Linux Cmd 2011

Front 1

display all running process

Back 1

ps aux | less

-A: select all process
a: select all process on a terminal
x: select processes without controlling

Front 2

to see every process on the system

Back 2

ps -A
ps -e

Front 3

See every process except those running as root

Back 3

ps -U root -u root -N

Front 4

to display a debug view of running processes

Back 4

top

Front 5

display tree of processes

Back 5

pstree

Front 6

process tree using ps

Back 6

ps -ejH
ps axjf

Front 7

security info

Back 7

ps -eo euser,ruser,suser,fuser,f,comm,lablel
ps axZ
ps -eM

Front 8

save process snap shot to a file

Back 8

top -b -n1 > /tmp/process.log

Front 9

mail process snapshot to a file

Back 9

top -b -n1 |mail -s 'Process snapshot' [e-mail]

Front 10

lookup process

Back 10

pgrep firefox

Front 11

list the process called sshd which is owned by router

Back 11

pgrep -u root sshd

Front 12

ls -l | less

Back 12

In this example, ls is the Unix directory lister, and less is an interactive text pager with searching capabilities. The pipeline lets the user scroll up and down a directory listing that may not fit on the screen.

Front 13

curl "http://en.wikipedia.org/wiki/Pipeline_(Unix)" | \
sed 's/[^a-zA-Z ]/ /g' | \
tr 'A-Z ' 'a-z\n' | \
grep '[a-z]' | \
sort -u | \
comm -23 - <(sort /usr/share/dict/words) | \
less

Back 13

curl obtains the HTML contents of a web page (could use wget on some systems).
sed removes all characters that are not spaces or letters from the web page's content, replacing them with spaces.
tr changes all of the uppercase letters into lowercase and converts the spaces in the lines of text to newlines (each 'word' is now on a separate line).
grep includes only lines that contain at least one lowercase alphabetical character (removing any blank lines).
sort sorts the list of 'words' into alphabetical order, and the -u switch removes duplicates.
comm finds lines in common between two files, -23 suppresses lines unique to the second file, and those that are common to both, leaving only those that are found only in the first file named. The - in place of a filename causes comm to use its standard input (from the pipe line in this case). sort /usr/share/dict/words sorts the contents of the words file alphabetically, as comm expects, and <( ... ) outputs the results to a temporary file (via process substitution), which comm reads. The result is a list of words (lines) that are not found in /usr/share/dict/words.
less allows the user to page through the results.

Front 14

bash

Back 14

the gnu borne again shell is based on the earlier bourne shell for unix. Common default shell for user accounts

Front 15

bsh

Back 15

the bourne shell upon which bash is based also goes by the name of bsh

Front 16

tsch

Back 16

based in earlier c shell(csh). Its fairly popular in some circles, but no major linux distribution make it the defaul shell. Although it's similar to bash

Front 17

csh

Back 17

the original C shell

Front 18

ksh

Back 18

the Korn shell was designed to take the best feature of the Bourne shell and the C shell and extend them further

Front 19

zsh

Back 19

the z shell takes shell evolution further than the ksh incorporating feature from earlier shells and adding still more

Front 20

/bin/sh use

Back 20

is a symbolic link to the system's default shell - normally /bin/bash

Front 21

Linux cmd are ______

Back 21

external
they are separate programs from the shell. few cmd are internal to the shell

Front 22

xterm or konsole cmd

Back 22

this will launch an xterm-type program that will rin a shell

Front 23

internal shell cmd

shell and running directory

Back 23

built into the shell

whenever you are running a shell it is in a specific directory

Front 24

Directory
/
/bin
/boot

Back 24

/ - represents the root directory of the Linux system
/bin - contains binary cmd taht are available to all users
/boot - contains the kernel and boot loader

Front 25

cd cmd
pwd cmd

Back 25

changes the current dir
displays the current working directory

Front 26

cd ~

Back 26

the tilde ~ character us a short cut, that stands for your home dir
cd ~ same as
cd /home/sally

Front 27

Directory
/dev
/etc
/home

Back 27

/dev - contains device files
/etc - contains configuration files specific to the system
/home - contains default user home directories

Front 28

echo <test string>

Back 28

causes the system to display the <text string>

Front 29

exec <myprog>

Back 29

the exec cmd runs an external program that you specify under <myprog> but keep in mind that using the exec cmd causes the current shell process with the <myprog> process

Front 30

time <other cmd> cmd

Back 30

the time cmd times how long subsequent cmd tale to execute
example:
time pwd
tells you how long the system took to execute the pws cmd

