[VPS] Toàn bộ câu lệnh sử dụng trong Server Linux từ A

Toàn bộ câu lệnh sử dụng trong Server Linux từ A – Z

Linux Commands Line A – Z

A Command Description

# alias hh=’history’ set an alias for a command – hh = history

# apropos …keyword display a list of commands that pertain to keywords of a program , useful when you know what your program does, but you don’t know the name of the command

# apt-cache search [package] returns list of packages which corresponds string “searched-packages”

# apt-cdrom install [package] install / upgrade a deb package from cdrom

# apt-get install [package] install / upgrade a deb package

# apt-get update update the package list

# apt-get upgrade upgrade all of the installed packages

# apt-get remove [package] remove a deb package from system

# apt-get check verify correct resolution of dependencies

# apt-get clean clean up cache from packages downloaded

# arch show architecture of machine(1)

# cat example.txt | awk ‘NR%2==1′ remove all even lines from example.txt

# echo a b c | awk ‘{print $1}’ view the first column of a line

# echo a b c | awk ‘{print $1,$3}’ view the first and third column of a line

B Command Description

# badblocks -v /dev/hda1 check bad blocks on disk hda1

# bunzip2 file1.bz2 decompress a file called ‘file1.bz2′

# bzip2 file1 compress a file called ‘file1′

# find /var/log -name ‘*.log’ | tar cv –files-from=- | bzip2 > log.tar.bz2 find all files with ‘.log’ extention and make an bzip archive

C Command Description

# cal 2007 show the timetable of 2007

# cat /proc/cpuinfo show information CPU info

# cat /proc/interrupts show interrupts

# cat /proc/meminfo verify memory use

# cat /proc/swaps show file(s) swap

# cat /proc/version show version of the kernel

# cat /proc/net/dev show network adpters and statistics

# cat /proc/mounts show mounted file system(s)

# cat file1 view the contents of a file starting from the first row

# cat -n file1 number row of a file

# cd /home enter to directory ‘/ home’

# cd .. go back one level

# cd ../.. go back two levels

# cd go to home directory

# cd ~user1 go to home directory

# cd - go to previous directory

# cd-paranoia -B rip audio tracks from a CD to wav files

# cd-paranoia – rip first three audio tracks from a CD to wav files

# cdrecord -v gracetime=2 dev=/dev/cdrom -eject blank=fast -force clean a rewritable cdrom

# cdrecord -v dev=/dev/cdrom cd.iso burn an ISO image

# gzip -dc cd_iso.gz | cdrecord dev=/dev/cdrom - burn a compressed ISO image

# cdrecord –scanbus scan bus to identify the channel scsi

# chage -E 2005-12-31 user1 set deadline for user password

# chattr +a file1 allows write opening of a file only append mode

# chattr +c file1 allows that a file is compressed / decompressed automatically by the kernel

# chattr +d file1 makes sure that the program ignores Dump the files during backup

# chattr +i file1 makes it an immutable file, which can not be removed, altered, renamed or linked

# chattr +s file1 allows a file to be deleted safely

# chattr +S file1 makes sure that if a file is modified changes are written in synchronous mode as with sync

# chattr +u file1 allows you to recover the contents of a file even if it is canceled

# chgrp group1 file1 change group of files

# chmod ugo+rwx directory1 set permissions reading (r), write (w) and (x) access to users owner (u) group (g) and others (o)

# chmod go-rwx directory1 remove permits reading (r), write (w) and (x) access to users group (g) and others (or

# chmod u+s /bin/file1 set SUID bit on a binary file – the user that running that file gets same privileges as owner

# chmod u-s /bin/file1 disable SUID bit on a binary file

# chmod g+s /home/public set SGID bit on a directory – similar to SUID but for directory

# chmod g-s /home/public disable SGID bit on a directory

# chmod o+t /home/public set STIKY bit on a directory – allows files deletion only to legitimate owners

# chmod o-t /home/public disable STIKY bit on a directory

# chown user1 file1 change owner of a file

# chown -R user1 directory1 change user owner of a directory and all the files and directories contained inside

# chown user1:group1 file1 change user and group ownership of a file

# chsh change shell command

# chsh –list-shells nice command to know if you have to remote into another box

# clock -w save date changes on BIOS

# comm -1 file1 file2 compare contents of two files by deleting only unique lines from ‘file1′

# comm -2 file1 file2 compare contents of two files by deleting only unique lines from ‘file2′

# comm -3 file1 file2 compare contents of two files by deleting only the lines that appear on both files

# cp file1 file2 copying a file

# cp dir/* . copy all files of a directory within the current work directory

# cp -a /tmp/dir1 . copy a directory within the current work directory

# cp -a dir1 dir2 copy a directory

# find /home/user1 -name ‘*.txt’ | xargs cp -av –target-directory=/home/backup/ –parents find and copy all files with ‘.txt’ extention from a directory to another

D Command Description

# date show system date

# date 041217002007.00 set date and time – MonthDayhoursMinutesYear.Seconds

# dd bs=1M if=/dev/hda | gzip | ssh user@ip_addr ‘dd of=hda.gz’ make a backup of a local hard disk on remote host via ssh

# dd if=/dev/sda of=/tmp/file1 backup content of the harddrive to a file

# dd if=/dev/hda of=/dev/fd0 bs=512 count=1 make a copy of MBR (Master Boot Record) to floppy

# dd if=/dev/fd0 of=/dev/hda bs=512 count=1 restore MBR from backup copy saved to floppy

# df -h show list of partitions mounted

# dhclient eth0 active interface ‘eth0′ in dhcp mode

# diff file1 file2 find differences between two files

# dmidecode -q show hardware system components – (SMBIOS / DMI)

# dos2unix filedos.txt fileunix.txt convert a text file format from MSDOS to UNIX

# dosfsck /dev/hda1 repair / check integrity of dos filesystems on disk hda1

# dpkg-query -W -f=’${Installed-Size;10}t${Package}n’ | sort -k1,1n show the used space by installed deb packages, sorting by size (debian, ubuntu and alike)

