/bin = BINaries
/sbin = Superuser BINaries
/dev = DEVices
/etc = Editable Text Configuration
/opt = Optional application software packages
/lib = LIBrary
/proc = PROCesses
/usr = Unix Shared Resources
/var = VARiable ? 是储存各种变化的文件，比如log等等

su：Swith user 切换用户，切换到root用户
sudo:Superuser do
cat: Concatenate 串联
uname: Unix name 系统名称
df: Disk free 空余硬盘
du: Disk usage 硬盘使用率
chown: Change owner 改变所有者
chgrp: Change group 改变用户组
ps：Process Status 进程状态
tar：Tape archive 解压文件
chmod: Change mode 改变模式
umount: Unmount 卸载
ldd：List dynamic dependencies 列出动态相依
insmod：Install module 安装模块
rmmod：Remove module 删除模块
lsmod：List module 列表模块
bash :GNU Bourne-Again Shell linux内核
grep:global regular expression print
cwd: current working directory
pwd = print working Directory (打印工作目录)。
apt = Advanced Packaging Tool
ed = editor

ar = archiver
as = assembler
cpp = C Pre Processor
bg = BackGround
cd = Change Directory
cmp = compare
cobra = Common Object Request Broker Architecture
comm = common
cups = Common Unix Printing System
cvs = Current Version System
daemon = Disk And Execution MONitor
dc = Desk Calculator
dd = Disk Dump

elf = Extensible Linking Format

eval = EVALuate
ex = EXtended
exec = EXECute
fd = file descriptors
fg = ForeGround
fgrep = Fixed GREP
fmt = format
fsck = File System ChecK
fstab = FileSystem TABle
gawk = GNU AWK
lex = LEXical analyser
ln = LiNk
ls = list
lsof = LiSt Open Files
mkfs = MaKe FileSystem
nl = Number of Lines
nm = names
nohup = No HangUP
od = Octal Dump
passwd = PASSWorD
pg = pager
pico = PIne's message COmposition editor
pine = "Program for Internet News & Email" = "Pine is not Elm"
ping = Packet InterNet Grouper
printf = PRINT Formatted
ps = Processes Status
pwd = Print Working Directory
rm = ReMove
rn = Read News
rpm = RPM Package Manager = RedHat Package Manager
sed = Stream EDitor
seq = SEQuence

ssh = Secure SHell
ssl = Secure Sockets Layer
stty = Set TTY
svn = SubVersioN
tr = traslate
tty = TeleTypewriter
tz = TimeZone
ulimit = User's LIMIT
umask = User's MASK
wall = write all
wc = Word Count