Linux Basic Commands

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Linux Basic Commands

List of most commonly used common used by Development, Testing, and System Administrator engineers in Linux Environment.

  • SYSTEM
      • uname  -a      : Display linux system information
      • uname -r       : Display kernel release information
      • uptime           : Show how long the system has been running + load
      • hostname     : Show system host name
      • hostname -i : Display the IP address of the host
      • last reboot   : Show system reboot history
      • date : Show the current date and time
      • cal : Show this month calendar
      • w  : Display who is online
      • whoami : Who you are logged in as
      • finger user : Display information about user
  • HARDWARE
      • dmesg  : Detected hardware and boot messages
      • cat /proc/cpuinfo : CPU model
      • cat /proc/meminfo  : Hardware memory
      • cat /proc/interrupts : Lists the number of interrupts per CPU per I/O device
      • lshw : Displays information on hardware configuration of the system
      • lsblk : Displays block device related information in Linux
      • free -m : Used and free memory (-m for MB)
      • lspci -tv : Show PCI devices
      • lsusb -tv : Show USB devices
      • dmidecode : Show hardware info from the BIOS
      • hdparm -i /dev/sda : Show info about disk sda
      • hdparm -tT /dev/sda : Do a read speed test on disk sda
      • badblocks -s /dev/sda : Test for unreadable blocks on disk sda USERS
      • id : Show the active user id with login and group
      • last : Show last logins on the system
      • who : Show who is logged on the system
      • groupadd admin : Add group “admin”
      • useradd -c “Sam” : g admin -m sam #Create user “sam”
      • userdel sam  : Delete user sam
      • adduser sam : Add user “sam”
      • usermod : Modify user information
      • chgrp : Changes a users group
  • Networking
      • ip addr show : Display all network interfaces and ip address
      • ip address add 192.168.0.1 dev eth0 : Set ip address
      • ethtool eth0 : Linux tool to show ethernet status
      • mii-tool eth0 : Linux tool to show ethernet status
      • ping host : Send echo request to test connection
      • whois domain : Get who is information for domain
      • dig domain : Get DNS information for domain
      • dig -x host : Reverse lookup host
      • host google.com : Lookup DNS ip address for the name
      • hostname –i : Lookup local ip address
      • wget file : Download file
      • netstat -tupl : Listing all active listening ports
  • DISK USAGE
      • df –h : Show free space on mounted filesystems
      • df -i : Show free inodes on mounted filesystems
      • fdisk -l : Show disks partitions sizes and types
      • du -ah : Display disk usage in human readable form
      • du -sh : Display total disk usage on the current directory
      • findmnt : Displays target mount point for all filesystem
      • mount device-path mount-point : Mount a device
  • DIRECTORY TRAVERSE
      • cd .. : To go up one level of the directory tree
      • cd     : Go to $HOME directory
      • cd /test : Change to /test directory
  • FILE COMMANDS
      • ls –al : Display all information about files/ directories
      • pwd : Show the path of current directory
      • mkdir directory-name : Create a directory
      • rm file-name : Delete file
      • rm -r directory-nam : Delete directory recursively
      • rm -f file-name : Forcefully remove file
      • rm -rf directory-name : Forcefully remove directory recursively
      • cp file1 file2 : Copy file1 to file2
      • cp -r dir1 dir2  : Copy dir1 to dir2, create dir2 if it doesn’t exist
      • mv file1 file2 : Rename source to dest / move source to directory
      • ln –s /path/to/file-name link-name :Create symbolic link to file-name
      • touch file : Create or update file
      • cat > file : Place standard input into file
      • more file : Output contents of file
      • head file : Output first 10 lines of file
      • tail file : Output last 10 lines of file
      • tail -f file :Output contents of file as it grows starting with the last 10 lines
      • gpg -c file : Encrypt file
      • gpg file.gpg : Decrypt file
      • wc :print the number of bytes, words, and lines in files
      • xargs : Execute command lines from standard input
        PROCESS RELATED
      • ps : Display your currently active processes
      • ps aux | grep ‘telnet’ :Find all process id related to telnet process
      • pmap : Memory map of process
      • top : Display all running processes
      • kill pid : Kill process with mentioned pid id
      • killall proc : Kill all processes named proc
      • pkill process-name : Send signal to a process with its name
      • bg    : Resumes suspended jobs without bringing them toforeground
      • fg     : Brings the most recent job to foreground
  • FILE PERMISSION RELATED
      • chmod octal file-name  : Change the permissions of file to octal
        • Example
        • chmod 777 /data/test.c :Set rwx permission for owner,group,world
        • chmod 755 /data/test.c :Set rwx permission for owner, rx for group and world
      • chown owner-user file : Change owner of the file
      • chown owner-user:owner-group file-name  : Change owner and group owner of the file
      • chown owner-user:owner-group directory  : Change owner and group owner of the directory
  • COMPRESSION / ARCHIVES
      • tar cf home.tar home : Create tar named home.tar containing home/
      • tar xf file.tar : Extract the files from file.tar
      • tar czf file.tar.gz files : Create a tar with gzip compression
      • gzip file : Compress file and renames it to file.gz
  • INSTALL PACKAGE
      • rpm -i pkgname.rpm =>Install rpm based package
      • rpm -e pkgname =>Remove package
      • INSTALL FROM SOURCE
        ./configure
        make
        make install
  • SEARCH
      • grep pattern files : Search for pattern in files
      • grep -r pattern dir : Search recursively for pattern in dir
      • locate file =>Find all instances of file
      • find /home/tom -name ‘index*’ : Find files names that start with “index”
      • find /home -size +10000k : Find files larger than 10000k in /home
  • LOGIN (SSH AND TELNET)
      • ssh user@host : Connect to host as user
      • ssh -p port user@host : Connect to host using specific port
      • telnet host : Connect to the system using telnet port
  • FILE TRANSFER
      • sftp 192.16875.2 : Connect remote host
      • scp
        scp file.txt server2:/tmp : Secure copy file.txt to remote host /tmp folder
      • rsync
        rsync -a /home/apps /backup/ : Synchronize source to destination

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