Linux commands
- 2. Creating Files touch file To update the timestamp of file (if file exit) Create an empty file (if doesn’t exit) touch a b c To create multiple files a b c touch {1..10} To create file from 1 to 10 touch {a..z} To create files from a to z touch file {1..10} Creates file1, file2… file10 cat > file Create file If file exist: Overwrite If file doesn’t exist: creates new cat >> file Create file If file exist: append If file doesn’t exist: creates new vi file Open a file in vi editor
- 3. To Logout To Shutdown To Reboot ctrl + d init 0 init 6 logout halt reboot exit shutdown –h o shutdown –r o Help Commands man command Manual of Command whatis command Definition of command info command Information about command command --help Help details of command
- 4. To Display files cat file Display file cat –n files Display files with line numbers more file Display file from starting line (page by page) less file Same as more * head file Display 1st 10 lines of file head –n file Display n number of lines from starting line of file tail file Display bottom 10 lines tail –n file Display n number of files (bottom) tail –f file Display bottom lines dynamically
- 5. File operations cat file1 > file1 overwrite the file2 with file 1 contents cat file1 >> file2 append file1 contents to file2 rm –f file1 file2 file3 remove files cp file1 file2 copy file1 to file2 mv oldfile newfile move or rename file To create Directories mkdir dir Creates directory with name dir mkdir –p main/sub To create parent and sub directory mkdir –p a/b/c To create multiple hierarchy mkdir –p main/{sub1,sub2} Crates sub1 and sub2 inside main
- 6. To List the directory contents ls List contents of current directory ls –l Long list ls –a List including hidden files (.files) ls -t Modification time based listing ls –r Reverse listing ls –ltr Long list, time based, reverse order listing ls / List contents under / ls /tmp List contents under /tmp
- 7. Process ps Display currently active process ps –ef Display detailed info about process pstree Shows running process as tree top Display all running processes ps –eo pid,ppid,pcpu,comm Print processes details in customized format kill pid Kill process using pic kill -9 pid Force kill the given process id pkill pname Kill process supplying process name killall name Kill all processes with names beginning name
- 8. Word count wc file Displays no of (lines, words, characters) wc –l file Displays no of lines wc –w file Displays no of words wc –c file Display no of characters
- 9. Keyboard shortcuts Ctrl +a Moves cursor to start of line Ctrl + b Moves cursor to one character backwards Ctrl + c Terminate the current line without executing Ctrl + d Close current shell Ctrl + e Moves cursor point to end of line Ctrl + f Moves cursor one character forward Ctrl + g Cancel the search and restore the original line Ctrl + h Delete previous character Ctrl + j Acts as enter button Ctrl + k Deletes the line from cursor point to end of line Ctrl + l Clear the screen Ctrl + r Reverse search history Ctrl + u Delete the entire line before cursor point Ctrl + y Yank the content from current position Ctrl + z Stop / suspend the current running process
- 10. Filter commands grep –i pattern filename To search for a pattern in a file grep –v pattern file name To print the lines in a file except the matching line egrep –i “pat1|pat2” file Print the lines using multiple pattern match command 1 | command2 Pipe symbol; stdout of command1 to command 2 fine To find and processing files find –name Name of file or dir find –iname Ignore case name find –user To find user find –group To find group find –uid To find using uid find –gid To find files using gid find –perm To print files based on permission find –ctime Find files based on creation time find –aime Find files based on access time find -ctime Find files based on creation time find -seze Find files based on size of file
- 11. Network ping hostname Ping host and output the result ssh hostname ssh ipaddress ssh username@hostname ssh usename@ipaddress Ssh into the remote server dig hostname Query dns info dig –x hostname Reverse lookup host wget file To download the file ifconfig Config network interface and to view network info ethtool eth0 Query/control network driver and hardware settings ifup eth0 Enable eth0 interface ifdown eht0 Disable eth0 interface tracerout Print the route packets trace to network host netstat Display connection info, routing table info etc nslookup Query internet name servers interactively
- 12. Disk related commands df –h Report file system disk space usage df –ht Shows file system type df –ih Shows inode usage lsblk List block devices blkid Print block device attributes fdisk –l List available partitions cat /proc/partitions To print read only file system grep –w ro /proc/mounts To check whether mount point has ROFS issue lsscsi List scsi devices on host mkfs To create file system e2label To label the partiion smartctl –h /dev/sdb To conduct smartctl test on device smartctl –i /dev/sdb To see the detailed info about drive hdparm –l /dev/sdx To print h/w parameters of drive
- 13. At job tty To check the console at time To schedule job at –l (or) atq To check the list of at jobs at –c jobid To check what is scheduled atrm jobid To remove a job /etc/at.deny If add any single user in deny file only that user can be deny /etc/at.allow If add any single user in allow file then remaining all users will be blocked/deny
