Administración de sistemas Cheat Sheet

A Software › Linux cheat sheet in English by torvic98

Useful commnads and programs

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Sections of man pages

1	User-level commands and applications
2	System calls and kernel error codes
3	Library calls
4	Device drivers and network protocols
5	Standard file formats
6	Games and demonstrations
7	Miscellaneous files and documents
8	System administration commands
9	Obscure kernel specs and interfaces

Substitution order

1. Redirect I/O

2. Replace {} expansion

3. Replace `~` expansion

4. Params and variable expansion

5. Commnad $() substitution

6. Arithmetic expansion

7. Process <() substitution

8. Word splitting (IFS)

9. File name expansion

wget(1)

`-q, --quiet`	Turns off Wget's output
`-B, --base`	Relative links using URL
`-t, --tries`	Set number of retries
`-O {file\|-}`	Redirect output
`-T, --timeout`	Network timeout to seconds

date(1)

`-d, --date=`	Display time described, not now
`-s, --set=`	Set time to described ¡
`%a, %A`	Sun, Sunday
`%b, %B`	Jan, January
`%c`	Thu Mar 3 23:05:25 2005
`%d`	day of month
`%F`	full date; same as `%Y-%m-%d`
`%H, %I`	hour (00..23), hour (01..12)
`%m`	month (01..12)
`%M`	minute (00..59)
`%s`	seconds since epoch
`%S`	second (00..60)
`%T`	time; same as `%H:%M:%S`
`%Y`	Year

tar(1)

`-c, --create`	create new
`-r, --append`	append files
`-t, --list`	list the contents
`-u, --update`	only append newer
`-x, --extract`	extract files
`-C, --directory=`	change to directory
`-f, --file=`	use archive file or device
`-j, --bzip2`	bzip2
`-z, --gzip`	gzip

sort(1)

`-b`	ignore leading blanks
`-d`	only blanks and alphanumeric
`-f`	case insensitive
`-i`	ignore non-printable
`-M`	compare 3-letter month
`-h`	human numeric (2K < 1G)
`-n`	numeric
`-R`	random short (hash)
`-r`	reverse result, i. e. descending
`-k`	Key start at pos (origin 1)
`-u`	Delete duplicates
`-z`	Zero terminated lines

read(1)

`-p prompt`	Shows prompt text
`-r`	One line only (no backslash)
`-s`	Silent. No echo.
`-t`	Timeout in seconds
`-u fd`	Read from file descriptor
`-n`	Number of chars
`-d`	Set delimiter

du(1)

`-a`	All files (not just dirs)
`--files0-from=`	Null separated. '-' is stdin
`-h`	Human readable
`--max-depth`	'0' => just given argument

lvm(8) - pv / vg / lv

~change	Change attributes
~create	Initialize for use by LVM.
~display	Display attributes
~resize	Resize a LVM ~
~extend -L	Extends ~ by [+]bytes
~scan	Shows all LVM ~

Tips: mkfs -t ext3 part / resize2fs lv_name

/etc/passwd

/etc/shadow

/etc/group

name:passwd:GID:login-list

passwd(1)

`-e`	Expire date
`-d`	Delete password
`-l, -u`	Lock or unlock
`-n`	Min days between changes
`-x`	Max days of validity
`-w`	Warn days before expire
`-i`	Deactivate days
`-S`	Show status of account

Shell and tools (I)

type	Shows type of the program or command given as first paramether
stty	Change and print terminal line settings
chpasswd	Reads from stdin pairs of type USER:PASSWORD
id	Returns user info `uid=1000(name) gid=1000(name)`. Exit code is set.
bc	Math expresions from stdin. Tip: use `scale=n;` for div precision
seq	[FISR [INCREMENT]] LAST

Shell and tools (II)

cat	who	whoami	head
echo	cp	mv	ln
mkdir	rm	rmdir	ln -s
cat	less	more	bg
tee	exec	jobs	fg
env	printenv	readonly	export
local	$(())	pwd	ls
paste	uniq	wc -l	fmt
join	split	tac	rev
nl	expand	od	chown
chgrp	chmod	passwd	useradd
userdel	usermod	groupadd

find(1) [OPTIONS]

`-maxdepth`	Descend at most levels
`-mindepth`	No actions at less than levels

find(1) [TESTS]

`+n, -n, n`	greater, less, exactly n
`-amin n`	Last accessed n minutes ago
`-atime n`	Last accessed n days ago
`-cmin, -ctime n`	Last changed
`-mmin, -mtime n`	Last modified
`-empty`	Empty regular or directory
`-executable`	File or directory +x
`-group gname`	File belongs to group
`-gid n`	Numeric group ID
`-user uname`	File belongs to user
`-uid n`	Numeric user ID
`-name`	Base name matches pattern
`-iname`	-name, but case insensitive
`-path`	File name matches pattern
`-perm mode`	Permission bits are...
`g=u, +g=u, /g=u`	exactly, at least, any of
`-size n[cwbkMG]`	File uses space
`-type [bcdpfls]`	File is of type
`-readable`	With read permission
`-writable`	With write permission

find(1) [ACTIONS]