# dpkg -i [package.deb] install / upgrade a deb package

# dpkg -r [package] remove a deb package from the system

# dpkg -l show all deb packages installed on the system

# dpkg -l | grep httpd show all deb packages with the name “httpd”

# dpkg -s [package] obtain information on a specific package installed on system

# dpkg -L [package] show list of files provided by a package installed on system

# dpkg –contents [package.deb] show list of files provided by a package not yet installed

# dpkg -S /bin/ping verify which package belongs to a given file

# du -sh dir1 estimate space used by directory ‘dir1′

# du -sk * | sort -rn show size of the files and directories sorted by size

# dump -0aj -f /tmp/home0.bak /home make a full backup of directory ‘/home’

# dump -1aj -f /tmp/home0.bak /home make a incremental backup of directory ‘/home’

E Command Description

# e2fsck /dev/hda1 repair / check integrity of ext2 filesystem on disk hda1

# e2fsck -j /dev/hda1 repair / check integrity of ext3 filesystem on disk hda1

# ethtool eth0 show network statistics of eth0

F Command Description

# fdformat -n /dev/fd0 format a floppy disk

# cp file file1 outputs the mime type of the file as text

# find / -name file1 search file and directory into root filesystem from ‘/’

# find / -user user1 search files and directories belonging to ‘user1′

# find /home/user1 -name \*.bin search files with ‘. bin’ extension within directory ‘/ home/user1′

# find /usr/bin -type f -atime +100 search binary files are not used in the last 100 days

# find /usr/bin -type f -mtime -10 search files created or changed within 10 days

# find / -name *.rpm -exec chmod 755 ‘{}’ \; search files with ‘.rpm’ extension and modify permits

# find / -xdev -name \*.rpm search files with ‘.rpm’ extension ignoring removable partitions as cdrom, pen-drive, etc.…

# find / -perm -u+s view all files on the system with SUID configured

# free -m displays status of RAM in megabytes

# fsck /dev/hda1 repair / check integrity of linux filesystem on disk hda1

# fsck.ext2 /dev/hda1 repair / check integrity of ext2 filesystem on disk hda1

# fsck.ext3 /dev/hda1 repair / check integrity of ext3 filesystem on disk hda1

# fsck.vfat /dev/hda1 repair / check integrity of fat filesystem on disk hda1

# fsck.msdos /dev/hda1 repair / check integrity of dos filesystem on disk hda1

# fuser -km /mnt/hda2 force umount when the device is busy

G Command Description

# gpg -c file1 encrypt a file with GNU Privacy Guard

# gpg file1.gpg decrypt a file with GNU Privacy Guard

# grep Aug /var/log/messages look up words “Aug” on file ‘/var/log/messages’

# grep ^Aug /var/log/messages look up words that begin with “Aug” on file ‘/var/log/messages’

# grep [0-9] /var/log/messages select from file ‘/var/log/messages’ all lines that contain numbers

# grep Aug -R /var/log/* search string “Aug” at directory ‘/var/log’ and below

# groupadd [group] create a new group

# groupdel [group] delete a group

# groupmod -n moon sun rename a group from moon to sun

# grpck check correct syntax and file format of ‘/etc/group’ and groups existence

# gunzip file1.gz decompress a file called ‘file1.gz’

# gzip file1 compress a file called ‘file1′

# gzip -9 file1 compress with maximum compression

H Command Description

# hdparm -i /dev/hda displays the characteristics of a hard-disk

# hdparm -tT /dev/sda perform test reading on a hard-disk

# head -2 file1 view first two lines of a file

# host www.example.com lookup hostname to resolve name to ip address and viceversa

# hostname show hostname of system

I Command Description

# iconv -l lists known encodings

# iconv -f fromEncoding -t toEncoding inputFile > outputFile converting the coding of characters from one format to another

# find . -maxdepth 1 -name *.jpg -print -exec convert batch resize files in the current directory and send them to a thumbnails directory (requires convert from Imagemagick)

# ifconfig eth0 show configuration of an ethernet network card

# ifconfig eth0 192.168.1.1 netmask 255.255.255.0 configure IP Address

# ifconfig eth0 promisc configure ‘eth0′ in promiscuous mode to gather packets (sniffing)

# ifdown eth0 disable an interface ‘eth0′

# ifup eth0 activate an interface ‘eth0′

# init 0 shutdown system(2)

# ip link show show link status of all network interfaces

# iptables -t filter -L show all chains of filtering table

# iptables -t nat -L show all chains of nat table

# iptables -t filter -F clear all rules from filtering table

# iptables -t nat -F clear all rules from table nat

# iptables -t filter -X delete any chains created by user

# iptables -t filter -A INPUT -p tcp –dport telnet -j ACCEPT allow telnet connections to input

# iptables -t filter -A OUTPUT -p tcp –dport http -j DROP block HTTP connections to output

# iptables -t filter -A FORWARD -p tcp –dport pop3 -j ACCEPT allow POP3 connections to forward chain

# iptables -t filter -A INPUT -j LOG –log-prefix Logging on input chain

# iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE configure a PAT (Port Address Traslation) on eth0 masking outbound packets

# iptables -t nat -A PREROUTING -d 192.168.0.1 -p tcp -m tcp –dport 22 -j DNAT –to-destination 10.0.0.2:22 redirect packets addressed to a host to another host

