Running several storage servers on the same machine

[Mark s2c]

Hello
I've created 4 VDIs, attached them to 4 Ubuntu Precise VMs, partitioned them with ext4 and mounted them under /mnt/tahoe{1..4}. 
I created 4 users tahoe{1..4}, each home dir in /home/tahoe{1..4}, and as each user create a client and introducer. Each users home dir .tahoe/tahoe.cfg specifies a nickname, the introducer ref and enabled=true

When I came to do a tahoe start as each user, I notice that 4 tahoe processes are not starting. 

What am I doing wrong?