RHCSA Command command cheat sheet

##Touch command
#touch <file_name> - create single empty file
#touch <file_name1> <filename2> <filename3> - create multiple empty files
#touch <filename1..10> - create multiple file from filename1 to filename10

PWD – Present working Directory
#pwd – to see the present working directory path

Clear command
#clear – to clear the screen

History Command
#history – to see the history of the command
#history –c – to clear the history command
#!< Command number > - to execute particular command 
#!! – execute last executed command.


Cat command
#cat <filename> - to see the file content
#cat <filename1> <filename2> >> filename3 – to concatenate file into filename3
#cat <filename> | w – work count, -l – line count, - c – character count
#cat <filename> | wc – it will show full details of line, word and character.

CD – Change directory
#cd <directory name> - to get into directory
#cd .. – to get back from the directory
#cd - = it will take to last change directory
#cd ~ - it will take to home directory

MKDIR command – Make directory
#mkdir <directory name> - to create directory
#mkdir <dir1> <dir2> <dir3> - to make multiple directory
#mkdir –p dir1/dir2/dir3/dir4 – to make directory inside the directory

RMDIR Command – remove directory
#rmdir <directory name> - to remove the empty directory

RM command – remove 
#rm <filename> - remove file
#rm –rf <file or directory name> - remove file or directory forcefully without any confirmation
#rm –i <Filename> – remove the file with confirmation, i – use for interactive.
#rm –r <filename> - recursive mode to delete directory
#rm –f <filename> – remove the file forcefully without confirmation.
#rm –v <file name> - display information as deleting the file or folder.

MV Command – Move command
#mv oldfilename newfilename – it will change the old filename to new filename
#mv file1 file2 file3 file4 <path to move the files> - it will move the file.
#mv –u items <directory path> - update the items
#mv –v…… - v use for verbose
#mv –i items <directory> – it will give warning before overriding the file, interactive mode.

UNAM –
#uname –a – show the machine detail and its version 

Date command
#date – show the current date
#date +%F – show the full date
#date +%D-%M-%Y – show the full date with – format
#cal – to see the calendar.
#cal 11 2014 – to display the calendar November 2014.


CP command – Copy the file
#cp <filename> <destination path> - copy the file to destination directory
#cp *.txt <destination path> - copy all the .txt file to destination directory
#cp –pv <filename> <destination name> - copy the files without changing its properties
#cp –Rv <Directory name> <Destination> - copy the directory to destination path
#cp –u <source file> <destination directory> - update the missing file

LS command – List file and directory
#ls –la – show all the file and directory in present directory along with hidden files
#ls –ltr – show directory along with time
#ls –lah – show the file or directory in human readable format
#ls –d – show directory only
#ls –m – show the file using command list
#ls –la >> filename – to append the output in filename
#ls –la > filename – to override the file with output 
#ls –lt –reverse – to reverse the listing directory and files
#ls –S – short the result by file size
#ls –l – show the result in reverse format

DF command – Disk Fragment 
#df – show the free space details
#df –h – show partition in human readable format 
#df –T – show current path

Hard and Soft link – LN
#ln fun fun-hard – create a hardlink file
#ln fun dir1/hard – same as above
#ln –s fun fun-sym – create  soft link

Help command – display usage information
#mkdir –help – to see the command details how to use it
#man – display program manual page

APROPOS – Display Appropriate Commands
#apropos floppy – it show the command details

More command
#more – read more log file, q to quit

WHO Command
#who – show who logged in currently
#who –r – run level
#who –H – show who logged in and when
#w – show how my user logged in
#who –m –H – show the details in table format
#who –p –H – show all the active process
#who –d –H – show all dead process

PS command
#ps – list all the process 
#ps –aux – show running process with details
#ps –U <User name> - show the process about users
#pstree – it will show all the parent and child process in tree format
#ps –aux –z – the process which is died as zombie
#ps –a – it will show all the running process
#ps –r – it will show all the process owned by you
#ps –fU <username> - it will show all the process of particular user
#ps –fG <Group Name> - it will show all the process of that particular group
#ps –eo pid, ppid, user, cmd – view custom field
#ps –ef – it will show all the process
#ps –ef | grep sleep – it will show sleep process.
#ps –C <process name> - search with name process
#jobs – show background running process
#fg %<process id> - to bring the process from back ground to fore ground.
#kill -<process id> - to end or terminate the process
#pgrep –u <root> - it will show root processes
#pgrep –u root  ssh – it will show root process with ssh
#pgrep –l – 
#kill –l- show all the process

CHMOD Command – change mode
#chmod +/-<permission number > <File/Directory name> - to change read write and execute permission(RWE), read -4, write -2 and execute -1. 
#chmod +x <file name> - to add execute permission.
#chmod +r <file name> - to add read permission.
#chmod +w <file name> - to add write permission.
#chmod 777 <file name> - to add rwe permission to all.

