To make the smskannel run in the background you need to run the following two commands.
Smskannel consists of two applications. Bearerbox and the SMSBox. Run both of them using nohup.
nohup /usr/local/sbin/bearerbox -v 1 /usr/src/kannel/gateway-1.4.3/gw/smskannel.conf & nohup /usr/local/sbin/smsbox -v 1 /usr/src/kannel/gateway-1.4.3/gw/smskannel.conf & tail -f /root/nohup.out
If you want to see if there is already a running process then check and then kill it, before you run the above commands.
ps aux|grep kannel #This will return all running processes for kannel #Now kill one by one using the process id kill xxxxxx