[LINUX] Network settings and confirmation in CentOS7

environment

Execution result


[[email protected] ~]# cat /etc/redhat-release
CentOS Linux release 7.7.1908 (Core)
[[email protected] ~]#

1. Host name

1.1. Confirmation of host name

hostname Or cat /etc/hostname

Execution result


[[email protected] ~]# hostname
CENTOS7
[[email protected] ~]#

Execution result


[[email protected] ~]# cat /etc/hostname
CENTOS7
[[email protected]CENTOS7 ~]#

1.2. Change the host name

nmcli general hostname <hostname> Or hostnamectl set-hostname <hostname>

Execution result


[[email protected] ~]# nmcli general hostname CENTOS7AF
[[email protected] ~]# hostname
CENTOS7AF
[[email protected] ~]# cat /etc/hostname
CENTOS7AF
[[email protected] ~]#

Execution result


[[email protected] ~]# hostnamectl set-hostname CENTOS7AF
[[email protected] ~]# hostname
centos7af
[[email protected] ~]# cat /etc/hostname
centos7af
[[email protected] ~]#

For hostnamectl set-hostname <hostname>, it was set in lowercase.

2. Network interface

2.1. List of network physical interfaces (devices)

nmcli device

Execution result


[[email protected] ~]# nmcli device
DEVICE  TYPE      STATE     CONNECTION
enp0s3 ethernet connected enp0s3
lo loopback No management--
[[email protected] ~]#

2.2 Detailed display of network physical interface (device)

nmcli device show <device name>

Execution result


[[email protected] ~]# nmcli device show enp0s3
GENERAL.DEVICE:                         enp0s3
GENERAL.TYPE:                           ethernet
GENERAL.HWADDR:                         08:00:27:57:A3:39
GENERAL.MTU:                            1500
GENERAL.STATE:                          100 (Connected)
GENERAL.CONNECTION:                     enp0s3
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveCo
WIRED-PROPERTIES.CARRIER:on
IP4.ADDRESS[1]:                         192.168.0.11/24
IP4.GATEWAY:                            192.168.0.1
IP4.ROUTE[1]:                           dst = 192.168.0.0/24, nh = 0.0.0.0, mt =
IP4.ROUTE[2]:                           dst = 0.0.0.0/0, nh = 192.168.0.1, mt =
IP4.DNS[1]:                             8.8.8.8
IP4.DNS[2]:                             8.8.4.4
IP6.ADDRESS[1]:                         fe80::2eca:a058:c18f:fd7e/64
IP6.GATEWAY:                            --
IP6.ROUTE[1]:                           dst = fe80::/64, nh = ::, mt = 100
IP6.ROUTE[2]:                           dst = ff00::/8, nh = ::, mt = 256, table
[[email protected] ~]#

2.3. List of network logical interfaces (connections)

nmcli connection

Execution result


[[email protected] ~]# nmcli connection
NAME    UUID                                  TYPE      DEVICE
enp0s3  0f174b12-5dc6-40c9-99fc-06c6ce550c24  ethernet  enp0s3
[[email protected] ~]#