CHOWN Change owner
#chwon <username> root:<filename> - change the file permission to root

CHGRP Change group
#

DU Command
#du –sh </filepath> - show the file size

Compress and decompress – z use for gunzip, j use for bunzip
#tar –cvzf <filename with .gz> </path to compress the files> - to compress the files using gun zip.
#tar –cvzf <filename of the compress> *.txt  - compress all the .txt file.
#tar –xvf <zipped file name> - to unzip the compressed file
#tar –cvf <filename with .tar> <filenam1> <file2> <file3> - it will compress given file name in .tar.
#tar –uvf <archive file.tar> <file1 file2 file3> - update the file in .tar.
#tar –tf <file name with .tar> - list all the 
#tar –cvjf <file name with .tar.bz2> <file1 file2 file3 file4> - compress using bun zip
#zip <filename with .zip> <file1 file2 etc> - normal zip
#zip –d <zipfile name> - to delete the fil

SCP Secure copy command
#scp <filename> root:<IP address>:</filepath or remote machine path> - to copy the file from remote machine.
#scp <multiple file name> <destination user name>@<destination IP>:/<path to store the data> - it will transfer multiple file at given user directory
#scp –C filename <Destination User name>@... – it will compress the data then it will send.
#scp –r <directory name> <destination user>@... – it will transfer the directory to destination
#scp –rvp <filename> <username>@... – it will send the file/directory while preserving the metadata.
#scp –l 500 <filename> <username>@... – it will reduce the bandwidth then send the data


FIND command
# find /<Path> -iname <file name>           - to search files with file name
# find /<Path> -perm 770                            - to search files with their permissions
# find /<Path> -user <user name>            - to search files with user ownership
# find /<Path> -size 10M                             - to search files with their size
#locate <filename> - search the file based on string name

GREP Command – Regular expression
#grep –V – show the version of grep command
#grep <string name> <File name> - search the string in file
#grep –i <string name> <File name> - ignore the case sensitive
#grep –v <string name> <File name> - ignore that line and rest will show
#grep –iv <string name> <File name> - ignore which is matching and show rest of the line.
#grep –A 2 <string name> <File name> - it will match then print after 2 line
#grep – C 1 <string name> <File name> - show one line up and one line down
#grep –B <string name> <File name> - show the up lines after matching it

MAN Command
#man passwd – to show the passwd file usage
#man –s 5 passwd – to see the developer file usage
#man –k printf – it will show the short of this file
#pinfo – its same as man
#info – its same as above
#whereis <command name> - show the where command does exist
#whatis <command> - tells about command 
1 - User commands 
2 - Programming interfaces kernel system calls 
3 - Programming interfaces to the C library 
4 - Special files such as device nodes and drivers 
5 - File formats 
6 - Games and amusements such as screen savers 
7 - Miscellaneous 
8 - System administration commands
#man 5 passwd – it will show the details about passwd file

Create and Delete Partitions
#lsblk – it will show the block details of drive
#fdisk –l – it will list all the partition details which is updated in dev file system
#udevadm – it will update the partition in dev file system after creating
#mkfs.<filesystem name> /dev/<partitionname> - to convert the partition into particular file system.
#mkfs.xfs /dev/dv1 – convert dv1 partition into xfs file system, you can use ext4 for ext4 partion.
#mkdir <directoryname> - create a directory to mount the partition
#mount /dev/<partitionname> </directoryname> - mount the partition to directory.
#unmount /<partitionname> - it will unmount partition.

#fdisk /dev/<partitionname> - follow the procedure to delete or create partition, press d for delete the partition, n – to create new partition and many more.
#udevadm trigger – to update the partition table after deleting the partition
#df –h – to see the mounted partition
#partprobe /dev/<partitionname> - to update the partition
#fdisk /dev/<partitionname> - type L to see all the partition conversation list, 8e – for LVM.