- 14. crontab crontab format Minute(0-59) hour(0-23) day of month(1 – 31) month of the year(1 -12) day of week (0-6) command to be executed * All possible values * */2 * * * It treated as every 2 hours */5 * * * * It treated as every 5 minutes crontab –e Edit crontab file crontab –l To check the cron jobs crontab –l –u username To check the cron jobs of particular user crontab –r To remove crontab files @yearly Every year @monthly Every month @daily Every day
- 15. Managing Services services service name status To check the status of service service servicename stop To stop the running service service servicename restart To restart the service service servicename reload To reload/refresh the service chkconfig –list To display available services chkconfig –list |grep –i service To display specific service chkconfig service on To make service enabled at boot time chkconfig service off to make service off at boot time chkconfig service on –level 12345 To make service level on across runlevels
- 16. Group management /etc/group It will store all group information /etc/gshadow It will store all group password information groupadd groupname Create group name groupadd –g gid groupname Create group with user specified group id groupmod –g gid groupname To change group id groupmod –n newname oldname To change group name groupdel groupname To delete group account gpasswd groupname To set group password gpasswd –r group name To delete group password gpasswd –a username groupname To add single user into group gpasswd –m user1,user2 groupname To add multiple users into group gpasswd –d username groupname To delete user with particular group
- 17. User management /etc/passwd It will store all user information /etc/shadow It will store all user password information useradd username Add a user passwd username Assigning password to the user usermod –l newname oldname To change user name usermod –u newid username To change user id usermod -g newgid username To change group id usermod –c “hello” username To change comment usermod –d /home/newname username To change home directory name usermod -s /bin/newshell username To change the shell id username To display uid,gid & groups for user (or ) it will give group names groups username To display only groups in particular user passwd –l username To lock user passwd –u username To unlock user passwd –d username To remove/delete password passwd –s username To check the user is locked or not
- 18. USER MANAGEMENT userdel username Only delete user account userdel –r username To delete user account including all files passwd –x –l username To set the passwd never expiry chage –l username To see the user password information chage username To set the password user chage –f username Force to change password for first time login usermod –g group1,group2 username One user can add into multiple groups id –a username to check primary and secondary group of user usermod –yy—dd—mm username to set expire date for user or account usermod –g gid username to change secondary group name
- 19. YUM(YELLOWDOG UPDATED MODIFIED) /etc/yum.repos.d/ To create local repository yum clean all Like clean or refresh the package yum list available to check our repository is functioning or not yum list to list all available packages yum install packagename To install package yum install packagename –y To install package without prompt y/n yum install packagename To install multiple packages at a time yum remove packagename To remove (or) uninstall the package yum remove packagename –y To remove package without prompt y/n yum list installed to see all installed packages yum list install packagename To see particular package is installed or not yum info packagename To information of installed package yum update packagename To update the package yum repolist To see available repo lists yum depist packagename It will display how many dependencies there in package yum repolist all We can see repo is enabled or disabled yum install packagename –skip –broken To install package no dependency (incase error will occur ie no dependency package) yum install –downloadonly packagename It will download package only not install yum info packagename To display package information yum –downgrade packagename To download the package
- 20. RPM (REDHAT PACKAGE MANAGER) rpm –qa packagename to check all installed packages rpm –ivh packagename(v =verbose, h=hash) To install the rpm package rpm –ivh packagename --force To install the package forcefully rpm-ivh packganame --nodeps To install the package without dependency rpm packagename rpm –qa |grep –i packgaename to check the package is installed (or) not rpm –qi packagename to see the information about installed package rpm –qc packagename to see the configuration file about installed package rpm –qd packagename to see the directory with which package is associated rpm –u packagename Upgrade the package if package exit upgrade the package if not exit install the package rpm –F packagename Update the package if package exit update the package if not exit skip the package rpm –V packagename Verify the package if any file are missing rpm –e packagename to remove/erase the package