# iwconfig eth1 show wireless networks

# iwlist scan wifi scanning to display the wireless connections available

K Command Description

# kill -9 process_id force closure of the process and finish it

# kill -1 process_id force a process to reload configuration

L Command Description

# last reboot show history reboot

# ldd /usr/bin/ssh show shared libraries required by ssh program

# less file1 similar to ‘more’ command but which allows backward movement in the file as well as forward movement

# ln -s file1 lnk1 create a symbolic link to file or directory

# ln file1 lnk1 create a physical link to file or directory

# locate \*.ps find files with the ‘.ps’ extension – first run ‘updatedb’ command

# logout leaving session

# ls view files of directory

# ls -F view files of directory

# ls -l show details of files and directory

# ls -a show hidden files

# ls *[0-9]* show files and directory containing numbers

# ls -lSr |more show size of the files and directories ordered by size

# ls -lh show permits on files

# ls /tmp | pr -T5 -W$COLUMNS divide terminal into 5 columns

# lsattr show specials attributes

# lsmod display kernel loaded

# lsof -p process_id display a list of files opened by processes

# lsof /home/user1 displays a list of open files in a given path system

# lspci -tv display PCI devices

# lstree show files and directories in a tree starting from root(2)

# lsusb -tv show USB devices

M Command Description

# man ping display the on-line manual pages for example on ping command – use ‘-k’ option to find any related commands

# dd if=/dev/hdc | md5sum perform an md5sum on a device, like a CD

# mii-tool eth0 show link status of ‘eth0′

# mkbootdisk –device /dev/fd0 `uname -r` create a boot floppy

# mkdir dir1 create a directory called ‘dir1′

# mkdir dir1 dir2 create two directories simultaneously

# mkdir -p /tmp/dir1/dir2 create a directory tree

# mke2fs /dev/hda1 create a filesystem type linux ext2 on hda1 partition

# mke2fs -j /dev/hda1 create a filesystem type linux ext3 (journal) on hda1 partition

# mkfs /dev/hda1 create a filesystem type linux on hda1 partition

# mkfs -t vfat 32 -F /dev/hda1 create a FAT32 filesystem

# mkisofs /dev/cdrom > cd.iso create an iso image of cdrom on disk

# mkisofs /dev/cdrom | gzip > cd_iso.gz create a compressed iso image of cdrom on disk

# mkisofs -J -allow-leading-dots -R -V create an iso image of a directory

# mkswap /dev/hda3 create a swap filesystem

# mkswap /dev/hda3 create a swap filesystem

# more file1 view content of a file along

# mount /dev/hda2 /mnt/hda2 mount disk called hda2 – verify existence of the directory ‘/ mnt/hda2′

# mount /dev/fd0 /mnt/floppy mount a floppy disk

# mount /dev/cdrom /mnt/cdrom mount a cdrom / dvdrom

# mount /dev/hdc /mnt/cdrecorder mount a cdrw / dvdrom

# mount /dev/hdb /mnt/cdrecorder mount a cdrw / dvdrom

# mount -o loop file.iso /mnt/cdrom mount a file or iso image

# mount -t vfat /dev/hda5 /mnt/hda5 mount a Windows FAT32 file system

# mount /dev/sda1 /mnt/usbdisk mount a usb pen-drive or flash-drive

# mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share mount a windows network share

# mount -o loop cd.iso /mnt/iso mount an ISO image

# mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share mount a windows network share

# mv dir1 new_dir rename / move a file or directory [man]

N Command Description

# nbtscan ip_addr netbios name resolution

# netstat -tup show all active network connections and their PID

# netstat -tupl show all network services listening on the system and their PID

# netstat -rn show routing table alike “route -n”

# newgrp – [group] log into a new group to change default group of newly created files

# nmblookup -A ip_addr netbios name resolution

# nslookup www.example.com lookup hostname to resolve name to ip address and viceversa

P Command Description

# pacman -S name Install package ‘name’ with dependencies

# pacman -R name Delete package ‘name’ and all files of it

# passwd change password

# passwd user1 change a user password (only by root)

# paste file1 file2 merging contents of two files for columns

# paste -d ‘+’ file1 file2 merging contents of two files for columns with ‘+’ delimiter on the center

# ps -eafw displays linux tasks

# ps -e -o pid,args –forest displays linux tasks in a hierarchical mode

# pstree Shows a tree system processes

# pwck check correct syntax and file format of ‘/etc/passwd’ and users existence

# pwd show the path of work directory

R Command Description

# rar a file1.rar test_file create an archive rar called ‘file1.rar’

# rar a file1.rar file1 file2 dir1 compress ‘file1′, ‘file2′ and ‘dir1′ simultaneously

# rar x file1.rar decompress rar archive

# reboot reboot(2)

# recode ..HTML < page.txt > page.html convert a text file to html

# recode -l | more show all available formats conversion

# restore -if /tmp/home0.bak restoring a backup interactively

# rm -f file1 delete file called ‘file1′

# rm -rf dir1 remove a directory called ‘dir1′ and contents recursively

# rm -rf dir1 dir2 remove two directories and their contents recursively

# rmdir dir1 delete directory called ‘dir1′

# route -n show routing table

# route add -net 0/0 gw IP_Gateway configure default gateway

# route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1 configure static route to reach network ’192.168.0.0/16′

# route del 0/0 gw IP_gateway remove static route

# echo “1″ > /proc/sys/net/ipv4/ip_forward activate ip routing temporarily

# rpm -q -a –qf ‘%10{SIZE}t%{NAME}n’ | sort -k1,1n show the used space by rpm packages installed sorted by size (fedora, redhat and alike)

# rpm -ivh [package.rpm] install a rpm package

# rpm -ivh –nodeeps [package.rpm] install a rpm package ignoring dependencies requests [

# rpm -U [package.rpm] upgrade a rpm package without changing configuration files

# rpm -F [package.rpm] upgrade a rpm package only if it is already installed

# rpm -e [package] remove a rpm package

# rpm -qa show all rpm packages installed on the system

# rpm -qa | grep httpd show all rpm packages with the name “httpd”

# rpm -qi [package] obtain information on a specific package installed [man]

# rpm -qg “System Environment/Daemons” show rpm packages of a group software

# rpm -ql [package] show list of files provided by a rpm package installed

# rpm -qc [package] show list of configuration files provided by a rpm package installed

# rpm -q [package] –whatrequires show list of dependencies required for a rpm packet

# rpm -q [package] –whatprovides show capability provided by a rpm package

# rpm -q [package] –scripts show scripts started during installation / removal

# rpm -q [package] –changelog show history of revisions of a rpm package

# rpm -qf /etc/httpd/conf/httpd.conf verify which rpm package belongs to a given file

# rpm -qp [package.rpm] -l show list of files provided by a rpm package not yet installed

# rpm –import /media/cdrom/RPM-GPG-KEY import public-key digital signature

# rpm –checksig [package.rpm] verify the integrity of a rpm package

# rpm -qa gpg-pubkey verify integrity of all rpm packages installed

# rpm -V [package] check file size, permissions, type, owner, group, MD5 checksum and last modification

# rpm -Va check all rpm packages installed on the system – use with caution

# rpm -Vp [package.rpm] verify a rpm package not yet installed

# rpm -ivh /usr/src/redhat/RPMS/`arch`/[package.rpm] install a package built from a rpm source

# rpm2cpio [package.rpm] | cpio –extract –make-directories *bin* extract executable file from a rpm package

# rpmbuild –rebuild [package.src.rpm] build a rpm package from a rpm source

# rsync -rogpav –delete /home /tmp synchronization between directories

# rsync -rogpav -e ssh –delete /home ip_address:/tmp rsync via SSH tunnel

# rsync -az -e ssh –delete ip_addr:/home/public /home/local synchronize a local directory with a remote directory via ssh and compression

