Linux - Misc

Front 1

difference between soft and hard links

Back 1

Front 2

command: &

Back 2

Run the specified program in the background.

Front 3

command: ^z

Back 3

Suspend the current foreground process.

Front 4

command: bg

Back 4

put specified process in the background

Front 5

command: fg

Back 5

put specified process in the foreground

Front 6

fuser

Back 6

Display the PID of any process using a specified file.

Front 7

command: fuser

Back 7

identify processes using files or sockets

Front 8

command: jobs

Back 8

show list of background processes

Front 9

kill

Back 9

Stop the execution of a process

Front 10

killall

Back 10

kill all processes executing a specified command.

Front 11

nice

Back 11

Change the priority of a process.

Front 12

command: nohup

Back 12

no hangup -- Run a command immune to hangups.

Front 13

command: pidof

Back 13

locate and print the process id of the specified program.

Front 14

command: ps

Back 14

get process status information.

Front 15

command: pstree

Back 15

display the family tree of running processes.

Front 16

command: renice

Back 16

Change the id of a running process.

Front 17

command: top

Back 17

Display Linux tasks .... and their resource use.

Front 18

signal for: hang up

Back 18

(1) SIGHUP

Front 19

signal for: Interrupt from keyboard

Back 19

(2) SIGINT (default action:terminate)

Front 20

signal for: Quit from keyboard

Back 20

(3) SIGQUIT (default action is: terminate and do CORE dump)

Front 21

signal for: Illegal Instruction

Back 21

(4) SIGILL (default action is: terminate and do CORE dump)

Front 22

signal for: Abort signal from abort(3)

Back 22

(6) SIGABRT (default action is: terminate and do CORE dump)

Front 23

signal for: Floating point exception

Back 23

(8) SIGFPE (default action is: terminate and do CORE dump)

Front 24

signal for: Kill signal

Back 24

(9) SIGKILL (default action: term)

NOTE: SIGKILL cannot be caught, blocked, or trapped

Front 25

signal for: Invalid memory reference

Back 25

(11) SIGSEGV (default action is: terminate and do CORE dump)

Front 26

signal for: Broken pipe: write to pipe with no readers

Back 26

(13) SIGPIPE (default action is: Terminate)

Front 27

signal for: Timer signal from alarm(2)

Back 27

(14) SIGALRM (default action is: Terminate)

Front 28

signal for: Termination signal

Back 28

(15) SIGTERM (default action is: Terminate)

Front 29

signal for: User-defined signal 1

Back 29

(30,10,16) SIGUSR1 (default action is: Terminate)

Front 30

signal for: User-defined signal 2

Back 30

SIGUSR2 31,12,17 (default action is: Terminate)

Front 31

signal for: Child stopped or terminated

Back 31

(20,17,18) SIGCHLD (default action is IGNore)

Front 32

signal for: Continue if stopped

Back 32

(19,18,25) SIGCONT (default action is: CONTinue process if stopped)

Front 33

signal for: Stop process

Back 33

(17,19,23) SIGSTOP default action:stop)

NOTE: SIGKILL cannot be caught, blocked, or trapped

Front 34

signal for: Stop typed at tty

Back 34

(18,20,24) SIGTSTP (default action is: stop)

Front 35

signal for: tty input for background process

Back 35

(21,21,26) SIGTTIN (default action is: stop)

Front 36

signal for: tty output for background process

Back 36

(22,22,27) SIGTTOU (default action is: stop)

Front 37

signal for: Pollable event (Sys V).

Back 37

SIGPOLL (default action: Terminate)

Synonym of SIGIO

Front 38

signal for: Profiling timer expired

Back 38

(27,27,29) SIGPROF (default action is: Terminate)

Front 39

signal for: Bad argument to routine (SVr4)

Back 39

(12,-,12) SIGSYS (default action is: Terminate and dump CORE)

Front 40

signal for: Trace/breakpoint trap

Back 40

(5) SIGTRAP (default action is: Core)

Front 41

Signal for: Urgent condition on socket (4.2BSD)

Back 41

(16,23,21) SIGURG (default action: Ignore)

Front 42

TRAP syntax?

