rc.dhcpd has an odd error.

Richard Cranium · 10-29-2023, 09:29 PM

This hasn't come up because who the devil restarts their dhcpd while the system is running? (At least that's my story and I'm sticking to it.)

It turns out I've been doing that while attempting to fix a dynamic DNS issue. The issue comes about because the dhcpd binary looks for the pid file and won't start if it finds one.

For example, the first time you run restart:

Code:

root@testbed:~# /etc/rc.d/rc.dhcpd restart
Shutting down dhcpd: 
Starting dhcpd:  /usr/sbin/dhcpd  Internet Systems Consortium DHCP Server 4.4.3-P1
Copyright 2004-2022 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Config file: /etc/dhcpd.conf
Database file: /var/state/dhcp/dhcpd.leases
PID file: /var/run/dhcpd.pid
There's already a DHCP server running.

If you think you have received this message due to a bug rather
than a configuration issue please read the section on submitting
bugs on either our web page at www.isc.org or in the README file
before submitting a bug.  These pages explain the proper
process and the information we find helpful for debugging.

exiting.

root@testbed:~#

...but the second time you run that command, you get...

Code:

root@testbed:~# /etc/rc.d/rc.dhcpd restart
Shutting down dhcpd: dhcpd: no process found

Starting dhcpd:  /usr/sbin/dhcpd  Internet Systems Consortium DHCP Server 4.4.3-P1
Copyright 2004-2022 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Config file: /etc/dhcpd.conf
Database file: /var/state/dhcp/dhcpd.leases
PID file: /var/run/dhcpd.pid
Wrote 0 deleted host decls to leases file.
Wrote 0 new dynamic host decls to leases file.
Wrote 1 leases to leases file.
Listening on LPF/virbr0/52:54:00:0a:3c:64/192.168.122.0/24
Sending on   LPF/virbr0/52:54:00:0a:3c:64/192.168.122.0/24
Listening on LPF/eth0/b4:2e:99:4c:f8:21/10.10.0.0/24
Sending on   LPF/eth0/b4:2e:99:4c:f8:21/10.10.0.0/24
Listening on LPF/eth1/00:13:3b:0e:d0:9e/172.16.0.0/24
Sending on   LPF/eth1/00:13:3b:0e:d0:9e/172.16.0.0/24
Sending on   Socket/fallback/fallback-net

root@testbed:~#

There are a couple of ways to fix the issue:

You can make "--no-pid" a default DHCPD_OPTIONS value, so there won't be a pid file to check
You can add "rm /var/run/dhcpd.pid" in the stop() block

I don't have an opinion upon which option is superior. The stop() bit of the script doesn't bother to look at /var/run/dhcpd.pid but instead just kills everything named dhcpd.

Richard Cranium · 10-29-2023, 11:18 PM

Derp. That's running Slackware64 15.0 that's up-to-date as of 4:40AM CDT this morning.

gus3 · 10-30-2023, 12:33 PM

My first step is, trace it with

Code:

sh -vx /etc/rc.d/rc.dhcpd restart

Richard Cranium · 11-01-2023, 09:01 PM

Quote:

Originally Posted by gus3

My first step is, trace it with

Code:

sh -vx /etc/rc.d/rc.httpd restart

Maybe you replied to the wrong thread; I know what the problem is.

pan64 · 11-02-2023, 04:13 AM

When you want to stop a service:
if the process/service is not running (stopped already) nothing will happen, therefore the pidfile will not be checked and removed.
if the process/service is running it should be terminated and also the pidfile(s) should be removed.

An existing pidfile without running process means incorrect termination or a bug in the software somewhere. The fix is: remove the pidfile manually or find/fix/report the bug. Don't add --no-pid as it will probably make things worse (because the pidfile is still there).
And I wouldn't add force remove to the stop function (it looks like an ugly workaround for me), but I would rather try to terminate it properly.

GazL · 11-02-2023, 04:14 AM

I don't use network-manager and I replaced slackware's stock networking scripts with my own, but I find dhcpcd manages its pidfiles itself if you issue the 'dhcpcd -k' or 'dhcpcd -x' commands to stop it.

One caveat is that the pidfile name used is somewhat dynamic and can change depending on what options were provided to dhcpcd when you started it: 'dhcpcd -P' can help with that though.

Petri Kaukasoina · 11-02-2023, 07:57 AM

Quote:

Originally Posted by Richard Cranium

Code:

root@testbed:~# /etc/rc.d/rc.dhcpd restart

Quote:

Originally Posted by gus3

Code:

sh -vx /etc/rc.d/rc.httpd restart

Quote:

Originally Posted by GazL

'dhcpcd -k' or 'dhcpcd -x'.

dhcpcd != dhcpd != httpd

gus3 · 11-02-2023, 10:32 AM

Quote:

Originally Posted by Petri Kaukasoina

dhcpcd != dhcpd != httpd

That was my (really stupid) goof.

But my suggestion remains. Running "sh -vx /etc/rc.d/rc.[service]" in that directory, to examine what's going on, is the best place to start. It might be simple timing, so a simple fix; or maybe something worse, especially when it's wrong or suspicious. But the first step is to gather that extra, unusual information.

GazL · 11-02-2023, 11:21 AM

Quote:

Originally Posted by Petri Kaukasoina

dhcpcd != dhcpd

Oops!

Petri Kaukasoina · 11-02-2023, 12:14 PM

By the way, there is actually no /etc/rc.d/rc.dhcpd in Slackware. You have probably copied it from usb-and-pxe-installers/README_PXE.TXT like I did when I used PXE to install Slackware.

I noticed this in https://www.isc.org/dhcp/:

Quote:

ISC has announced the end of maintenance for ISC DHCP as of the end of 2022. ISC will continue providing professional support services for existing subscribers, but does not intend to issue any further maintenance releases. For resources that may help in migrating your existing ISC DHCP server deployment to our newer DHCP server, Kea, please ...

This is the new one: https://www.isc.org/download/#Kea
In slackbuilds.org: https://slackbuilds.org/repository/15.0/network/kea/

Richard Cranium · 11-03-2023, 07:38 PM

Quote:

Originally Posted by Petri Kaukasoina

By the way, there is actually no /etc/rc.d/rc.dhcpd in Slackware. You have probably copied it from usb-and-pxe-installers/README_PXE.TXT like I did when I used PXE to install Slackware.

I noticed this in https://www.isc.org/dhcp/:

This is the new one: https://www.isc.org/download/#Kea
In slackbuilds.org: https://slackbuilds.org/repository/15.0/network/kea/

You are absolutely correct about rc.dhcpd. I guess I pulled it in a loooong time ago on one of my Slackware machines and cloned it to the others I run.

The tell (had I been paying attention) would have been that it was launched via rc.local versus a block in rc.M.

I've never done a real PXE boot on my networks (I did look at it more than a decade ago), so I probably pulled rc.dhcpd out of one of the /usr/doc/ files that had it.

(I hadn't looked for kea in slackbuilds.org; I rather assumed that Slackware itself would pull that in. For all I know, it's in -current.)

Thank you very much, Petri Kaukasoina, for clarity. I apologize for the noise here.

HQuest · 11-06-2023, 12:13 PM

Quote:

Originally Posted by Richard Cranium

who the devil restarts their dhcpd while the system is running?

Me reading this thread: