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I installed nrpe on new servers. Nagios is already running and checking other server (I haven't installed).

I've got several error lines in my syslog file :

Oct 31 15:17:01 myservername nrpe[41848]: Host nagios_ip is not allowed to talk to us!

My nrpe.cfg file includes the following line :


What am I doing wrong ?

(with nagios_ip the actual IP for my nagios server)

share|improve this question
Have you tried restarting the nrpe service on the target server? – norrland Oct 31 '13 at 14:45
Yes I did but it had no effect – Jean-Philippe Caruana Oct 31 '13 at 14:47
Which OS and Nagios/NRPE version is installed? – norrland Oct 31 '13 at 14:52
Also. Check nrpe.conf for whitespaces after allowed_hosts=<ip>. In vim :set list – norrland Oct 31 '13 at 14:54
up vote 2 down vote accepted

I found the solution, but the error message is totally misleading. The user nagios has to be in the suders...


nagios  ALL=(ALL) NOPASSWD: /usr/lib/nagios/plugins/
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this is not correct at all, actually – Keith Oct 31 '13 at 18:02
well, this solved the problem at once. Could you be more specific ? – Jean-Philippe Caruana Nov 4 '13 at 9:16

Had the same entry in my syslog. Editing /etc/nagios/nrpe.cfg and enter missing IP will fixed it at all.


After editing you have to restart or even reload nrpe deamon.

/etc/init.d/nagios-nrpe-server reload

Check if it is all fine with your configuration. Syslog should have an entry like this:

Allowing connections from:,

I advise you not to add user nagios to sudoers because of security issues.

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"I advise you not to add user nagios to sudoers because of security issues." Could you elaborate on this? – gf_ Dec 9 '15 at 20:57

A lot of how-to's here and there ask you to allow your monitoring server IP like this in your host's /etc/nagios/nrpe.cfg :


On some distribs (Ubuntu 14.04 LTS for instance), it's working. On other (Ubuntu 12.04 LTS - tested on Microsoft Azure in my case), it does not.

Just remove the space before second IP :


Then, of course, restart your host's nrpe service :

$ service nagios-nrpe-server restart
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You do not want to add nagios to your sudoers file. If you're nagios server is in allowed_hosts but you're still getting this error, the following work flow will probably fix it (at least it did with mine):

sudo@host: ls -l /usr/lib/nagios/plugins/ if any are -rwxr-x-r-x then

sudo@host: chmod 777 /usr/lib/nagios/plugins/* sudo@host: /etc/init.d/nagios-nrpe-server reload

then to check, do on your nagios server

/usr/lib/nagios/plugins/check_nrpe -H <server>

Good Luck!

share|improve this answer
chmod 777 is a quite bad advice; making all the files world write-/read-/executable? Really...? – gf_ Dec 9 '15 at 20:56
"You do not want to add nagios to your sudoers file." Could you elaborate on this? – gf_ Dec 9 '15 at 20:57
you're making these perl/python/bash scripts that check system information rwx by everyone instead of giving sudo access to a user. If you don't understand how sudo works, or what it is I encourage you to google it. if you're worried about it, chmod 755 – A.C Dec 10 '15 at 18:23
Thanks for your comment; I'm appreciating your hints...good to see, that you are in fact quite clueless what's possible with sudo, and how to limit access. Just giving a user access to sudo doesn't mean anything, in contrast to your chmod 777. – gf_ Dec 10 '15 at 18:32

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