Back 42

trap [COMMANDS] [SIGNALS]

example:
trap "echo VARIABLE used" DEBUG

Front 43

redirection: script

Back 43

Save the activity on your screen to a file.

Front 44

redirection: tee

Back 44

...copy to stdin to file and screen

Front 45

redirection: xargs

Back 45

Read multiple arguments from standard input and use them as arguments to some specified command.

Front 46

redirection: 2>

Back 46

redirect standard-error as specified

Front 47

command:
make prompt show current working directory (pwd)

Back 47

export PS1='$PWD> '

NOTE: to make it permanent, add to ~/.bashrc

Front 48

command (users): change information displayed by finger

Back 48

chfn

Front 49

command (users): change user information in bulk

Back 49

chpasswd

Front 50

command (users): display information about a user

Back 50

finger

Front 51

command (users): modify information in the system group files

Back 51

groupmod

Front 52

commands (user): check system group files for validity

Back 52

grpck

Front 53

commands (user): display group information for a user

Back 53

groups

Front 54

commands (user): display information about a user

Back 54

id

Front 55

commands (user): change user password

Back 55

passwd

Front 56

commands (user): check system password for validity

Back 56

pwck

Front 57

commands (user): change to a new user id.

Back 57

su

Front 58

commands (user): add a new user

Back 58

useradd

Front 59

commands (user): delete a user

Back 59

userdel

Front 60

commands (user): modify user information

Back 60

usermod

Front 61

commands (user): display a list of current users

Back 61

users OR who

Front 62

commands (user): Secure group information

Back 62

/etc/gshadow

Front 63

commands: check paths for portability and validity?

Back 63

pathchk

Front 64

commands: Follow a path to the end, if it has one?

Back 64

namei

Front 65

commands: take a full path...and display all but the last element

Back 65

dirname

Front 66

commands: take a full path...and display only the last element

Back 66

basename

Front 67

commands: Display your current environment variables and their values with the command.

Back 67

env

Front 68

files: executed when starting a bash subshell

Back 68

~/.bashrc

Front 69

files: executed at login time

Back 69

~/.bash_profile

Front 70

files: system-wide profile

Back 70

/etc/profile

Front 71

files: Synonym for bash_profile

Back 71

~/.bash_login

Front 72

files: executed when a bash shell exits.

Back 72

~/.bash_logout

Front 73

INVOKING BASH: don't read the "~/.bashrc" initialization file in an interactive shell.

Back 73

-norc

Front 74

INVOKING BASH: Execute commands from the specified file rather than ~/.bashrc in an interactive shell.

Back 74

-rcfile FILENAME

Front 75

INVOKING BASH: Don't load the system-wide startup file /etc/profile OR any of the personal initialization files (~/.bash_profile, ~/.bash_login, ~/.profile).

Back 75

-noprofile

Front 76

INVOKING BASH: display version information

Back 76

-version

Front 77

INVOKING BASH: Make this shell act as if it were directly invoked from login.

Back 77

-login

Front 78

INVOKING BASH: do not perform curly brace expansion.

Back 78

-nobraceexpansion

Front 79

INVOKING BASH: do not use the GNU Readline library to read interactive command lines.

Back 79

-nolineediting

Front 80

INVOKING BASH: force bash to conform to the Posiz 1003.2 standard

Back 80

-posix

Front 81

INVOKING BASH: read and execute commands from STRING after processing the options and then exit.

Back 81

-c STRING

Front 82

INVOKING BASH: force the shell to run interactively.

Back 82

-i

Front 83

STEPS: Interactive bash...at login

Back 83

1. If /etc/profile exists, then source it.
2. If ~/.bash_profile exists,
then source it,
else if ~/.bash_login exists
then source it,
else if ~/.profile exists
then source it.

Front 84

STEPS: Interactive bash...at logout

Back 84

If ~/.bash_logout exists,
source it.

