Edits to `etc/resolv.conf` being overwritten

Edits to `etc/resolv.conf` being overwritten

[Bone Baboon]

Any suggestion on how to stop my edits of `etc/resolv.conf` from being
overwritten?

`/etc/resolv.conf` is being overwritten removing changes I save to it.
My edits to `etc/resolv.conf` specify some name servers.  Some time
after my edits are saved the file is completely rewritten to it's
original contents before I made my edits.  The original contents include
nameserver, domain and search for my internet service provider's DNS. 

When I run `sudo herd status` it outputs:

```
Started:
 + console-font-tty1
 + console-font-tty2
 + console-font-tty3
 + console-font-tty4
 + console-font-tty5
 + console-font-tty6
 + dbus-system
 + elogind
 + file-system-/dev/pts
 + file-system-/dev/shm
 + file-system-/gnu/store
 + file-system-/run/systemd
 + file-system-/run/user
 + file-system-/sys/firmware/efi/efivars
 + file-system-/sys/fs/cgroup
 + file-system-/sys/fs/cgroup/blkio
 + file-system-/sys/fs/cgroup/cpu
 + file-system-/sys/fs/cgroup/cpuacct
 + file-system-/sys/fs/cgroup/cpuset
 + file-system-/sys/fs/cgroup/devices
 + file-system-/sys/fs/cgroup/elogind
 + file-system-/sys/fs/cgroup/freezer
 + file-system-/sys/fs/cgroup/memory
 + file-system-/sys/fs/cgroup/perf_event
 + file-system-/sys/fs/cgroup/pids
 + file-system-/sys/kernel/debug
 + file-systems
 + guix-daemon
 + loopback
 + mcron
 + nscd
 + root
 + root-file-system
 + swap-/swapfile
 + syslogd
 + term-tty1
 + term-tty2
 + term-tty3
 + term-tty4
 + term-tty5
 + term-tty6
 + udev
 + urandom-seed
 + user-file-systems
 + user-processes
 + virtual-terminal
Stopped:
 - term-auto
One-shot:
 * host-name
 * sysctl
 * user-homes
```

Re: Edits to `etc/resolv.conf` being overwritten

[Jérémy Korwin-Zmijowski]

Hey Bone !

If I am right: you have to set the content of /etc/resolv.conf in your system configuration file. 
Anytime you reconfigure the system this file is regenerated based on your system configuration.

Jérémy


-- 
Envoyé de mon appareil Android avec Courriel K-9 Mail. Veuillez excuser ma brièveté.

Re: Edits to `etc/resolv.conf` being overwritten

[phil]

I found when using GuixSD with Gnome that the network manager would periodically overwrite my DNS changes made directly to resolv.conf.

If you experience this issue it should leave a comment on the first line.

I was able to make it work by changing it through Gnome's Settings GUI, rather than editing the file myself.  Even then I have to disable and re-enable the network interface for the new settings to take effect.



-----Original Message-----
From: Bone Baboon <bone.baboon@disroot.org>
To: help-guix@gnu.org
Sent: Fri, 02 Apr 2021 2:37
Subject: Edits to `etc/resolv.conf` being overwritten

Any suggestion on how to stop my edits of `etc/resolv.conf` from being
overwritten?

`/etc/resolv.conf` is being overwritten removing changes I save to it.
My edits to `etc/resolv.conf` specify some name servers.  Some time
after my edits are saved the file is completely rewritten to it's
original contents before I made my edits.  The original contents include
nameserver, domain and search for my internet service provider's DNS. 

When I run `sudo herd status` it outputs:

```
Started:
 + console-font-tty1
 + console-font-tty2
 + console-font-tty3
 + console-font-tty4
 + console-font-tty5
 + console-font-tty6
 + dbus-system
 + elogind
 + file-system-/dev/pts
 + file-system-/dev/shm
 + file-system-/gnu/store
 + file-system-/run/systemd
 + file-system-/run/user
 + file-system-/sys/firmware/efi/efivars
 + file-system-/sys/fs/cgroup
 + file-system-/sys/fs/cgroup/blkio
 + file-system-/sys/fs/cgroup/cpu
 + file-system-/sys/fs/cgroup/cpuacct
 + file-system-/sys/fs/cgroup/cpuset
 + file-system-/sys/fs/cgroup/devices
 + file-system-/sys/fs/cgroup/elogind
 + file-system-/sys/fs/cgroup/freezer
 + file-system-/sys/fs/cgroup/memory
 + file-system-/sys/fs/cgroup/perf_event
 + file-system-/sys/fs/cgroup/pids
 + file-system-/sys/kernel/debug
 + file-systems
 + guix-daemon
 + loopback
 + mcron
 + nscd
 + root
 + root-file-system
 + swap-/swapfile
 + syslogd
 + term-tty1
 + term-tty2
 + term-tty3
 + term-tty4
 + term-tty5
 + term-tty6
 + udev
 + urandom-seed
 + user-file-systems
 + user-processes
 + virtual-terminal
Stopped:
 - term-auto
One-shot:
 * host-name
 * sysctl
 * user-homes
```

