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When your Linux machine obtains an IP address via DHCP, it's actually leasing the address for a specific duration. The DHCP client (typically dhclient or systemd-networkd) handles this process automatically, but sometimes manual intervention is needed.

The most direct way to force a DHCP renewal is using the dhclient command:

sudo dhclient -r eth0  # Release current lease
sudo dhclient eth0     # Request new lease

Replace "eth0" with your actual interface name (check with ip a or ifconfig). The -r flag releases the current lease before requesting a new one.

For modern Debian systems using systemd-networkd:

sudo networkctl renew eth0
# Alternatively:
sudo systemctl restart systemd-networkd

If using NetworkManager (common on desktop installations):

sudo nmcli con up id 'YourConnectionName'
# Or to release/renew specifically:
sudo nmcli c down id 'YourConnectionName' && sudo nmcli c up id 'YourConnectionName'

To modify DHCP client behavior permanently, edit /etc/dhcp/dhclient.conf:

# Request specific options from DHCP server
request subnet-mask, broadcast-address, routers, domain-name-servers;

# Set lease timeout (in seconds)
timeout 60;
retry 10;

If renewal fails, check these logs:

journalctl -u systemd-networkd -f   # For systemd systems
tail -f /var/log/syslog             # Traditional syslog
dhclient -v eth0                    # Run dhclient in verbose mode

To request a completely fresh lease (including new DNS servers and routes):

sudo dhclient -v -r eth0
sudo rm /var/lib/dhcp/dhclient.leases.eth0
sudo dhclient -v eth0

Warning: This completely clears the lease history for the interface.

Create a renewal script (e.g., /usr/local/bin/renew_dhcp.sh):

#!/bin/bash
INTERFACE=${1:-eth0}
echo "Renewing DHCP lease for $INTERFACE"
sudo dhclient -r $INTERFACE && sudo dhclient $INTERFACE
exit $?

Make it executable with chmod +x /usr/local/bin/renew_dhcp.sh.

After renewal, verify your new IP configuration:

ip a show eth0
ip route show
cat /etc/resolv.conf

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The Dynamic Host Configuration Protocol (DHCP) assigns IP addresses dynamically with a lease time. When you need to immediately acquire a new IP configuration rather than waiting for lease expiration, manual intervention is required.

The most straightforward method for Debian-based systems:

sudo dhclient -r eth0  # Release current lease
sudo dhclient eth0     # Request new lease

For modern systems using predictable network interface names (like enp0s3):

sudo dhclient -r enp0s3
sudo dhclient enp0s3

For systems using systemd-networkd (common in newer Debian/Ubuntu versions):

sudo networkctl renew eth0

Alternatively:

sudo systemctl restart systemd-networkd

If using NetworkManager (common in desktop environments):

sudo nmcli connection down "Wired connection 1"
sudo nmcli connection up "Wired connection 1"

After renewal, verify with:

ip a show eth0
dhclient -v eth0

To modify DHCP client behavior, edit /etc/dhcp/dhclient.conf:

# Example configuration
interface "eth0" {
    send host-name "myhost";
    request subnet-mask, broadcast-address, routers;
    require subnet-mask;
}

If renewal fails, check DHCP server logs or test with:

sudo dhclient -d -v eth0  # Debug mode
journalctl -u systemd-networkd -f  # Monitor networkd logs