nmcli

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Understanding basic nmcli in Rocky Linux 9

In Rocky Linux 9, the nmcli command-line tool (Network Manager Command Line) replaces the traditional ifcfg files that we have been using since Rocky Linux 8. If you can Google “Why nmcli is replacing the ifcfg”, you will find a comprehensive list of key reasons why the transition took place. One thing that I like best is this particular answer

nmcli commands are designed to be easily automated and scripted (e.g., using Ansible), offering better control and error checking (syntax validation) compared to generating flat text files through scripts.

Usage 1a: List the NetworkManager connection profiles

# nmcli con
NAME   UUID                                  TYPE      DEVICE 
ens33  xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx  ethernet  ens33  
lo     yyyyyyyy-yyyy-yyyy-yyyy-yyyyyyyyyyyy  loopback  lo

Usage 1b: List the Network Devices and their status

# nmcli dev
DEVICE  TYPE      STATE                   CONNECTION 
ens33   ethernet  connected               ens33      
lo      loopback  connected (externally)  lo        

Usage 2a: Disable the connection of ens33

# nmcli con down ens33
Connection 'ens33' successfully deactivated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/2)

Usage 2b: Enable the connection of ens33

# nmcli con up ens33
Connection 'ens33' successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/2)

Usage 2c: Show Connection Details

# nmcli con show ens33
[root@hpc-wfly-rl9 ~]# nmcli con show ens33
connection.id:                          ens33
connection.uuid:                        817c4ac5-49f4-3752-9a16-9d7460bed1c9
connection.stable-id:                   --
connection.type:                        802-3-ethernet
connection.interface-name:              ens33
connection.autoconnect:                 yes
connection.autoconnect-priority:        -999
connection.autoconnect-retries:         -1 (default)
connection.multi-connect:               0 (default)
connection.auth-retries:                -1
connection.timestamp:                   1763952141
connection.permissions:                 --
connection.zone:                        --
connection.controller:                  --
connection.master:                      --
connection.slave-type:                  --
connection.port-type:                   --
connection.autoconnect-slaves:          -1 (default)
connection.autoconnect-ports:           -1 (default)
connection.down-on-poweroff:            -1 (default)
connection.secondaries:                 --
connection.gateway-ping-timeout:        0
connection.ip-ping-timeout:             0
connection.ip-ping-addresses:           --
connection.ip-ping-addresses-require-all:-1 (default)
connection.metered:                     unknown
connection.lldp:                        default
.....
.....

Usage 3: Set the static IP Address of the Ethernet Connection

# nmcli con mod ens33 ipv4.method manual ipv4.address 10.10.1.2/24 ipv4.gateway 10.10.1.1
# nmcli con up ens33

Usage 4a: Using conn to update DNS (replace manual scripting of /etc/resolv.conf)

# nmcli con mod ens33 ipv4.dns '8.8.8.8,8.8.8.4' 
# nmcli con show |grep dns
# nmcli con up ens33

At /etc/resolv.conf, you will notice

# Generated by NetworkManager
search myown.domain.com
nameserver 8.8.8.8
nameserver 8.8.8.4

Usage 4b: Using nmcli to update domain search (replace manual scripting of /etc/resolv.conf)

# nmcli con mod ens33 ipv4.dns-search 'myown.domain.com'
# nmcli con up ens33

Usage 5a: Disable IPv6 

# nmcli con mod ens33 ipv6.method "disabled"
# nmcli con up ens33
.....
....
ipv6.method:                            disabled
ipv6.dns:                               --
ipv6.dns-search:                        --
ipv6.dns-options:                       --
ipv6.dns-priority:                      0
ipv6.addresses:                         --
....
.....

Display the IP settings of the device. If there is no inet6 entry is displayed, IPv6 is disabled on the device.

# ip address show ens33
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
altname enp2s1
inet 192.168.x.x/19 brd 192.168.x.x scope global noprefixroute ens33
    valid_lft forever preferred_lft forever

References:

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Using NMCLI to manage Network on Rocky Linux 8

Point 1: View all the saved connections

# nmcli connection show
ens1f0     XXXX-XXXX-XXXX-XXXX-XXXX  ethernet  ens1f0
ens1f1     YYYY-YYYY-YYYY-YYYY-YYYY  ethernet  ens1f1
ens10f0    ZZZZ-ZZZZ-ZZZZ-ZZZZ-ZZZZ  ethernet  --
ens10f1    AAAA-AAAA-AAAA-AAAA-AAAA  ethernet  --

Point 2a: Stop Network

You can use the command “nmcli connection down ssid/uuid". For example 

# nmcli connection down XXXX-XXXX-XXXX-XXXX-XXXX
Connection 'eno0' successfully deactivated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/3)

Point 2b: Start Network

You can use the command “nmcli connection up ssid/uuid". For example 

# nmcli connection up XXXX-XXXX-XXXX-XXXX-XXXX
Connection 'eno0' successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/3)

Point 3: Device Connection

To check the Device status

# nmcli dev status
ens1f0  ethernet  connected     ens1f0
eno1f1  ethernet  connected     ens1f1
eno10f0  ethernet  disconnected  --
eno10f1  ethernet  disconnected  --

Point 4: List all Device 

# nmcli device show
GENERAL.DEVICE:                         ens1f0
GENERAL.TYPE:                           ethernet
GENERAL.HWADDR:                         XX:XX:XX:XX:XX:XX
GENERAL.MTU:                            1500
GENERAL.STATE:                          100 (connected)
GENERAL.CONNECTION:                     ens1f0
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveConnection/2
WIRED-PROPERTIES.CARRIER:               on
IP4.ADDRESS[1]:                         192.168.0.1
IP4.GATEWAY:                            192.168.0.254
IP4.ROUTE[1]:                           dst = 0.0.0.0/0, nh = 192.168.0.254, mt = 101
IP4.ROUTE[2]:                           dst = 198.168.0.0/19, nh = 0.0.0.0, mt = 101
IP6.ADDRESS[1]:                         xxxx::xxxx:xxxx:xxxx:xxxx/64
IP6.GATEWAY:                            --
IP6.ROUTE[1]:                           dst = fe80::/64, nh = ::, mt = 1024

GENERAL.DEVICE:                         eno1f1
GENERAL.TYPE:                           ethernet
GENERAL.HWADDR:                         94:6D:AE:9B:76:1C
GENERAL.MTU:                            1500
GENERAL.STATE:                          100 (connected)
GENERAL.CONNECTION:                     eno1f1
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveConnection/4
WIRED-PROPERTIES.CARRIER:               on
IP4.ADDRESS[1]:                         192.168.200.201/19
IP4.GATEWAY:                            --
IP4.ROUTE[1]:                           dst = 192.168.192.0/19, nh = 0.0.0.0, mt = 102
IP6.ADDRESS[1]:                         fe80::966d:aeff:fe9b:761c/64
IP6.GATEWAY:                            --
IP6.ROUTE[1]:                           dst = fe80::/64, nh = ::, mt = 1024

Point 5: Start and Stop Device 

# nmcli con down ens1d1
# nmcli con up ens1d1

References:

  1. nmcli command in Linux with Examples