[gentoo-user] resolv.conf is different after every reboot

[gentoo-user] resolv.conf is different after every reboot

[Grand Duet]

This is a continuation of the thread:
"Something went wrong with DNS, plz help!"

Now, the issue became clearer, so I decided to start
a new thread with more descriptive Subject.

In short: the contents of the file /etc/resolv.conf
is unpredictably different from one reboot to another.
It is either
  # Generated by net-scripts for interface lo
  domain mynetwork
or
  # Generated by net-scripts for interface "eth0"
  nameserver My.First.DNS-Server.IP
  nameserver My.Second.DNS-Server.IP
  nameserver 8.8.8.8

I tried to chmod this file to be unwrittable even for root
but after a reboot it have been overwritten anyway.

Re: [gentoo-user] resolv.conf is different after every reboot

[Neil Bothwick]

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On Sun, 27 Jul 2014 12:21:23 +0300, Grand Duet wrote:

> In short: the contents of the file /etc/resolv.conf
> is unpredictably different from one reboot to another.
> It is either
>   # Generated by net-scripts for interface lo
>   domain mynetwork

That's what you get when lo comes up.

> or
>   # Generated by net-scripts for interface "eth0"
>   nameserver My.First.DNS-Server.IP
>   nameserver My.Second.DNS-Server.IP
>   nameserver 8.8.8.8

That's what replaces it when eth0 comes up. It looks like eth0 is not
being brought up fully, what do your logs say?

It might be worth putting logger commands in preup(), postup() and
failup() in conf.d/net.

> I tried to chmod this file to be unwrittable even for root
> but after a reboot it have been overwritten anyway.

You can't stop root overwriting a file, root laughs in the face of file
permissions.

BTW, I'm not sure if it's still relevant, but I don't think you ever
posted the contents of /etc/resolvconf.conf, if it exists.


-- 
Neil Bothwick

If at first you don't succeed, call in an airstrike.

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Re: [gentoo-user] resolv.conf is different after every reboot

[Grand Duet]

2014-07-27 12:29 GMT+03:00 Neil Bothwick <neil@digimed.co.uk>:
> On Sun, 27 Jul 2014 12:21:23 +0300, Grand Duet wrote:
>
>> In short: the contents of the file /etc/resolv.conf
>> is unpredictably different from one reboot to another.
>> It is either
>>   # Generated by net-scripts for interface lo
>>   domain mynetwork
>
> That's what you get when lo comes up.
>
>> or
>>   # Generated by net-scripts for interface "eth0"
>>   nameserver My.First.DNS-Server.IP
>>   nameserver My.Second.DNS-Server.IP
>>   nameserver 8.8.8.8
>
> That's what replaces it when eth0 comes up.
> It looks like eth0 is not being brought up fully

It sounds logical. But how can I fix it?

Can carrier_timeout_eth0= setting in /etc/conf.d/net file help?
If so, how much seconds should I use?

> what do your logs say?

Could you, please, be more precise where to look for "logs".

> It might be worth putting logger commands in preup(),
> postup() and failup() in conf.d/net.

Currently, I have no such functions in my /etc/conf.d/net file.
Shall I copy them there from
  /usr/share/doc/netifrc-0.2.2/net.example

Could you, please, be more specific on these "logger commands" too.

>> I tried to chmod this file to be unwrittable even for root
>> but after a reboot it have been overwritten anyway.
>
> You can't stop root overwriting a file, root laughs in the face of file
> permissions.
>
> BTW, I'm not sure if it's still relevant, but I don't think you ever
> posted the contents of /etc/resolvconf.conf, if it exists.

I do not have such file. Of course, if you do not mean /etc/resolv.conf
But I have posted its content above.

Re: [gentoo-user] resolv.conf is different after every reboot

[Walter Dnes]

On Sun, Jul 27, 2014 at 12:21:23PM +0300, Grand Duet wrote
> This is a continuation of the thread:
> "Something went wrong with DNS, plz help!"
> 
> Now, the issue became clearer, so I decided to start
> a new thread with more descriptive Subject.
> 
> In short: the contents of the file /etc/resolv.conf
> is unpredictably different from one reboot to another.
> It is either
>   # Generated by net-scripts for interface lo
>   domain mynetwork
> or
>   # Generated by net-scripts for interface "eth0"
>   nameserver My.First.DNS-Server.IP
>   nameserver My.Second.DNS-Server.IP
>   nameserver 8.8.8.8
> 
> I tried to chmod this file to be unwrittable even for root
> but after a reboot it have been overwritten anyway.
> 
> 

  A similar problem was noted at...
https://forums.gentoo.org/viewtopic-t-816332-start-0.html

  Can you post the contents of your /etc/conf.d/net and also
the output of the "rc-update show" command?  That should help narrow
down the potential sources of your problem.

-- 
Walter Dnes <waltdnes@waltdnes.org>
I don't run "desktop environments"; I run useful applications

Re: [gentoo-user] resolv.conf is different after every reboot

[Dale]

Grand Duet wrote:
> 2014-07-27 12:29 GMT+03:00 Neil Bothwick <neil@digimed.co.uk>:
> It sounds logical. But how can I fix it? Can carrier_timeout_eth0=
> setting in /etc/conf.d/net file help? If so, how much seconds should I
> use?
>> what do your logs say?
> Could you, please, be more precise where to look for "logs".

Could be /var/log/messages or dmesg.  I'd check both.

Dale

:-)  :-) 

Re: [gentoo-user] resolv.conf is different after every reboot

[Grand Duet]

2014-07-27 13:39 GMT+03:00 Walter Dnes <waltdnes@waltdnes.org>:
> On Sun, Jul 27, 2014 at 12:21:23PM +0300, Grand Duet wrote
>> This is a continuation of the thread:
>> "Something went wrong with DNS, plz help!"
>>
>> Now, the issue became clearer, so I decided to start
>> a new thread with more descriptive Subject.
>>
>> In short: the contents of the file /etc/resolv.conf
>> is unpredictably different from one reboot to another.
>> It is either
>>   # Generated by net-scripts for interface lo
>>   domain mynetwork
>> or
>>   # Generated by net-scripts for interface "eth0"
>>   nameserver My.First.DNS-Server.IP
>>   nameserver My.Second.DNS-Server.IP
>>   nameserver 8.8.8.8
>>
>> I tried to chmod this file to be unwrittable even for root
>> but after a reboot it have been overwritten anyway.
>>
> A similar problem was noted at...
> https://forums.gentoo.org/viewtopic-t-816332-start-0.html

Like in the thread above, I also have a line
    dns_domain_lo="mynetwork"
in my /etc/conf.d/net file. It says nothing to me
and I do not remember how it got there.