Front 31

directory
/initrd
/lib
/media

Back 31

/initrd - dir is used during the boot process to hold the initial RAM
/lib - contains shared probram libraries and kernel modules
/media - contains the /cdrom and /floppy dir

Front 32

logout cmd

exit cmd

Back 32

terminates the shell
but only the login shell

exit - terminates the shell

Front 33

How you execute an external cmd that matches an internal cmd

Back 33

the internal cmd takes precedence unless you provide the complete path to the external cmd on the cmd line as in typing /nin/pwd rather than pwd

Front 34

sudo /usr/sbin/dmidecode | less

Back 34

info about the moder board and other hardware configurations

Front 35

Environmental variables in Linux

Back 35

they can be sat in bash by using the = operator followed by the export cmd

$NNTPSERVER-news.abifisp.com
$export NNTPSERVER

set NTTPSERVER to url

Front 36

directory
/mnt
/opt
/proc

Back 36

/mnt - an empty dir. used to be the mount point fro mount cmd
/opt - contains additional programs
/proc -contains information about the system state and processes

Front 37

unset cmd

Back 37

to delete an environmental variable use

unset >name var>

Front 38

man man cmd

env cmd

Back 38

description of the man cmd

displays a list of environmental variables

Front 39

man section numbers

Back 39

1 - exec programs and shell cmd
2 - system class provided by the kernel
3 - library calls provided by program libraries
4 - device files
5 - file formats
6 - games
7 - miss
8 - system administrator commands
9 - kernel reoutines

Front 40

info info

once in man mode press q

Back 40

some cmd have moved away from man pages and replaced them with http

quites the man/info mode

Front 41

streams

Back 41

Linux treats the input to and output form programs as a stream, which is a data entity that can be manipulated

Front 42

directory
/sbin
/root
/srv

Back 42

/sbin - contains binary system cmd
/root - root user's home dir
/srv - contains files for services like the FTP and Web Server

Front 43

stdout
stderr

Back 43

standard output stream
standard error stream

Front 44

> cmd

>> cmd

Back 44

> re-director operator that creates a new file containing standard output. if the specified file exist it is overwritten
>> redirector operator that appends standard output to the existing file

Front 45

/sys
/tmp
/usr

Back 45

/sys - takes some of the system state
/tmp - contains temporary files created by programs
/usr - contains system cmd and utils

Front 46

2> cmd

2>> cmd

Back 46

2> redirector operator that create a new file containing standard error

2>> redirector operator that appends to file containing standard error

Front 47

&> cmd

< cmd

Back 47

&> - redirector operator that creates a new file containing both stdout and stderr

< - Sends the contents of the specified file to be used as standard input

Front 48

File Type (special) - Symbolic Link
File Type (special) - Character
File Type (special) - Block

Back 48

File Type (special) - Symbolic Link - is a file system entry that point to another file system entry

File Type (special) - Character -
File Type (special) - Block

Front 49

<> cmd

Back 49

causes the specified file to be used for both standard input and standard output

Front 50

netstat -t -u
netstat -t -u -c

Back 50

display only tcp and udp connections
-c continuous

Front 51

clear screen cmd

Back 51

clear

Front 52

tee cmd

Back 52

this cmd splits standard input so that it's displayed on standard output and on as many file as you specify example

someprog | tee output.txt

Front 53

data pipes

Back 53

first | second

Front 54

deleting all of the backup files denoted by the ~ char

Back 54

find ./ -name
*~" | xargs rm

the first part of this cmd find all the files in the current directory or its subs with a name that ends in a ~.
This list is then piped to xargs, which adds each one to its own rm cmd

Front 55

backtick `

Back 55

text within backticks is treated as a separate cmd whose results are substituted on the cmd line

rm `find ./ -name "*~"

Front 56

cat cmd + example

Back 56

it links together an arbitrary number of files end to end and sends the result to standard output

cat first.txt second.txt > combined.txt

Front 57

cat cmd second use

Back 57

although cat is officially a tool for combining files, its also commonly used to dusplay the contents of a short file.

