How to change network interface name

Question

I am trying to write a bash script to configure a number of network interfaces and have issues with some of the NICs getting a Wired Connection name instead of the device name. E.g.

$ nmcli dev status
DEVICE  TYPE      STATE      CONNECTION         
ens22   ethernet  connected  ens22              
ens18   ethernet  connected  Wired connection 2 
ens19   ethernet  connected  ens19              
ens20   ethernet  connected  Wired connection 1 
ens21   ethernet  connected  ens21              
lo      loopback  unmanaged  --     

The impact of that is these commands fail because it is expecting the Connection Name, not the Device Name:

printf "\n${YELLOW}### Configure ens20: ###${NC}\n"
sudo nmcli con mod ens20 ipv4.addresses 10.70.20.254/24
sudo nmcli con mod ens20 ipv4.dns 8.8.8.8
sudo nmcli con mod ens20 ipv4.method manual

Questions:

1. What causes only some of the interfaces to get the name "Wired Connection?"
2. Is there an option in nmcli to use the interface name instead?
3. Is it possible to rename a connection? I have tried to rename the Connection attribute but I can only do it if I modify the connection, not the device.

This works:

sudo nmcli connection modify "Wired connection 2" connection.id "ens18"

This does not work:

sudo nmcli device modify ens18 connection.id "ens18" 

Thanks

Answer 1

In NetworkManager terminology, a device is the NIC (or a virtual abstraction of one), and a connection is a set of network configuration parameters that can apply to any suitable device, unless specifically restricted to match a particular device only. Even if so restricted, the connections and devices are separate configuration objects.

1.) Wired connection <number> is the default connection name format used by some GUI tools (including the RHEL OS installer), while <interface name> might be the default name used when creating a new connection using nmcli and not specifying a name for it - e.g. if you use nmcli device connect <interface name> and there is no existing connection definition that can apply to that interface.

2.) The only ways to refer to a particular connection are by its name, its UUID, or by its D-Bus connection path number (path <N> for /org/freedesktop/NetworkManager/Settings/<N>, or apath <N> for /org/freedesktop/NetworkManager/ActiveConnection/<N>).

If you want a quick way to refer to "whatever is the active connection on this device", you could make a shell function like this:

nm_connection_of() {
    # $1 = name of network interface to query
    con_name=$(nmcli -g GENERAL.CONNECTION device show "$1")
    if [ "$con_name" = "" ]; then
        echo "ERROR: no connection associated with $1" >&2
        return 1
    fi
    echo "$con_name"
}

Then you could use it like this:

sudo nmcli connection modify "$(nm_connection_of ens18)" connection.id ens18

Note that it's possible that a network interface is not currently associated with any connection at all, in which case $(nm_connection_of <interface name>) would return an error.

3.) You already answered this question yourself.

To rename a connection, you must un-ambiguously identify the connection you wish to rename, not a device that might be associated with any number of possible connections, or with no connection at all.