59

Short of rebooting, how can I release and renew my DHCP lease? It would be useful to know a GUI and terminal method.

I'd especially like to know if there is a means to do this without requiring admin privileges.

18

In the network drop-down selector from the system tray you can press the network you are already connected to, this will make network-manager ask for a new lease from a DHCP server.

alt text

(This also works for wired networks, but i don't think it works for PPP connections (mobile broadband))

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51

To renew your dhcp lease at the terminal:

sudo dhclient -r; sudo dhclient
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  • 10
    I think sudo service networking restart is a better way to go. What you suggest didn't work for me on an 11.10 box with dhclient3. Instead, I ended up with two DHCP clients running: one dhclient3 and one dhclient. See ubuntuforums.org/showthread.php?t=1868368 – Adam Monsen Feb 7 '12 at 19:14
  • @AdamMonsen Does restarting the networking service actually work with NetworkManager? – rakslice Dec 13 '12 at 0:21
  • 1
    @AdamMonsen restarting networking does not seem to renew the dhcp lease for me – dogmatic69 Apr 9 '14 at 21:36
  • sudo service network-manager restart in Ubuntu 13.10 64-bit desktop appears to properly restart network stuff and renew my DCHP lease. (From askubuntu.com/a/230751/2273 ) – Adam Monsen Apr 9 '14 at 22:02
  • 4
    Useful to know for debugging: on Ubuntu 14.04 sudo service network-manager restart didn't completely renew IP lease from DHCP. It just send a DHCP Request packet instead of a Discover. If you just want to renew your lease it's enough, but if you are debugging DHCP you want to use the original solution. – gerlos Nov 25 '14 at 14:58
37

In my case I had to specify which card to renew:

Note: you might want to join the two on one line, as otherwise you might lose the remote connection you're on after the first!

First release the current IP address:

sudo dhclient -r eth0

then renew the IP address

sudo dhclient eth0

.. or do them together to avoid losing connection:

sudo dhclient -r eth0 && sudo dhclient eth0
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  • 4
    This is the correct answer if you have more than one interface. – Tek Feb 17 '15 at 1:38
  • Better: Join the commands with AND - sudo dhclient -r enp7s0 && sudo dhclient enp7s0 (replace with your eth network device) – bshea Jan 11 '19 at 15:37
  • Please edit this answer to join these together, I just got kicked off a remote box trying these separately. – Graham Russell Jan 21 '19 at 21:07
  • Worked for me in Ubuntu server 18.04 – Indika K Jun 2 at 5:55
10

This works on Ubuntu 12.04 LTS:

sudo service network-manager restart

When I do that, Network Manager asks for a new DHCP lease.

I prefer this to manually (re)starting dhclient because I've had problems by stale dhclient processes (ones not managed by Network Manager) spontaneously and incorrectly reconfiguring my network settings at random points when it's least convenient.

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  • 2
    Still relevant on Ubuntu 16.04. dhclient -r just silently does nothing with a successful exit code otherwise. :-( – studog Sep 18 '18 at 11:45
  • This worked fine on 18.04! – Roel Van de Paar Jun 15 '19 at 4:31
8

Maverick comes with nmcli, a command line interface to the network manager.

I can't see a simple way of telling it to renew a lease, but running:

nmcli con

Gets you a connection list, and running:

nmcli con down id 'Connection Name'
nmcli con up id 'Connection Name'

Takes the connection down and back up. It may be possible to do something similar with the device instead.

The connection list seems to include all connections, so this will probably work with PPTP and VPN connections too.

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  • 1
    My DHCP server still shows the lease there... (I'm trying to force a release to make a static assignment take effect) – Gert van den Berg Sep 4 '18 at 7:28
6

If you're on a systemd based-version of Ubuntu without a GUI (i.e. server version) then this is the way to renew the DHCP lease:

sudo systemctl restart systemd-networkd

Note: If you're connected via the interface whose DHCP lease you're renewing you may get disconnected, unless you're connected via a statically configured interface or the console.

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  • I was testing this with dhcpdump listening on other terminal. Didn't seem to work, only the dhclient way. – Pablo Bianchi Sep 23 '19 at 6:28
  • If your machine is using dhclient then you would use that. In newer versions of Ubuntu dhclient is not used and instead the DHCP client in system-networkd is used. – Pierz Jun 27 at 10:37
1

Having just upgraded to Maverick Meerkat Beta 1, something broke in my standard, vanilla eth0 configuration which I've not debugged yet. The quick and dirty workaround has been

sudo dhclient

which notices that there was a (possibly dead) client already and obtains a new lease:

There is already a pid file /var/run/dhclient.pid with pid 2436
killed old client process, removed PID file
Internet Systems Consortium DHCP Client V3.1.3
Listening on LPF/eth0/00:1a:92:24:9c:85
Sending on   LPF/eth0/00:1a:92:24:9c:85
Sending on   Socket/fallback
DHCPDISCOVER on vboxnet0 to 255.255.255.255 port 67 interval 3
DHCPREQUEST of 192.168.2.2 on eth0 to 255.255.255.255 port 67
DHCPACK of 192.168.2.2 from 192.168.2.1
bound to 192.168.2.2 -- renewal in 118389830 seconds.

This isn't a fix, just a hack. I'll follow-up when I figure what went bad.

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1

Lacking this specific capability via nmcli, I believe the best CLI solution is to release and kill the dhclient instance managed by NetworkManager, rather than starting a new one. NM will then bring it back up again automatically, avoiding having to restart the entire NM infrastructure.

sudo dhclient -v -r -pf /run/sendsigs.omit.d/network-manager.dhclient-eth0.pid
  • -v - make verbose
  • -r - release and shut down
  • -pf - pid file of NM's instance
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