CentOS is a RedHat-like Linux distro, so you should follow the Fedora instructions. Two additional gotchas may present themselves.
/dev/null is not world-writable. You need to
chmod 777 /dev/null
in order for Instiki to be able to function.
/dev/urandom is not a “special character device.” You need to
rm /dev/urandom mknod -m 644 /dev/urandom c 1 9 chown root:root /dev/urandom
in order for BZR to function.
In both cases, these need to be placed in a startup script, because rebooting the server will recreate the problem.