前来挖坟。留下个人理解，供后面同学参考。

对于第一个all的理解，比如用xshell远程登陆linux，物理机ip是192.168.1.100，把这个ip写到第一个all的位置，使用sudo，会提示不可以，但是把虚拟机中linux的ip写到这个位置去，就可以使用sudo了。因此，第一个all位置的确是被管理主机的ip地址，而不是用户登录的ip地址，当然，很多时候两者有重叠。

还有，老师举例j的jack   CSNETS = ALL中有这样一句：

The user jack may run any command on the machines in the CSNETS alias (the networks 128.138.243.0,128.138.204.0, and 128.138.242.0).

这一句翻译起来很容易使人产生疑惑，会认为是用户登陆的主机IP，我个人理解是即便我们使用远程连接登录上服务器，但执行指令还是在服务器上，而不是我们操作的计算机上，这里的machines还是指被管理的主机，不然的话，这种sudo机制，就局限在规定的几台计算机上了。

命令英文全称

su：Swith user  切换用户，切换到root用户
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
alias :Create your own name for a command
bash :GNU Bourne-Again Shell  linux内核
grep:global regular expression print
httpd :Start Apache
ipcalc :Calculate IP information for a host
ping :Send ICMP ECHO_Request to network hosts
reboot: Restart your computer
sudo:Superuser do

/bin = BINaries
/dev = DEVices
/etc = ETCetera
/lib = LIBrary
/proc = PROCesses
/sbin = Superuser BINaries
/tmp = TeMPorary
/usr = Unix Shared Resources
/var = VARiable ?
FIFO = First In, First Out
GRUB = GRand Unified Bootloader
IFS = Internal Field Seperators
LILO = LInux LOader
MySQL = My最初作者的名字SQL = Structured Query Language
PHP = Personal Home Page Tools = PHP Hypertext Preprocessor
PS = Prompt String
Perl = "Pratical Extraction and Report Language" = "Pathologically Eclectic Rubbish Lister"
Python Monty Python's Flying Circus
Tcl = Tool Command Language
Tk = ToolKit
VT = Video Terminal
YaST = Yet Another Setup Tool
apache = "a patchy" server
apt = Advanced Packaging Tool
ar = archiver
as = assembler
bash = Bourne Again SHell
bc = Basic (Better) Calculator
bg = BackGround
cal = CALendar
cat = CATenate
cd = Change Directory
chgrp = CHange GRouP
chmod = CHange MODe
chown = CHange OWNer
chsh = CHange SHell
cmp = compare
cobra = Common Object Request Broker Architecture
comm = common
cp = CoPy
cpio = CoPy In and Out
cpp = C Pre Processor
cups = Common Unix Printing System
cvs = Current Version System
daemon = Disk And Execution MONitor
dc = Desk Calculator
dd = Disk Dump
df = Disk Free
diff = DIFFerence
dmesg = diagnostic message
du = Disk Usage
ed = editor
egrep = Extended GREP
elf = Extensible Linking Format
elm = ELectronic Mail
emacs = Editor MACroS
eval = EVALuate
ex = EXtended
exec = EXECute
fd = file descriptors
fg = ForeGround
fgrep = Fixed GREP
fmt = format
fsck = File System ChecK
fstab = FileSystem TABle
fvwm = F*** Virtual Window Manager
gawk = GNU AWK
gpg = GNU Privacy Guard
groff = GNU troff
hal = Hardware Abstraction Layer
joe = Joe's Own Editor
ksh = Korn SHell
lame = Lame Ain't an MP3 Encoder
lex = LEXical analyser
lisp = LISt Processing = Lots of Irritating Superfluous Parentheses
ln = LiNk
lpr = Line PRint
ls = list
lsof = LiSt Open Files
m4 = Macro processor Version 4
man = MANual pages
mawk = Mike Brennan's AWK
mc = Midnight Commander
mkfs = MaKe FileSystem
mknod = MaKe NODe
motd = Message of The Day
mozilla = MOsaic GodZILLa
mtab = Mount TABle
mv = MoVe
nano = Nano's ANOther editor
nawk = New AWK
nl = Number of Lines
nm = names
nohup = No HangUP
nroff = New ROFF
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
pirntcap = PRINTer CAPability
popd = POP Directory
pr = pre
printf = PRINT Formatted
ps = Processes Status
pty = pseudo tty
pushd = PUSH Directory
pwd = Print Working Directory
rc = runcom = run command, shell
rev = REVerse
rm = ReMove
rn = Read News
roff = RunOFF
rpm = RPM Package Manager = RedHat Package Manager
rsh, rlogin, = Remote
rxvt = ouR XVT
sed = Stream EDitor
seq = SEQuence
shar = SHell ARchive
slrn = S-Lang rn
ssh = Secure SHell
ssl = Secure Sockets Layer
stty = Set TTY
su = Substitute User
svn = SubVersioN
tar = Tape ARchive
tcsh = TENEX C shell
telnet = TEminaL over Network
termcap = terminal capability
terminfo = terminal information
tr = traslate
troff = Typesetter new ROFF
tsort = Topological SORT
tty = TeleTypewriter
twm = Tom's Window Manager
tz = TimeZone
udev = Userspace DEV
ulimit = User's LIMIT
umask = User's MASK
uniq = UNIQue
vi = VIsual = Very Inconvenient
vim = Vi IMproved
wall = write all
wc = Word Count
wine = WINE Is Not an Emulator
xargs = eXtended ARGuments
xdm = X Display Manager
xlfd = X Logical Font Description
xmms = X Multimedia System
xrdb = X Resources DataBase
xwd = X Window Dump
yacc = yet another compiler compiler