Re: Edits to `etc/resolv.conf` being overwritten

[Bone Baboon]

In this case I am not using Gnome or NetworkManager.  There are no
comment on the first line of `resolv.conf`.  I am connecting to the
internet using `wpa_supplicant` and `dhclient`.

phil@beadling.co.uk writes:

> I found when using GuixSD with Gnome that the network manager would
> periodically overwrite my DNS changes made directly to resolv.conf. 
>
> If you experience this issue it should leave a comment on the first line.
>
> I was able to make it work by changing it through Gnome's Settings
> GUI, rather than editing the file myself.  Even then I have to disable
> and re-enable the network interface for the new settings to take
> effect. 
>
> -----Original Message-----
> From: Bone Baboon <bone.baboon@disroot.org>
> To: help-guix@gnu.org
> Sent: Fri, 02 Apr 2021 2:37
> Subject: Edits to `etc/resolv.conf` being overwritten
>
> Any suggestion on how to stop my edits of `etc/resolv.conf` from being
> overwritten?
>
> `/etc/resolv.conf` is being overwritten removing changes I save to it.
> My edits to `etc/resolv.conf` specify some name servers.  Some time
> after my edits are saved the file is completely rewritten to it's
> original contents before I made my edits.  The original contents include
> nameserver, domain and search for my internet service provider's DNS. 

Re: Edits to `etc/resolv.conf` being overwritten

[Gary Johnson]

Bone Baboon <bone.baboon@disroot.org> writes:

>> Any suggestion on how to stop my edits of `etc/resolv.conf` from being
>> overwritten?
>>
>> `/etc/resolv.conf` is being overwritten removing changes I save to it.
>> My edits to `etc/resolv.conf` specify some name servers.  Some time
>> after my edits are saved the file is completely rewritten to it's
>> original contents before I made my edits.  The original contents include
>> nameserver, domain and search for my internet service provider's DNS. 

When running Guix System, your OS configuration is meant to be fully
derived from evaluating your `operating-system` definition. This
means, in particular, that you should not manually edit any files
outside of your home directories (i.e., /root and /home/*). This
includes, of course, any files under /etc.

Instead, any custom changes that you want to see under /etc need to be
included in your `operating-system` definition. The way to do this
depends on the change you want to make.

For example, if you want to edit /etc/sudoers, you should include this
field in your `operating-system` definition (on the same level as
`packages`, `services`, and so on):

(sudoers-file (plain-file "sudoers" my-sudoers))

Then remember to define `my-sudoers` somewhere above the
`operating-system` form. Here's an example:

(define my-sudoers
  "root ALL=(ALL) ALL
%wheel ALL=(ALL) ALL
")

Similarly, if you want to modify /etc/hosts, you add this to `operating-system`:

(hosts-file (plain-file "hosts"
                         (string-append (local-host-aliases host-name)
                                        my-host-aliases)))

And again define my-host-aliases somewhere above `operating-system`:

(define my-host-aliases
  "
# Some Servers
123.123.123.100 foo
123.123.123.101 bar
123.123.123.102 baz
")

Most other files under /etc are managed by different services. You
should review the "Guix Services" section of the info pages to find
the appropriate service for whatever files you want to modify.

As of today, I'm not aware of a Guix service that modifies
/etc/resolv.conf other than the network-manager-service-type (which is
what I use on my system).

However, if you are not using NetworkManager and want to manually set
the values in /etc/resolv.conf such that they persist across calls to
`guix system reconfigure`, you should add this form to the `services`
list in your `operating-system` definition:

(simple-service 'resolv-service
                etc-service-type
                `(("resolv.conf" ,(plain-file "resolv.conf" my-resolv.conf))))

And finally remember to define `my-resolv.conf` above `operating-system`:

(define my-resolv.conf
  "# Generated by Guix!
nameserver 255.255.255.1
nameserver ffff:ffff:ffff::1
")

Have fun and happy hacking!
  Gary

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Re: Edits to `etc/resolv.conf` being overwritten

[Bone Baboon]

Thank you for the explanation and detailed examples.

I now have my system configuration providing the contents of
`/etc/resolv.conf` with a service.

However the contents of `/etc/resolv.conf` is still being overwritten
with entries for my internet service provider's DNS.  After some testing
it appears to be happening when I run this command `sudo dhclient
<wireless-interface>`.