2.4. Detailed display of network logical interface (connection)

nmcli connection show <connection name>

Execution result


[[email protected] ~]# nmcli connection show enp0s3
connection.id:                          enp0s3
connection.uuid:                        0f174b12-5dc6-40c9-99fc-06c6ce550c24
connection.stable-id:                   --
connection.type:                        802-3-ethernet
connection.interface-name:              enp0s3
connection.autoconnect:Yes
connection.autoconnect-priority:        0
connection.autoconnect-retries:         -1 (default)
connection.multi-connect:               0 (default)
connection.auth-retries:                -1
connection.timestamp:                   1584364512
connection.read-only:No
connection.permissions:                 --
connection.zone:                        --
connection.master:                      --
connection.slave-type:                  --
connection.autoconnect-slaves:          -1 (default)
connection.secondaries:                 --
connection.gateway-ping-timeout:        0
connection.metered:unknown
connection.lldp:                        default
connection.mdns:                        -1 (default)
connection.llmnr:                       -1 (default)
802-3-ethernet.port:                    --
802-3-ethernet.speed:                   0
802-3-ethernet.duplex:                  --
802-3-ethernet.auto-negotiate:No
802-3-ethernet.mac-address:             --
802-3-ethernet.cloned-mac-address:      --
802-3-ethernet.generate-mac-address-mask:--
802-3-ethernet.mac-address-blacklist:   --
802-3-ethernet.mtu:Automatic
802-3-ethernet.s390-subchannels:        --
802-3-ethernet.s390-nettype:            --
802-3-ethernet.s390-options:            --
802-3-ethernet.wake-on-lan:             default
802-3-ethernet.wake-on-lan-password:    --
ipv4.method:                            manual
ipv4.dns:                               8.8.8.8,8.8.4.4
ipv4.dns-search:                        --
ipv4.dns-options:                       ""
ipv4.dns-priority:                      0
ipv4.addresses:                         192.168.0.11/24
ipv4.gateway:                           192.168.0.1
ipv4.routes:                            --
ipv4.route-metric:                      -1
ipv4.route-table:                       0 (unspec)
ipv4.routing-rules:                     --
ipv4.ignore-auto-routes:No
ipv4.ignore-auto-dns:No
ipv4.dhcp-client-id:                    --
ipv4.dhcp-timeout:                      0 (default)
ipv4.dhcp-send-hostname:Yes
ipv4.dhcp-hostname:                     --
ipv4.dhcp-fqdn:                         --
ipv4.never-default:No
ipv4.may-fail:Yes
ipv4.dad-timeout:                       -1 (default)
ipv6.method:                            auto
ipv6.dns:                               --
ipv6.dns-search:                        --
ipv6.dns-options:                       ""
ipv6.dns-priority:                      0
ipv6.addresses:                         --
ipv6.gateway:                           --
ipv6.routes:                            --
ipv6.route-metric:                      -1
ipv6.route-table:                       0 (unspec)
ipv6.routing-rules:                     --
ipv6.ignore-auto-routes:No
ipv6.ignore-auto-dns:No
ipv6.never-default:No
ipv6.may-fail:Yes
ipv6.ip6-privacy:                       0 (disabled)
ipv6.addr-gen-mode:                     stable-privacy
ipv6.dhcp-duid:                         --
ipv6.dhcp-send-hostname:Yes
ipv6.dhcp-hostname:                     --
ipv6.token:                             --
proxy.method:                           none
proxy.browser-only:No
proxy.pac-url:                          --
proxy.pac-script:                       --
GENERAL.NAME:                           enp0s3
GENERAL.UUID:                           0f174b12-5dc6-40c9-99fc-06c6ce550c24
GENERAL.DEVICES:                        enp0s3
GENERAL.STATE:Activated
GENERAL.DEFAULT:Yes
GENERAL.DEFAULT6:No
GENERAL.SPEC-OBJECT:                    --
GENERAL.VPN:No
GENERAL.DBUS-PATH:                      /org/freedesktop/NetworkManager/ActiveCo
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/Settings
GENERAL.ZONE:                           --
GENERAL.MASTER-PATH:                    --
IP4.ADDRESS[1]:                         192.168.0.11/24
IP4.GATEWAY:                            192.168.0.1
IP4.ROUTE[1]:                           dst = 192.168.0.0/24, nh = 0.0.0.0, mt =
IP4.ROUTE[2]:                           dst = 0.0.0.0/0, nh = 192.168.0.1, mt =
IP4.DNS[1]:                             8.8.8.8
IP4.DNS[2]:                             8.8.4.4
IP6.ADDRESS[1]:                         fe80::2eca:a058:c18f:fd7e/64
IP6.GATEWAY:                            --
IP6.ROUTE[1]:                           dst = fe80::/64, nh = ::, mt = 100
IP6.ROUTE[2]:                           dst = ff00::/8, nh = ::, mt = 256, table
[[email protected] ~]#

The command to change the above settings is as follows. nmcli connection modify <connection name> <item name> <value>

Change IP address to 192.168.0.12/24 nmcli connection modify enp0s3 ipv4.address 192.168.0.12/24

Execution result


[[email protected] ~]# nmcli connection modify enp0s3 ipv4.address 192.168.0.12/24
[[email protected] ~]#

Changed DNS server to 208.67.222.222 and 208.67.220.220 nmcli connection modify enp0s3 ipv4.dns "208.67.222.222 208.67.220.220"

Execution result


[[email protected] ~]# nmcli connection modify enp0s3 ipv4.dns "208.67.222.222 208.67.220.220"
[[email protected] ~]#

It will take effect by restarting NetworkManager.

systemctl restart NetworkManager

Execution result


[[email protected] ~]# systemctl restart NetworkManager
[[email protected] ~]#

With the above settings, changing the IP address required restarting the interface connection (inactive → active).

You can manually set the interface connection to active / inactive with the following command.

Deactivate the interface connection. nmcli connection down <connection name>

Execution result


[[email protected] ~]# nmcli connection down enp0s3
Connect'enp0s3'Was successfully deactivated(D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/2)
[[email protected] ~]#

Activate the interface connection. nmcli connection up <connection name>

Execution result


[[email protected] ~]# nmcli connection up enp0s3
The connection was activated successfully(D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/4)
[[email protected] ~]#

2.5. Check network interface (instead of old ifconfig)

ip addr show

Execution result


[[email protected] ~]# ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 08:00:27:57:a3:39 brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.11/24 brd 192.168.0.255 scope global noprefixroute enp0s3
       valid_lft forever preferred_lft forever
    inet6 fe80::2eca:a058:c18f:fd7e/64 scope link noprefixroute
       valid_lft forever preferred_lft forever
[[email protected] ~]#

3. Network settings using TUI (text user interface)

You can set the network with TUI (text user interface) with the following command.

nmtui

[[email protected] ~]# nmtui

01.png

4. Other

CentOS7 does not include network related commands such as ʻifconfig, route, netstat, and ʻarp. These commands are made available by adding the "net-tools" package.

yum install net-tools

In an environment where the "net-tools" package is not installed, use commands such as "ip, ss" included in the "iproute2" package.

Command correspondence table

net-tools iproute2
ifconfig ip addr、ip link
route ip route
netstat ss
netstat -i ip -s link
arp ip neighbor

that's all

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