# rsync -az -e ssh –delete /home/local ip_addr:/home/public synchronize a remote directory with a local directory via ssh and compression

S Command Description

# sdiff file1 file2 find differences between two files and merge interactively alike “diff”

# sed ‘s/string1/string2/g’ example.txt replace “string1″ with “string2″ in example.txt

# sed ‘/^$/d’ example.txt remove all blank lines from example.txt

# sed ‘/ *#/d; /^$/d’ example.txt remove comments and blank lines from example.txt

# sed -e ’1d’ exampe.txt eliminates the first line from file example.txt

# sed -n ‘/string1/p’ view only lines that contain the word “string1″

# sed -e ‘s/ *$//’ example.txt remove empty characters at the end of each row

# sed -e ‘s/string1//g’ example.txt remove only the word “string1″ from text and leave intact all

# sed -n ’1,5p’ example.txt print from 1th to 5th row of example.txt

# sed -n ’5p;5q’ example.txt print row number 5 of example.txt

# sed -e ‘s/00*/0/g’ example.txt replace more zeros with a single zero

# shutdown -h now shutdown system(1)

# shutdown -h 16:30 & planned shutdown of the system at 16:30

# shutdown -c cancel a planned shutdown of the system

# shutdown -r now reboot(1)

# smartctl -A /dev/hda monitoring reliability of a hard-disk through SMART

# smartctl -i /dev/hda check if SMART is active on a hard-disk

# smbclient -L ip_addr/hostname show remote shares of a windows host

# smbget -Rr smb://ip_addr/share like wget can download files from a host windows via smb

# sort file1 file2 sort contents of two files

# sort file1 file2 | uniq sort contents of two files omitting lines repeated

# sort file1 file2 | uniq -u sort contents of two files by viewing only unique line

# sort file1 file2 | uniq -d sort contents of two files by viewing only duplicate line

# strace -c ls >/dev/null display system calls made and received by a process

# strace -f -e open ls >/dev/null display library calls

# swapon /dev/hda3 activating a new swap partition

# swapon /dev/hda2 /dev/hdb3 activate two swap partitions

T Command Description

# tac file1 view the contents of a file starting from the last line

# tail -2 file1 view last two lines of a file

# tail -f /var/log/messages view in real time what is added to a file

# tail /var/log/dmesg show events inherent to the process of booting kernel

# tail /var/log/messages show system events

# tar -cvf archive.tar file1 create a uncompressed tarball

# tar -cvf archive.tar file1 file2 dir1 create an archive containing ‘file1′, ‘file2′ and ‘dir1′

# tar -tf archive.tar show contents of an archive

# tar -xvf archive.tar extract a tarball

# tar -xvf archive.tar -C /tmp extract a tarball into / tmp

# tar -cvfj archive.tar.bz2 dir1 create a tarball compressed into bzip2

# tar -xvfj archive.tar.bz2 decompress a compressed tar archive in bzip2

# tar -cvfz archive.tar.gz dir1 create a tarball compressed into gzip

# tar -xvfz archive.tar.gz decompress a compressed tar archive in

# tar -Puf backup.tar /home/user make a incremental backup of directory ‘/home/user’

# ( cd /tmp/local/ && tar c . ) | ssh -C user@ip_addr ‘cd /home/share/ && tar x -p’ copy content of a directory on remote directory via ssh

# ( tar c /home ) | ssh -C user@ip_addr ‘cd /home/backup-home && tar x -p’ copy a local directory on remote directory via ssh

# tar cf – . | (cd /tmp/backup ; tar xf – ) local copy preserving permits and links from a directory to another

# tcpdump tcp port 80 show all HTTP traffic

# telinit 0 shutdown system(3)

# top display linux tasks using most cpu

# touch -t 0712250000 file1 modify timestamp of a file or directory – (YYMMDDhhmm)

# echo ‘word’ | tr ‘[:lower:]‘ ‘[:upper:]‘ convert from lower case in upper case

# tree show files and directories in a tree starting from root(1)

U Command Description

# umount /dev/hda2 unmount disk called hda2 – exit from mount point ‘/ mnt/hda2′ first

# umount -n /mnt/hda2 run umount without writing the file /etc/mtab – useful when the file is read-only or the hard disk is full

# uname -m show architecture of machine(2)

# uname -r show used kernel version

# unix2dos fileunix.txt filedos.txt convert a text file format from UNIX to MSDOS

# unrar x file1.rar decompress rar archive

# unzip file1.zip decompress a zip archive

# useradd -c “User Linux” -g admin -d /home/user1 -s /bin/bash user1 create a new user “user1″ belongs “admin” group

# useradd user1 create a new

# userdel -r user1 delete a user ( ‘-r’ eliminates home directory)

# usermod -c “User FTP” -g system -d /ftp/user1 -s /bin/nologin user1 change user attributes as description, group and other

W Command Description

# watch -n1 ‘cat /proc/interrupts’ display interrupts in real-time

# wget -r www.example.com download an entire web site

# wget -c www.example.com/file.iso download a file with the ability to stop the download and resume later

# echo ‘wget -c www.example.com/files.iso’ | at 09:00 start a download at any given time

# whatis …keyword displays description of what a program does

# whereis halt show location of a binary file, source or man

# which halt show full path to a binary / executable

# who -a show who is logged on, and print: time of last system boot, dead processes, system login processes, active processes spawned by init, current runlevel, last system clock change

# whois www.example.com lookup on Whois database

Y Command Description

# yum -y install [package] download and install a rpm package

# yum localinstall [package.rpm] That will install an RPM, and try to resolve all the dependencies for you using your repositories.

