Re: [arch-general] Cannot no longer resolve local hostname with the new nsswitch.conf

[Chi-Hsuan Yen via arch-general]

On Wed, Nov 9, 2016 at 1:53 AM, Damjan Georgievski via arch-general <
arch-general@archlinux.org> wrote:

> On 8 November 2016 at 18:43, Patrick Burroughs (Celti) via
> arch-general  wrote:
> > On Tue, 8 Nov 2016 18:01:32 +0100
> > Damjan Georgievski via arch-general  wrote:
> >
> >> > $ getent -s resolve hosts $(hostname)
> >>
> >> this should fail since you don't have the resolved service running.
> >
> > nss-resolve will chainload nss-dns when systemd-resolved is not running
> > (see `man 8 nss-resolve`).
>
> ah right, that fallback should be removed *in the future* and I was
> under the impression it already happened
>
> https://github.com/systemd/systemd/commit/344874fcd0a3fc1f9bc6cdf34ecaf5
> 37c10a3ad3
>
>
>
>
> --
> damjan
>

getent -s dns hosts $(hostname) also returns 2
getent -s myhostname hosts $(hostname) gives reasonable results:

fe80::ae22:bff:fe77:e20b NEWSLAB-PC12574
fe80::800:27ff:fe00:0 NEWSLAB-PC12574

The package testing/systemd is the latest r232. My machine has been online
for half a month. Should I reboot to use the latest systemd?

By the way, from your commit, seems r232 has fixed it?

Many thanks,

Yen Chi Hsuan

Re: [arch-general] Cannot no longer resolve local hostname with the new nsswitch.conf

[Damjan Georgievski via arch-general]

On 8 November 2016 at 18:43, Patrick Burroughs (Celti) via
arch-general  wrote:
> On Tue, 8 Nov 2016 18:01:32 +0100
> Damjan Georgievski via arch-general  wrote:
>
>> > $ getent -s resolve hosts $(hostname)
>>
>> this should fail since you don't have the resolved service running.
>
> nss-resolve will chainload nss-dns when systemd-resolved is not running
> (see `man 8 nss-resolve`).

ah right, that fallback should be removed *in the future* and I was
under the impression it already happened

https://github.com/systemd/systemd/commit/344874fcd0a3fc1f9bc6cdf34ecaf537c10a3ad3




-- 
damjan

Re: [arch-general] Cannot no longer resolve local hostname with the new nsswitch.conf

[Patrick Burroughs (Celti) via arch-general]

On Tue, 8 Nov 2016 18:01:32 +0100
Damjan Georgievski via arch-general  wrote:

> > $ getent -s resolve hosts $(hostname)  
> 
> this should fail since you don't have the resolved service running.

nss-resolve will chainload nss-dns when systemd-resolved is not running
(see `man 8 nss-resolve`).

> but, when using `hosts: files mymachines resolve [!UNAVAIL=return] dns
> myhostname` standard resolving should then go to the dns source, and
> then to the myhostname source.

The `resolve [!UNAVAIL=return]` entry in the new default nsswitch.conf
causes NSS to /only/ continue down the list if the nss-resolve module
is /not available/; i.e., in a standard Arch setup nss-resolve will
always be queried, and pass the query on to systemd-resolved if it is
running, or fall back to nss-dns if it is not.

Nothing after the conditional will be queried — that is, in this
configuration myhostname will /always/ be skipped unless nss-resolve
fails to load. See `man 5 nsswitch.conf` for details on how the
conditional works.

There is actually a sensible reason for this: if both `resolve` and
`dns` are in there without the conditional, querying a non-existent DNS
record will cause the query to go out twice: once for nss-resolve and
once for nss-dns, because a NOTFOUND result automatically falls back to
the next item in the chain (that is, from nss-resolve to nss-dns).

Sensible solution: change the hosts line as follows.

hosts: files myhostname mymachines resolve [!UNAVAIL=return] dns

Or if you you use Zeroconf (Avahi)...

hosts: files myhostname mymachines mdns_minimal [NOTFOUND=return] resolve 
[!UNAVAIL=return] dns

~Celti


pgpAotMpvEZcR.pgp
Description: OpenPGP digital signature

Re: [arch-general] Cannot no longer resolve local hostname with the new nsswitch.conf

[Damjan Georgievski via arch-general]

> $ getent -s resolve hosts $(hostname)

this should fail since you don't have the resolved service running.

but, when using `hosts: files mymachines resolve [!UNAVAIL=return] dns
myhostname` standard resolving should then go to the dns source, and
then to the myhostname source.

what does
getent -s dns hosts $(hostname)
getent -s myhostname hosts $(hostname)
return ?

also are you up-to-date with systemd 232?

