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                       

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 

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"