network

netcat : NC(1) BSD General Commands Manual NC(1) nc — arbitrary TCP and UDP connections and listens
ping : 6 send ICMP ECHO_REQUEST to network hosts
nmcli : – commandline tool for controlling NetworkManager
telnet : user interface to the TELNET protocol
openssl : OpenSSL command line tool
sftp : secure file transfer program
...

shell

gnome-terminal : is a terminal emulation application.
busybox : The Swiss Army Knife of Embedded Linux
usermod : modify a user account
which : locate a command
fusermount : mount and unmount FUSE filesystems
watch : execute a program periodically, showing output fullscreen
...

filesystem

resize2fs : ext2/ext3/ext4 file system resizer
fsck : check and repair a Linux filesystem
chown : change file owner and group
passwd : change user password
hdparm : get/set SATA/IDE device parameters
mkfs.ext3 : create an ext2/ext3/ext4 filesystem
...

programming

strace : trace system calls and signals
MAKEDEV : create devices
busybox : The Swiss Army Knife of Embedded Linux
startpar : start runlevel scripts in parallel
ncurses5-config : helper script for ncurses libraries
ppmtosixel : convert a portable pixmap into DEC sixel format
...

file

egrep : , fgrep, rgrep print lines matching a pattern
hexdump : , hd ASCII, decimal, hexadecimal, octal dump
passwd : change user password
su : change user ID or become superuser
mkfs.ext2 : create an ext2/ext3/ext4 filesystem
ping : 6 send ICMP ECHO_REQUEST to network hosts
...

graphic manipulation

gimp : an image manipulation and paint program.
start-stop-daemon : start and stop system daemon programs
bmp2tiff : create a TIFF file from a Microsoft Windows Device Independent Bitmap image file
MAKEDEV : create devices
debugfs : ext2/ext3/ext4 file system debugger
djpeg : decompress a JPEG file to an image file
...

database

mysqlimport : a data import program
mysqld_safe : MySQL server startup script
nm-tool : utility to report NetworkManager state and devices
telnet : user interface to the TELNET protocol
arch : print machine hardware name (same as uname -m)
rmsgmerge : Extract translatable string from given input ruby script files.
...

X

gnome-terminal : is a terminal emulation application.
xfreerdp : FreeRDP X11 client
gksudo : GTK+ frontend for su and sudo
xload : system load average display for X
passwd : change user password
start-stop-daemon : start and stop system daemon programs
...

package management

dpkg-reconfigure : reconfigure an already installed package
apt-config : APT Configuration Query program
passwd : change user password
cweave : translate CWEB to C and/or TeX
python2.7 : an interpreted, interactive, object-oriented programming language
dh_installdeb : install files into the DEBIAN directory
...

printer

ppdc : cups ppd compiler
ghostscript : Ghostscript (PostScript and PDF language interpreter and previewer)
sldtoppm : convert an AutoCAD slide file into a portable pixmap
lprm : cancel print jobs
sensible-pager : pager, sensible-browser - sensible editing, paging, and web browsing
cweave : translate CWEB to C and/or TeX
...

text manipulation

passwd : change user password
start-stop-daemon : start and stop system daemon programs
cut : remove sections from each line of files
grep : print lines matching a pattern
chcon : change file security context
airtun-ng : a virtual tunnel interface creator for aircrack-ng
...

privacy

passwd : change user password
tor-gencert : Generate certs and keys for Tor directory authorities
lame : create mp3 audio files
start-stop-daemon : start and stop system daemon programs
wpa_passphrase : Generate a WPA PSK from an ASCII passphrase for a SSID
gpgsplit : Split an OpenPGP message into packets
...

sound manipulation

gst-launch-1.0 : build and run a GStreamer pipeline
audacity : Graphical cross-platform audio editor
start-stop-daemon : start and stop system daemon programs
ogmsplit : Split OGG/OGM files into several smaller OGG/OGM files
sndfile-metadata-set : set metadata in a sound file
spd-conf : A simple tool for basic configuration of Speech Dispatcher and problem diagnostics
...

Access Control List

su : change user ID or become superuser
pdb3.3 : the Python debugger
spd-conf : A simple tool for basic configuration of Speech Dispatcher and problem diagnostics
groupadd : create a new group
ping : 6 send ICMP ECHO_REQUEST to network hosts
iconv : Convert encoding of given files from one encoding to another
...

file compression

passwd : change user password
loadunimap : load the kernel unicode-to-font mapping table
dvdrip : GUI for copying DVDs
sha1sum : compute and check SHA1 message digest
zipsplit : split a zipfile into smaller zipfiles
unrar : extract files from rar archives
...

boot settings

update-grub : stub for grub-mkconfig
syslinux : install the SYSLINUX bootloader on a FAT filesystem
iconv : Convert encoding of given files from one encoding to another
nohup : run a command immune to hangups, with output to a non-tty
pdb3.3 : the Python debugger
airtun-ng : a virtual tunnel interface creator for aircrack-ng
...

text editor

sha1sum : compute and check SHA1 message digest
view : Vi IMproved, a programmers text editor
bibtex.original : make a bibliography for (La)TeX
lame : create mp3 audio files
loadunimap : load the kernel unicode-to-font mapping table
find : search for files in a directory hierarchy
...

webserver

a2ensite : enable or disable an apache2 site / virtual host
passwd : change user password
iconv : Convert encoding of given files from one encoding to another
arping : send ARP REQUEST to a neighbour host
lame : create mp3 audio files
loadunimap : load the kernel unicode-to-font mapping table
...

font

sha1sum : compute and check SHA1 message digest
nohup : run a command immune to hangups, with output to a non-tty
lame : create mp3 audio files
start-stop-daemon : start and stop system daemon programs
iwlist : Get more detailed wireless information from a wireless interface
spd-conf : A simple tool for basic configuration of Speech Dispatcher and problem diagnostics
...

mail

nohup : run a command immune to hangups, with output to a non-tty
ping : 6 send ICMP ECHO_REQUEST to network hosts
start-stop-daemon : start and stop system daemon programs
avconv : avconv video converter
jack_connect : JACK toolkit clients for connecting & disconnecting ports
airtun-ng : a virtual tunnel interface creator for aircrack-ng
...

Media Player

lame : create mp3 audio files
start-stop-daemon : start and stop system daemon programs
amarok : The audio player for KDE
gst-xmllaunch-0.10 : build and run a GStreamer pipeline from an XML serialization
sha1sum : compute and check SHA1 message digest
nohup : run a command immune to hangups, with output to a non-tty
...

virtualization

lame : create mp3 audio files
loadunimap : load the kernel unicode-to-font mapping table
sha1sum : compute and check SHA1 message digest
innochecksum : offline InnoDB file checksum utility
ping : 6 send ICMP ECHO_REQUEST to network hosts
start-stop-daemon : start and stop system daemon programs
...

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