-- 
damjan

Re: [arch-general] Cannot no longer resolve local hostname with the new nsswitch.conf

[Chi-Hsuan Yen via arch-general]

On Tue, Nov 8, 2016 at 10:02 PM, Damjan Georgievski via arch-general <
arch-general@archlinux.org> wrote:

> On 8 November 2016 at 13:37, Chi-Hsuan Yen via arch-general
>  wrote:
> > Hi Arch enthuasiasts,
> >
> > With testing/filesystem 2016.11-2, I can no longer use my local hostname
> to
> > acess services on the local machine. For example:
> >
> > $ hostname
> > PC12574
> >
> > $ ping PC12574
> > ping: PC12574: Name or service not known
> >
> > Seems changes in nsswitch.conf [1] does the effect. If I change the
> hosts:
> > line in nsswitch.conf back to the old configuration "files resolve
> > mymachines myhostname", or remove the [!UNAVAIL=return] part from this
> > line, ping works fine:
>
> do you have systemd-resolved running?
> what does `getent -s resolve hosts ` return?
>
> --
> damjan
>

Here it is:

$ getent -s resolve hosts $(hostname)

[2] $ systemctl status systemd-resolved.service
● systemd-resolved.service - Network Name Resolution
   Loaded: loaded (/usr/lib/systemd/system/systemd-resolved.service;
disabled; vendor preset: enabled)
   Active: inactive (dead)
 Docs: man:systemd-resolved.service(8)
   http://www.freedesktop.org/wiki/Software/systemd/resolved

http://www.freedesktop.org/wiki/Software/systemd/writing-network-configuration-managers

http://www.freedesktop.org/wiki/Software/systemd/writing-resolver-clients

The getent command prints nothing and exits with 2. And from strace, it
asks Google DNS, which is set in my /etc/resolv.conf:

$ strace -f getent -s resolve hosts "$(hostname)" |& grep recvfrom
recvfrom(6, "^\236\201\203\0\1\0\0\0\1\0\0\17PC12574\0\0\34\0"..., 1024, 0,
{sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.8.8")},
[28->16]) = 108
recvfrom(6, "\314d\201\203\0\1\0\0\0\1\0\0\17PC12574\0\0\1\0"..., 1024, 0,
{sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.8.8")},
[28->16]) = 108

Is it normal?

Best,

Yen Chi Hsuan

Re: [arch-general] Cannot no longer resolve local hostname with the new nsswitch.conf

[Damjan Georgievski via arch-general]

On 8 November 2016 at 13:37, Chi-Hsuan Yen via arch-general
 wrote:
> Hi Arch enthuasiasts,
>
> With testing/filesystem 2016.11-2, I can no longer use my local hostname to
> acess services on the local machine. For example:
>
> $ hostname
> PC12574
>
> $ ping PC12574
> ping: PC12574: Name or service not known
>
> Seems changes in nsswitch.conf [1] does the effect. If I change the hosts:
> line in nsswitch.conf back to the old configuration "files resolve
> mymachines myhostname", or remove the [!UNAVAIL=return] part from this
> line, ping works fine:

do you have systemd-resolved running?
what does `getent -s resolve hosts ` return?

-- 
damjan

Re: [arch-general] Cannot no longer resolve local hostname with the new nsswitch.conf

[Chi-Hsuan Yen via arch-general]

On Tue, Nov 8, 2016 at 9:11 PM, Jan Alexander Steffens via arch-general <
arch-general@archlinux.org> wrote:

> On Tue, Nov 8, 2016 at 1:37 PM Chi-Hsuan Yen via arch-general <
> arch-general@archlinux.org> wrote:
>
> > Hi Arch enthuasiasts,
> >
> > With testing/filesystem 2016.11-2, I can no longer use my local hostname
> to
> > acess services on the local machine. For example:
> >
> > $ hostname
> > PC12574
> >
> > $ ping PC12574
> > ping: PC12574: Name or service not known
> >
> > Seems changes in nsswitch.conf [1] does the effect. If I change the
> hosts:
> > line in nsswitch.conf back to the old configuration "files resolve
> > mymachines myhostname", or remove the [!UNAVAIL=return] part from this
> > line, ping works fine:
> >
> > $ ping PC12574
> > PING PC12574(PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0)) 56 data bytes
> > 64 bytes from PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0): icmp_seq=1
> ttl=64
> > time=0.025 ms
> > 64 bytes from PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0): icmp_seq=2
> ttl=64
> > time=0.078 ms
> >
> > Is it a bug? Or such a usage is just a non-standard coincidence?
> >
> > Thanks for any help.
> >
> > Yen Chi Hsuan
> >
> > [1]
> >
> > https://git.archlinux.org/svntogit/packages.git/commit/
> trunk?h=packages/filesystem=f1cd9f7fb4cdf7617a1b875e14be212733f9c67a
>
>
> This is an effect of putting "myhostname" at the end of the list. If you
> don't want your network to be able to override lookup for your hostname
> move "myhostname" to after "files".
>
>
Thanks for the solution! Maybe it should be the default? I see
https://bugs.archlinux.org/task/51709 changed nsswitch.conf to the current
settings.