Front 58

cat display line ends

Back 58

if you want to see where lines end, add the
-E or
--show-ends

the result is an % sign at the end of each line

Front 59

cat number lines

Back 59

-n
--number
option adds line number to the beginning of every line

Front 60

cat number only non empty lines

Back 60

-b
--number-nonblank

option adds line number to the beginning of meaningful lines skipping lines containing empty space

Front 61

cat minimiza blank line

Back 61

-s
--squeeze-blanks

compresses groups of blank line down to a single blank line

Front 62

xargs cmd description

Back 62

with xargs you can combine the output of two or more different cmds

example
trying to remove all files ending with ~ in a directory structure
use find to find the files than rm to remove the files

Front 63

xargs cmd syntax

Back 63

xargs [option] [command [initial-arguments]]

initial arguments - list of arguments you want to pass to the cmd

Front 64

xargs cmd example
delete all files ending with ~

Back 64

find ./ -name "*~" | xargs rm

Front 65

cmd to find all files in the current directory (./) and its sub directories with a name that ends with ~

Back 65

find ./ -name "*~"

Front 66

back tick ` char usage

Back 66

similar to the xargs
text within back-ticks is treated as a separate cmd whose results are substituted on the cmd line

rm `find ./ -name "*~"`

Front 67

join cmd

Back 67

combines two files by matching the contents of specified fields within the files. Usually space, comma, tab separated files

f1
555 david
666 dimittar
f2
555 beckham
666 berbatov

join f1 f2
555 david beckham
666 dimitar berbatov

Front 68

join cmd -i switch

Back 68

ignores case sensitivity

Front 69

join cmd -t switch

Back 69

specify another separator instead of space

Front 70

join cmd -1 -2 switch

Back 70

by default join uses the first field as key
by specifying number -1 3 -2 4 specifies to make a match on between the 3rd field from first file and 4th field from second file

Front 71

paste cmd

Back 71

merges files line by line
separate the lines each file with tabs

Front 72

converting tab to spaces cmd

Back 72

expand

by default tab is every 8 chars with

-t num you specify num for tab length

Front 73

displaying files in octal cmd

Back 73

od filename

(comes from octal dump)

Front 74

sorting files cmd

Back 74

sort

Front 75

sort cmd switch for ignoring case when sorting

Back 75

-f
--ignore-case

by default sorts bu ASCII value, which makes difference between upper and lower case letters

Front 76

sort cmd switch for sorting by 3 letter month

Back 76

-M
--mont-sort

Front 77

sort cmd switch for sorting by number

Back 77

-n
--numeric-sort

Front 78

sort cmd switch for sorting in reverse order

Back 78

-r
--reverse

Front 79

sort cmd switch for sorting field

Back 79

-k field
--key=field

by default sort uses the first field as its sort field

Front 80

cmd to break file in peace

Back 80

split
requires on output filename
and how large each split is to be

Front 81

split cmd switch for splitting by bytes

Back 81

-b size
--bytes=size

This option can usually have an undesirable consequence of splitting file mid line

Front 82

split cmd option for splitting a file in line size chunks

Back 82

-C=size
--line-bytes=size

Front 83

split cmd option for splitting a file based on number of lines

Back 83

-l lines
--lines=lines

Front 84

cmd for translating characters

Back 84

tr [options] SET1 [SET2]

set1 - chars you want to replaces
set2 - chars to replace with
each char from set1 is match to corresponding char from set2