But somewhere on Gentoo forum I have found the following
explanation: "If you only specify dns_domain_lo="foo" and
restart the lo interface it will put "domain foo" in /etc/resolv.conf
and remove everything else."

So, I guess I should try to remove that line from my /etc/conf.d/net file.

But why the system worked fine for about a year *with* this line then?

>   Can you post the contents of your /etc/conf.d/net

hostname="myhostname"
dns_domain_lo="mynetwork"

config_eth0="My.Local.IP netmask My.Net.Mask broadcast
Broadcast.IPof.My.LocalNetwork"
routes_eth0="default via Local.IPof.My.Gateway"

dns_servers_eth0="My.First.DNS.IP My.Second.DNS.IP 8.8.8.8"

mtu_eth0="1500" # if needed

# The network scripts are now part of net-misc/netifrc
# In order to avoid sys-apps/openrc-0.12.4 from removing this file,
this comment was
# added; you can safely remove this comment.  Please see
# /usr/share/doc/netifrc*/README* for more information.

> and also the output of the "rc-update show" command?

# rc-update show
             alsasound | boot
               bootmisc | boot
                      dbus |      default
                     devfs |                       sysinit
                   dmesg |                       sysinit
                       fsck | boot
              hostname | boot
                 hwclock | boot
                keymaps | boot
                 killprocs |              shutdown
kmod-static-nodes |                       sysinit
                       local |      default
            localmount | boot
               loopback | boot
                metalog |      default
               modules | boot
              mount-ro |              shutdown
                     mtab | boot
               net.eth0 |      default
                    net.lo | boot
             netmount |      default
                 privoxy |      default
                   procfs | boot
                       root | boot
             savecache |              shutdown
                      swap | boot
               swapfiles | boot
                     sysctl | boot
                      sysfs |                       sysinit
      termencoding | boot
         tmpfiles.dev |                       sysinit
      tmpfiles.setup | boot
                      udev |                       sysinit
          udev-mount |                       sysinit
              urandom | boot

Everywhere above eth0 has been put instead of its udev "predictable" name.

Do you think that I need
    carrier_timeout_eth0=20
somewhere in /etc/conf.d/net ?

Thank you.

> That should help narrow down the potential sources of your problem.

Re: [gentoo-user] resolv.conf is different after every reboot

[Matti Nykyri]

> On Jul 27, 2014, at 13:33, Grand Duet <grand.duet@gmail.com> wrote:
> 
> 2014-07-27 12:29 GMT+03:00 Neil Bothwick <neil@digimed.co.uk>:
>>> On Sun, 27 Jul 2014 12:21:23 +0300, Grand Duet wrote:
>>> 
>>> In short: the contents of the file /etc/resolv.conf
>>> is unpredictably different from one reboot to another.
>>> It is either
>>>  # Generated by net-scripts for interface lo
>>>  domain mynetwork
>> 
>> That's what you get when lo comes up.
>> 
>>> or
>>>  # Generated by net-scripts for interface "eth0"
>>>  nameserver My.First.DNS-Server.IP
>>>  nameserver My.Second.DNS-Server.IP
>>>  nameserver 8.8.8.8
>> 
>> That's what replaces it when eth0 comes up.
>> It looks like eth0 is not being brought up fully
> 
> It sounds logical. But how can I fix it?
> 
> Can carrier_timeout_eth0= setting in /etc/conf.d/net file help?
> If so, how much seconds should I use?
> 
>> what do your logs say?
> 
> Could you, please, be more precise where to look for "logs".
> 
>> It might be worth putting logger commands in preup(),
>> postup() and failup() in conf.d/net.
> 
> Currently, I have no such functions in my /etc/conf.d/net file.
> Shall I copy them there from
>  /usr/share/doc/netifrc-0.2.2/net.example
> 
> Could you, please, be more specific on these "logger commands" too.
> 
>>> I tried to chmod this file to be unwrittable even for root
>>> but after a reboot it have been overwritten anyway.
>> 
>> You can't stop root overwriting a file, root laughs in the face of file
>> permissions.
>> 
>> BTW, I'm not sure if it's still relevant, but I don't think you ever
>> posted the contents of /etc/resolvconf.conf, if it exists.
> 
> I do not have such file. Of course, if you do not mean /etc/resolv.conf
> But I have posted its content above.
> 

Depending on your filesystem a temporary solution to your problem is to setup /etc/resolv.conf correctly and then:
chattr +i /etc/resolv.conf

After that the content of the file will not change.

-- 
-Matti

Re: [gentoo-user] resolv.conf is different after every reboot

[Grand Duet]

2014-07-27 16:10 GMT+03:00 Matti Nykyri <matti.nykyri@iki.fi>:
>> On Jul 27, 2014, at 13:33, Grand Duet <grand.duet@gmail.com> wrote:
>>
>> 2014-07-27 12:29 GMT+03:00 Neil Bothwick <neil@digimed.co.uk>:
>>>> On Sun, 27 Jul 2014 12:21:23 +0300, Grand Duet wrote:
>>>>
>>>> In short: the contents of the file /etc/resolv.conf
>>>> is unpredictably different from one reboot to another.
>>>> It is either
>>>>  # Generated by net-scripts for interface lo
>>>>  domain mynetwork
>>>
>>> That's what you get when lo comes up.
>>>
>>>> or
>>>>  # Generated by net-scripts for interface "eth0"
>>>>  nameserver My.First.DNS-Server.IP
>>>>  nameserver My.Second.DNS-Server.IP
>>>>  nameserver 8.8.8.8
>>>
>>> That's what replaces it when eth0 comes up.
>>> It looks like eth0 is not being brought up fully
>>
>> It sounds logical. But how can I fix it?
>>
>> Can carrier_timeout_eth0= setting in /etc/conf.d/net file help?
>> If so, how much seconds should I use?
>>
>>> what do your logs say?
>>
>> Could you, please, be more precise where to look for "logs".
>>
>>> It might be worth putting logger commands in preup(),
>>> postup() and failup() in conf.d/net.
>>
>> Currently, I have no such functions in my /etc/conf.d/net file.
>> Shall I copy them there from
>>  /usr/share/doc/netifrc-0.2.2/net.example
>>
>> Could you, please, be more specific on these "logger commands" too.
>>
>>>> I tried to chmod this file to be unwrittable even for root
>>>> but after a reboot it have been overwritten anyway.
>>>
>>> You can't stop root overwriting a file, root laughs in the face of file
>>> permissions.
>>>
>>> BTW, I'm not sure if it's still relevant, but I don't think you ever
>>> posted the contents of /etc/resolvconf.conf, if it exists.
>>
>> I do not have such file. Of course, if you do not mean /etc/resolv.conf
>> But I have posted its content above.
>>
>
> Depending on your filesystem a temporary solution to your problem is to setup /etc/resolv.conf correctly and then:
> chattr +i /etc/resolv.conf
>
> After that the content of the file will not change.

Thank you. I will try it if deleting the line
    dns_domain_lo="mynetwork"
from my /etc/conf.d/net file will not work.

But does chattr +i differ from chmod a-w ?
(The latter did not work for me. I use ext4 file system.)

Re: [gentoo-user] resolv.conf is different after every reboot

[Daniel Frey]

On 07/27/2014 04:30 AM, Grand Duet wrote:
> 
>> and also the output of the "rc-update show" command?
> 
> # rc-update show
>              alsasound | boot
>                bootmisc | boot
>                       dbus |      default
>                      devfs |                       sysinit
>                    dmesg |                       sysinit
>                        fsck | boot
>               hostname | boot
>                  hwclock | boot
>                 keymaps | boot
>                  killprocs |              shutdown
> kmod-static-nodes |                       sysinit
>                        local |      default
>             localmount | boot
>                loopback | boot
>                 metalog |      default
>                modules | boot
>               mount-ro |              shutdown
>                      mtab | boot
>                net.eth0 |      default
>                     net.lo | boot
>              netmount |      default
>                  privoxy |      default
>                    procfs | boot
>                        root | boot
>              savecache |              shutdown
>                       swap | boot
>                swapfiles | boot
>                      sysctl | boot
>                       sysfs |                       sysinit
>       termencoding | boot
>          tmpfiles.dev |                       sysinit
>       tmpfiles.setup | boot
>                       udev |                       sysinit
>           udev-mount |                       sysinit
>               urandom | boot
> 
> Everywhere above eth0 has been put instead of its udev "predictable" name.
> 
> Do you think that I need
>     carrier_timeout_eth0=20
> somewhere in /etc/conf.d/net ?
> 

Have you tried disabling network hotplugging in /etc/rc.conf?

i.e. setting rc_hotplug="!net.*"

Sounds like the interfaces are being brought up out of order.

Dan

Re: [gentoo-user] resolv.conf is different after every reboot

[Grand Duet]

2014-07-27 17:50 GMT+03:00 Daniel Frey <djqfrey@gmail.com>:
> On 07/27/2014 04:30 AM, Grand Duet wrote:
>>
>>> and also the output of the "rc-update show" command?
>>
>> # rc-update show
>>              alsasound | boot
>>                bootmisc | boot
>>                       dbus |      default
>>                      devfs |                       sysinit
>>                    dmesg |                       sysinit
>>                        fsck | boot
>>               hostname | boot
>>                  hwclock | boot
>>                 keymaps | boot
>>                  killprocs |              shutdown
>> kmod-static-nodes |                       sysinit
>>                        local |      default
>>             localmount | boot
>>                loopback | boot
>>                 metalog |      default
>>                modules | boot
>>               mount-ro |              shutdown
>>                      mtab | boot
>>                net.eth0 |      default
>>                     net.lo | boot
>>              netmount |      default
>>                  privoxy |      default
>>                    procfs | boot
>>                        root | boot
>>              savecache |              shutdown
>>                       swap | boot
>>                swapfiles | boot
>>                      sysctl | boot
>>                       sysfs |                       sysinit
>>       termencoding | boot
>>          tmpfiles.dev |                       sysinit
>>       tmpfiles.setup | boot
>>                       udev |                       sysinit
>>           udev-mount |                       sysinit
>>               urandom | boot
>>
>> Everywhere above eth0 has been put instead of its udev "predictable" name.
>>
>> Do you think that I need
>>     carrier_timeout_eth0=20
>> somewhere in /etc/conf.d/net ?
>>
>
> Have you tried disabling network hotplugging in /etc/rc.conf?
> i.e. setting rc_hotplug="!net.*"

No, I have rc_hotplug="*" in my /etc/rc.conf file.

I will try it, thank you for the tip.

> Sounds like the interfaces are being brought up out of order.

Yes, I have just written about it the following:

I finally got an idea why everything went wrong after
the last system update.

During my last system update, portage instructed me to add
    dev-lang/tk-8.5.15 threads
line to my /etc/portage/package.use file.

Here is the portage message about it:

The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by dev-lang/ruby-1.9.3_p484[tk]
# required by dev-ruby/rake-0.9.6[ruby_targets_ruby19]
# required by dev-lang/ruby-2.0.0_p353
# required by dev-ruby/racc-1.4.9[ruby_targets_ruby20]
# required by dev-ruby/rdoc-4.0.1-r1[ruby_targets_ruby19]
=dev-lang/tk-8.5.15 threads

And in my /etc/portage/package.use file this line has already
been commented. So, I just uncommented it. But I do remember
that it was commented for a reason, though do not remember
exactly why.

May be uncommenting that line allowed bringing up
lo and eth0 interfaces *in parallel*. If it is the case,
then I have an easy explanation why the contents
of /etc/resolv.conf file after boot is unpredictable.

If eth0 starts after lo, then I have the right /etc/resolv.conf
file, however if lo starts after eth0, then the DNS IPs in
resolv.conf file are overwritten with dummy instruction
for lo interface.

But, now, after your suggestion, I have looked into
my /etc/rc.conf file, and have found there the option
rc_parallel="NO"
which softens my previous arguments a bit, but not completely:
may be lo and eth0 are brought up not in parallel but in different
order, anyway.

Re: [gentoo-user] resolv.conf is different after every reboot

[Matti Nykyri]

> On Jul 27, 2014, at 16:39, Grand Duet <grand.duet@gmail.com> wrote:
> 
> 2014-07-27 16:10 GMT+03:00 Matti Nykyri <matti.nykyri@iki.fi>:
>>> On Jul 27, 2014, at 13:33, Grand Duet <grand.duet@gmail.com> wrote:
>>> 
>>> 2014-07-27 12:29 GMT+03:00 Neil Bothwick <neil@digimed.co.uk>:
>>>>> On Sun, 27 Jul 2014 12:21:23 +0300, Grand Duet wrote:
>>>>> 
>>>>> In short: the contents of the file /etc/resolv.conf
>>>>> is unpredictably different from one reboot to another.
>>>>> It is either
>>>>> # Generated by net-scripts for interface lo
>>>>> domain mynetwork
>>>> 
>>>> That's what you get when lo comes up.
>>>> 
>>>>> or
>>>>> # Generated by net-scripts for interface "eth0"
>>>>> nameserver My.First.DNS-Server.IP
>>>>> nameserver My.Second.DNS-Server.IP
>>>>> nameserver 8.8.8.8
>>>> 
>>>> That's what replaces it when eth0 comes up.
>>>> It looks like eth0 is not being brought up fully
>>> 
>>> It sounds logical. But how can I fix it?
>>> 
>>> Can carrier_timeout_eth0= setting in /etc/conf.d/net file help?
>>> If so, how much seconds should I use?
>>> 
>>>> what do your logs say?
>>> 
>>> Could you, please, be more precise where to look for "logs".
>>> 
>>>> It might be worth putting logger commands in preup(),
>>>> postup() and failup() in conf.d/net.
>>> 
>>> Currently, I have no such functions in my /etc/conf.d/net file.
>>> Shall I copy them there from
>>> /usr/share/doc/netifrc-0.2.2/net.example
>>> 
>>> Could you, please, be more specific on these "logger commands" too.
>>> 
>>>>> I tried to chmod this file to be unwrittable even for root
>>>>> but after a reboot it have been overwritten anyway.
>>>> 
>>>> You can't stop root overwriting a file, root laughs in the face of file
>>>> permissions.
>>>> 
>>>> BTW, I'm not sure if it's still relevant, but I don't think you ever
>>>> posted the contents of /etc/resolvconf.conf, if it exists.
>>> 
>>> I do not have such file. Of course, if you do not mean /etc/resolv.conf
>>> But I have posted its content above.
>> 
>> Depending on your filesystem a temporary solution to your problem is to setup /etc/resolv.conf correctly and then:
>> chattr +i /etc/resolv.conf
>> 
>> After that the content of the file will not change.
> 
> Thank you. I will try it if deleting the line
>    dns_domain_lo="mynetwork"
> from my /etc/conf.d/net file will not work.
> 
> But does chattr +i differ from chmod a-w ?
> (The latter did not work for me. I use ext4 file system.)

Yes it does. Ext-filesystem supports immutable bit which is enforced by kernel so even root can't modify the file in any way. -i unsets the bit.

-- 
-Matti

[gentoo-user] Re: resolv.conf is different after every reboot

[James]

Grand Duet <grand.duet <at> gmail.com> writes:


> >> In short: the contents of the file /etc/resolv.conf
> >> is unpredictably different from one reboot to another.
> >> It is either
> >>   # Generated by net-scripts for interface lo
> >>   domain mynetwork or
> >>   # Generated by net-scripts for interface "eth0"
> >>   nameserver My.First.DNS-Server.IP
> >>   nameserver My.Second.DNS-Server.IP
> >>   nameserver 8.8.8.8


I set my nameservers all manually in this file and they do
not every change. I do not run systemd. I'm not sure
of your issue(s) but, historically, resolv.conf should not
be displaying this behavior.

> > and also the output of the "rc-update show" command?
> 
> # rc-update show

>                      mtab | boot
>                net.eth0 |      default
>                     net.lo | boot
>              netmount |      default


> Everywhere above eth0 has been put instead of its udev "predictable" name.
> Do you think that I need
>     carrier_timeout_eth0=20
> somewhere in /etc/conf.d/net ?

I do not try and force the "eth' names onto an interface
I have these in rc-status:

mtab | boot                          
net.enp5s0 |      default
netmount |      default

I just look at the dmesg output and use the new, default
funky names. You can read up on these evolving interface
names by googling.

Here is one link (often posted to this user group) to get you started:

   
http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/


hth,
James

Re: [gentoo-user] Re: resolv.conf is different after every reboot

[Grand Duet]

2014-07-27 19:33 GMT+03:00 James <wireless@tampabay.rr.com>:
> Grand Duet <grand.duet <at> gmail.com> writes:
>
>
>> >> In short: the contents of the file /etc/resolv.conf
>> >> is unpredictably different from one reboot to another.
>> >> It is either
>> >>   # Generated by net-scripts for interface lo
>> >>   domain mynetwork or
>> >>   # Generated by net-scripts for interface "eth0"
>> >>   nameserver My.First.DNS-Server.IP
>> >>   nameserver My.Second.DNS-Server.IP
>> >>   nameserver 8.8.8.8
>
>
> I set my nameservers all manually in this file and they do
> not every change.

I also thought that /etc/resolv.conf do not change at every
reboot before run into this problem and tried to write down
my own /etc/resolv.conf

> I do not run systemd. I'm not sure of your issue(s) but,
> historically, resolv.conf should not be displaying this behavior.

Historically, may be, but currently the main net config file is
/etc/config.d/net, at least for openRC. /etc/resolv.conf is produced
at every boot from /etc/config.d/net by net-scripts.

>> > and also the output of the "rc-update show" command?
>>
>> # rc-update show
>
>>                      mtab | boot
>>                net.eth0 |      default
>>                     net.lo | boot
>>              netmount |      default
>
>
>> Everywhere above eth0 has been put instead of its udev "predictable" name.
>> Do you think that I need
>>     carrier_timeout_eth0=20
>> somewhere in /etc/conf.d/net ?
>
> I do not try and force the "eth' names onto an interface
> I have these in rc-status:
>
> mtab | boot
> net.enp5s0 |      default
> netmount |      default
>
> I just look at the dmesg output and use the new, default
> funky names. You can read up on these evolving interface
> names by googling.

