[afterbox]

Well we're getting somewhere, ~/.profile successfully executed:

cd /mnt/us
exec esys/bin/busybox ash

But echo $PATH returns:

/usr/local/bin:/bin:/usr/bin:/usr/sbin:/sbin:/usr/local/python/bin

So the export PATH=/mnt/us/esys/bin:/mnt/us/esys/usr/bin:$PATH didn't work...

PS: Same result with a shell script, can't export the PATH variable.