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Shell Commands Collection

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User Management

  • Add group sudo groupadd groupname
  • Add user and specify group and home folder sudo useradd username -g groupname -d path_to_home_folder
  • Add user home folder mkdir /path/to/home_folder && sudo chmod -R groupname:username /path/to/home_folder
  • Set password for user sudo passwd username
  • Add existing user to exising group sudo usermod -a -G groupname username
  • Check user information id will show up username, primary group name and all group names
  • Switch user su [username] if no username specified, default switch to supersuer
  • Switch user and load simimar environment as if it’s a direct user login su - username
  • Add user to sudoer list sudo adduser username sudo


  • Delete one words before cursor <CTRL+w>
  • Delete all words after cursor <CTRL+k>
  • Move to head of line <CTRL+a>
  • Move to end of line <CTRL+e>
  • Clean line <CTRL+u>
  • Clean screen <CTRL+l>

  • Paste last parameter of last command <ESC+.>

  • Generate random number echo $RANDOM

  • Show full path ls -d $PWD/*


  • MAC refresh DNS sudo dscacheutil -flushcache or sudo discoveryutil udnsflushcaches
  • Windows refresh DNS ipconfig /flushdns
  • Linux refresh DNS sudo /etc/init.d/networking restart
  • show public IP curl ifconfig.me
  • show local DNS cat /etc/resolv.conf
  • Resolve Agent admitted failure to sign using the key
    • generate private key and public key on machine ssh-keygen
    • (ssh-add ~/.ssh/id_dsa.pub) add content of local public key to remote machine’s ~/.ssh/authorized_keys
    • specify location of private key on local machine ssh-add ~/.ssh/id_dsa

File System

  • Check total size of a folder du -shm
    • -s — summarize the sizes of all available files in a folder
    • -h — show resulted value in Human readable format
    • -m — show the result in Megabytes


  • save read-only file :w !sudo tee %

  • Change to uppercase visual + U

  • Change to lowercase visual + u
  • Toggle case visual + ~


  • Fix the problem that title bar dispear on ubuntu compiz-decorator --replace

File Operation

  • Batch moZipve files mv src_folder1 src_folder2 src_folder3 -t dest_folder
  • Compress a folder into zip file zip -r filename.zip folder_name