Front 85

STEPS: NON-login Interactive bash at Startup Time.

Back 85

If ~/.bashrc exists,
then source it.

Front 86

STEPS: NON-interactive Shells at Startup Time.

Back 86

If the environment variable ENV is non-null......expand the variable and source the file named by the value.

If bash is not started in Posix mode.....it looks for BASH_ENV before ENV.

So, typically, your ~/.bash_profile contains the following line:

if [ -f ~/.bashrc ];
then source ~/.bashrc;
fi

Front 87

alias syntax

Back 87

alias [-p] [name[=value] ... ]

note: -p option prints the list of aliases (same as alias with no argument)

Front 88

command: remove an alias

Back 88

unalias

note: -a would remove all aliases

Front 89

history shortcut: move up

Back 89

arrow up
or
<Ctrl>-P

Front 90

history shortcut: move down

Back 90

arrow down
or
<CTRL>-n

Front 91

history shortcut: move to the first line in history.

Back 91

<Meta>-<

Front 92

history shortcut: move to the end of input history.

Back 92

<Meta>->

Front 93

HISTORY SHORTCUT: search backward starting at the current line and moving "up" through the history as necessary.

Back 93

<Ctrl>-r

Front 94

HISTORY SHORTCUT: search forward starting at the current line and moving "down" through the history as necessary.

Back 94

<Ctrl>-s

Front 95

HISTORY SHORTCUT: search backward starting at the current line and moving "up" through the history as necessary....using a non-incremental search for a string supplied by the user.

Back 95

<Meta>-p

Front 96

HISTORY SHORTCUT: search forward starting at th ecurrent line and moving "down" through history as necessary .... using non-incremental search for a string supplied by the user.

Back 96

<Meta-n

Front 97

HISTORY SHORTCUT: yank nth argument of previous command.

Back 97

<Meta>-Ctrl>-y

Front 98

HISTORY SHORTCUT: Insert last argument to the previous command.

Back 98

<Meta>-. , M-_

Front 99

HISTORY SHORTCUT: start a history substitution, except when followed by a space, tab, the end of the line, = or (

Back 99

! (bang)

Front 100

HISTORY SHORTCUT: refer to the previous command. This the synonym for !-1

Back 100

!! (bang bang)

Front 101

HISTORY SHORTCUT: refer to command line N.

Back 101

!n (bang number)

Front 102

HISTORY SHORTCUT: refer to the command N lines back

Back 102

!-n

Front 103

HISTORY SHORTCUT: refer to the most recent command starting with STRING

Back 103

!string

Front 104

HISTORY SHORTCUT: refer to the most recent command containing STRING

Back 104

!?string[`?]

Front 105

HISTORY SHORTCUT: the entire command line typed so far.

Back 105

!# (bang sharp)

Front 106

HISTORY SHORTCUT:
quick substitution. Repeat the last command, replacing STRING1 with STRING2. Equivalent to "!!:s/string1/string2".

Back 106

^string1^string2^

Front 107

HISTORY SHORTCUT:
write out the current history to the history file.

Back 107

history -w

Front 108

HISTORY SHORTCUT:
read the current history file and make its contents the history list.

Back 108

history -r

Front 109

HISTORY SHORTCUT:
append the new history lines.

Back 109

history -a

Front 110

HISTORY SHORTCUT:
read the history lines not already read from the history file into the current list.

Back 110

history -n

Front 111

COMMAND COMPLETION:
attempt to do completion on the text before the cursor.

Back 111

<Tab>

Front 112

COMMAND COMPLETION:
list the possible completions of the text before the cursor.

Back 112

<Meta>-?

Front 113

COMMAND COMPLETION:
read in the contents of your init file and incorporate any bindings or variable assignments found there.

Back 113

<ctrl>-x, <ctrl>-r

Front 114

COMMAND COMPLETION:
abort the current editing command and ring the terminal's bell (subject to the setting of "bell-style"

Back 114

<ctrl>-g

Front 115

COMMAND COMPLETION:
make the next character that you type metafied.

