Execute command without keeping it in hostory:

• Sometimes shell commands must be kept form history, e.g. when setting secrets to environment variables for configuring applications according to the Twelve-Factor-App.
• Configure the shell to not record history when starting with a space: $ export HISTCONTROL=ignorespace
• Execute the command with a secret with a leading space: $ export MY_PASSWORD=the-secret
• Verified in Bash. The command will not be recorded in ~/.bash_history.

• Set owner: $ chown myfolder myuser
• Set owner and group: $ chown myowner:mygroup myfolder
• Change password: $ passwd
• List user's groups: $ groups somebody

• Set group: $ chgrp mygroup myfolder
• Set owner and group: $ chown myowner:mygroup myfolder
• List group members: $ getent group some-group

• Flag s: created folders and files inherit the group of the upper folder. $ chmod g+s file.txt
• List permissions:
  • $ getfacl file.txt
  • $ ls -lV
• Set specific group permissions:
  • $ setfacl -m u:somebody:rwx file.txt
  • $ setfacl -m g:some-group:rw file.txt
• Set default group permissions:
  • $ setfacl -m default:g::rwx file.txt
  • $ setfacl -m default:g:some-group:r file.txt
• Remove a group: $ setfacl -x g:some-group file.txt
• http://manpages.ubuntu.com/manpages/xenial/man1/setfacl.1.html