#pvcreate /dev/<LVM partitionname> - to create physical volume.
#pvs – to see the physical volume list
#pvdisplay –m – it will give details information how many physical extend are used

#vgcreate <Virtual Group Name> </dev/PV1 /dev/pv2> - to add all the PV in a single Virtual group.
#vgs – to list all the virtual group details

#lvcreate –n <name for logical volume to create> -L <size of the volume to create> <Virtual group name> - it will create a Logical volume
#lvcreate –n lv0 –L 4G VG0 – it will create 4GB logical volume from the Virtual group VG0.
#lvdisplay /dev/VG0 – show all the logical volume 
#mkfs.ext4 /dev/VG0/lv0 – create a lv0 as a ext4 file system.
#mount – to see the mounted details
#lvs – to see login volume

#lvextend –L +1G /dev/VG0/lv0 – it will extend lv0 partition size to 1GB
#resize2fs /dev/VG0/lv0 – it will show exact size of extended partition.
#e2fsck –f /dev/VG0/lv0 – to check file details if there is any error
#resize2fs /dev/VG0/lv0 1G – it will reduce 1GB size from that partition

#free –m – to see the swap memory
#fdisk /dev/<partitionname> - select 82 to make swap memory
#partprobe /dev/<partionname> - to update and save the new partion
#mkswap /dev/<partition name> - to make swap of particular partition
Update in fstab
#swapon –s – to on the swap partition details
#swapoff /dev/<partition name> – to off the swap partition.
#blkid /dev/sdc1 – verify the swap 
 
User Management 
#useradd <username> - to add the user. It will modify following files - home, login shell, group, .bash_profile, .bash_logout, -/etc/passwd, etc/shadow, etc/gshadow(this will modify only while using group users, users), etc/skel, etc/group
#cat /etc/default/useradd – it will show default user in this file.
#cd /etc/skel – it’s a default directory which get assigned while creating user.
#cat /etc/login.defs – it will have the login definition.
#useradd –u 2000 –g <primary groupname> -G <secondary group1 group2> -c <comment> -s </bin/bash> -d <specify the home path> –e <account expiry date – ex 2021-11-24> -p <password> <username to create> - it will create new user with given details.
#usermod – to change the properties.
#usermod –l <new usernam> <old usernam> - change the username
#usermod –aG group1, group2, group3 <username> - it will append the user in secondary group.
#id <username> - to see the user details
#usermod –s /bin/bash <username> - it will provide the shell to login
#usermod –s /sbin/nologin <username> - it will not allow user to login.
#cat /etc/shells – to see all the login shells
#usermod –L <username> - it will lock the account. You can see the escalation mark! in shadow file.
#usermod –U <username> - to unlock the user account
#usermod –f <username> - make user inactive completely.

Usermod command options – 
-c = We can add comment field for the user account.
-d = To modify the directory for any existing user account.
-e = Using this option we can make the account expiry in specific period.
-g = Change the primary group for a User.
-G = To add a supplementary groups.
-a = To add anyone of the group to a secondary group.
-l = To change the login name
-L = To lock the user account. This will lock the password so we can’t use the account.
-m = moving the contents of the home directory from existing home dir to new dir.
-p = To Use un-encrypted password for the new password. (NOT Secured).
-s = Create a Specified shell for new accounts.
-u = Used to Assigned UID for the user account between 0 to 999.
-U = To unlock the user accounts. This will remove the password lock and allow us to use the user account.

#chage –l <usernam> - to see the account details
#chage –m 0 –M 90 –W 10 –E 2021-11-25 <username> - it will change the account details accordingly. –m – minimum password change day, -M – Maximum password change day, -W- no of warning, -E- password expiry date.

#groupadd <groupname> - create group
#cat /etc/group – to see the group name
#gpasswd –a <username> <groupname> - give special permission to user to modify the group.
#gpasswd –M user1 user2 user3 etc <group name> - to add multiple user at a time in group.
#groupmod –ptest <Group username> - protect from password


ACL Access control list
#ls –ltr – list all the file and directory
#setfacl –m u:<username>:r<filename> - grant read permission to a particular user for that file
#setfacl –x u:<username> <filename> - it will revoke user permission from the particular file.
#getfacl <file/directory name> - it will show the user permission.
#su -<username> - switch the user 
#setfacl –m g:<groupname>:rwx<directory name> - set the rwx permission for that group.
#getfacl <filename> | setfacl –set-file=-<filename2> - it will set the same permission of file1 to file2.
#getfacl –access <old directory> | setfacl –d –M- <new directory> - it will copy or replicate same old directory permission to new directory.
#setfacl –b <filename> - it will remove all the permission from that file.
#cat /etc/profile – to see the umask value

