How to configure the network to use DHCP in a Linux instance -

Configuring an instance to use DHCP instead of a static IP address lets it automatically get a network configuration. This simplifies setup and helps prevent manual configuration errors. Before you create a custom image, you must configure the instance to use DHCP. This ensures that new instances created from the image do not inherit a static IP, which can cause IP address conflicts or network connectivity issues.

Alibaba Cloud Linux

Alibaba Cloud Linux 3

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0 
```
2. Ensure the file contains the following parameters, then save and exit.
```
BOOTPROTO=dhcp
DEVICE=eth0
ONBOOT=yes
TYPE=Ethernet
```
Restart the network service.
1. Reload all network interface card (NIC) configurations.
```
sudo nmcli c reload
```
2. Activate the NIC.
```
sudo nmcli d connect eth0
```

Alibaba Cloud Linux 4

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration file.
1. Identify the active connection's ID name to find its configuration file.
```
sudo nmcli connection show --active
```
```
NAME  UUID                                  TYPE      DEVICE 
eth0  1dd9a779-d327-56e1-8454-c65e2556c12c  ethernet  eth0   
lo    0973d353-93a1-41f8-8b7b-5922ade582c6  loopback  lo 
```
  In this example, eth0 is the NAME of the active network connection.
2. Determine the path of the network configuration file.
  Replace <id_name> with the NAME from the previous step.
```
sudo find /etc/NetworkManager/system-connections/ -type f -exec grep -l "id=<id_name>" {} \;
```
```
/etc/NetworkManager/system-connections/1.nmconnection
```
  The example output shows the file path is /etc/NetworkManager/system-connections/1.nmconnection.
3. Check the file and ensure that the method under [ipv4] is set to auto.
  Replace <network_configuration_file_path> with the path from the previous step.
```
sudo vi <network_configuration_file_path>
```
Restart the network service.
1. Reload all NIC configurations.
```
sudo nmcli c reload
```
2. Activate the NIC.
```
sudo nmcli d connect eth0
```

Alibaba Cloud Linux 2

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0 
```
2. Ensure the file contains the following parameters, then save and exit.
```
BOOTPROTO=dhcp
DEVICE=eth0
ONBOOT=yes
TYPE=Ethernet
```
Restart the network service.
```
sudo systemctl restart network
```

CentOS

CentOS 6

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0 
```
2. Ensure the file contains the following parameters, then save and exit.
```
BOOTPROTO=dhcp
DEVICE=eth0
ONBOOT=yes
TYPE=Ethernet
```
Restart the network service.
```
sudo service network restart
```

CentOS 7

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0 
```
2. Ensure the file contains the following parameters, then save and exit.
```
BOOTPROTO=dhcp
DEVICE=eth0
ONBOOT=yes
TYPE=Ethernet
```
Restart the network service.
```
sudo systemctl restart network
```

CentOS 8

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0 
```
2. Ensure the file contains the following parameters, then save and exit.
```
BOOTPROTO=dhcp
DEVICE=eth0
ONBOOT=yes
TYPE=Ethernet
```
Restart the network service.
1. Reload all network interface card (NIC) configurations.
```
sudo nmcli c reload
```
2. Activate the NIC.
```
sudo nmcli d connect eth0
```

Ubuntu

Ubuntu 16 and earlier

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/network/interfaces
```
2. Ensure the file contains the following parameters, then save and exit.
```
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp 
```
Restart the network service.
- For Ubuntu 14, run sudo reboot to restart the system and apply the configuration.
- For other versions, run sudo systemctl restart networking.