# yum -y update update all rpm packages installed on the system

# yum update [package] upgrade a rpm package

# yum remove [package] remove a rpm package

# yum list list all packages installed on the system

# yum search [package] find a package on rpm repository

# yum clean [package] clean up rpm cache erasing downloaded packages

# yum clean headers remove all files headers that the system uses to resolve dependency

# yum clean all remove from the cache packages and headers files

A Command	Description
# alias hh=’history’	set an alias for a command – hh = history
# apropos …keyword	display a list of commands that pertain to keywords of a program , useful when you know what your program does, but you don’t know the name of the command
# apt-cache search [package]	returns list of packages which corresponds string “searched-packages”
# apt-cdrom install [package]	install / upgrade a deb package from cdrom
# apt-get install [package]	install / upgrade a deb package
# apt-get update	update the package list
# apt-get upgrade	upgrade all of the installed packages
# apt-get remove [package]	remove a deb package from system
# apt-get check	verify correct resolution of dependencies
# apt-get clean	clean up cache from packages downloaded
# arch	show architecture of machine(1)
# cat example.txt \| awk ‘NR%2==1′	remove all even lines from example.txt
# echo a b c \| awk ‘{print $1}’	view the first column of a line
# echo a b c \| awk ‘{print $1,$3}’	view the first and third column of a line

B Command	Description
# badblocks -v /dev/hda1	check bad blocks on disk hda1
# bunzip2 file1.bz2	decompress a file called ‘file1.bz2′
# bzip2 file1	compress a file called ‘file1′
# find /var/log -name ‘*.log’ \| tar cv –files-from=- \| bzip2 > log.tar.bz2	find all files with ‘.log’ extention and make an bzip archive

C Command	Description
# cal 2007	show the timetable of 2007
# cat /proc/cpuinfo	show information CPU info
# cat /proc/interrupts	show interrupts
# cat /proc/meminfo	verify memory use
# cat /proc/swaps	show file(s) swap
# cat /proc/version	show version of the kernel
# cat /proc/net/dev	show network adpters and statistics
# cat /proc/mounts	show mounted file system(s)
# cat file1	view the contents of a file starting from the first row
# cat -n file1	number row of a file
# cd /home	enter to directory ‘/ home’
# cd ..	go back one level
# cd ../..	go back two levels
# cd	go to home directory
# cd ~user1	go to home directory
# cd -	go to previous directory
# cd-paranoia -B	rip audio tracks from a CD to wav files
# cd-paranoia –	rip first three audio tracks from a CD to wav files
# cdrecord -v gracetime=2 dev=/dev/cdrom -eject blank=fast -force	clean a rewritable cdrom
# cdrecord -v dev=/dev/cdrom cd.iso	burn an ISO image
# gzip -dc cd_iso.gz \| cdrecord dev=/dev/cdrom -	burn a compressed ISO image
# cdrecord –scanbus	scan bus to identify the channel scsi
# chage -E 2005-12-31 user1	set deadline for user password
# chattr +a file1	allows write opening of a file only append mode
# chattr +c file1	allows that a file is compressed / decompressed automatically by the kernel
# chattr +d file1	makes sure that the program ignores Dump the files during backup
# chattr +i file1	makes it an immutable file, which can not be removed, altered, renamed or linked
# chattr +s file1	allows a file to be deleted safely
# chattr +S file1	makes sure that if a file is modified changes are written in synchronous mode as with sync
# chattr +u file1	allows you to recover the contents of a file even if it is canceled
# chgrp group1 file1	change group of files
# chmod ugo+rwx directory1	set permissions reading (r), write (w) and (x) access to users owner (u) group (g) and others (o)
# chmod go-rwx directory1	remove permits reading (r), write (w) and (x) access to users group (g) and others (or
# chmod u+s /bin/file1	set SUID bit on a binary file – the user that running that file gets same privileges as owner
# chmod u-s /bin/file1	disable SUID bit on a binary file
# chmod g+s /home/public	set SGID bit on a directory – similar to SUID but for directory
# chmod g-s /home/public	disable SGID bit on a directory
# chmod o+t /home/public	set STIKY bit on a directory – allows files deletion only to legitimate owners
# chmod o-t /home/public	disable STIKY bit on a directory
# chown user1 file1	change owner of a file
# chown -R user1 directory1	change user owner of a directory and all the files and directories contained inside
# chown user1:group1 file1	change user and group ownership of a file
# chsh	change shell command
# chsh –list-shells	nice command to know if you have to remote into another box
# clock -w	save date changes on BIOS
# comm -1 file1 file2	compare contents of two files by deleting only unique lines from ‘file1′
# comm -2 file1 file2	compare contents of two files by deleting only unique lines from ‘file2′
# comm -3 file1 file2	compare contents of two files by deleting only the lines that appear on both files
# cp file1 file2	copying a file
# cp dir/* .	copy all files of a directory within the current work directory
# cp -a /tmp/dir1 .	copy a directory within the current work directory
# cp -a dir1 dir2	copy a directory
# find /home/user1 -name ‘*.txt’ \| xargs cp -av –target-directory=/home/backup/ –parents	find and copy all files with ‘.txt’ extention from a directory to another

D Command	Description
# date	show system date
# date 041217002007.00	set date and time – MonthDayhoursMinutesYear.Seconds
# dd bs=1M if=/dev/hda \| gzip \| ssh user@ip_addr ‘dd of=hda.gz’	make a backup of a local hard disk on remote host via ssh
# dd if=/dev/sda of=/tmp/file1	backup content of the harddrive to a file
# dd if=/dev/hda of=/dev/fd0 bs=512 count=1	make a copy of MBR (Master Boot Record) to floppy
# dd if=/dev/fd0 of=/dev/hda bs=512 count=1	restore MBR from backup copy saved to floppy
# df -h	show list of partitions mounted
# dhclient eth0	active interface ‘eth0′ in dhcp mode
# diff file1 file2	find differences between two files
# dmidecode -q	show hardware system components – (SMBIOS / DMI)
# dos2unix filedos.txt fileunix.txt	convert a text file format from MSDOS to UNIX
# dosfsck /dev/hda1	repair / check integrity of dos filesystems on disk hda1
# dpkg-query -W -f=’${Installed-Size;10}t${Package}n’ \| sort -k1,1n	show the used space by installed deb packages, sorting by size (debian, ubuntu and alike)
# dpkg -i [package.deb]	install / upgrade a deb package
# dpkg -r [package]	remove a deb package from the system
# dpkg -l	show all deb packages installed on the system
# dpkg -l \| grep httpd	show all deb packages with the name “httpd”
# dpkg -s [package]	obtain information on a specific package installed on system
# dpkg -L [package]	show list of files provided by a package installed on system
# dpkg –contents [package.deb]	show list of files provided by a package not yet installed
# dpkg -S /bin/ping	verify which package belongs to a given file
# du -sh dir1	estimate space used by directory ‘dir1′
# du -sk * \| sort -rn	show size of the files and directories sorted by size
# dump -0aj -f /tmp/home0.bak /home	make a full backup of directory ‘/home’
# dump -1aj -f /tmp/home0.bak /home	make a incremental backup of directory ‘/home’