Special permission
#chmod u+s <file name> - set setuid permission. Setuid value is 4
#chmod 4755 <filename> - it will set the setuid permission
#chmod g+s <filename> - setgid permission, setgid value is 2.
#chmod 2755 <filename – to set the gid permission
#chmod +t <filename> - to assign sticky bit permission, its value is 1

Networking
#ip route show – it will show the rout details
#ip addr – show the network interfaces
#whatis ifconfig – you can see about ifconfig
#whatis netstat – print network connection
#netstat –r – it will show the network details with connected devices details.
#netstat –t - show all the TCP connection
#netstat –l – listen the ports
#netstat –lt – listening tcp connection, u at place of t is use for udp connection
#netdiscover – it will show all the connected network devices

#htop – show all the process column wise


Download files
#curl –O <filename> <file or directory url to download> - it will download and save as filename
#curl –O <file URL> - it will download without changing the name, with default name.
#curl –L <weburl> - it will redirect to website and it will show the content in command
#curl –I <web URL> - it will show the cookie details and other website details
#curl –v <web URL> - it will show the entire content of the website


NMCLI Network Management CLI
#nmcli device status – to see the network device status
#nmcli connection show – it will show the connection 
#nmcli connection add type ethernet con-name Home ifname eth22 – a connection profile will be created with Home name.
#nmcli general status – show the connection status
#nmcli device status – it will show how many devices are connected.
#nmcli device show <device name> - show the particular device name
#nmcli connection delete <device name > - to remove the connection.
#nmcli connection modify <network name> ipv4.address <IP address> ipv4.g <gateway IP> ipv4.dns <DNS address> +ipv4.dns <secondary DNS address> connection.autoconnect <yes or no> ipv4.method manual – it will modify the connection.
#cat /etc/sysconfig/network-scripts/ifcfg-<connectionname> - you can see the connection details in this file.
#nmcli device monitor –device related information
#nmcli connection down <connection name> - it will down the connection
#nmcli connection up <connection name> - it will up the connection
#nmcli connection modify <Connection name> connection.permission users:<username> - it will give particular use to down or up the connection.
#nmtui – it will open graphical user interface to setup the connection.
#nmtui edit Home – it will edit the Home connection in gui.

NIC Teaming –
#nmcli connection add type team con-name team0 ifname team0 config’{“runner”:{“name”:”activebackup”}}’ – it will create team0 connection then modify it.
#nmcli connection modify team0 ipv4.address <ipaddress> ipv4.gateway <IP gateway> ipv4.dns <dns ip> connection.autoconnect yes ipv4.method manual – it will modify the connection.
#nmcli connection add type team-slave con-name team0-port0 ifname <devicename ex ens37> master team0 – it will make team0 a master connection and it will in that, similarly we can add other connection into that for load balancing 
#teamdctl team0 status - 

Firewall configuration –
-systemctl disable iptables
	- systemctl disable ip6tables
	- systemctl stop ipv6tables
	- systemctl stop iptables
	- systemctl mask ip6tables
	- systemctl mask iptables
	- systemctl status iptables
	- systemctl status ip6tables
	- yum install –y firewalld firewall-config
	- systemctl status firewall
	- systemctl enable firewall.service
	- systemctl start firewall.service
	#firewall-cmd –get-default-zone
	#firewall-cmd –set-default-zone=home
	#firewall-cmd –get-default-zone
	#firewall-cmd –get-active-zone
	#firewall-cmd –version
	#firewall-cmd –zone=public –list-iterface
	#firewall-cmd –add-interface=eth0 –zone=public
	#firewall-cmd –remove-interface=eth0 –zone=public
	#firewall-cmd –get-services
	#firewall-cmd –permanent –get-services
	#firewall-cmd –panic-on [Disable incoming and outgoing packets]

SELinux command
#cat /etc/selinux/config – it will show all the selinux configuration details
#getenforce – show the current status of selunx whether its enforce or not
#sestatus – show the status