`-delete`	Delete files
`-exec cmd;`	Execute for every file (multiple {})
`-exec cmd+`	Execute appending file (single {})
`-fprint`	Print into file
`-ok cmd ;`	Like -exec, but ask user first
`-print0`	Null seperated
`-printf`	Print with format

cut(1)

`-b`	Select bytes
`-c`	Select characters
`-f`	Select fields
`-d`	Field delimiter
`--complement`	Complement selector
`N, N-, N-M, -M`	Specifies selector

ping(8)

`-c`	Number of requests

tail(1)

`-c K`	Bytes to print
`-n K`	Lines to print
`K`	May have sufix (b, kB, K...)
`+K`	Print from...

ps(1)

`-e`	All process
`-a`	All except leaders and no-terminal
`-g`	By group
`-p`	By pid
`-t`	By tty
`-u`	By user
`-F`	Full output format
`-o`	Custom output format

wc(1)

`-l`	Number of lines
`-w`	Number of words
`-c`	Number of bytes
`-L`	Length of longest line

Predefined variables

$0	Program name
$1-$9	Normal params
${10}, ${11}...	More params
$#	Number of params
$*	List of params
$@	List of params (*)
$?	Exit status code
$$	Process id
$!	Last child process id

(*) Use "$@" when reading in for-loop

/etc/sudoers

user ALL=ALL
%group ALL=NOPASSWD:/usr/bin/true

Shell and tools (III)

if *cond*; then
[elif *cond*; then]
else
fi

IF=$' \t\n'
while *cond*
do
[break | continue]
done

until *cond*

for i in list
do
done

Shell special characters

'	"	\	&
<	>	<<	>>
*	\|	?	[ ]
[!^ ]	$	;	`

Between " " only $, `cmd` and \

Extended regex

.	[ ]	[^ ]	^
$	*	( )	\
{n,m}	+	?	\w
\s	\b	\B

egrep(1)

`-e`	Specifies the pattern
`-f`	Get patterns from file lines
`-i`	Case insensitive
`-v`	Select non-matching lines
`-w`	Match whole words only
`-c`	Show (non-)matching lines count
`-q`	Quiet (exit 0 when match)

test(1)

`( EXPRESSION )`	is true
`! EXPRESSION`	is false
`EXP -a EXP`	Logic AND
`EXP -o EXP`	Logic OR
`-n STRING`	Not null string
`-z STRING`	Null string
`STR = STR`	Strings are equal
`STR != STR`	Strings are different
`INT -eq INT`	Numbers are equal
`INT -ne INT`	Numbers are different
`-ge, -gt`	>=, >
`-le, -lt`	<=, <
`FILE1 -ef FILE2`	Same device and inode
`FILE1 -nt FILE2`	F1 is newer than F2
`FILE1 -ot FILE2`	F1 is older than F2
`-b, -c, -d, -f`	block, chars, dir, regular
`-e, -r, -w, -x`	exists, read, write, exec
`-t FD`	File descriptor FD is opened

stat(1)

`-c`	Specifies output format
`%a, %A`	Access rights octal, human
`%b, %s`	Size in block, bytes
`%F`	File type
`%g, %G`	Group owner id, name
`%h`	Number of names (links)
`%i`	Inode number
`%n, $N`	File name, quoted
`%t, %T`	Device major, minor
`%u, %U`	User owner id, name
`%x, %X`	Last access time, epoch
`%y, %Y`	Last modified time, epoch
`%z, %Z`	Last changed time, epoch

tr(1)

-c	Use complement of SET1
-d	delete chars from SET1

Translation occurs if -d is not given and both SET1 and SET2 appear. SET2 is extended to length of SET1 by repeating its last character as necessary. Excess characters of SET2 are ignored.

sed(1)

`-e cmd`	Multi-command mode
`=`	Current line number
`a`	Append text
`i`	Insert text
`c`	Replace lines
`d`	Delete pattern
`s`	Replace pattern
`g`	Apply globally (more than once)

[ line_n [ ,line_n ] ] commnad [ parameters ]
! line_n command [parameters]
[ line_n, $ ] commnad [ parameters ]

ps(1) [FORMAT]

pid	state	user
ruser	group	rgroup
pid	ppid	pgid
pcpu	nice	etime
time	tty	comm
args

xargs(1)

`-i`	permite el uso de {}
`-r`	No run if empty
`--null, -0`	Null terminated args
`-d`	Delimiter
`-n`	Max args

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