E Command	Description
# e2fsck /dev/hda1	repair / check integrity of ext2 filesystem on disk hda1
# e2fsck -j /dev/hda1	repair / check integrity of ext3 filesystem on disk hda1
# ethtool eth0	show network statistics of eth0

F Command	Description
# fdformat -n /dev/fd0	format a floppy disk
# cp file file1	outputs the mime type of the file as text
# find / -name file1	search file and directory into root filesystem from ‘/’
# find / -user user1	search files and directories belonging to ‘user1′
# find /home/user1 -name \*.bin	search files with ‘. bin’ extension within directory ‘/ home/user1′
# find /usr/bin -type f -atime +100	search binary files are not used in the last 100 days
# find /usr/bin -type f -mtime -10	search files created or changed within 10 days
# find / -name *.rpm -exec chmod 755 ‘{}’ \;	search files with ‘.rpm’ extension and modify permits
# find / -xdev -name \*.rpm	search files with ‘.rpm’ extension ignoring removable partitions as cdrom, pen-drive, etc.…
# find / -perm -u+s	view all files on the system with SUID configured
# free -m	displays status of RAM in megabytes
# fsck /dev/hda1	repair / check integrity of linux filesystem on disk hda1
# fsck.ext2 /dev/hda1	repair / check integrity of ext2 filesystem on disk hda1
# fsck.ext3 /dev/hda1	repair / check integrity of ext3 filesystem on disk hda1
# fsck.vfat /dev/hda1	repair / check integrity of fat filesystem on disk hda1
# fsck.msdos /dev/hda1	repair / check integrity of dos filesystem on disk hda1
# fuser -km /mnt/hda2	force umount when the device is busy

G Command	Description
# gpg -c file1	encrypt a file with GNU Privacy Guard
# gpg file1.gpg	decrypt a file with GNU Privacy Guard
# grep Aug /var/log/messages	look up words “Aug” on file ‘/var/log/messages’
# grep ^Aug /var/log/messages	look up words that begin with “Aug” on file ‘/var/log/messages’
# grep [0-9] /var/log/messages	select from file ‘/var/log/messages’ all lines that contain numbers
# grep Aug -R /var/log/*	search string “Aug” at directory ‘/var/log’ and below
# groupadd [group]	create a new group
# groupdel [group]	delete a group
# groupmod -n moon sun	rename a group from moon to sun
# grpck	check correct syntax and file format of ‘/etc/group’ and groups existence
# gunzip file1.gz	decompress a file called ‘file1.gz’
# gzip file1	compress a file called ‘file1′
# gzip -9 file1	compress with maximum compression

H Command	Description
# hdparm -i /dev/hda	displays the characteristics of a hard-disk
# hdparm -tT /dev/sda	perform test reading on a hard-disk
# head -2 file1	view first two lines of a file
# host www.example.com	lookup hostname to resolve name to ip address and viceversa
# hostname	show hostname of system

I Command	Description
# iconv -l	lists known encodings
# iconv -f fromEncoding -t toEncoding inputFile > outputFile	converting the coding of characters from one format to another
# find . -maxdepth 1 -name *.jpg -print -exec convert	batch resize files in the current directory and send them to a thumbnails directory (requires convert from Imagemagick)
# ifconfig eth0	show configuration of an ethernet network card
# ifconfig eth0 192.168.1.1 netmask 255.255.255.0	configure IP Address
# ifconfig eth0 promisc	configure ‘eth0′ in promiscuous mode to gather packets (sniffing)
# ifdown eth0	disable an interface ‘eth0′
# ifup eth0	activate an interface ‘eth0′
# init 0	shutdown system(2)
# ip link show	show link status of all network interfaces
# iptables -t filter -L	show all chains of filtering table
# iptables -t nat -L	show all chains of nat table
# iptables -t filter -F	clear all rules from filtering table
# iptables -t nat -F	clear all rules from table nat
# iptables -t filter -X	delete any chains created by user
# iptables -t filter -A INPUT -p tcp –dport telnet -j ACCEPT	allow telnet connections to input
# iptables -t filter -A OUTPUT -p tcp –dport http -j DROP	block HTTP connections to output
# iptables -t filter -A FORWARD -p tcp –dport pop3 -j ACCEPT	allow POP3 connections to forward chain
# iptables -t filter -A INPUT -j LOG –log-prefix	Logging on input chain
# iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE	configure a PAT (Port Address Traslation) on eth0 masking outbound packets
# iptables -t nat -A PREROUTING -d 192.168.0.1 -p tcp -m tcp –dport 22 -j DNAT –to-destination 10.0.0.2:22	redirect packets addressed to a host to another host
# iwconfig eth1	show wireless networks
# iwlist scan	wifi scanning to display the wireless connections available

K Command	Description
# kill -9 process_id	force closure of the process and finish it
# kill -1 process_id	force a process to reload configuration

L Command	Description
# last reboot	show history reboot
# ldd /usr/bin/ssh	show shared libraries required by ssh program
# less file1	similar to ‘more’ command but which allows backward movement in the file as well as forward movement
# ln -s file1 lnk1	create a symbolic link to file or directory
# ln file1 lnk1	create a physical link to file or directory
# locate \*.ps	find files with the ‘.ps’ extension – first run ‘updatedb’ command
# logout	leaving session
# ls	view files of directory
# ls -F	view files of directory
# ls -l	show details of files and directory
# ls -a	show hidden files
# ls [0-9]	show files and directory containing numbers
# ls -lSr \|more	show size of the files and directories ordered by size
# ls -lh	show permits on files
# ls /tmp \| pr -T5 -W$COLUMNS	divide terminal into 5 columns
# lsattr	show specials attributes
# lsmod	display kernel loaded
# lsof -p process_id	display a list of files opened by processes
# lsof /home/user1	displays a list of open files in a given path system
# lspci -tv	display PCI devices
# lstree	show files and directories in a tree starting from root(2)
# lsusb -tv	show USB devices

