DHCP Server Fails When Forking

[Christopher Barry]

Generally, when backgrounded, dhcpd runs with reduced privs, e.g. as
dhcpd:dhcpd (your configured user/group may be different). Can you su as
that user and run dhcpd in the foreground? I'm suspecting that user may not
have write perms to the leases file.


On Mon, Jan 6, 2020, 4:15 PM Jay Foster <jay at systech.com> wrote:

> Can you be more specific?  /usr/sbin/dhcpd is root:root.  /usr/sbin/dhcpd
> is being run as root.
>
> On 1/6/2020 12:58 PM, Christopher Barry wrote:
>
> Make sure user/group perms are valid.
>
>
> On Mon, Jan 6, 2020, 1:42 PM Jay Foster <jay at systech.com> wrote:
>
>> I am using the ISC DHCP server (dhcpd) version 4.3.6 from a rocko Yocto
>> build.  When dhcpd is started without the '-f' or '-d' options (forks to
>> the background) it does not work.  DHCP DISCOVER requests are sent, but
>> the dhcpd application does not respond.  I can attach strace to the
>> dhcpd process and see that dhcpd just sleeps in an futex() call.
>>
>> If I start dhcpd with either the '-f' or '-d' options so it does not
>> fork, then it works properly.
>>
>> I have run dhcpd (both forking and non forking) using strace to see if I
>> could spot any differences.  The only thing I notice is that when
>> forking, the parent process terminates (expected) along with 3 other
>> child processes/threads.  It looks like these other threads are supposed
>> to handle the ISC tasks/messages, but are not cloned by the fork and are
>> not present after forking.
>>
>> For reference, with an older version of ISC DHCP server (4.1.1-P1) on an
>> older product, this problem does not occur.
>>
>> Any ideas where to look?
>>
>>
>>
>>
>>
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>>
>
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