You did not understood my remark above correctly:
in my system config files I do use these "fu*ky" names
but instead of exposing them to the whole Internet
I have changed a "fu*ky" name for eth0 back to eth0
for better clarity and security. :)

> Here is one link (often posted to this user group) to get you started:
>
>
> http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/
>
>
> hth,
> James
>
>

Re: [gentoo-user] resolv.conf is different after every reboot

[Kerin Millar]

On 27/07/2014 12:30, Grand Duet wrote:
> 2014-07-27 13:39 GMT+03:00 Walter Dnes <waltdnes@waltdnes.org>:
>> On Sun, Jul 27, 2014 at 12:21:23PM +0300, Grand Duet wrote
>>> This is a continuation of the thread:
>>> "Something went wrong with DNS, plz help!"
>>>
>>> Now, the issue became clearer, so I decided to start
>>> a new thread with more descriptive Subject.
>>>
>>> In short: the contents of the file /etc/resolv.conf
>>> is unpredictably different from one reboot to another.
>>> It is either
>>>    # Generated by net-scripts for interface lo
>>>    domain mynetwork
>>> or
>>>    # Generated by net-scripts for interface "eth0"
>>>    nameserver My.First.DNS-Server.IP
>>>    nameserver My.Second.DNS-Server.IP
>>>    nameserver 8.8.8.8
>>>
>>> I tried to chmod this file to be unwrittable even for root
>>> but after a reboot it have been overwritten anyway.
>>>
>> A similar problem was noted at...
>> https://forums.gentoo.org/viewtopic-t-816332-start-0.html
>
> Like in the thread above, I also have a line
>      dns_domain_lo="mynetwork"
> in my /etc/conf.d/net file. It says nothing to me
> and I do not remember how it got there.
>
> But somewhere on Gentoo forum I have found the following
> explanation: "If you only specify dns_domain_lo="foo" and
> restart the lo interface it will put "domain foo" in /etc/resolv.conf
> and remove everything else."

You can specify dns_domain - without an interface suffix - which ought 
to prevent this behaviour. However, you'd be better off getting rid of 
it altogether. All the option does is define the suffix(es) that are 
appended by the resolver under certain conditions. These conditions are 
as follows:

   a) the initial name isn't qualified (contains no dots) [1]
   b) the initial name could not be resolved (NXDOMAIN response)

Making up fake domains for this setting, as many Gentoo users are 
induced into doing, serves no purpose. Let's assume that I have 
"fakedomain" as a search domain in resolv.conf.

Let's see what happens for a short name:

   $ host -t A -v shorthost | grep -e Trying -e NX
   Trying "shorthost.fakedomain"
   Trying "shorthost"
   Host shorthost not found: 3(NXDOMAIN)

Result: two spurious DNS lookups, each resulting in NXDOMAIN. You may 
use tcpdump to confirm that there are indeed two.

Now, let's try looking up a fully qualified hostname that happens not to 
exist:

   $ host -t A -v nonexistent.google.com | grep -e Trying -e NX
   Trying "nonexistent.google.com"
   Trying "nonexistent.google.com.fakedomain"
   Host nonexistent.google.com not found: 3(NXDOMAIN)

Result: The first lookup fails and is immediately followed by an another 
lookup that is completely and utterly useless. Had a search domain _not_ 
been defined, then the resolver could have concluded its efforts after 
the first NXDOMAIN response.

The bottom line is that it only makes sense to define search domain(s) 
if the following two conditions hold true.

   1) You want to be able to resolve hostnames in their short form
   2) Records for said names will exist in a known, *valid* domain

Otherwise, don't bother and leave it to the DHCP server to decide [2]. 
While I haven't looked at the handbook lately, it has had a history of 
prescribing dns/domain related options without adequate explanation and, 
in some cases, with outright misleading information [3].

On a related note, some people prefer to manage resolv.conf themselves 
and it is not initially obvious as to how to do this while also using 
DHCP. Trying to make the file immutable is not a proper approach. The 
trick is as follows:

   * Specify dhcpd_eth0="nodns" (do this for any dhcp-using interfaces)
   * Do not specify any dns or nameserver related settings in conf.d/net

The netifrc scripts will then leave resolv.conf alone.

--Kerin

[1] Check out the ndots option in the resolv.conf(5) manpage
[2] DHCP servers may specify a search domain for clients with option 15
[3] https://bugs.gentoo.org/show_bug.cgi?id=341349

Re: [gentoo-user] resolv.conf is different after every reboot

[Neil Bothwick]

[-- Attachment #1: Type: text/plain, Size: 1731 bytes --]

On Sun, 27 Jul 2014 13:33:47 +0300, Grand Duet wrote:

> > That's what replaces it when eth0 comes up.
> > It looks like eth0 is not being brought up fully  
> 
> It sounds logical. But how can I fix it?

By identifying how far it is getting and why no further. But it appears
that eth0 is being brought up correctly and then the config is
overwritten by the lo config. I'd suggest going with the suggestion of
disabling hotplugging for net.* interfaces.
 
> > what do your logs say?  
> 
> Could you, please, be more precise where to look for "logs".

/var/log/messages, dmesg, the standard places.

> > It might be worth putting logger commands in preup(),
> > postup() and failup() in conf.d/net.  
> 
> Currently, I have no such functions in my /etc/conf.d/net file.
> Shall I copy them there from
>   /usr/share/doc/netifrc-0.2.2/net.example

Yes, they are run are various stages of bringing up the interface.

> Could you, please, be more specific on these "logger commands" too.

I meant to add a logger call to each function to see how far it gets

logger "eth0 going up"
logger "eth0 up"
logger "eth0 failed"

or something like that. but it appears this is moot and eth0 is up
successfully. 

> > BTW, I'm not sure if it's still relevant, but I don't think you ever
> > posted the contents of /etc/resolvconf.conf, if it exists.  
> 
> I do not have such file. Of course, if you do not mean /etc/resolv.conf
> But I have posted its content above.

I meant /etc/resolvconf.conf, which you were asked for before, but as
you don't have it, the problem isn't there. 


