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===== SU, SUDO =====

==== su ====
Start a programm or script as user xy.

Example:

  su - username -c /path/to/programm/or/binary
  su - oracle -c script.sh                      #Starts "script.sh" with user "oracle"
  su - user -c whoami  
  su -s /bin/bash -c "/scripts/script.sh" mysql 
  sudo -u mysql /scripts/script.sh                       

==== sudo ====

Execute a single command as root user.

Example:
  sudo /etc/init.d/ssh restart
  sudo apt-get update
  sudo apt-get upgrade
  sudo apt-get install [package name]
  sudo apt-get remove [package name]
  sudo cp /var/lib/dpkg/available-old /var/lib/dpkg/available
  sudo rm /var/lib/dpkg/lock 
 
==== sudoers ====

If you want to grant a permission - such as restart a service - as non-root you can edit the "/etc/sudoers" file:

  # User privilege specification
  root    ALL=(ALL) ALL
  %wheel ALL=(ALL) NOPASSWD: ALL
  username ALL=NOPASSWD: /etc/init.d/tomcat6 restart
  username ALL=(ALL:ALL) NOPASSWD: ALL
  
Full access for user "myuser" on host "myhostname":

  myuser myhostname=(ALL) NOPASSWD:ALL

Allows running a script as root without any arguments.
  nrpeuser    ALL=(root)  NOPASSWD: /path/to/script ""
 
Allows running a script as root with fixed arguments.
  nrpeuser    ALL=(root)  NOPASSWD: /path/to/script --option-1 "a" --option-2 "b"
 
Allows running a script as root with any arguments. THIS COULD BE DANGEROUS AND IS _NOT_ RECOMMENDED!
  nrpeuser    ALL=(root)  NOPASSWD: /path/to/script
  
If you want to grant permission to edit files and folders there´s "sudoedit".

  username ALL=NOPASSWD: sudoedit /srv/etc/tomcat/*
  
To edit afterwards a file as "non-root" execute:

  sudoedit /path/to/file
  
and vi commands (:w, :wq to save and exit).

chmod:

  test          ALL=(ALL) NOPASSWD: /usr/bin/chmod [0-7][0-5][0-5] /testfolder/*
  
chown:

  test          ALL=(ALL) NOPASSWD: /usr/bin/chown test\:test /testfolder/*

**Pipe** with sudo as non root (user1 has "user1 ALL=(ALL) NOPASSWD: ALL" entry in /etc/sudoers!):

  sudo sh -c "cat id_rsa.pub >> /home/user2/.ssh/authorized_keys"