Nagios Support Forum

I have seen similar questions asked, but I have not seen one which fits this use case specifically.

Basically executing the base check-nrpe to the remote host will return the remote nrpe version:
[root@nagios agile-u2]# /usr/lib/nagios/plugins/check_nrpe -H agile-db-u2
NRPE v2.15

When you add a command to the end of the check command it returns the following:
[root@nagios agile-u2]# /usr/lib/nagios/plugins/check_nrpe -H agile-db-u2 -c check_root
NRPE: Unable to read output

The remote command defined in /etc/nagios/nrpe.cfg:
command[check_root]=/usr/lib/nagios/plugins/check_disk -w 20% -c 10% /dev/mapper/vg_agiledbd1-lv_root

Disk path confirmed:
/dev/mapper/vg_agiledbd1-lv_root

Plugin path confirmed:
[root@agile-db-u2 plugins]# pwd
/usr/lib/nagios/plugins
[root@agile-db-u2 plugins]# ls
check_disk
[root@agile-db-u2 plugins]#

Executing the check_disk command locally works as well:
[root@agile-db-u2 plugins]# /usr/lib/nagios/plugins/check_disk -v -v
DISK OK - free space: / 0 MB (0% inode=97%); /dev/shm 7974 MB (99% inode=99%); /boot 333 MB (73% inode=99%); /u02 23333 MB (24% inode=99%); /agileNAS 138148 MB (38% inode=99%);| /=65256MB;;;0;68165 /dev/shm=0MB;;;0;7975 /boot=117MB;;;0;476 /u02=72208MB;;;0;100661 /agileNAS=220251MB;;;0;358400
[root@agile-db-u2 plugins]#

I have used this same nrpe.cfg file on a couple of other servers and it has worked without issue. This seems to be currently effecting 4 out of 12 in the deployment. All of the systems are running identical version of SSL, NRPE, OS..etc.

Has anyone else experienced this issue?

How did you install NRPE? Is this running as a standalone daemon, or using xinetd?

I installed it from the EPEL repos, it is currently running under init.d.
**For startup reasons it's running under init.d, but to actually start the command for testing and such, I'm using "service nrpe restart/start/stop"

I have tried running it standalone: nrpe -n -c /etc/nagios/nrpe.cfg -d and received a socket timeout, which I believe was due to the -n flag.

Actually, I just ran standalone without the -n flag:
[root@agile-db-u2 init.d]# nrpe -c /etc/nagios/nrpe.cfg -d

Tested from the server and received:
[root@nagios agile-u2]# /usr/lib/nagios/plugins/check_nrpe -H agile-db-u2 -c check_root
DISK CRITICAL - free space: / 0 MB (0% inode=97%);| /=65256MB;54532;61348;0;68165

What would be the difference between running under init.d and standalone?

-R

RyanW wrote:[root@agile-db-u2 init.d]# nrpe -c /etc/nagios/nrpe.cfg -d

There is your difference most likely. Try launching as user nagios and see if you get the same results.

jdalrymple you are correct:

[root@agile-db-u2 xinetd.d]# ps -ef | grep -i nrpe
nrpe 19770 1 0 13:14 ? 00:00:00 /usr/sbin/nrpe -c /etc/nagios/nrpe.cfg -d

[root@nagios agile-u2]# /usr/lib/nagios/plugins/check_nrpe -H agile-db-u2 -c check_root
NRPE: Unable to read output

When it is run as root I do receive output, as the user specified in the nrpe.cfg (nrpe) I do NOT receive output.

Does it help if you put the following line in sudoers on the remote box?

lmiltchev wrote:Does it help if you put the following line in sudoers on the remote box?

Code: Select all

nagios   ALL = NOPASSWD:/usr/lib/nagios/plugins/check_disk *

Just gave it a try and restarted services, but it was unsuccessful.
I'm taking a look at the other systems now to look for discrepancies in users/groups, but so far, the process gets spawned as the nrpe user on other systems and it is working!

Working client:
[root@agile-proxy-u2 ~]# ps -ef | grep -i nrpe
nrpe 14943 1 0 Nov04 ? 00:00:00 /usr/sbin/nrpe -c /etc/nagios/nrpe.cfg -d

Broken client:
[root@agile-db-u2 nagios]# ps -ef | grep -i nrpe
nrpe 20530 1 0 14:27 ? 00:00:00 /usr/sbin/nrpe -c /etc/nagios/nrpe.cfg -d

These are using the same nrpe.cfg file with tweaks to the custom check dev path.

-R

RyanW wrote:jdalrymple you are correct:

[root@agile-db-u2 xinetd.d]# ps -ef | grep -i nrpe
nrpe 19770 1 0 13:14 ? 00:00:00 /usr/sbin/nrpe -c /etc/nagios/nrpe.cfg -d

[root@nagios agile-u2]# /usr/lib/nagios/plugins/check_nrpe -H agile-db-u2 -c check_root
NRPE: Unable to read output

When it is run as root I do receive output, as the user specified in the nrpe.cfg (nrpe) I do NOT receive output.

IF your user is nrpe then the sudoers line needs to start with nrpe (I'm pretty sure):

Box293 wrote:IF your user is nrpe then the sudoers line needs to start with nrpe (I'm pretty sure):

I noticed the user is NRPE and added that line to the sudoers file as well, still returned the same results.

Thanks for all of the input, from everything I've gathered it's a user/group issue.
As to why it is working on the other machines, I have not been able to figure that one out yet.

If I get a definitive solution I will report back.

Thanks guys!