Back 115

<Esc>

Front 116

COMMAND COMPLETION:
incremental undo, separately remembered for each line.

Back 116

<Ctrl>-_, <Ctrl>-x, <Ctrl>-u

Front 117

COMMAND COMPLETION:
Undo all changes made to this line.

Back 117

<Meta>-r

Front 118

Command Line Editing:
move back one character

Back 118

<ctrl>-b

Front 119

Command Line Editing:
move forward one character

Back 119

<ctrl>-f

Front 120

Command Line Editing:
delete the character to the left of the cursor

Back 120

<del> , <backspace>

Front 121

Command Line Editing:
delete the character underneath the cursor

Back 121

<Ctrl>-d

Front 122

Command Line Editing:
undo the last thing that you did.

Back 122

<Ctrl>-u

Front 123

Command Line Editing:
move to the start of the line

Back 123

<Ctrl>-a

Front 124

Command Line Editing:
move to the end of the line.

Back 124

<Ctrl>-e

Front 125

Command Line Editing:
move forward a word.<Anchor2>

Back 125

<Meta>-f

Front 126

Command Line Editing:
move backward a word.

Back 126

<Meta>-b

Front 127

Command Line Editing:
clear the screen, reprinting the current line at the top.

Back 127

<Ctrl>-I

Front 128

Command Line Editing:
Kill the text from the current cursor position to the end of the line.

Back 128

<ctrl>-k

Front 129

Command Line Editing:
Kill from the cursor to the end of the current word, or, if between words, to the end of the next word.

Back 129

<Meta>-d

Front 130

Command Line Editing:
Kill from the cursor the start of the previous word, or, if between words, to the start of the previous word

Back 130

<Meta>-DEL

Front 131

Command Line Editing:
kill from the cursor to the previous whitespace. This is different from M-DEL because the word boundaries differ.

Back 131

<Ctrl>-w

Front 132

Command Line Editing:
Yank the most recently killed taext back into the buffer at the cursor

Back 132

<Ctrl>-y

Front 133

Command Line Editing:
Rotate the kill-ring, and yank the new top. You can do this only if the prior command is yank or yank-pop.

Back 133

<Meta>-y

Front 134

Command Line Editing:
Delete the character under the cursor.

Back 134

<Ctrl>-d

Front 135

Command Line Editing:
Add the next character that you type to the line vertabim.

Back 135

<Ctrl>-q, C-w

Front 136

Command Line Editing:
Insert a tab character.

Back 136

<Meta>-<Tab>

Front 137

Command Line Editing:
Drag the chaaracter before the cursor forward over the character at the cursor....moving the cursor forward as well.

Back 137

<Ctrl>-t

Front 138

Command Line Editing:
Drag the word behind the cursor, past the word in front of the cursor....moving the cursor over that word as well.

Back 138

<Meta>-t

Front 139

Command Line Editing:
Uppercase the current (or following) word.

Back 139

<Meta>-u

Front 140

Command Line Editing:
Lowercase the current (or following) word.

Back 140

<Meta>-I

Front 141

Command Line Editing:
Capitalize the current (or following) word.

Back 141

<Meta>-c

Front 142

SHELL PROMPT (special characters):
The time, in HH:MM:SS format

Back 142

\t

Front 143

SHELL PROMPT (special characters):
The time in 12-hour HH:MM:SS format.

Back 143

\T

Front 144

SHELL PROMPT (special characters):
The time in 12-hour am/pm format.

Back 144

\@

Front 145

SHELL PROMPT (special characters):
The date, in "Weekday Month Date" format (e.g., "Tue May 26").

Back 145

\d

Front 146

SHELL PROMPT (special characters):
ASCII escape character.

Back 146

\e

Front 147

SHELL PROMPT (special characters):
newline

Back 147

\n

Front 148

SHELL PROMPT (special characters):
The name of the shell.

Back 148

\s

Front 149

SHELL PROMPT (special characters):
The current working directory.

Back 149

\w

Front 150

SHELL PROMPT (special characters):
The basename of $PWD.