-- 
Neil Bothwick

Vital papers will demonstrate their vitality by moving to where you
can't find them.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 181 bytes --]

Re: [gentoo-user] resolv.conf is different after every reboot

[Grand Duet]

2014-07-27 21:14 GMT+03:00 Kerin Millar <kerframil@fastmail.co.uk>:
> On 27/07/2014 12:30, Grand Duet wrote:
>>
>> 2014-07-27 13:39 GMT+03:00 Walter Dnes <waltdnes@waltdnes.org>:
>>>
>>> On Sun, Jul 27, 2014 at 12:21:23PM +0300, Grand Duet wrote
>>>>
>>>> This is a continuation of the thread:
>>>> "Something went wrong with DNS, plz help!"
>>>>
>>>> Now, the issue became clearer, so I decided to start
>>>> a new thread with more descriptive Subject.
>>>>
>>>> In short: the contents of the file /etc/resolv.conf
>>>> is unpredictably different from one reboot to another.
>>>> It is either
>>>>    # Generated by net-scripts for interface lo
>>>>    domain mynetwork
>>>> or
>>>>    # Generated by net-scripts for interface "eth0"
>>>>    nameserver My.First.DNS-Server.IP
>>>>    nameserver My.Second.DNS-Server.IP
>>>>    nameserver 8.8.8.8
>>>>
>>>> I tried to chmod this file to be unwrittable even for root
>>>> but after a reboot it have been overwritten anyway.
>>>>
>>> A similar problem was noted at...
>>> https://forums.gentoo.org/viewtopic-t-816332-start-0.html
>>
>>
>> Like in the thread above, I also have a line
>>      dns_domain_lo="mynetwork"
>> in my /etc/conf.d/net file. It says nothing to me
>> and I do not remember how it got there.
>>
>> But somewhere on Gentoo forum I have found the following
>> explanation: "If you only specify dns_domain_lo="foo" and
>> restart the lo interface it will put "domain foo" in /etc/resolv.conf
>> and remove everything else."
>
>
> You can specify dns_domain - without an interface suffix - which ought to
> prevent this behaviour. However, you'd be better off getting rid of it
> altogether.

It is my first reboot after commenting out the line
     dns_domain_lo="mynetwork"
and so far it went good.

Moreover, the file /etc/resolv.conf has not been overwritten.

I still have to check if everything else works fine and
if I will get the same result on the next reboot
but I hope that the problem has been solved.

> All the option does is define the suffix(es) that are appended
> by the resolver under certain conditions. These conditions are as follows:
>
>   a) the initial name isn't qualified (contains no dots) [1]
>   b) the initial name could not be resolved (NXDOMAIN response)
>
> Making up fake domains for this setting, as many Gentoo users are induced
> into doing, serves no purpose. Let's assume that I have "fakedomain" as a
> search domain in resolv.conf.
>
> Let's see what happens for a short name:
>
>   $ host -t A -v shorthost | grep -e Trying -e NX
>   Trying "shorthost.fakedomain"
>   Trying "shorthost"
>   Host shorthost not found: 3(NXDOMAIN)
>
> Result: two spurious DNS lookups, each resulting in NXDOMAIN. You may use
> tcpdump to confirm that there are indeed two.
>
> Now, let's try looking up a fully qualified hostname that happens not to
> exist:
>
>   $ host -t A -v nonexistent.google.com | grep -e Trying -e NX
>   Trying "nonexistent.google.com"
>   Trying "nonexistent.google.com.fakedomain"
>   Host nonexistent.google.com not found: 3(NXDOMAIN)
>
> Result: The first lookup fails and is immediately followed by an another
> lookup that is completely and utterly useless. Had a search domain _not_
> been defined, then the resolver could have concluded its efforts after the
> first NXDOMAIN response.
>
> The bottom line is that it only makes sense to define search domain(s) if
> the following two conditions hold true.
>
>   1) You want to be able to resolve hostnames in their short form
>   2) Records for said names will exist in a known, *valid* domain
>
> Otherwise, don't bother and leave it to the DHCP server to decide [2]. While
> I haven't looked at the handbook lately, it has had a history of prescribing
> dns/domain related options without adequate explanation and, in some cases,
> with outright misleading information [3].
>
> On a related note, some people prefer to manage resolv.conf themselves and
> it is not initially obvious as to how to do this while also using DHCP.
> Trying to make the file immutable is not a proper approach. The trick is as
> follows:
>
>   * Specify dhcpd_eth0="nodns" (do this for any dhcp-using interfaces)
>   * Do not specify any dns or nameserver related settings in conf.d/net
>
> The netifrc scripts will then leave resolv.conf alone.

Thank you for the nice explanation that convinced me that I do
not need that feature at all.

I do not use DHCP at all but I got the general point.

> [1] Check out the ndots option in the resolv.conf(5) manpage
> [2] DHCP servers may specify a search domain for clients with option 15
> [3] https://bugs.gentoo.org/show_bug.cgi?id=341349

Re: [gentoo-user] resolv.conf is different after every reboot

[Daniel Frey]

On 07/27/2014 08:08 AM, Grand Duet wrote:
> 
> If eth0 starts after lo, then I have the right /etc/resolv.conf
> file, however if lo starts after eth0, then the DNS IPs in
> resolv.conf file are overwritten with dummy instruction
> for lo interface.
> 
> But, now, after your suggestion, I have looked into
> my /etc/rc.conf file, and have found there the option
> rc_parallel="NO"
> which softens my previous arguments a bit, but not completely:
> may be lo and eth0 are brought up not in parallel but in different
> order, anyway.
> 

The first thing I do on any new build is disable network hotplugging in
/etc/rc.conf, as I've run into lots of problems, especially if you have
multiple network devices and need to bring them up in a specific order.
udev processes these items and apparently brings the interfaces up on
its own unless you tell it otherwise (the !net.* in rc.conf). I've just
gotten used to disabling that automagic because I want things to start
in a certain order and udev can mess that up.

During boot, you'll see something like 'processing events' and that's
when udev is automagically doing it's start. From what I recall, this
happens before the boot runlevel. So yes, it can mess things up as
you've seen.

