Linux Commands PDF

ls ---> used to list files and dirs. ls -l --> list files and dirs with long format touch test1 ---> used to create empty file ls -lt ---> recently created files will be displayed at beginning ls -lrt --> recently created files will be displayed at the end pwd...

ls ---> used to list files and dirs. ls -l --> list files and dirs with long format touch test1 ---> used to create empty file ls -lt ---> recently created files will be displayed at beginning ls -lrt --> recently created files will be displayed at the end pwd ---> present working directory --------------------------------------------------------------------------------------- mkdir dirname ----> create dir cd dirname ----> change directory cd dir/dir2/ cd.. --> used to come out of directory cd../../.. ---> mkdir -p temp1/temp2/temp3 ---> create complete directory structure --------------------------------------------------------------------------------- cat filename ---> used to check content of a file ======================================================================================== vi is used to edit file vi filename esc --> i ---> insert esc --> :wq! ---> save content of a file (write and quit ) esc ---> :q! --> quit without saving content how do replace particular string or word in a file? esc :%s/current-string/new-string/g esc :%s/linux/windows/g ------------------------------------------------------- Need to replace only in 4th line esc:4s/linux/windows/g --------------------------------------------------------- need to replace from 2nd to 4th line esc:2,4s/linux/windows/g ----------------------------------------------------------------- how do you replace from 2nd line to end of a file esc:2,$s/linux/windows/g ---------------------------------------------------------------- how do set line numbers esc : set nu --> set line numbers esc : set nonu ---> remove line number -------------------------------------------------- need to move cursor to particular line esc :line_number esc : 4 ---> cursor will move to 4th line ----------------------------------------------------------------------------- delete particular line in vi esc press dd --------------------------------------------------------------------- ========================================================================================== cp is used to copy file cp file1 file2 ----> file1 will be copied to file2 ------------------------------------------------------------------------- cp test1 temp1/temp2/temp3/ ---------------------------------------------------------------------- copy dir to another dir cp -r dir1 dir2 ---------------------------------------------------------------------- cp test1 file1 test3 temp ---> copy multiple files or dirs to another dir --------------------------------------------------------------------------------- how do rename file or dir? mv file1 file2 -------------------------------------------------------- mv file1 dir2 ------------------------------------------------------- mv file1 file2 file3 dir1 ---> move multiple files to directory install tree command sudo yum install tree ---------------------------------------------------------------------------- rwxr-xr-- 7 5 4 chmod is used to change permission of a file or dir chmod 777 filename --------------------------------------------------------------------- chmod -R 777 dir all subdirectories and files permission will be changed to 777 --------------------------------------------------------- u--> user, g--> group and o--> others chmod u+rwx filename --------------------------------------------------------------------------------------- chown --> used change ownership of a file or a dir chmod newowner filename --------------------------------------------- if new onwer belongs to different group chmod newonwer:groupname filename ------------------------------------------------------------------------------------ df -h. ----> used to check disk size. indicates present disk ------------------------------------------------------------- du -sh filename (disk usage) used to check size of a file du -sh * ---> all files and dirs size in present directory ------------------------------------------------------------------- echo "hi how r u" is used to print echo -e "hi\nhow r u" ---------------------------------------------------------------------------- > (redirect) used to store output of a command to file ls -lrt > log --------------------------------------------------------------------------- >> (append) used to attach output of a command to end of a file echo "this is linux class" >> log =============================================================== =============================================================== wc filename lines words chars filename wc -l log ---> number of lines wc -w log ---> words wc -c log --> chars -------------------------------------------------------------------------- "head" is used to display 1st portion of a file head -3 filename ---> 1st 3 lines head -12 filename ---> 1st 12 lines of a file head filename ---> 10 lines by default ------------------------------------------------------------------------- tail is used to display last portion of a file tail -3 filename --> last 3 lines tail -5 filename ----> last 5 lines tail filename -----> last 10lines by default ---------------------------------------------------------------------------- | (pipe) is used to give output of one command as input to next command ls -lrt | wc -l ------------------------------------------------------------ head -4 log | tail -1 --> display 4th line --------------------------------------------------------------- how do you display 99th line of a file head -99 file | tail -1 -------------------------------------------------- display 4th to 7th line head -7 file | tail -3 --------------------------------------------------------------------- count number of words in 99th line of a file head -99 log | tail -1 | wc -w ----------------------------------------------------------------------------- display 2nd last line of a file tail -2 log | head -1 --------------------------------------------------------------------------------------- grep --> pattern search used to search string in file grep "pattern" filename grep -w "string" filename ----> search only specified word grep -i "Linux" test_1 ---> i --> case insensitive how do you search multiple pattern? grep -e "linux" -e "windows" test_1 or egrep how do you list filenames if files have particular word or string grep -R -l "linux" * how do you prnt lines which don't have specified pattern grep -v "linux" test_1 list lines if starts with particular pattern grep "^pattern" filename grep "s$" test_1 ---> list lines ends with particular pattern get command to print lines which start with "M" and ends with "s" grep -c "linux" test_1 ---> count number lines which have specified pattern ======================================================== how do you replace string in a file? sed --> used to replace string in a file sed 's/linux/unix/g' filename sed -i 's/linux/unix/g' test_1 sed '4s/linux/unix/g' ---> replace string in 4th line only sed '2,6s/linux/unix/g' ---> from 2nd to 6th line sed '$s/linux/unix/g' ---> replace string only in the last line delete particular line sed '4d' test_1 --> delete 4th line of a file sed '$d' test_1 --> delete last line sed '2,6 d' test_1 --> delete 2nd to 6th line sed '1d;3d' test_1 how do you print particular line? sed -n '3p' test_1 ---> print 3rd line sed -n '$p' test_1 ---> print last line sed -n '2,6p' test_1 ---> print 2nd to 6th line sed -n '2p;6p' test_1 ---> print 2nd to 6th line ----------------------------------------------------------------- cut --> used to cut file colounwise cut -d " " -f1 data --> 1st coloumn cut -d " " f1,3 data ---> 1st and 3rd coloumn cut -d " " f3-6 data ---> 3rd to 6th column -------------------------------------------------------- awk is used to cut file rowwise and coloumn wise but we use awk command to cut file coloumn wise awk -F " " '{print $1}' data ----> 1st coloumn $1 ---> 1st coloumn $2 --> 2nd coloumn $NF ---> last coloumn $(NF-1) --> 2nd last coloumn awk -F " " '{print $NF}' data ---> last coloumn awk -F " " '{print $(NF-1)}' data --> 2nd last coloumn ------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------- find ---> used to find location of a file find. -iname "filename" i --> case insensitive list files which are modified 3months back find. -type f -mtime +90 find. -type d -mtime +90 find. -mtime +90 -->both files and dirs list files which are modified within 3months find. -type d -mtime -90 find files which are modified with in 50mins find. -type f -mmin -50 find files which modified 50mins ago find. -type f -mmin +50 find files which have 777 permission find. -type f -perm 777 find all empty files find. -type f -empty -----commnad to list all non empty files----- find. -maxdepth 1 -iname "test1" maxdepth is used to retrict automatic recursive maxdepth 1 ---> 1st level dir maxdepth 2 ---> 2nd level dir ------------------------------------------------------------- delete all files which are modified 3 months ago find. -tyep f -mtime +90 | xargs rm -rf xargs is used to pass output of one command to next command as arguements Assigment: 1. command to list files if their size is more than 1MB 2. use -exec option in find command to delete files =============================================================================== softlink it's shortcut to a file. if you make any changes in the actual file, it will get reflected in the softlink if you delete actual file, softlink will not work ln -s /home/ec2-user/file1 link1 ------------------------------------------------------------------ hardlink ln /home/ec2-user/file1 hard1 ---------------------------------------------------------------------------------- diff b/w hard link and softlink if I delete actual file, softlink will not work if I delete actual file, hardlink works fine because it points to inode of a file (inode is uniq number indicates memory address) ===================================================================================================================== Assigment: 1. command to list files if their size is more than 1MB 2. use -exec option in find command to delete files ------------------------------------------------------------------------------------------------------------- ps --> used list current running processes on the system need to check whether particular process is running or not ps -ef | grep "processname" 3.need to list all processes started by particular user ------------------------------------------------------------------ stop process (forceful stop) kill -9 PID 4.kill all process started by paticular user 5. kill all process by name you can use sleep command for practice sleep 10 sleep 100 =========================================================================== how do stop process gracefully sudo service name stop sudo service name start sudo service name restart 6. get systemctl command sudo systemctl stop name ====================================================================================== ------------------------------------------------------------------ umask is used to set default permission on system. it should run with root user umask 000 ---> whoever creates file or dir will have full permission umask 777 ---> no permission --------------------------------------- rwxr-xr-x = 755 777 755 --- 022 ---- umask 0222 --------------------------------------------------------------------- r-xr-xr-- = 554 777 554 --- 223 --- umask 233 ----------------------------------------------------------------------------- su (switch user or superuser) is used to login as other user or root user su - username password: ------------------------------------------------------------------------------------- sudo (superuser does) sudo ---> used to execute command with root permission sudo yum install vim wget ---------------------------------------------------------------------------------------- add user ABC abd and give sudo permission sudo useradd ABC sudo passwd ABC password: password: sudo su - (login as root user from ec2-user) vi /etc/sudoers.d/90-cloud-init-users go to last line of this file give same permission for ABC also like ec2-user you need to add another line and change ec2-user to ABC save file ABC also will have sudo permission ------------------------------------------------------------------------------------------ more command is used to display content of a file page wise more filename less ---> used to display content of a file pagewise, but you can scroll up and scroll down using up and down arrrows less filename ( press q to quit ) ------------------------------------------------------------------------------------------------------- date --> used to print system date and time date +%m ------------------------------------------------------------------------------------------- uniq --> print onlu uniq data and removes deplicates. use this along with sort sort --> used to sort data --> ascending sort sort -r filename ---> decending sort cat test | sort | uniq we need to use uniq command always with sort command ------------------------------------------------------------------------------------------------------- how do you check linux version uname -v ---> only version uname -a ---> all info -------------------------------------------------------- who ---> who all logged into system whoami ---> check ur username hostname --> hostname or ip of current server ----------------------------------------------------------------------- ssh --> used to login to remote server and uses port 22 ssh username@server password: -------------------------------------------------------------------------------- ssh -i aws-keys/devops-june-21.pem [email protected] you need to private IP run command on remote server ssh -i aws-keys/devops-june-21.pem [email protected] "ls" 1. install winscp 2. using winscp copy pem file to server1 3. login to server1 using putty 4. change permission to 400 using chmod 400 filename.pem 5. ssh -i filename.pem ec2-user@server2-private-ip ------------------------------------------------------------------------------------ scp is used to copy files from one server to another (uses port 22) scp filename username@server:/path/ password: =================================================================================== scp is used to copy files from one server to another (uses port 22) scp filename username@server:/path/ password: ----------------------------------------------------------------------------------- aws ec2-instance copy file scp -i aws-keys/devops-june-21.pem data [email protected]:/home/ec2-user/ copy dir scp -i aws-keys/devops-june-21.pem -r temp1/* [email protected]:/home/ec2-user/temp1/ scp -i aws-keys/devops-june-21.pem [email protected]:/home/ec2-user/temp1/file1. rsync ---> used to copy files or dirs within server and also between servers rsync -i key.pem dir1 username@server2:/home/ec2-user/dir1 diff rsync and scp while copying while data from one server to another, if copy is stopped in between due to network issue. if use scp command, it will start copying from begining if use rsync command, it will start copying from where it was stopped (because it will comapre and copy and it's slower than scp) ----------------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------------ ping is used to check server is running or not. ping uses ICMP protocal (you can server is shutdown or not) ping ipaddress or servername ---------------------------------------------------------------------------------- telnet --> used to break firewall. it uses port 23. used to authenticate account credentials on remote server telnet IPaddress or servername username: password: ---------------------------------------------------------------------------------------------------- how do you setup passwordless connection between servers ? we need to run "ssh-keygen -t rsa" on server1 and generate rsa key. take this public key and copy it to another server to file called authorized_keys under.ssh directory. save it next time when you login from server1 to server2, it will be passwordless connection steps: login to server1 ssh-keygen -t rsa (keep pressing enter key till key get generated) cat /home/ec2-user/.ssh/id_rsa.pub (copy this key) login to server2 cd.ssh vi authorized_keys paste key at the end of a file and save it go to server1 and run "ssh ec2-user@server2" (check logged in to server2 whithout password) ====================================================================================================== How to enable password connection on ec2 instance sudo su - (login as root) cd /etc/ssh/sshd_config.d vi 50-cloud-init.conf (change passwordAuthentication yes) set password for user using below command passwd ec2-user Restart sshd service service sshd restart systemctl restart sshd go to other server and try logging from other server with password ssh ec2-user@serverIP --------------------------------------------------------------------------.bashrc what is.bashrc or.bash_profile? an auto-execute file which gets executed automatically as soon as log into system what is diff b/w.bashrc , bash_profile and bash_history? --------------------------------------------------------------------------------------------------------------------- how do you check available ports or free ports on the system? netstat assignment 1. get all options in netstat ------------------------------------------------------------------------------------------- tee ---> used to display output of a command on console as well as write to file tee -a --> a indicates append ------------------------------------------------------------------------------------------------------------- wget --> used to download file to linux server from browser ubuntu sudo apt-get install vim ---> installation command on ubuntu sudo yum install vim -----> installation command on redhat Assigment2: install tomcat on ubuntu and download calendar.war file and copy it to /webapps folder under tomcat ps -ef | grep tomcat =========================================================================