How is /etc/resolv.conf updated?

scotia

scotia

Hi all,

I'm trying to comprehend how FreeBSD updates /etc/resolv.conf. Upon boot my interface gets an IP from the DHCP server, but resolv.conf remains missing. Running dhclient vxm0 gets an IP, but does not populate the various kenv variables that /etc/rc.d/resolv uses.

Does anyone know what chain of events sets up /etc/resolv.conf? Who sets the kenv variables? TIA.

OS: FreeBSD 13.1-RELEASE.

/etc/rc.d is:
Code: 
hostname="host.example.com"
ifconfig_vmx0="DHCP"
sshd_enable="YES"
ntpdate_enable="YES"
dumpdev="AUTO"
 
Zirias said:
resolvconf(8).
/sbin/dhclient-script will use it (or directly update resolv.conf if it is disabled) to add DNS configuration obtained from DHCP.
Click to expand...

Thanks. So should dhclient call dhclient-script? dhclient() mentions dhclient-script only in the SEE ALSO section, nowhere else.

Running dhclient under truss shows no sign of dhclient calling dhclient-script.

Given my rc.conf on a fresh install of FreeBSD, would you expect resolv.conf to be populated?

Thanks,
Scott
 
Zirias said:
Yes, it's the default script if nothing else is configured, see https://cgit.freebsd.org/src/tree/sbin/dhclient/clparse.c?h=releng/13.1#n54

So, I'd bet either your dhclient has some special configuration, or your DHCP server doesn't offer nameservers...
Click to expand...

Thanks. My current thinking is that an earlier invocation of local_unbound created resolvconf.conf which, although I subsequently disabled local_unbound, prevented the creation/update of resolv.conf. So I deleted it.

Now if I delete resolv.conf and dhclient.leases.* and reboot the resolv.conf gets created and correctly populated.

The only niggling thing I have is that if I delete resolv.conf and dhclient.leases.* and restart dhclient (without rebooting) dhclient gets a lease, creates the leases file, but still does not create resolv.conf. However a reboot restores it. Any thoughts as to why?

The lease offer definitely contains domain information.
 
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