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Re: [SOLVED] Re: Why does resolv.conf keep changing?




On Wed, Oct 25, 2017 at 02:26:35PM -0400, Roberto C. Sánchez wrote:
> 
> As an additional note, it is strange to me that none of the dhclient
> interactions are logged in syslog.  When I ran dhclient directly and
> specified the verbose option, that resulted in the exhanges being logged
> to syslog, except for the error message.  It appears that the scripts
> are not properly capturing/redirecting the standard error stream.  I
> will also investigate if a bug has been filed for that.  If one has not
> been filed I will do that as well.
> 

I sort of stumbled upon something peculiar related to this.

debian:/etc# systemctl restart networking
debian:/etc# systemctl status networking
● networking.service - Raise network interfaces
   Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor preset: enabled)
   Active: active (exited) since Thu 2017-10-26 08:51:35 EDT; 5s ago
     Docs: man:interfaces(5)
  Process: 30299 ExecStop=/sbin/ifdown -a --read-environment --exclude=lo (code=exited, status=0/SUCCESS)
  Process: 30455 ExecStart=/sbin/ifup -a --read-environment (code=exited, status=0/SUCCESS)
  Process: 30451 ExecStartPre=/bin/sh -c [ "$CONFIGURE_INTERFACES" != "no" ] && [ -n "$(ifquery --read-en
 Main PID: 30455 (code=exited, status=0/SUCCESS)
    Tasks: 1 (limit: 9830)
   CGroup: /system.slice/networking.service
           └─30573 /sbin/dhclient -4 -v -pf /run/dhclient.eth1.pid -lf /var/lib/dhcp/dhclient.eth1.leases

Oct 26 08:51:31 debian ifup[30455]: Listening on LPF/eth1/a0:48:1c:b8:01:d1
Oct 26 08:51:31 debian ifup[30455]: Sending on   LPF/eth1/a0:48:1c:b8:01:d1
Oct 26 08:51:31 debian ifup[30455]: Sending on   Socket/fallback
Oct 26 08:51:31 debian ifup[30455]: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 3
Oct 26 08:51:35 debian ifup[30455]: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 5
Oct 26 08:51:35 debian ifup[30455]: DHCPREQUEST of 192.168.63.197 on eth1 to 255.255.255.255 port 67
Oct 26 08:51:35 debian ifup[30455]: DHCPOFFER of 192.168.63.197 from 192.168.63.1
Oct 26 08:51:35 debian ifup[30455]: DHCPACK of 192.168.63.197 from 192.168.63.1
Oct 26 08:51:35 debian ifup[30455]: bound to 192.168.63.197 -- renewal in 16926 seconds.
Oct 26 08:51:35 debian systemd[1]: Started Raise network interfaces.

Is this the new normal, for things to get captured in some systemd log
that I cannot grep out of /var/log?  I specifically recall in the past
on older pre-systemd systems that these exchanges between the DHCP
client and server would get logged by syslog.

I guess this explains why things that I recalled being logged in the
past suddenly disappeared from syslog.

> Why dhclient-script(8) mentions the hook scripts for overriding the
> behavior of make_resolv_conf() but not the configuration directives that
> can be used to affect specific values is also somewhat puzzling.
> 
Based on comments by Greg and Mike, it seems like the configuration
options are not quite as useful and concrete as I thought, so perhaps it
is better to direct users to the hook script.

-- 
Roberto C. Sánchez