Back 150

\W

Front 151

SHELL PROMPT (special characters):
Your username.

Back 151

\u

Front 152

SHELL PROMPT (special characters):
hostname

Back 152

\h

Front 153

SHELL PROMPT (special characters):
The command number of this command.

Back 153

\#

Front 154

SHELL PROMPT (special characters):
The history number of this command.

Back 154

\!

Front 155

SHELL PROMPT (special characters):
The character corresponding to the octal number nnn.

Back 155

\nnn

Front 156

SHELL PROMPT (special characters):
If the effective uid is 0, #; otherwise, $.

Back 156

\$

Front 157

SHELL PROMPT (special characters):
A backslash.

Back 157

\\

Front 158

SHELL PROMPT (special characters):
Begin a sequence of nonprinting characters.

Back 158

\[

Front 159

SHELL PROMPT (special characters):
End a sequence of nonprinting characters.

Back 159

\]

Front 160

SHELL ARITHMETIC:
two formats for math expansion

Back 160

$[ expression ]
or
$(( expression ))

Front 161

SHELL ARITHMETIC:
builtin for performing math on variables

Back 161

let

Front 162

SYNTAX:
"for" loop statement (simple)

Back 162

for name in word1 word2 ... wordN
do
list
done

OR:
for name in wordlist; do list; done

Front 163

SYNTAX:
"until" loop statement (simple)

Back 163

until [ condition ]
do
list
done

OR:
until cmd; do list; done

Front 164

SYNTAX:
"while" loop statement (simple)

Back 164

while [ condition ]
do
list
done

OR:
while test-cmd; do list; done

Front 165

SYNTAX:
"case" flow control statement (simple)

Back 165

case word in
pattern1)
list1 ;;
pattern2)
list2 ;;
pattern3)
list2 ;;
patternN)
list-N ;;
esac

Front 166

SYNTAX:
"if then else" flow control statement

Back 166

if [ condition ]
then
perform-list-2
elif [ condition ]
then
perform-list-4
else
perform-list-5
fi

Front 167

Login Banner location?

Back 167

/etc/issue

Front 168

Message of the day (at login)?

Back 168

/etc/motd

Front 169

If this file exists, ONLY root may login.

Back 169

/etc/nologin

Front 170

If this file exists, login is quiet.

Back 170

.hushlogin

Front 171

database of users currently logged in?

Back 171

/var/run/utmp

Front 172

Store login and logout history?

Back 172

/var/log/wtmp

Front 173

File that defines which ttys that root may log in from.

Back 173

/etc/securetty

Front 174

COMMAND:
...that will set terminal config values.

Back 174

setterm

Front 175

COMMAND:
...display or set tty config values

Back 175

stty

Front 176

COMMAND:
...display information about filesystems

Back 176

df

Front 177

KERNEL:
...program to add and remove modules from the linux kernel

Back 177

modprobe

Front 178

KERNEL:
...a module to create a module dependency list.

Back 178

depmod (creates modules.dep)

Front 179

KERNEL:
...simple tool for installing modules

Back 179

insmod (modprobe is "cleverer")

Front 180

KERNEL:
...show the status of modules in the Linux kernel

Back 180

lsmod
(formats contents of /proc/modules)

Front 181

KERNEL:
...remove modules from kernel

Back 181

rmmod
OR modprobe -r

Front 182

COMMAND:
...concatenate and print files in reverse

Back 182

tac (remember cat backwards)

Front 183

COMMAND:
...reverse lines

Back 183

rev (think forward = drawrof)

Front 184

COMMAND:
...compare two sorted files line by line

Back 184

comm
(this outputs common lines)

Front 185

COMMAND:
..compare two files, usually binary files

Back 185

cmp

Front 186

COMMAND:
...find the difference between two files

Back 186

diff

Front 187

COMMAND:
...find the difference between three files

Back 187

diff3

Front 188

COMMAND:
...merge differences between two files (interactively)

Back 188

sdiff

Front 189

COMMAND:
...columnate input

Back 189

column

Front 190

COMMAND:
...remove columns from a file

Back 190

colrm

Front 191

COMMAND:
...split a file into sections determined by context lines

Back 191

csplit

Front 192

COMMAND:
...remove sections from each line of files

Back 192

cut

Front 193

COMMAND:
...convert tabs to spaces

Back 193

expand

Front 194

COMMAND:
...Reformat each paragraph (width) in the FILE(s), writing to standard output.