I also appreciate the `hosts-file` example you shared as I am thinking
about using `https://github.com/StevenBlack/hosts` as a block list.  In
this case the contents of `my-host-aliases` would be very large.  With
Guile how would I have the definition of `my-host-aliases` in it's own
file and import and use it in my system configuration?

Gary Johnson writes:

> When running Guix System, your OS configuration is meant to be fully
> derived from evaluating your `operating-system` definition. This
> means, in particular, that you should not manually edit any files
> outside of your home directories (i.e., /root and /home/*). This
> includes, of course, any files under /etc.
>
> Instead, any custom changes that you want to see under /etc need to be
> included in your `operating-system` definition. The way to do this
> depends on the change you want to make.
>
> For example, if you want to edit /etc/sudoers, you should include this
> field in your `operating-system` definition (on the same level as
> `packages`, `services`, and so on):
>
> (sudoers-file (plain-file "sudoers" my-sudoers))
>
> Then remember to define `my-sudoers` somewhere above the
> `operating-system` form. Here's an example:
>
> (define my-sudoers
>   "root ALL=(ALL) ALL
> %wheel ALL=(ALL) ALL
> ")
>
> Similarly, if you want to modify /etc/hosts, you add this to `operating-system`:
>
> (hosts-file (plain-file "hosts"
>                          (string-append (local-host-aliases host-name)
>                                         my-host-aliases)))
>
> And again define my-host-aliases somewhere above `operating-system`:
>
> (define my-host-aliases
>   "
> # Some Servers
> 123.123.123.100 foo
> 123.123.123.101 bar
> 123.123.123.102 baz
> ")
>
> Most other files under /etc are managed by different services. You
> should review the "Guix Services" section of the info pages to find
> the appropriate service for whatever files you want to modify.
>
> As of today, I'm not aware of a Guix service that modifies
> /etc/resolv.conf other than the network-manager-service-type (which is
> what I use on my system).
>
> However, if you are not using NetworkManager and want to manually set
> the values in /etc/resolv.conf such that they persist across calls to
> `guix system reconfigure`, you should add this form to the `services`
> list in your `operating-system` definition:
>
> (simple-service 'resolv-service
>                 etc-service-type
>                 `(("resolv.conf" ,(plain-file "resolv.conf" my-resolv.conf))))
>
> And finally remember to define `my-resolv.conf` above `operating-system`:
>
> (define my-resolv.conf
>   "# Generated by Guix!
> nameserver 255.255.255.1
> nameserver ffff:ffff:ffff::1
> ")

Re: Edits to `etc/resolv.conf` being overwritten

[Gary Johnson]

Bone Baboon <bone.baboon@disroot.org> writes:

> Thank you for the explanation and detailed examples.
>
> I now have my system configuration providing the contents of
> `/etc/resolv.conf` with a service.
>
> However the contents of `/etc/resolv.conf` is still being overwritten
> with entries for my internet service provider's DNS.  After some testing
> it appears to be happening when I run this command `sudo dhclient
> <wireless-interface>`.

That's unfortunate to hear. Perhaps you could check out the
network-manager-service-type? I believe it includes a parameter that
lets you tell NetworkManager not to overwrite /etc/resolv.conf. The
command-line interface for NetworkManager is called nmtui. This is what
I use on my machine.

> I also appreciate the `hosts-file` example you shared as I am thinking
> about using `https://github.com/StevenBlack/hosts` as a block list.  In
> this case the contents of `my-host-aliases` would be very large.  With
> Guile how would I have the definition of `my-host-aliases` in it's own
> file and import and use it in my system configuration?

(use-modules (ice-9 rdelim))

(define my-host-aliases (with-input-from-file "/path/to/your/file"
                                               (lambda () (read-delimited ""))))

Happy hacking,
  Gary

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Re: Edits to `etc/resolv.conf` being overwritten

[Bone Baboon]

Gary Johnson writes:
> That's unfortunate to hear. Perhaps you could check out the
> network-manager-service-type? I believe it includes a parameter that
> lets you tell NetworkManager not to overwrite /etc/resolv.conf. The
> command-line interface for NetworkManager is called nmtui. This is what
> I use on my machine.

I do not have NetworkManager installed and am not using
`network-manager-service-type`.  There is no NetworkManager service
listed when I run `sudo herd status`.

The commands I am using to connect to the internet are:

```
sudo ip link set <wireless-interface> up
sudo wpa_supplicant -Dnl80211 -i<wireless-interface> -c/path/to/wpa/config.conf -B
sudo dhclient <wireless-interface>
```
It is almost like `sudo dhclient <wireless-interface>` is taking
instruction from the router (provided by my internet service provider)
to overwrite `/etc/resolv.conf` to the DNS of my internet service
provider.

> (use-modules (ice-9 rdelim))
>
> (define my-host-aliases (with-input-from-file "/path/to/your/file"
>                                                (lambda () (read-delimited ""))))

Thank you for sharing this.  It works for me.

