Run process as another user in init.d script

start-stop-daemon --start --quiet --chuid $USER:$GROUP --exec $SCRIPT

Installing Cassandra on Ubuntu server

# enable add-apt-repository
sudo apt-get install python-software-properties
# add repository for java
sudo add-apt-repository ppa:ferramroberto/java
# update
sudo apt-get update
# install Sun (I hate Oracle) java
sudo apt-get install sun-java6-jdk sun-java6-plugin
# create directory for installation
sudo mkdir /opt/cassandra
# add cassandra user [set password]
sudo adduser cassandra
# change owner of istallation directory
sudo chown cassandra:cassandra /opt/cassandra/
# switch to cassandra user
su -l cassandra
# go to installation directory
cd /opt/cassandra
# download latest version (check address on cassandra.apache.org)
wget http://www.apache.net.pl//cassandra/1.0.7/apache-cassandra-1.0.7-bin.tar.gz
# untar
tar xvzf apache-cassandra-1.0.7-bin.tar.gz
# back to admin account, create cassandra var directory
logout
sudo mkdir /var/lib/cassandra/
sudo chown cassandra:cassandra /var/lib/cassandra/
sudo mkdir /var/log/cassandra/
sudo chown cassandra:cassandra /var/log/cassandra/
# switch again to cassandra user
su -l cassandra
mkdir /var/lib/cassandra/data
mkdir /var/lib/cassandra/commitlog
mkdir /var/lib/cassandra/saved_caches

Add to /etc/init.d/cassandra

start-stop-daemon --start --quiet --chuid cassandra:cassandra --exec /opt/cassandra/apache-cassandra-1.0.7/bin/cassandra