Back 194

fmt

Front 195

COMMAND:
... wrap each input line to fit in specified width

Back 195

fold

Front 196

COMMAND:
...merge lines of files.
Write lines consisting of the sequentially corresponding lines from each FILE, separated by TABs, to standard output.

Back 196

paste

Front 197

COMMAND:
... split a file into pieces

Back 197

split

Front 198

COMMAND:
...Translate, squeeze, and/or delete characters from standard input, writing to standard output.

Back 198

tr

Front 199

COMMAND:
... convert spaces to tabs

Back 199

unexpand

Front 200

COMMAND:
...Discard all but one of successive identical lines from INPUT

Back 200

uniq

Front 201

COMMAND:
...show current run level

Back 201

runlevel

Front 202

COMMAND:
...display bootup messages

Back 202

dmesg

Front 203

COMMAND:
...add a job to the scheduling queue.

Back 203

at

Front 204

COMMAND:
...display the contents of the scheduling queue.

Back 204

atq

Front 205

COMMAND:
...remove a job from the scheduling queue.

Back 205

atrm.

Front 206

COMMAND:
...wait some number of seconds

Back 206

sleep n

Front 207

COMMAND:
...wait some number of micro-seconds

Back 207

usleep n

Front 208

COMMAND:
... batch executes commands when system load levels permit; in other words, when the load average drops below 0.8, or the
value specified in the invocation of atrun.

Back 208

batch

Front 209

FILE:
..defines users permitted to use 'at'

Back 209

/etc/at.allow

Front 210

FILE:
...defines users permitted to use 'cron'

Back 210

/etc/cron.allow

Front 211

FILE:
...defines users NOT permitted to use 'at'

Back 211

/etc/cron.deny

Front 212

FILE:
...defines users NOT permitted to use 'cron.deny'

Back 212

/etc/cron.deny

Front 213

FILE:
..contains system load average

Back 213

/proc/loadavg

Front 214

COMMAND:
...display amount of free and used memory in the system

Back 214

free

Front 215

COMMAND:
...graphic representation of system load average

Back 215

tload

Front 216

COMMAND:
...report virtual memory statistics

Back 216

vmstat

Front 217

COMMAND:
...display shared memory, semaphores, message queues.

Back 217

ipcs

Front 218

COMMAND:
...an encryption and signing tool

Back 218

gpg (GNU Privacy Guard)

Front 219

COMMAND:
...a signature verification tool

Back 219

gpgv

Front 220

COMMAND:
...display a calendar

Back 220

cal

Front 221

COMMAND:
... a spell checker designed to eventually replace Ispell.
It can either be used as a library or as an independent spell checker.

Back 221

aspell

Front 222

OSI Reference Model
...layers? (just another reminder :-)

Back 222

1. Physical
2. Data Link
3. Network
4. Transport
5. Session
6. Presentation
7. Application

Front 223

TCP MODEL
..."five layer Internet Model"

Back 223

5. Application
4. Transport
3. Network
2. Data Link
1. Physical

Front 224

COMMAND:
...network status information

Back 224

netstat

Front 225

COMMAND:
...display and manipulate routing information

Back 225

route

Front 226

FILE:
...contains Internet services by number

Back 226

/etc/services

Front 227

FILE:
...contains DNS server information

Back 227

/etc/resolv.conf

Front 228

COMMANDS:
...is a program to maintain identical copies of files over multiple hosts.

Back 228

rdist

Front 229

COMMAND:
...list open files for a user

Back 229

lsof -u username

Front 230

COMMAND:
...list active processes for a particular program

Back 230

lsof -c sshd (example)