I've never had the issue you have, even though I use a static ip, routes
and dns servers in /etc/conf.d/net, but I would presume that this is
just udev. FYI it doesn't always process things in the same order, as
I've experienced with udev and my TV tuner cards... it can be random.

Dan

Re: [gentoo-user] resolv.conf is different after every reboot

[Grand Duet]

2014-07-27 22:13 GMT+03:00 Neil Bothwick <neil@digimed.co.uk>:
> On Sun, 27 Jul 2014 13:33:47 +0300, Grand Duet wrote:
>
>> > That's what replaces it when eth0 comes up.
>> > It looks like eth0 is not being brought up fully
>>
>> It sounds logical. But how can I fix it?
>
> By identifying how far it is getting and why no further.
> But it appears that eth0 is being brought up correctly
> and then the config is overwritten by the lo config.

I think so.

As I have already reported in another reply to this thread,
it is my first reboot after commenting out the line
     dns_domain_lo="mynetwork"
and so far it went good.

Moreover, the file /etc/resolv.conf has not been overwritten.

I still have to check if everything else works fine and
if I will get the same result on the next reboot
but I hope that the problem has been solved.

But it looks like a bug in the net csript.
Why lo configuration should overwrite eth0 configuration at all?

> I'd suggest going with the suggestion of disabling hotplugging for net.* interfaces.

Thank you for the advice, I will try this if it appears that the
problem has not been solved yet.

>> > what do your logs say?
>>
>> Could you, please, be more precise where to look for "logs".
>
> /var/log/messages, dmesg, the standard places.
>
>> > It might be worth putting logger commands in preup(),
>> > postup() and failup() in conf.d/net.
>>
>> Currently, I have no such functions in my /etc/conf.d/net file.
>> Shall I copy them there from
>>   /usr/share/doc/netifrc-0.2.2/net.example
>
> Yes, they are run are various stages of bringing up the interface.
>
>> Could you, please, be more specific on these "logger commands" too.
>
> I meant to add a logger call to each function to see how far it gets
>
> logger "eth0 going up"
> logger "eth0 up"
> logger "eth0 failed"
>
> or something like that. but it appears this is moot and eth0 is up
> successfully.

Thank you for this explanation as well. I will try it a bit later
but I feel that before doing it I should refresh my knowledge
of scripts in general.

>> > BTW, I'm not sure if it's still relevant, but I don't think you ever
>> > posted the contents of /etc/resolvconf.conf, if it exists.
>>
>> I do not have such file. Of course, if you do not mean /etc/resolv.conf
>> But I have posted its content above.
>
> I meant /etc/resolvconf.conf, which you were asked for before, but as
> you don't have it, the problem isn't there.
>
>
> --
> Neil Bothwick
>
> Vital papers will demonstrate their vitality by moving to where you
> can't find them.

Re: [gentoo-user] resolv.conf is different after every reboot

[Grand Duet]

2014-07-27 23:28 GMT+03:00 Daniel Frey <djqfrey@gmail.com>:
> On 07/27/2014 08:08 AM, Grand Duet wrote:
>>
>> If eth0 starts after lo, then I have the right /etc/resolv.conf
>> file, however if lo starts after eth0, then the DNS IPs in
>> resolv.conf file are overwritten with dummy instruction
>> for lo interface.
>>
>> But, now, after your suggestion, I have looked into
>> my /etc/rc.conf file, and have found there the option
>> rc_parallel="NO"
>> which softens my previous arguments a bit, but not completely:
>> may be lo and eth0 are brought up not in parallel but in different
>> order, anyway.
>>
>
> The first thing I do on any new build is disable network hotplugging in
> /etc/rc.conf, as I've run into lots of problems, especially if you have
> multiple network devices and need to bring them up in a specific order.
> udev processes these items and apparently brings the interfaces up on
> its own unless you tell it otherwise (the !net.* in rc.conf). I've just
> gotten used to disabling that automagic because I want things to start
> in a certain order and udev can mess that up.

Thank you. Now, I will be aware of this issue and disabling hotplugging
in this way will be the next thing I will try if the problem will not be solved
by just removing
   dns_domain_lo="mynetwork"
from my /etc/conf.d/net file.

It is not because I am stubborn (though it may be :) but because I want
to do changes step by step to identify the cause of the problem.

P.S. As far as I know, I have only one network interface on this computer,
eth0, not counting lo, of course. :)

> During boot, you'll see something like 'processing events' and that's
> when udev is automagically doing it's start. From what I recall, this
> happens before the boot runlevel. So yes, it can mess things up as
> you've seen.
>
> I've never had the issue you have, even though I use a static ip, routes
> and dns servers in /etc/conf.d/net, but I would presume that this is
> just udev. FYI it doesn't always process things in the same order, as
> I've experienced with udev and my TV tuner cards... it can be random.

Thank you for your explanations once more.

Re: [gentoo-user] resolv.conf is different after every reboot

[Kerin Millar]

On 27/07/2014 21:38, Grand Duet wrote:
> 2014-07-27 22:13 GMT+03:00 Neil Bothwick <neil@digimed.co.uk>:
>> On Sun, 27 Jul 2014 13:33:47 +0300, Grand Duet wrote:
>>
>>>> That's what replaces it when eth0 comes up.
>>>> It looks like eth0 is not being brought up fully
>>>
>>> It sounds logical. But how can I fix it?
>>
>> By identifying how far it is getting and why no further.
>> But it appears that eth0 is being brought up correctly
>> and then the config is overwritten by the lo config.
>
> I think so.
>
> As I have already reported in another reply to this thread,
> it is my first reboot after commenting out the line
>       dns_domain_lo="mynetwork"
> and so far it went good.
>
> Moreover, the file /etc/resolv.conf has not been overwritten.
>
> I still have to check if everything else works fine and
> if I will get the same result on the next reboot
> but I hope that the problem has been solved.
>
> But it looks like a bug in the net csript.
> Why lo configuration should overwrite eth0 configuration at all?

I would consider it be a documentation bug at the very least. Being able 
to propagate different settings to resolv.conf depending on whether a 
given interface is up may be of value for some esoteric use-case, 
although I cannot think of one off-hand. Some other distros use the 
resolvconf application to handle these nuances.