> It seems this only happens when you're part of a domain. AFAICT resolve/dns
> won't ask upstream for unqualified names.
>

How to check whether I'm in a domain or not? Here's my /etc/resolv.conf:

$ cat /etc/resolv.conf
# Generated by resolvconf
nameserver 8.8.8.8

And another seemingly related command:

$ hostname --domain
(none)

Best,

Yen Chi Hsuan

Re: [arch-general] Cannot no longer resolve local hostname with the new nsswitch.conf

[Jan Alexander Steffens via arch-general]

On Tue, Nov 8, 2016 at 1:37 PM Chi-Hsuan Yen via arch-general <
arch-general@archlinux.org> wrote:

> Hi Arch enthuasiasts,
>
> With testing/filesystem 2016.11-2, I can no longer use my local hostname to
> acess services on the local machine. For example:
>
> $ hostname
> PC12574
>
> $ ping PC12574
> ping: PC12574: Name or service not known
>
> Seems changes in nsswitch.conf [1] does the effect. If I change the hosts:
> line in nsswitch.conf back to the old configuration "files resolve
> mymachines myhostname", or remove the [!UNAVAIL=return] part from this
> line, ping works fine:
>
> $ ping PC12574
> PING PC12574(PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0)) 56 data bytes
> 64 bytes from PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0): icmp_seq=1 ttl=64
> time=0.025 ms
> 64 bytes from PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0): icmp_seq=2 ttl=64
> time=0.078 ms
>
> Is it a bug? Or such a usage is just a non-standard coincidence?
>
> Thanks for any help.
>
> Yen Chi Hsuan
>
> [1]
>
> https://git.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/filesystem=f1cd9f7fb4cdf7617a1b875e14be212733f9c67a


This is an effect of putting "myhostname" at the end of the list. If you
don't want your network to be able to override lookup for your hostname
move "myhostname" to after "files".

It seems this only happens when you're part of a domain. AFAICT resolve/dns
won't ask upstream for unqualified names.

Re: [arch-general] Cannot no longer resolve local hostname with the new nsswitch.conf

[Chi-Hsuan Yen via arch-general]

On Tue, Nov 8, 2016 at 8:37 PM, Chi-Hsuan Yen  wrote:

> Hi Arch enthuasiasts,
>
> With testing/filesystem 2016.11-2, I can no longer use my local hostname
> to acess services on the local machine. For example:
>
> $ hostname
> PC12574
>
> $ ping PC12574
> ping: PC12574: Name or service not known
>
> Seems changes in nsswitch.conf [1] does the effect. If I change the hosts:
> line in nsswitch.conf back to the old configuration "files resolve
> mymachines myhostname", or remove the [!UNAVAIL=return] part from this
> line, ping works fine:
>
> $ ping PC12574
> PING PC12574(PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0)) 56 data bytes
> 64 bytes from PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0): icmp_seq=1
> ttl=64 time=0.025 ms
> 64 bytes from PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0): icmp_seq=2
> ttl=64 time=0.078 ms
>
> Is it a bug? Or such a usage is just a non-standard coincidence?
>
> Thanks for any help.
>
> Yen Chi Hsuan
>
> [1] https://git.archlinux.org/svntogit/packages.git/commit/
> trunk?h=packages/filesystem=f1cd9f7fb4cdf7617a1b875e14be212733f9c67a
>

Sorry, the title should be: "Can no longer resolve local hostname with the
new nsswitch.conf"

[arch-general] Cannot no longer resolve local hostname with the new nsswitch.conf

[Chi-Hsuan Yen via arch-general]

Hi Arch enthuasiasts,

With testing/filesystem 2016.11-2, I can no longer use my local hostname to
acess services on the local machine. For example:

$ hostname
PC12574

$ ping PC12574
ping: PC12574: Name or service not known

Seems changes in nsswitch.conf [1] does the effect. If I change the hosts:
line in nsswitch.conf back to the old configuration "files resolve
mymachines myhostname", or remove the [!UNAVAIL=return] part from this
line, ping works fine:

$ ping PC12574
PING PC12574(PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0)) 56 data bytes
64 bytes from PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0): icmp_seq=1 ttl=64
time=0.025 ms
64 bytes from PC12574 (fe80::ae22:bff:fe77:e20b%enp3s0): icmp_seq=2 ttl=64
time=0.078 ms

Is it a bug? Or such a usage is just a non-standard coincidence?

Thanks for any help.

Yen Chi Hsuan

[1]
https://git.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/filesystem=f1cd9f7fb4cdf7617a1b875e14be212733f9c67a