warning: hostname localhost does not resolve to address ::1: No address associated with hostname

[Jelle de Jong]

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Hello everyone,

I have a dual stack IPv6/IPv4 postfix server that been running on
debian stable quite happy.

At 9 februari I did some system updates for debian:
apache2-mpm-prefork apache2-utils apache2.2-bin apache2.2-common
base-files libc-bin libc6 libc6-i686 libssl1.0.0
linux-image-3.2.0-4-686-pae locales multiarch-support openssl tzdata
wget whois

And now im getting the following lines in my log checks:

postfix/smtpd[15247]: warning: hostname localhost does not resolve to
address ::1: No address associated with hostname

1. should I be worried?
2. why is the warning popping up now?

I listed some some output of my own investigation of the below
commands in my pastbin here: http://paste.debian.net/81152

# postconf | grep mynetworks
# cat /etc/hosts
# cat /etc/nsswitch.conf
# ping6 localhost
# cat /etc/host.conf
# cat /proc/cmdline
# getent hosts localhost
# getent hosts ::1

I got the feeling it may have something to do with changes in libc?
and multi on dns resolutions but I am not sure.

Thanks in advance,

Kind regards,

Jelle de Jong
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[li...@rhsoft.net]

Am 10.02.2014 16:33, schrieb Jelle de Jong:
> I have a dual stack IPv6/IPv4 postfix server that been running on
> debian stable quite happy.
>

> postfix/smtpd[15247]: warning: hostname localhost does not resolve to
> address ::1: No address associated with hostname
>
> 1. should I be worried?
> 2. why is the warning popping up now?
>
> I listed some some output of my own investigation of the below
> commands in my pastbin here: http://paste.debian.net/81152
>
> # postconf | grep mynetworks
> # cat /etc/hosts
> # cat /etc/nsswitch.conf
> # ping6 localhost
> # cat /etc/host.conf
> # cat /proc/cmdline
> # getent hosts localhost
> # getent hosts ::1
>
> I got the feeling it may have something to do with changes in libc?
> and multi on dns resolutions but I am not sure

none of your commands above makes a dns request
postfix does

getent - get entries from Name Service Switch libraries
and so it takes the value from /etc/hosts, postfix not

in other words: fix your DNS servers PTR

[Wietse Venema]

Jelle de Jong:

> postfix/smtpd[15247]: warning: hostname localhost does not resolve to
> address ::1: No address associated with hostname

..

> 2. why is the warning popping up now?

Because the system getnameinfo() function cannot resolve "localhost"
to "::1".

# cat /etc/hosts
127.0.0.1 localhost
::1 localhost [other names omitted]

You have two lines with "localhost" and by default many Linux
distributions allow only one line per hostname. This is wrong
because it prevents some programs from using the ::1 address.

Search for "linux host.conf multi on". Then complain to your
distribution provider.

Wietse