Head, Sort, Tail, Uniq, Paste, Cut, Tr, Sed and diff commands 
#head –n <no of line to show> <filename> - it use to display the output with specific number of lines.
#sort –r <filename > - it will short the command, below option use for this command.
  -b         ignores leading blanks
  -d         considers only blanks and alphanumeric characters
  -f          fold lower case to upper case characters
  -g         compare according to general numerical value
  -i          consider only printable characters
  -M       compare (unknown) < `JAN' < ... < `DEC'
  -n         compare according to string numerical value
  -r        reverse the result of comparisons
  -c         check whether input is sorted; does not sort
  -k         start a key at POS1, end it at POS2 (origin 1)
  -m        merges already sorted files; do not sort
  -o         write result to FILE instead of standard output
  -s         stabilize sort by disabling last-resort comparison
  -S         use SIZE for main memory buffer
  -t         use SEP instead of non-blank to blank transition
  -T        use DIR for temporaries, not $TMPDIR or /tmp
  -z         end lines with 0 byte, not newline
#uniq <filename> - it will print only unique value, remove the duplicate one
#paste – use to merge the file.
#paste –s <filename> - print multiple lines as a single line
#paste –d, file1 file2 – combine the file1 and file2 with separate , comma
#cut –cl -<number of char to print> <filename> - it will print number of char only from the each line of file.
#tr – convert upper to lower case vice versa
#tr ‘a-f’ ‘A-F’ <filename> - convert the a to f letter to upper case.
#diff file1 file2 – it will show the difference between two files.

AT – Automatic task scheduling Command
#at 10:10 – schedule the job at 10:10.
#atq – see scheduled jobs
#atrm <job number > - to remove the scheduled job.

Crontab Command
#crontab –e – to edit the job
#crontab –l – to list scheduled jobs.
#crontab –c –u <username> - to see particular user jobs.
#crontab –r – to remove the crontab file.

Quota Management
#rpm –qa | grep quota – to verify whether rpm quota is installed or not.
#quotacheck –cugm /qcheck – to create the quota.
       -v scans and prints verbose
                      -c performs a new scan
                      -g scan quota for groups
                      -m remount the scanned file system
                      -u scan quota for users
                      -a Check all quota-enabled, locally-mounted FS
#quotaon –avug – switch on the quota
#edquota <usernam> - to apply the quota on particular user
# dd if=/dev/zero of=/qcheck/test bs=1024 count=10 – it will show the detail, please run after loggin with user account to check the limit.
#quota –u <username> - to verify the quota setting.
#edquota –T <username> - to increase the grace period for a user.
#edquota –g <group name> - to create quota for group
#quotaoff –avug – to remove the quota
#cat /etc/fstab | grep qcheck – clear the quota entry

AWK command in Unix/Linux
awk options 'selection _criteria {action }' input-file > output-file
-f program-file : Reads the AWK program source from the file 
                  program-file, instead of from the 
                  first command line argument.
-F fs            : Use fs for the input field separator

$cat > employee.txt 
ajay manager account 45000
sunil clerk account 25000
varun manager sales 50000
amit manager account 47000
tarun peon sales 15000
deepak clerk sales 23000
sunil peon sales 13000
satvik director purchase 80000 

$ awk '{print}' employee.txt – it will print same as above
$ awk '/manager/ {print}' employee.txt – Print the lines which match the given pattern.
$ awk '{print $1,$4}' employee.txt  - Splitting a Line Into Fields : For each record i.e line, the awk command splits the record delimited by whitespace character by default and stores it in the $n variables. If the line has 4 words, it will be stored in $1, $2, $3 and $4 respectively. Also, $0 represents the whole line.
$ awk '{print NR,$0}' employee.txt - Use of NR built-in variables (Display Line Number)
$ awk '{print $1,$NF}' employee.txt  - Use of NF built-in variables (Display Last Field)  
$ awk 'NR==3, NR==6 {print NR,$0}' employee.txt  - Another use of NR built-in variables (Display Line From 3 to 6)
$ awk '{print NR "- " $1 }' geeksforgeeks.txt - To print the first item along with the row number(NR) separated with ” – “ from each line in geeksforgeeks.txt.
$ awk '{print $2}' geeksforgeeks.txt  - To return the second column/item from geeksforgeeks.txt
$ awk 'NF < 0' geeksforgeeks.txt - To print any non empty line if present
$ awk '{ if (length($0) > max) max = length($0) } END { print max }' geeksforgeeks.txt - To find the length of the longest line present in the file.
$ awk 'END { print NR }' geeksforgeeks.txt  - To count the lines in a file.
$ awk '{ if($3 == "B6") print $0;}' geeksforgeeks.txt - To find/check for any string in any specific column.