An A-Z Index of the Bash command line for Linux.

alias Create an alias •
apropos Search Help manual pages (man -k)
apt-get
Search for and install software packages
(Debian/Ubuntu)
aptitude Search for and install software packages
(Debian/Ubuntu)
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 file(s)

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
Compare two files
comm Compare two sorted files line by line
command Run a command - ignoring shell functions •
continue Resume the next iteration of a loop •
cp
Copy one or more files to another location
cron Daemon to execute scheduled commands
crontab Schedule a command to run at a later time
csplit Split a file into context-determined pieces
cut
Divide a file into several parts

d

date Display or change the date & time
dc
Desk Calculator
dd
Convert and copy a file, write disk headers, boot
records
ddrescue Data recovery tool
declare Declare variables and give them attributes •
df
Display free disk space
diff Display the differences between two files
diff3 Show differences among three files
dig
DNS lookup
dir
Briefly list directory contents
dircolors Colour setup for `ls'
dirname Convert a full pathname to just a path
dirs Display list of remembered directories
dmesg Print kernel & driver messages
du
Estimate file space usage

e

echo Display message on screen •
egrep
Search file(s) for lines that match an extended
expression
eject Eject removable media
enable Enable and disable builtin shell commands •
env
Environment variables
ethtool Ethernet card settings
eval Evaluate several commands/arguments
exec Execute a command
exit Exit the shell
expect Automate arbitrary applications accessed over a
terminal
expand Convert tabs to spaces
export Set an environment variable
expr Evaluate expressions

f

false Do nothing, unsuccessfully
fdformat Low-level format a floppy disk
fdisk Partition table manipulator for Linux
fg
Send job to foreground
fgrep Search file(s) for lines that match a fixed string
file Determine file type
find Search for files that meet a desired criteria
fmt
Reformat paragraph text
fold Wrap text to fit a specified width.
for
Expand words, and execute commands
format Format disks or tapes
free Display memory usage
fsck File system consistency check and repair
ftp
File Transfer Protocol

function Define Function Macros
fuser Identify/kill the process that is accessing a file

g

gawk Find and Replace text within file(s)
getopts Parse positional parameters
grep Search file(s) for lines that match a given pattern
groupadd Add a user security group
groupdel Delete a group
groupmod Modify a group
groups Print group names a user is in
gzip Compress or decompress named file(s)

h

hash
Remember the full pathname of a name
argument
head Output the first part of file(s)
help Display help for a built-in command •
history Command History
hostname Print or set system name

i

iconv Convert the character set of a file
id
Print user and group id's
if
Conditionally perform a command
ifconfig Configure a network interface
ifdown Stop a network interface
ifup Start a network interface up
import Capture an X server screen and save the image
to file
install Copy files and set attributes

j

jobs
join

k

kill Stop a process from running
killall Kill processes by name

l

less Display output one screen at a time
let
Perform arithmetic on shell variables •
ln
Make links between files
local Create variables •
locate Find files
logname Print current login name
logout Exit a login shell •
look Display lines beginning with a given string
lpc
Line printer control program
lpr
Off line print
lprint Print a file
lprintd Abort a print job
lprintq List the print queue
lprm Remove jobs from the print queue
ls
List information about file(s)
lsof List open files

m
make Recompile a group of programs
man
Help manual
mkdir Create new folder(s)
mkfifo Make FIFOs (named pipes)

List active jobs •
Join lines on a common field

mkisofs
Create an hybrid ISO9660/JOLIET/HFS
filesystem
mknod Make block or character special files
more Display output one screen at a time
mount Mount a file system
mtools Manipulate MS-DOS files
mtr
Network diagnostics (traceroute/ping)
mv
Move or rename files or directories
mmv
Mass Move and rename (files)

n

netstat Networking information
nice Set the priority of a command or job
nl
Number lines and write files
nohup Run a command immune to hangups
notify-send Send desktop notifications
nslookup Query Internet name servers interactively

o

open Open a file in its default application
op
Operator access

p

passwd Modify a user password
paste Merge lines of files
pathchk Check file name portability
ping Test a network connection
pkill Stop processes from running
popd
Restore the previous value of the current
directory
pr
Prepare files for printing

printcap Printer capability database
printenv Print environment variables
printf Format and print data •
ps
Process status
pushd Save and then change the current directory
pwd
Print Working Directory

q

quota Display disk usage and limits
quotacheck Scan a file system for disk usage
quotactl Set disk quotas

r

ram
ram disk device
rcp
Copy files between two machines
read Read a line from standard input •
readarray Read from stdin into an array variable •
readonly Mark variables/functions as readonly
reboot Reboot the system
rename Rename files
renice Alter priority of running processes
remsync Synchronize remote files via email
return Exit a shell function
rev
Reverse lines of a file
rm
Remove files
rmdir Remove folder(s)
rsync Remote file copy (Synchronize file trees)