Front 85

cmd to convert spaces to tabs

Back 85

unexpand

-t num
--tabs=num

sets tab spacing

Front 86

cmd to delete duplicate lines

Back 86

uniq

sort f1.txt | uniq

Front 87

cmd to reformat text files, such as man files having too long lines

Back 87

fmt

Front 88

cmd to number lines in of a file

Back 88

nl

Front 89

cmd that formats a document in pages suitable for printing

Back 89

pr

Front 90

nl cmd option for body numbering style

Back 90

-b style
--body-numbering=style

Front 91

nl cmd option for header and footer numbering style

Back 91

-h style
-header-numbering=style
-f style
-footer-numbering=style

the text needs to be formatted for printing

Front 92

nl cmd option to reset numbering on each page or other condition

Back 92

-d=code
--section-delimiter=code options

where code is a code for the character delimiting the pages

Front 93

nl cmd option for renumbering a new page

Back 93

-p
--no-renumber option

Front 94

nl cmd option to send number format

Back 94

-n format
--number-format=format

Where format
ln - left
rn - right
rz - right with leading zeroes

Front 95

nl cmd option to number only non-blank line

Back 95

the default behavior
corresponds to style of t

Front 96

nl cmd option to number all line

Back 96

style of a

Front 97

nl cmd option to number no lines

Back 97

style of n

Front 98

cmd to print a plain text file

Back 98

pr filename.txt

Front 99

cmd to see the first 10 lines of a file

Back 99

head

Front 100

head cmd option to display the first num bytes of a file

Back 100

head
-c num
--bytes=num

Front 101

head cmd option to display the first num lines of a file

Back 101

head
-n num
--bytes=num

Front 102

cmd to display the last 10 lines of a file

Back 102

tail

Front 103

tail -c
tail -bytes
--------------
tail -n
tail -line

Back 103

changes the amoun of data displayed

Front 104

tail -f
tail --follow

Back 104

keeps the file open and displays new lines as they are added

Front 105

tail -pid=pid

Back 105

tells tail to terminate tracking

Front 106

cut -b
cut --byre=list

Back 106

cuts the specofoed list of bytes from the input file

Front 107

cut -c
cut --charlist=list

Back 107

cuts the specified list of characters from the input file

Front 108

cut -f
cut --fileds=list

Back 108

cuts the specified list of fields from the input file

Front 109

cmd/script tp get the MAC address of eth0

Back 109

ifconfig ethh0 | grep HWaddr | cut -d " " -f 11

Front 110

cmd to obtain count of bytes in file

Back 110

wc file.txt

Front 111

cmd and switch to count the new lines

Back 111

wc --lines
wc -l

Front 112

cmd and switch to coumt
words
bytes
chars

Back 112

wc --words
wc -w
---------------
wc --bytes
wc -b
---------------
wc --char
wc -m

Front 113

get linux version

Back 113

$ cat /etc/*-release

Front 114

list running deamons

Back 114

ps aux

Front 115

/proc filesystem

Back 115

when adding new hardware to an existing Linux system, you may wish to verify which resources the existing devices are using.
/proc filesystem, the kernel's status repository contains this info
pric files, interrupts, dma and ioreports show how system resources are currently used

cat /proc/interrupts

Front 116

how to get list of interrupts

Back 116

CPU0
0: 80448940 XT-PIC timer
1: 174412 XT-PIC keyboard
2: 0 XT-PIC cascade
8: 1 XT-PIC rtc
10: 410964 XT-PIC eth0
12: 60330 XT-PIC PS/2 Mouse
14: 1314121 XT-PIC ide0
15: 5195422 XT-PIC ide1
NMI: 0
ERR: 0

Front 117

Use this utility to see the contents of a compressed file

End of File (EOD) character used to close a file?

Back 117

catz

CTRL - D

Front 118

You want to display the file June_report with the less pager, highlighting places where the word "data" appears. What command do you user?

Back 118

less +/data June_report

Front 119

What does Linux use to communicate with MacOS resources?

What protocol dose Samba use to communicate with Microsoft resources?

What two protocols were created to replace SMB?

Back 119

Netatalk

SMB

CIFS nad

Front 120

When searching man pages
"x" searches the description;
"y" stings searches the entire contents of the man pages;
"z" string finds all matching entries

Back 120

x="-k"
y="-K"
z="-a"

Front 121

Why can all users change their passwords even though only the owner can write to passwd?

Back 121

passwd uses setuid to set permissions when it is running

Front 122

What numeric value does write permission have?

What numeric value does execute permission have?

Back 122

write - 2

execute - 1

Front 123

In ipchains, what is the difference between deny and reject?

Back 123

reejct notifies the sender; deny does not

Front 124

Waht two advantages does ReiserFS have over ext2?

Back 124

faster recovery from errors and faster and more secure hard drive writes

Front 125

Dynamically linked executable

Back 125

examined at runtime by the shared object dynamic linker, ld.so

ld.so - looks for dependencies in the executable being loaded and attempts to satisfy any unresolved links.
if ld.so cant fined the specified library it fails to execute the application

Front 126

to find a new library lo.sd must be instructed to look in

Back 126

/usr/local/lib

2 ways it can be done
1)add a colon-separated list of dir to the shell environment var LD_LIBRARY_PATH
2)add new lib entry to the cache by first adding the entry to /etc/ld.so.conf which contains the dir to be indexed by the ldconfig utility

Front 127

/usr/local/lib

2 ways it can be done
1)add a colon-separated list of dir to the shell environment var LD_LIBRARY_PATH
2)add new lib entry to the cache by first adding the entry to /etc/ld.so.conf which contains the dir to be indexed by the ldconfig utility

Back 127

ldconfig [options] libs_dirs

Update the ld.so cache file with shared libraries specified on the command line in lib_dirs, in trusted directories /usr/lib and /lib and in the directories found in /etc/ld.so.conf

-p - displays the current cache instead of recreating it
-v - verbose mode, progress during execution

Front 128

What cmd will display default file permissions?

