1. In ubuntu, there are have Terminal and Root Terminal.
Terminal : Ctrl+Alt+t
Root Terminal : ???
Command line interface : Ctrl+Alt+F1 or Ctrl+Alt+F2 >> exit: Ctrl+Alt+F7 >> How use without password??
2. A picture show the structure:
3. Nine Categories and details in each category
File system >> Processes >> User environment >> Texting process >> Shell builtins >> Networking >> Searching >> Documentation >> Miscellaneous
File system: cat >> cd >> chmod >> chown >> chgrp >> cksum >> cmp >> cp >> dd >> du >> df >> file >fsck >> fuser >> in >> ls >> mkdir >> mount >> mv >> pax >> pwd >> rm >> rmdir >> size >> split >> tee >> touch >> type >> umask
Processes: at >> bg >> chroot >> cron >> fg >> kill >> killall >> nice >> pgrep >> pkill >> ps >> pstree >> time >> top
User environment: clear >> env >> exit >> finger >> history >> id >> logname >> mesg >> passwd >> su >> sudo >> uptime >> talk >> tput >> uname >> w >> wall >> who >> whoami >> write
Text processing: awk >> banner >> basename >> comm >> csplit >> cut >> diff >> dirname >> ed >> ex >> fmt >> fold >> head >> iconv >> join >> less >> more >> nl >> paste >> sed >> sort >> spell >> strings >> tail >> tr >> uniq >> vi >> wc >> xargs
Shell builtins: alias >> echo >> expr >> printf >> sleep >> test >> true and false >> unset >> wait >>yes
Networking: dig >> host >> ifconfig >> inetd >> netcat >> netstat >> nslookup >> ping >> rdate >> rlogin >> route >> ssh >> traceroute
Searching: find >> grep >> locate >> whatis >> whereis
Documentation: apropos >> help >> man
miscellaneous: bc >> dc >> cal >> lp >> od