apropos Search Help manual pages (man -k) apt-get Search for and install software packages (Debian) aptitude Search for and install software packages (Debian) aspell Spell Checker awk Find and Replace text, database sort/validate/index B basename Strip directory and suffix from filenames bash GNU Bourne-Again Shell bc Arbitrary precision calculator language bg Send to background break Exit from a loop builtin Run a shell builtin bzip2 Compress or decompress named files C cal Display a calendar case Conditionally perform a command cat Concatenate and print (display) the content of files cd Change Directory cfdisk Partition table manipulator for Linux chgrp Change group ownership chmod Change access permissions chown Change file owner and group chroot Run a command with a different root directory chkconfig System services (runlevel) cksum Print CRC checksum and byte counts clear Clear terminal screen cmp Co