Failed to send mail : Failed to lookup IP address for localhost

Submitted by neopraxis on Thu, 02/18/2016 - 07:24

Suddenly my customers are unable to send email with the following error Failed to send mail : Failed to lookup IP address for localhost

Also in Virtualmin I am presented with the following error Warning! A problem was detected with your Virtualmin license : An error occurred checking the licence : Invalid host or serial number When I click on Re-Check License Status I get the following
Now re-checking your Virtualmin license .. .. a problem was detected : An error occurred checking the licence : Invalid host or serial number

I am able to browse to software.virtualmin.com. I have edited the hostname since purchasing the license to reflect the reverse dns if that is relevant to this.

Status: 
Active

Comments

Submitted by andreychek on Thu, 02/18/2016 - 09:56

Howdy -- sorry that you're having problems sending email! What is the output of these commands:

cat /etc/hosts
cat /etc/nsswitch.conf

And, while the Virtualmin license error shouldn't be related, what is the output of this command:

virtualmin licence-info

Submitted by neopraxis on Thu, 02/18/2016 - 11:44

Hi, thanks for the fast response.

# cat /etc/hosts

# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost.localdomain localhost

# The following lines are desirable for IPv6 capable hosts
#(added automatically by netbase upgrade)

::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
178.33.227.173 demeter.neopraxis.co.uk demeter ns3.webpurity.net mail.webpurity.net ns338867.ip-178-33-227.eu
2001:41d0:8:24ad:: demeter.neopraxis.co.uk demeter

# cat /etc/nsswitch.conf

#
# /etc/nsswitch.conf
#
# An example Name Service Switch config file. This file should be
# sorted with the most-used services at the beginning.
#
# The entry '[NOTFOUND=return]' means that the search for an
# entry should stop if the search in the previous entry turned
# up nothing. Note that if the search failed due to some other reason
# (like no NIS server responding) then the search continues with the
# next entry.
#
# Valid entries include:
#
# nisplus Use NIS+ (NIS version 3)
# nis Use NIS (NIS version 2), also called YP
# dns Use DNS (Domain Name Service)
# files Use the local files
# db Use the local database (.db) files
# compat Use NIS on compat mode
# hesiod Use Hesiod for user lookups
# [NOTFOUND=return] Stop searching if not found so far
#

# To use db, put the "db" in front of "files" for entries you want to be
# looked up first in the databases
#
# Example:
#passwd:    db files nisplus nis
#shadow:    db files nisplus nis
#group:     db files nisplus nis

passwd:     files sss
shadow:     files sss
group:      files sss
#initgroups: files

#hosts:     db files nisplus nis dns
hosts: files dns myhostname

# Example - obey only what nisplus tells us...
#services:   nisplus [NOTFOUND=return] files
#networks:   nisplus [NOTFOUND=return] files
#protocols:  nisplus [NOTFOUND=return] files
#rpc:        nisplus [NOTFOUND=return] files
#ethers:     nisplus [NOTFOUND=return] files
#netmasks:   nisplus [NOTFOUND=return] files    

bootparams: nisplus [NOTFOUND=return] files

ethers:     files
netmasks:   files
networks:   files
protocols:  files
rpc:        files
services:   files sss

netgroup:   files sss

publickey:  nisplus

automount:  files
aliases:    files nisplus

# virtualmin licence-info

Serial number: GPL
License key: GPL
Expiry date:
Virtual servers: 9
Maximum servers: 10
Servers left: 1

Submitted by andreychek on Thu, 02/18/2016 - 11:47

Hmm, that all looks good. What is the output of this command:

host localhost

Also, where is it that you're seeing that error? That is, is that in your email logs on the server?

Submitted by neopraxis on Thu, 02/18/2016 - 13:06

# host localhost

Host localhost not found: 3(NXDOMAIN)

Submitted by andreychek on Thu, 02/18/2016 - 14:57

Oh, upon second look, I think I may see the issue.

In your /etc/nsswitch.conf file, I see this line:

hosts: files dns myhostname

Try changing that to just read as follows:

hosts: files dns

After doing that, run this command again:

host localhost

What does that produce now?

Submitted by neopraxis on Thu, 02/18/2016 - 15:05

ok,

# cat /etc/nsswitch.conf
#
# /etc/nsswitch.conf
#
# An example Name Service Switch config file. This file should be
# sorted with the most-used services at the beginning.
#
# The entry '[NOTFOUND=return]' means that the search for an
# entry should stop if the search in the previous entry turned
# up nothing. Note that if the search failed due to some other reason
# (like no NIS server responding) then the search continues with the
# next entry.
#
# Valid entries include:
#
# nisplus Use NIS+ (NIS version 3)
# nis Use NIS (NIS version 2), also called YP
# dns Use DNS (Domain Name Service)
# files Use the local files
# db Use the local database (.db) files
# compat Use NIS on compat mode
# hesiod Use Hesiod for user lookups
# [NOTFOUND=return] Stop searching if not found so far
#

# To use db, put the "db" in front of "files" for entries you want to be
# looked up first in the databases
#
# Example:
#passwd:    db files nisplus nis
#shadow:    db files nisplus nis
#group:     db files nisplus nis

passwd:     files sss
shadow:     files sss
group:      files sss
#initgroups: files

#hosts:     db files nisplus nis dns
hosts: files dns

# Example - obey only what nisplus tells us...
#services:   nisplus [NOTFOUND=return] files
#networks:   nisplus [NOTFOUND=return] files
#protocols:  nisplus [NOTFOUND=return] files
#rpc:        nisplus [NOTFOUND=return] files
#ethers:     nisplus [NOTFOUND=return] files
#netmasks:   nisplus [NOTFOUND=return] files    

bootparams: nisplus [NOTFOUND=return] files

ethers:     files
netmasks:   files
networks:   files
protocols:  files
rpc:        files
services:   files sss

netgroup:   files sss

publickey:  nisplus

automount:  files
aliases:    files nisplus # host localhost
Host localhost not found: 3(NXDOMAIN)

Submitted by andreychek on Thu, 02/18/2016 - 18:18

Do you know of any recent changes to that nsswitch.conf file?

I see a few unusual entries in it.

We corrected the issue with the "hosts" entry, but I'm curious if the other odd entries are causing a problem.

Before we get too far though -- can you verify that you're able to log into your server? That is, are SSH logins working?

Submitted by neopraxis on Thu, 02/18/2016 - 18:28

I'm not aware of any direct or indirect changes to the nsswitch.conf.

And yes I can log on to the web control panel and via SSH.

Submitted by neopraxis on Tue, 02/23/2016 - 17:40

I've rebooted and now email is working. Thanks. However, I am still getting this error.

# host localhost
Host localhost not found: 3(NXDOMAIN)

I have sorted the license issue by running the license script again given on the site in Virtualmin.com > Account > Software Licenses > Download And Install Command.

Submitted by neopraxis on Tue, 02/23/2016 - 17:40

I've sorted the above NXDOMAIN error now too. I just had to add 127.0.0.1 as the first DNS server listed in Webmin > Networking > Network Configuration > Hostname and DNS Client, and then apply the configuration.

Thanks for all your help.

Submitted by andreychek on Tue, 02/23/2016 - 22:07

Ah that's good to hear!

That really shouldn't have mattered, since the nsswitch file had "files" listed first, and your /etc/hosts file had the correct localhost entry. But perhaps an invalid entry was cached in a running daemon.

Either which way, I'm glad you figured it out! Please feel free to let us know if you have additional questions.