s

screen Multiplex terminal, run remote shells via ssh
scp
Secure copy (remote file copy)

sdiff Merge two files interactively
sed
Stream Editor
select Accept keyboard input
seq
Print numeric sequences
set
Manipulate shell variables and functions
sftp Secure File Transfer Program
shift Shift positional parameters
shopt Shell Options
shutdown Shutdown or restart linux
sleep Delay for a specified time
slocate Find files
sort Sort text files
source Run commands from a file `.'
split Split a file into fixed-size pieces
ssh
Secure Shell client (remote login program)
strace Trace system calls and signals
su
Substitute user identity
sudo Execute a command as another user
sum
Print a checksum for a file
suspend Suspend execution of this shell •
symlink Make a new name for a file
sync Synchronize data on disk with memory

t

tail Output the last part of file
tar
Tape ARchiver
tee
Redirect output to multiple files
test Evaluate a conditional expression
time Measure Program running time
times User and system times
touch Change file timestamps

top
List processes running on the system
traceroute Trace Route to Host
trap Run a command when a signal is set(bourne)
tr
Translate, squeeze, and/or delete characters
true Do nothing, successfully
tsort Topological sort
tty
Print filename of terminal on stdin
type Describe a command •

u

ulimit Limit user resources •
umask Users file creation mask
umount Unmount a device
unalias Remove an alias •
uname Print system information
unexpand Convert spaces to tabs
uniq Uniquify files
units Convert units from one scale to another
unset Remove variable or function names
unshar Unpack shell archive scripts
until Execute commands (until error)
uptime Show uptime
useradd Create new user account
userdel Delete a user account
usermod Modify user account
users List users currently logged in
uuencode Encode a binary file
uudecode Decode a file created by uuencode

v


Verbosely list directory contents (`ls -l -b')

vdir Verbosely list directory contents (`ls -l -b')
vi
Text Editor
vmstat Report virtual memory statistics

w
wait Wait for a process to complete •
watch Execute/display a program periodically
wc
Print byte, word, and line counts
whereis Search the user's $path, man pages and source
files for a program
which Search the user's $path for a program file
while Execute commands
who
Print all usernames currently logged in
whoami Print the current user id and name (`id -un')
wget
Retrieve web pages or files via HTTP, HTTPS or
FTP
write Send a message to another user

x

xargs
Execute utility, passing constructed argument
list(s)
xdg-open Open a file or URL in the user's preferred
application.
yes
Print a string until interrupted
.
Run a command script in the current shell
!!
Run the last command again
###
Comment / Remark

Cloud Computing - - >> Next Generation Computing

Cloud computing is a general term for anything that involves delivering hosted services over the Internet. These services are broadly divided into three categories: Infrastructure-as-a-Service (IaaS), Platform-as-a-Service(PaaS)  and Software-as-a-Service (SaaS). The name cloud computing was inspired by the cloud symbol that's often used to represent the Internet in flowcharts and diagrams.
A cloud service has three distinct characteristics that differentiate it from traditional hosting. It is sold on demand, typically by the minute or the hour; it is elastic -- a user can have as much or as little of a service as they want at any given time; and the service is fully managed by the provider (the consumer needs nothing but a personal computer and Internet access). Significant innovations in virtualization and distributed computing, as well as improved access to high-speed Internet and a weak economy, have accelerated interest in cloud computing.
A cloud can be private or public. A public cloud sells services to anyone on the Internet. (Currently, Amazon Web Services is the largest public cloud provider.) A private cloud is a proprietary network or a data center that supplies hosted services to a limited number of people. When a service provider uses public cloud resources to create their private cloud, the result is called a virtual private cloud. Private or public, the goal of cloud computing is to provide easy, scalable access to computing resources and IT services.

Infrastructure-as-a-Service like Amazon Web Services provides virtual server instanceAPI) to start, stop, access and configure their virtual servers and storage. In the enterprise, cloud computing allows a company to pay for only as much capacity as is needed, and bring more online as soon as required. Because this pay-for-what-you-use model resembles the way electricity, fuel and water are consumed, it's sometimes referred to as utility computing.

Platform-as-a-service in the cloud is defined as a set of software and product development tools hosted on the provider's infrastructure. Developers create applications on the provider's platform over the Internet. PaaS providers may use APIs, website portals or gateway software installed on the customer's computer. Force.com, (an outgrowth of Salesforce.com) and GoogleApps are examples of PaaS. Developers need to know that currently, there are not standards for interoperability or data portability in the cloud. Some providers will not allow software created by their customers to be moved off the provider's platform.

In the software-as-a-service cloud model, the vendor supplies the hardware infrastructure, the software product and interacts with the user through a front-end portal. SaaS is a very broad market. Services can be anything from Web-based email to inventory control and database processing. Because the service provider hosts both the application and the data, the end user is free to use the service from anywhere.