M Command	Description
# man ping	display the on-line manual pages for example on ping command – use ‘-k’ option to find any related commands
# dd if=/dev/hdc \| md5sum	perform an md5sum on a device, like a CD
# mii-tool eth0	show link status of ‘eth0′
# mkbootdisk –device /dev/fd0 `uname -r`	create a boot floppy
# mkdir dir1	create a directory called ‘dir1′
# mkdir dir1 dir2	create two directories simultaneously
# mkdir -p /tmp/dir1/dir2	create a directory tree
# mke2fs /dev/hda1	create a filesystem type linux ext2 on hda1 partition
# mke2fs -j /dev/hda1	create a filesystem type linux ext3 (journal) on hda1 partition
# mkfs /dev/hda1	create a filesystem type linux on hda1 partition
# mkfs -t vfat 32 -F /dev/hda1	create a FAT32 filesystem
# mkisofs /dev/cdrom > cd.iso	create an iso image of cdrom on disk
# mkisofs /dev/cdrom \| gzip > cd_iso.gz	create a compressed iso image of cdrom on disk
# mkisofs -J -allow-leading-dots -R -V	create an iso image of a directory
# mkswap /dev/hda3	create a swap filesystem
# mkswap /dev/hda3	create a swap filesystem
# more file1	view content of a file along
# mount /dev/hda2 /mnt/hda2	mount disk called hda2 – verify existence of the directory ‘/ mnt/hda2′
# mount /dev/fd0 /mnt/floppy	mount a floppy disk
# mount /dev/cdrom /mnt/cdrom	mount a cdrom / dvdrom
# mount /dev/hdc /mnt/cdrecorder	mount a cdrw / dvdrom
# mount /dev/hdb /mnt/cdrecorder	mount a cdrw / dvdrom
# mount -o loop file.iso /mnt/cdrom	mount a file or iso image
# mount -t vfat /dev/hda5 /mnt/hda5	mount a Windows FAT32 file system
# mount /dev/sda1 /mnt/usbdisk	mount a usb pen-drive or flash-drive
# mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share	mount a windows network share
# mount -o loop cd.iso /mnt/iso	mount an ISO image
# mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share	mount a windows network share
# mv dir1 new_dir	rename / move a file or directory [man]

N Command	Description
# nbtscan ip_addr	netbios name resolution
# netstat -tup	show all active network connections and their PID
# netstat -tupl	show all network services listening on the system and their PID
# netstat -rn	show routing table alike “route -n”
# newgrp – [group]	log into a new group to change default group of newly created files
# nmblookup -A ip_addr	netbios name resolution
# nslookup www.example.com	lookup hostname to resolve name to ip address and viceversa

P Command	Description
# pacman -S name	Install package ‘name’ with dependencies
# pacman -R name	Delete package ‘name’ and all files of it
# passwd	change password
# passwd user1	change a user password (only by root)
# paste file1 file2	merging contents of two files for columns
# paste -d ‘+’ file1 file2	merging contents of two files for columns with ‘+’ delimiter on the center
# ps -eafw	displays linux tasks
# ps -e -o pid,args –forest	displays linux tasks in a hierarchical mode
# pstree	Shows a tree system processes
# pwck	check correct syntax and file format of ‘/etc/passwd’ and users existence
# pwd	show the path of work directory

R Command	Description
# rar a file1.rar test_file	create an archive rar called ‘file1.rar’
# rar a file1.rar file1 file2 dir1	compress ‘file1′, ‘file2′ and ‘dir1′ simultaneously
# rar x file1.rar	decompress rar archive
# reboot	reboot(2)
# recode ..HTML < page.txt > page.html	convert a text file to html
# recode -l \| more	show all available formats conversion
# restore -if /tmp/home0.bak	restoring a backup interactively
# rm -f file1	delete file called ‘file1′
# rm -rf dir1	remove a directory called ‘dir1′ and contents recursively
# rm -rf dir1 dir2	remove two directories and their contents recursively
# rmdir dir1	delete directory called ‘dir1′
# route -n	show routing table
# route add -net 0/0 gw IP_Gateway	configure default gateway
# route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1	configure static route to reach network ’192.168.0.0/16′
# route del 0/0 gw IP_gateway	remove static route
# echo “1″ > /proc/sys/net/ipv4/ip_forward	activate ip routing temporarily
# rpm -q -a –qf ‘%10{SIZE}t%{NAME}n’ \| sort -k1,1n	show the used space by rpm packages installed sorted by size (fedora, redhat and alike)
# rpm -ivh [package.rpm]	install a rpm package
# rpm -ivh –nodeeps [package.rpm]	install a rpm package ignoring dependencies requests [
# rpm -U [package.rpm]	upgrade a rpm package without changing configuration files
# rpm -F [package.rpm]	upgrade a rpm package only if it is already installed
# rpm -e [package]	remove a rpm package
# rpm -qa	show all rpm packages installed on the system
# rpm -qa \| grep httpd	show all rpm packages with the name “httpd”
# rpm -qi [package]	obtain information on a specific package installed [man]
# rpm -qg “System Environment/Daemons”	show rpm packages of a group software
# rpm -ql [package]	show list of files provided by a rpm package installed
# rpm -qc [package]	show list of configuration files provided by a rpm package installed
# rpm -q [package] –whatrequires	show list of dependencies required for a rpm packet
# rpm -q [package] –whatprovides	show capability provided by a rpm package
# rpm -q [package] –scripts	show scripts started during installation / removal
# rpm -q [package] –changelog	show history of revisions of a rpm package
# rpm -qf /etc/httpd/conf/httpd.conf	verify which rpm package belongs to a given file
# rpm -qp [package.rpm] -l	show list of files provided by a rpm package not yet installed
# rpm –import /media/cdrom/RPM-GPG-KEY	import public-key digital signature
# rpm –checksig [package.rpm]	verify the integrity of a rpm package
# rpm -qa gpg-pubkey	verify integrity of all rpm packages installed
# rpm -V [package]	check file size, permissions, type, owner, group, MD5 checksum and last modification
# rpm -Va	check all rpm packages installed on the system – use with caution
# rpm -Vp [package.rpm]	verify a rpm package not yet installed
# rpm -ivh /usr/src/redhat/RPMS/`arch`/[package.rpm]	install a package built from a rpm source
# rpm2cpio [package.rpm] \| cpio –extract –make-directories bin	extract executable file from a rpm package
# rpmbuild –rebuild [package.src.rpm]	build a rpm package from a rpm source
# rsync -rogpav –delete /home /tmp	synchronization between directories
# rsync -rogpav -e ssh –delete /home ip_address:/tmp	rsync via SSH tunnel
# rsync -az -e ssh –delete ip_addr:/home/public /home/local	synchronize a local directory with a remote directory via ssh and compression
# rsync -az -e ssh –delete /home/local ip_addr:/home/public	synchronize a remote directory with a local directory via ssh and compression

