Network issue

hello i have 4 lan ports on my pc for linuxcnc, port 1 is for internet - port2 for mesa board, my issue are when i make both ports auto connect, i take port2 as first choice, even if i set port 1 priority 10 and port 2 -10, so i turn off auto connect for port 2, and have to manuel connect port 2 at start up, is there a easy solution for this
   

I would follow the instructions here to set the mesa network NIC on the PC
linuxcnc.org/docs/2.8/html/man/man9/hm2_...FACE%20CONFIGURATION

That removes any auto from the equation

everything works mesa and internet, the only problem i have is that i always have to click connect on port 2 ( the port for mesa at ip 10.10.10.10 crossover cable) on reboot, because it fails in auto mode, 
port 1 is connect to home lan network 192.168.1.--

i get this when i try to edit the interface file :
cnc@debian:~$ sudo edit /etc/networking/interfaces
Error: no write permission for file "/etc/networking/interfaces"
cnc@debian:~$ 
 

try it without the crossover cable. They have not been needed for years.

You may not be in the sudoers group.

Try su instead.

ups it is a straight cable   also when im in root user i can´t access it  
cnc@debian:~$ sudo edit /etc/networking/interfaces
[sudo] adgangskode for cnc: 
Error: no write permission for file "/etc/networking/interfaces"
cnc@debian:~$ sudo su
root@debian:/home/cnc#  edit /etc/networking/interfaces
Error: no write permission for file "/etc/networking/interfaces"
root@debian:/home/cnc# 

can it be network manager that´s deny accesses it ? 
 

Can you try
As root you should have access to any file in /etc unless something has gone wrong with your permissions

i just removed network manager by mistake   i have no internet on the machine now, is the only sulotion to install linuxcnc all over ? 

Info here:
wiki.debian.org/NetworkConfiguration

But first we need to fix the permissions and ownership of the interfaces file.

So if you can run the command in my previous post and relay the output can can go from there.

i get this
- rw - r - - r - - root root 240 aug 31 14:34 /etc/network/interfaces

ok you need to edit and follow the instructions in the link I supplied

/etc/network/interfaces

not
/etc/networking/interfaces

if you had of ran
you should have got