Back 128

unmask

Front 129

erase all other permissions and then add just read and write permissions to the projectX group on a file

Back 129

cd projectX
chmod g=rw <filename>

Front 130

change file permissions for a group to simply read permissions

Back 130

cd groupname
chmod g-w
chmod g+r
(g-w takes away the write permissions)

Front 131

show/list all the permissions or 'modes' a user has

Back 131

ls -l username

r = read
w = write
x = execute

Front 132

check to see all the groups bob is member of

Back 132

groups bob

Front 133

create a group called projectX then add users to that group check your work

Back 133

groupadd -r ProjectX
usermod -g ProjectX bob,candy
cat /etc/group

Front 134

Create an alias for the commonly used remove function

Completely remove a user (this will not remove all the user files saved but will remove all user info)

show the dir for your newly created password

Back 134

alias rm=rm -i

userdel -r joe

cat /etc/shadow

Front 135

Where is group information kept

check to see the comment was added to joe's name

list all of joe's newly created files

Back 135

cat /etc/group

cat /etc/passwd

ls -a joe

Front 136

What character is used in a filename to specify a backup file

How would you find every occurrence of the word dog n a file called pets (case insensitive)?

Back 136

~

grep -iw dog pets

Front 137

You want to get a list of all the directories in your home directory stored by time with the newest level at the top. What cmd would you use?

Back 137

ls -tdR *

Front 138

If you know the name of the file you want to extract, you can pass it directly to tar using this option?

Back 138

tar -xf myarchive.tar myfile

Front 139

To create a tar file of the PWD use the "-xy" option?
(where "x" create the tar file
"y" give the name for the new archive)

Back 139

-cf

Front 140

to permanently change your shell, use this cmd

Back 140

chsh -s shellname

Front 141

use the -"wxyz" option with tar to extract files in interactive mode

You can view the contents of your tar file using -"xy" option?
(where "x" causes tar to print the names of the tar files)

Back 141

-xvwf

-tf

Front 142

as part of your backup strategy you want to back up the /home dir to /backups on another partition. What would you type at the cmd line?

Back 142

tar -cf /backup/homebackup.tar home/*

Front 143

show cmd to create a tar file called myarchive.tar in the PWD & gzip it

Back 143

tar -cf myarchive.tar . | gzip myarchive.tar

Front 144

By default emacs config is kept here?

Back 144

/etc/inputrc

Front 145

you can uncompress a gzip file using these 2 methods

Back 145

gzip -d
gunzip

Front 146

Which cmd would you use to check the value for the variable DISPLAY?

To change a path for all users edit this file?

Where must aliases be entered for system wide use?

Back 146

echo $DISPLAY

/etc/profile

/etc/bashrc

Front 147

To make the change in your prompt permanent edit 1 of these files?

What cmd would you type to temporary add the date/time to your shell prompt?

Back 147

.bash_profile
or
.profile
-------------------
PS1='Date: \d Time: \t->>';
export PS1

Front 148

This utl lets you look at running processes, stats on memory & the swap file?

Back 148

top

Front 149

Use this cmd to suspend a running program & put it in the background?
Use this command to bring back to foreground?
Use this to kill the process?

Back 149

CTRL+Z
fg
CTRL+C

Front 150

File Type - Directory

File Type - Normal File

Back 150

File Type - Directory - A file type designed specifically to hold or point to other file types.

File Type - Normal File - Every file that is not a directory is generally a normal file.

Front 151

File Type (special) - Hard Link

Back 151

A hard link is a duplicate entry in the file system that points to a specific piece of data. Hard links are not often used. If the original entry in the file system is deleted, the hard link maintains a valid pointer to the data.

Front 152

File Type (special) - Symbolic Link

Back 152

A symbolic link is a file system entry that points to another file system entry, which in turn points to a valid piece of data. Symbolic links can work across volumes and file systems. Symbolic links are similar to shortcuts in Windows.

Front 153

File Type (special) - Character

Back 153

A file type that accepts input one character (i.e., byte) at a time. Character files often point to devices like sound cards, serial ports, or video port.

Front 154

File Type (special) - Block

File Type (special) - Pipe

Back 154

File Type (special) - Block - A file type that accept input in blocks (i.e., groups of bytes). Block files often point to storage devices.

File Type (special) - Pipe - A named pipe file allows you to send information between applications.