Package: isc-dhcp-client Version: 4.4.3-P1-2 X-Debbugs-CC: Thorsten Glaser <[email protected]>, Simon Richter <[email protected]> Control: retitle -1 isc-dhcp-client: dhclient exits uncleanly while DISCOVERing
On Tue, Nov 04, 2025 at 05:12:42PM +0100, Daniel Gröber wrote:
> > >Eeeeerm. Well. I've seen dhclient crash mysteriously after long runtime
> > >leaving systems without IPs somehow. So that's not a sure bet
> >
> > How? If it crashes it won’t remove the currently working IPs.
>
> You (and me) would think so! Somehow that's what the systems ended up
> looking like. I didn't check logs at the time unfortunately and switched to
> dhcpcd since, so I have no clue if it's still happening. I'm watching bugs
> on isc-dhcp so we'll see if anything crops up.
Actually. I still had a router running with dhclient on a bookworm system
and it just experienced this problem. The scenario is different from what I
remember though:
Just now a powercut caused a reboot and dhclient seems to have given up (or
crashed without leaving a trace in dmesg?) while the cable modem was still
booting.
I can see it tries to DISCOVER a couple of times, goes to sleep, tries
again but then it's not heard from again with no process left behind -
until I restarted the interface at 21:02.
# journalctl -t dhclient
17:17:24 dhclient[759]: Internet Systems Consortium DHCP Client 4.4.3-P1
17:17:24 dhclient[759]: Copyright 2004-2022 Internet Systems Consortium.
17:17:24 dhclient[759]: All rights reserved.
17:17:24 dhclient[759]: For info, please visit
https://www.isc.org/software/dhcp/
17:17:24 dhclient[759]:
17:17:25 dhclient[759]: Listening on LPF/enp1s0/00:0d:b9:4e:90:54
17:17:25 dhclient[759]: Sending on LPF/enp1s0/00:0d:b9:4e:90:54
17:17:25 dhclient[759]: Sending on Socket/fallback
17:17:25 dhclient[759]: DHCPREQUEST for X.X.X.X on enp1s0 to
255.255.255.255 port 67
17:17:30 dhclient[759]: DHCPREQUEST for X.X.X.X on enp1s0 to
255.255.255.255 port 67
17:17:36 dhclient[759]: DHCPDISCOVER on enp1s0 to 255.255.255.255 port 67
interval 8
17:17:44 dhclient[759]: DHCPDISCOVER on enp1s0 to 255.255.255.255 port 67
interval 10
17:17:54 dhclient[759]: DHCPDISCOVER on enp1s0 to 255.255.255.255 port 67
interval 15
17:18:09 dhclient[759]: DHCPDISCOVER on enp1s0 to 255.255.255.255 port 67
interval 7
17:18:16 dhclient[759]: DHCPDISCOVER on enp1s0 to 255.255.255.255 port 67
interval 12
17:18:28 dhclient[759]: DHCPDISCOVER on enp1s0 to 255.255.255.255 port 67
interval 9
17:18:37 dhclient[759]: No DHCPOFFERS received.
17:18:37 dhclient[759]: Trying recorded lease X.X.X.X
17:18:40 dhclient[759]: No working leases in persistent database - sleeping.
17:18:47 dhclient[759]: DHCPDISCOVER on enp1s0 to 255.255.255.255 port 67
interval 5
17:18:52 dhclient[759]: DHCPDISCOVER on enp1s0 to 255.255.255.255 port 67
interval 10
21:02:49 dhclient[38169]: Removed stale PID file
Curiously the "Removed stale PID file" would suggest to me that perhaps it
did crash or exit uncleanly somehow(?) since I can't see any segfault lines
in dmesg.
On dhcp release via ifdown /run/dhclient.enp1s0.pid does get removed
properly -- I checked.
I do have quite a bit of non-standard config on this system, but nothing in
/etc/dhcp/dhclient.conf that should prevent dhclient from retrying
forever.
I have a `retry` set to 10 seconds instead of the 5min default, use a
`reject 192.168.100.0/24` line to avoid using the temporary mmanagment LAN
the modem gives out leases for while it's still connecting to the CMTS and
`request` a reduced set of options.
Puzzling,
--Daniel
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