In any case, it is inexplicable that the user is invited to define 
dns_domain for the lo interface. Why would one want to push settings to 
resolv.conf based on the mere fact that the loopback interface has come 
up? Also, it would be a great deal less confusing if the option were 
named dns_search.

I think that the handbook should refrain from mentioning the option at 
all, for the reasons stated in my previous email. Those who know that 
they need to define a specific search domain will know why and be 
capable of figuring it out.

It's too bad that the handbook is still peddling the notion that this 
somehow has something to do with 'setting' the domain name. It is tosh 
of the highest order.

--Kerin

Re: [gentoo-user] Re: resolv.conf is different after every reboot

[Rich Freeman]

On Sun, Jul 27, 2014 at 12:33 PM, James <wireless@tampabay.rr.com> wrote:
>
> I set my nameservers all manually in this file and they do
> not every change. I do not run systemd. I'm not sure
> of your issue(s) but, historically, resolv.conf should not
> be displaying this behavior.
>

FWIW, systemd doesn't touch resolv.conf these days.  Instead
systemd-resolved can create one for you in /run, and if you want you
can symlink to it from /etc/resolv.conf.

Rich

Re: [gentoo-user] resolv.conf is different after every reboot

[Grand Duet]

2014-07-28 1:00 GMT+03:00 Kerin Millar <kerframil@fastmail.co.uk>:
> On 27/07/2014 21:38, Grand Duet wrote:
>>
>> 2014-07-27 22:13 GMT+03:00 Neil Bothwick <neil@digimed.co.uk>:
>>>
>>> On Sun, 27 Jul 2014 13:33:47 +0300, Grand Duet wrote:
>>>
>>>>> That's what replaces it when eth0 comes up.
>>>>> It looks like eth0 is not being brought up fully
>>>>
>>>>
>>>> It sounds logical. But how can I fix it?
>>>
>>>
>>> By identifying how far it is getting and why no further.
>>> But it appears that eth0 is being brought up correctly
>>> and then the config is overwritten by the lo config.
>>
>>
>> I think so.
>>
>> As I have already reported in another reply to this thread,
>> it is my first reboot after commenting out the line
>>       dns_domain_lo="mynetwork"
>> and so far it went good.
>>
>> Moreover, the file /etc/resolv.conf has not been overwritten.
>>
>> I still have to check if everything else works fine and
>> if I will get the same result on the next reboot
>> but I hope that the problem has been solved.
>>
>> But it looks like a bug in the net csript.
>> Why lo configuration should overwrite eth0 configuration at all?
>
>
> I would consider it be a documentation bug at the very least. Being able to
> propagate different settings to resolv.conf depending on whether a given
> interface is up may be of value for some esoteric use-case, although I
> cannot think of one off-hand. Some other distros use the resolvconf
> application to handle these nuances.
>
> In any case, it is inexplicable that the user is invited to define
> dns_domain for the lo interface. Why would one want to push settings to
> resolv.conf based on the mere fact that the loopback interface has come up?
> Also, it would be a great deal less confusing if the option were named
> dns_search.
>
> I think that the handbook should refrain from mentioning the option at all,
> for the reasons stated in my previous email. Those who know that they need
> to define a specific search domain will know why and be capable of figuring
> it out.
>
> It's too bad that the handbook is still peddling the notion that this
> somehow has something to do with 'setting' the domain name. It is tosh of
> the highest order.

I agree with you. But how to put it all in the right ears?

Re: [gentoo-user] resolv.conf is different after every reboot

[Kerin Millar]

On 28/07/2014 16:34, Grand Duet wrote:
> 2014-07-28 1:00 GMT+03:00 Kerin Millar <kerframil@fastmail.co.uk>:
>> On 27/07/2014 21:38, Grand Duet wrote:
>>>
>>> 2014-07-27 22:13 GMT+03:00 Neil Bothwick <neil@digimed.co.uk>:
>>>>
>>>> On Sun, 27 Jul 2014 13:33:47 +0300, Grand Duet wrote:
>>>>
>>>>>> That's what replaces it when eth0 comes up.
>>>>>> It looks like eth0 is not being brought up fully
>>>>>
>>>>>
>>>>> It sounds logical. But how can I fix it?
>>>>
>>>>
>>>> By identifying how far it is getting and why no further.
>>>> But it appears that eth0 is being brought up correctly
>>>> and then the config is overwritten by the lo config.
>>>
>>>
>>> I think so.
>>>
>>> As I have already reported in another reply to this thread,
>>> it is my first reboot after commenting out the line
>>>        dns_domain_lo="mynetwork"
>>> and so far it went good.
>>>
>>> Moreover, the file /etc/resolv.conf has not been overwritten.
>>>
>>> I still have to check if everything else works fine and
>>> if I will get the same result on the next reboot
>>> but I hope that the problem has been solved.
>>>
>>> But it looks like a bug in the net csript.
>>> Why lo configuration should overwrite eth0 configuration at all?
>>
>>
>> I would consider it be a documentation bug at the very least. Being able to
>> propagate different settings to resolv.conf depending on whether a given
>> interface is up may be of value for some esoteric use-case, although I
>> cannot think of one off-hand. Some other distros use the resolvconf
>> application to handle these nuances.
>>
>> In any case, it is inexplicable that the user is invited to define
>> dns_domain for the lo interface. Why would one want to push settings to
>> resolv.conf based on the mere fact that the loopback interface has come up?
>> Also, it would be a great deal less confusing if the option were named
>> dns_search.
>>
>> I think that the handbook should refrain from mentioning the option at all,
>> for the reasons stated in my previous email. Those who know that they need
>> to define a specific search domain will know why and be capable of figuring
>> it out.
>>
>> It's too bad that the handbook is still peddling the notion that this
>> somehow has something to do with 'setting' the domain name. It is tosh of
>> the highest order.
>
> I agree with you. But how to put it all in the right ears?
>

I'm not entirely sure. I'd give it another shot if I thought it was 
worth the effort. My experience up until now is that requests for minor 
documentation changes are dismissed on the basis that, if it does not 
prevent the installation from being concluded, it's not worth bothering 
with [1]. I do not rate the handbook and, at this juncture, my concern 
is slight except for where it causes demonstrable confusion among the 
user community. Indeed, that's why my interest was piqued by this thread.

--Kerin

[1] For example: bugs 304727 and 344753