S Command	Description
# sdiff file1 file2	find differences between two files and merge interactively alike “diff”
# sed ‘s/string1/string2/g’ example.txt	replace “string1″ with “string2″ in example.txt
# sed ‘/^$/d’ example.txt	remove all blank lines from example.txt
# sed ‘/ *#/d; /^$/d’ example.txt	remove comments and blank lines from example.txt
# sed -e ’1d’ exampe.txt	eliminates the first line from file example.txt
# sed -n ‘/string1/p’	view only lines that contain the word “string1″
# sed -e ‘s/ *$//’ example.txt	remove empty characters at the end of each row
# sed -e ‘s/string1//g’ example.txt	remove only the word “string1″ from text and leave intact all
# sed -n ’1,5p’ example.txt	print from 1th to 5th row of example.txt
# sed -n ’5p;5q’ example.txt	print row number 5 of example.txt
# sed -e ‘s/00*/0/g’ example.txt	replace more zeros with a single zero
# shutdown -h now	shutdown system(1)
# shutdown -h 16:30 &	planned shutdown of the system at 16:30
# shutdown -c	cancel a planned shutdown of the system
# shutdown -r now	reboot(1)
# smartctl -A /dev/hda	monitoring reliability of a hard-disk through SMART
# smartctl -i /dev/hda	check if SMART is active on a hard-disk
# smbclient -L ip_addr/hostname	show remote shares of a windows host
# smbget -Rr smb://ip_addr/share	like wget can download files from a host windows via smb
# sort file1 file2	sort contents of two files
# sort file1 file2 \| uniq	sort contents of two files omitting lines repeated
# sort file1 file2 \| uniq -u	sort contents of two files by viewing only unique line
# sort file1 file2 \| uniq -d	sort contents of two files by viewing only duplicate line
# strace -c ls >/dev/null	display system calls made and received by a process
# strace -f -e open ls >/dev/null	display library calls
# swapon /dev/hda3	activating a new swap partition
# swapon /dev/hda2 /dev/hdb3	activate two swap partitions

T Command	Description
# tac file1	view the contents of a file starting from the last line
# tail -2 file1	view last two lines of a file
# tail -f /var/log/messages	view in real time what is added to a file
# tail /var/log/dmesg	show events inherent to the process of booting kernel
# tail /var/log/messages	show system events
# tar -cvf archive.tar file1	create a uncompressed tarball
# tar -cvf archive.tar file1 file2 dir1	create an archive containing ‘file1′, ‘file2′ and ‘dir1′
# tar -tf archive.tar	show contents of an archive
# tar -xvf archive.tar	extract a tarball
# tar -xvf archive.tar -C /tmp	extract a tarball into / tmp
# tar -cvfj archive.tar.bz2 dir1	create a tarball compressed into bzip2
# tar -xvfj archive.tar.bz2	decompress a compressed tar archive in bzip2
# tar -cvfz archive.tar.gz dir1	create a tarball compressed into gzip
# tar -xvfz archive.tar.gz	decompress a compressed tar archive in
# tar -Puf backup.tar /home/user	make a incremental backup of directory ‘/home/user’
# ( cd /tmp/local/ && tar c . ) \| ssh -C user@ip_addr ‘cd /home/share/ && tar x -p’	copy content of a directory on remote directory via ssh
# ( tar c /home ) \| ssh -C user@ip_addr ‘cd /home/backup-home && tar x -p’	copy a local directory on remote directory via ssh
# tar cf – . \| (cd /tmp/backup ; tar xf – )	local copy preserving permits and links from a directory to another
# tcpdump tcp port 80	show all HTTP traffic
# telinit 0	shutdown system(3)
# top	display linux tasks using most cpu
# touch -t 0712250000 file1	modify timestamp of a file or directory – (YYMMDDhhmm)
# echo ‘word’ \| tr ‘[:lower:]‘ ‘[:upper:]‘	convert from lower case in upper case
# tree	show files and directories in a tree starting from root(1)

U Command	Description
# umount /dev/hda2	unmount disk called hda2 – exit from mount point ‘/ mnt/hda2′ first
# umount -n /mnt/hda2	run umount without writing the file /etc/mtab – useful when the file is read-only or the hard disk is full
# uname -m	show architecture of machine(2)
# uname -r	show used kernel version
# unix2dos fileunix.txt filedos.txt	convert a text file format from UNIX to MSDOS
# unrar x file1.rar	decompress rar archive
# unzip file1.zip	decompress a zip archive
# useradd -c “User Linux” -g admin -d /home/user1 -s /bin/bash user1	create a new user “user1″ belongs “admin” group
# useradd user1	create a new
# userdel -r user1	delete a user ( ‘-r’ eliminates home directory)
# usermod -c “User FTP” -g system -d /ftp/user1 -s /bin/nologin user1	change user attributes as description, group and other

W Command	Description
# watch -n1 ‘cat /proc/interrupts’	display interrupts in real-time
# wget -r www.example.com	download an entire web site
# wget -c www.example.com/file.iso	download a file with the ability to stop the download and resume later
# echo ‘wget -c www.example.com/files.iso’ \| at 09:00	start a download at any given time
# whatis …keyword	displays description of what a program does
# whereis halt	show location of a binary file, source or man
# which halt	show full path to a binary / executable
# who -a	show who is logged on, and print: time of last system boot, dead processes, system login processes, active processes spawned by init, current runlevel, last system clock change
# whois www.example.com	lookup on Whois database

Y Command	Description
# yum -y install [package]	download and install a rpm package
# yum localinstall [package.rpm]	That will install an RPM, and try to resolve all the dependencies for you using your repositories.
# yum -y update	update all rpm packages installed on the system
# yum update [package]	upgrade a rpm package
# yum remove [package]	remove a rpm package
# yum list	list all packages installed on the system
# yum search [package]	find a package on rpm repository
# yum clean [package]	clean up rpm cache erasing downloaded packages
# yum clean headers	remove all files headers that the system uses to resolve dependency
# yum clean all	remove from the cache packages and headers files

[VPS] Toàn bộ câu lệnh sử dụng trong Server Linux từ A – Z