Ubuntu 18 and later

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Determine the active network configuration file path.
```
ls /etc/netplan/*.yaml | sort
```
```
/etc/netplan/100-eth0.yaml
/etc/netplan/50-cloud-init.yaml
/etc/netplan/99-eth0.yaml
```
  Netplan applies configurations alphabetically. In this example, the last file, /etc/netplan/99-eth0.yaml, overrides earlier ones and is the active configuration.
2. Edit the network configuration file.
  Replace <network_configuration_file_path> with the path from the previous step.
```
sudo vi <network_configuration_file_path>
```
3. Ensure the file contains the following parameters, then save and exit.
```
network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
      dhcp4: yes
      dhcp6: no
```
Restart the network service.
```
sudo netplan apply
```

Debian

Debian 11 and earlier

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/network/interfaces
```
2. Ensure the file contains the following parameters, then save and exit.
  If the interfaces file contains source /etc/network/interfaces.d/*, edit the network configuration in /etc/network/interfaces.d/<network_config_file>.
```
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp 
```
Restart the network service.
```
sudo systemctl restart networking
```

Debian 12

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Determine the active network configuration file path.
```
ls /etc/netplan/*.yaml | sort
```
```
/etc/netplan/100-eth0.yaml
/etc/netplan/50-cloud-init.yaml
/etc/netplan/99-eth0.yaml
```
  Netplan applies configurations alphabetically. In this example, the last file, /etc/netplan/99-eth0.yaml, overrides earlier ones and is the active configuration.
2. Edit the network configuration file.
  Replace <network_configuration_file_path> with the path from the previous step.
```
sudo vi <network_configuration_file_path>
```
3. Ensure the file contains the following parameters, then save and exit.
```
network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
      dhcp4: yes
      dhcp6: no
```
Restart the network service.
```
sudo netplan apply
```

Red Hat

Red Hat 6

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0 
```
2. Ensure the file contains the following parameters, then save and exit.
```
BOOTPROTO=dhcp
DEVICE=eth0
ONBOOT=yes
TYPE=Ethernet
```
Restart the network service.
```
sudo service network restart
```

Red Hat 7

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0 
```
2. Ensure the file contains the following parameters, then save and exit.
```
BOOTPROTO=dhcp
DEVICE=eth0
ONBOOT=yes
TYPE=Ethernet
```
Restart the network service.
```
sudo systemctl restart network
```

Red Hat 8 and 9

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0 
```
2. Ensure the file contains the following parameters, then save and exit.
```
BOOTPROTO=dhcp
DEVICE=eth0
ONBOOT=yes
TYPE=Ethernet
```
Restart the network service.
1. Reload all network interface card (NIC) configurations.
```
sudo nmcli c reload
```
2. Activate the NIC.
```
sudo nmcli d connect eth0
```

Red Hat 10

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration file.
1. Identify the active connection's ID name to find its configuration file.
```
sudo nmcli connection show --active
```
```
NAME  UUID                                  TYPE      DEVICE 
eth0  1dd9a779-d327-56e1-8454-c65e2556c12c  ethernet  eth0   
lo    0973d353-93a1-41f8-8b7b-5922ade582c6  loopback  lo 
```
  In this example, eth0 is the NAME of the active network connection.
2. Determine the path of the network configuration file.
  Replace <id_name> with the NAME from the previous step.
```
sudo find /etc/NetworkManager/system-connections/ -type f -exec grep -l "id=<id_name>" {} \;
```
```
/etc/NetworkManager/system-connections/1.nmconnection
```
  The example output shows the file path is /etc/NetworkManager/system-connections/1.nmconnection.
3. Check the file and ensure that the method under [ipv4] is set to auto.
  Replace <network_configuration_file_path> with the path from the previous step.
```
sudo vi <network_configuration_file_path>
```
Restart the network service.
1. Reload all NIC configurations.
```
sudo nmcli c reload
```
2. Activate the NIC.
```
sudo nmcli d connect eth0
```

SUSE and OpenSUSE

Log on to the ECS instance.
1. Go to ECS console - Instance. In the top navigation bar, select the target region and resource group.
2. Go to the details page of the target instance. Click Connect and select Workbench. Follow the prompts on the page to log on to the terminal.
Modify the network configuration to use DHCP.
1. Edit the network configuration file.
```
sudo vi /etc/sysconfig/network/ifcfg-eth0
```
2. Ensure the file contains the following parameters, then save and exit.
```
BOOTPROTO='dhcp'
STARTMODE='auto'
```
Restart the network service to apply the configuration.
```
sudo systemctl restart wicked
```