isc-dhcpd logging breaks when syslog-ng HUP'd

Christopher Cowart ccowart at
Tue Mar 6 22:18:20 UTC 2007


I have 2 servers running isc-dhcp3-server and syslog-ng. I have
configured dhcpd to run in a chroot. The following (reproducible)
sequence of events cause dhcpd logging to break:
 1) Start syslog-ng
 2) Start isc-dhcpd (At this point, logging is working fine)
 3) `pkill -HUP syslog-ng` (This happens on the hour whenever logfiles
    need rotating, but can also be effected manually)
 4) dhcpd logging is now broken
 5) Restart isc-dhcpd (logging works again)

My theory is that when isc-dhcpd starts, it gets an fd to the syslog
socket. When syslog-ng receives a HUP, that socket is reopened and
isc-dhcpd's fd is now broken.

Relevant options from rc.conf:
| syslogd_enable="NO"
| newsyslog_enable="NO"
| syslog_ng_enable="YES"
| dhcpd_enable="YES"
| dhcpd_flags="-q"
| dhcpd_conf="/usr/local/etc/dhcpd.conf"
| dhcpd_includedir="/usr/local/etc/dhcpd.d"
| dhcpd_withumask="022"
| dhcpd_chuser_enable="YES"
| dhcpd_withuser="dhcpd"
| dhcpd_withgroup="dhcpd"
| dhcpd_devfs_enable="YES"
| dhcpd_rootdir="/var/jails/dhcpd"
| dhcpd_chroot_enable="YES"
| dhcpd_ifaces="bge0"

My workaround:
For the hosts in question, I've added to the logrotate postrotate
script: `/usr/local/etc/rc.d/isc-dhcpd restart > /dev/null`
This workaround makes me a little uncomfortable, because these instances
of dhcpd are critical for thousands of end users.

Is this a bug? Is there a better workaround? Logging from all other
applications on the system is unaffected by the HUP to syslog-ng,
including two jailed instances of bind9 (syslog-ng on the host opens up
the socket /var/run/log inside those jails). 

Any insight would be greatly appreciated.


Chris Cowart
Lead Systems Administrator
Network Infrastructure, RSSP-IT
UC Berkeley
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