.2.P1-1) ...
Selecting previously unselected package libirs160:amd64.
Preparing to unpack .../7-libirs160_1%3a9.11.2.P1-1_amd64.deb ...
Unpacking libirs160:amd64 (1:9.11.2.P1-1) ...
Selecting previously unselected package dnsutils.
Preparing to unpack .../8-dnsutils_1%3a9.11.2.P1-1_amd64.deb ...
Unpacking dnsutils (1:9.11.2.P1-1) ...
Setting up liblmdb0:amd64 (0.9.21-1) ...
Setting up libisc166:amd64 (1:9.11.2.P1-1) ...
Processing triggers for libc-bin (2.26-6) ...
Processing triggers for man-db (2.7.6.1-4) ...
Setting up liblwres160:amd64 (1:9.11.2.P1-1) ...
Setting up libisccc160:amd64 (1:9.11.2.P1-1) ...
Setting up libdns169:amd64 (1:9.11.2.P1-1) ...
Setting up libisccfg160:amd64 (1:9.11.2.P1-1) ...
Setting up libirs160:amd64 (1:9.11.2.P1-1) ...
Setting up libbind9-160:amd64 (1:9.11.2.P1-1) ...
Setting up dnsutils (1:9.11.2.P1-1) ...
Processing triggers for libc-bin (2.26-6) ...
$