Re: Edits to `etc/resolv.conf` being overwritten

[Vincent Legoll]

Hello,

On Thu, Apr 8, 2021 at 9:08 PM Bone Baboon <bone.baboon@disroot.org> wrote:
> It is almost like `sudo dhclient <wireless-interface>` is taking
> instruction from the router (provided by my internet service provider)
> to overwrite `/etc/resolv.conf` to the DNS of my internet service
> provider.

I'd try the "-R" command line option without giving "domain-name-servers"

See details in the dhclient's man page

-- 
Vincent Legoll

Re: Edits to `etc/resolv.conf` being overwritten

[Vladimir Sedach]

Bone Baboon <bone.baboon@disroot.org> writes:
> It is almost like `sudo dhclient <wireless-interface>` is taking
> instruction from the router (provided by my internet service provider)
> to overwrite `/etc/resolv.conf` to the DNS of my internet service
> provider.

That is in fact what dhclient does. There is a list of workarounds on
Debian Wiki:

https://wiki.debian.org/resolv.conf

I use the file attribute one on my Debian system.

The ideal solution is to re-implement dhclient in Guile, and make it
a configurable alternative to dhcp-client-service-type. That would be
a lot of work though.

--
Vladimir Sedach
Software engineering services in Los Angeles https://oneofus.la

Re: Edits to `etc/resolv.conf` being overwritten

[Bone Baboon]

Vladimir Sedach writes:
> That is in fact what dhclient does. There is a list of workarounds on
> Debian Wiki:
>
> https://wiki.debian.org/resolv.conf
>
> I use the file attribute one on my Debian system.
>
> The ideal solution is to re-implement dhclient in Guile, and make it
> a configurable alternative to dhcp-client-service-type. That would be
> a lot of work though.

Thank you for sharing that link.  I tried the methods mentioned and the
one that worked for me was to use `chattr +i /etc/resolv.conf`.  Using
this approach required me to stop having my system configuration manage
the contents of `/etc/resolv.conf`.

Re: Edits to `etc/resolv.conf` being overwritten

[Bone Baboon]

Vincent Legoll writes:
> I'd try the "-R" command line option without giving "domain-name-servers"
>
> See details in the dhclient's man page

Thank you for the suggestion.  Reading dhclient's man page it looks like
`-R` is related to IPV6.  I have IPV6 disabled.

When I try running `sudo dhclient -R <wireless-interface>` no IP address
is assigned to the interface.

Re: Edits to `etc/resolv.conf` being overwritten

[Vincent Legoll]

Hello,

On Sat, Apr 10, 2021 at 5:40 AM Bone Baboon <bone.baboon@disroot.org> wrote:
> Vincent Legoll writes:
> > I'd try the "-R" command line option without giving "domain-name-servers"
> >
> > See details in the dhclient's man page
>
> Thank you for the suggestion.  Reading dhclient's man page it looks like
> `-R` is related to IPV6.  I have IPV6 disabled.

Sorry, I just looked at the first hit for "dhclient man", which
is not the same as what "man dhclient" gives on guix (and
on others distros also) :facepalm:

I'm not seeing mention of IPv6 in "-R" text from :
https://linux.die.net/man/8/dhclient

But you're right that this was a wrong suggestion.

Let me try again :

Have a look at the "LEASE REQUIREMENTS AND REQUESTS"
section from man dhclient.conf, you should be able to make
it *NOT* require "name-servers"...

Hopefully this time, the suggestion will be right...

-- 
Vincent Legoll

Re: Edits to `etc/resolv.conf` being overwritten

[Bone Baboon]

Vincent Legoll writes:
> Have a look at the "LEASE REQUIREMENTS AND REQUESTS"
> section from man dhclient.conf, you should be able to make
> it *NOT* require "name-servers"...

Thanks you for this helpful suggestion.

After looking at the section you pointed out in man page for
dhclient.conf I have come up with something that stops `sudo dhclient
<wireless-interface>` from overwriting `/etc/resolv.conf`.  This
approach also allows the system configuration to manage the contents of
`/etc/resolv.conf` which is an improvement over using `chattr +i
/etc/resolv.conf` which did not.

Relevant sections of system configuration are:

At the top level outside the `operating-system` definition.
```
(define dhclient-configuration
  "request subnet-mask, broadcast-address, time-offsets, routers, host-name;
")
```
Note:
These were deliberately excluded from `request`: `domain-name`,
`domain-name-servers`, `name-servers` and `domain-search`.

A service in the services definition.
```
(simple-service 'dhclient-service
                etc-service-type
                `(("dhclient.conf",
                   (plain-file "dhclient.conf"
                               dhclient-configuration))))
```