Nagios Support Forum

I am using the check_disk command to monitor the disk usage for /opt/data mount on a client server from the Nagios server using check nrpe. However i am getting the following error "NRPE: Command 'check_disk' not defined"

These are the steps i have followed
1. Installed nrpe agent on client and able to communicate using the nagios server.Shows the nrpe version

[nagios@<nagios_server> etc]$ /usr/local/nagios/libexec/check_nrpe -H <client_server>
NRPE v2.15

2. /usr/local/nagios/etc/nrpe.cfg file

command: command[check_disk]=/usr/local/nagios/libexec/check_disk -w $ARG1$ -c $ARG2$ -p $ARG3$
allowed_hosts=<nagios_server_ip> //mentioned the nagios server name
dont_blame_nrpe=1

3. PFB the command i am using

define command {
command_name check_local_disk
command_line $USER1$/check_disk -w $ARG1$ -c $ARG2$ -p $ARG3$
}

4. PFB the service i am using

define service {
host_name uusrcpsplk01.fossil.com
service_description /opt/data Disk Usage
use xiwizard_nrpe_service
check_command check_nrpe!check_disk!-a '-w 20% -c 15% -p /opt/data'!!!!!!
max_check_attempts 5
check_interval 5
retry_interval 1
check_period xi_timeperiod_24x7
event_handler_enabled 0
notification_interval 60
notification_period xi_timeperiod_24x7
_xiwizard linux-server
register 1
}

I have also restarted the nrpe service after making any changes to the nrpe.cfg file. Can you please help me resolve the check_disk error.Thanks

What is the output of systemctl status nrpe from the remote system?

One thing that could cause that error is that the permissions for that plugin may be incorrect, can you run the following on the remote server and post the output so we can view the permissions?
ls -l /usr/local/nagios/libexec/check_disk

Make sure the nagios user can read and execute the plugin.

Another thing I see is that the command line options are defined on the nrpe.cfg file as well as the command on the Nagios server which will cause issues.
Edit the command on the Nagios server and change this line from to Save the config file and restart the nagios daemon.

If you are still having issues, please post a screen shot of the error here so we can view it.

Thanks for the reply. PFB the output of commands I executed

[nagios@uusrcpsplk01 libexec]$ systemctl status nrpe
-bash: systemctl: command not found

[nagios@uusrcpsplk01 libexec]$ ls -l /usr/local/nagios/libexec/check_disk
-rwxrwxrwx. 1 root nagios 7920 Nov 4 00:05 /usr/local/nagios/libexec/check_disk

Disk command on the command line works fine
[nagios@uusrcpsplk01 libexec]$ ./check_disk -w 80 -c 85 -p /opt/data
OK: '/opt/data' is at 1% capacity, total 984.2GB, used 142.6MB (0.0%), free 934.0GB (94.9%) | 'used space'=149524480B;845407898828;898245892505;0;1056759873536 'used space (pct.)'=0.0%;80;85;0;100

I have also changed the command to check_command check_nrpe!check_disk!-a '20% 15% /opt/data'!!!!!! as mentioned but I am still getting the same error
Would appreciate your help to resolve this error

Can you post the nrpe.cfg file from your remote server?
Also, run the following commands on the remote server and post the output here.

@tgriep: Thanks for your response

PFB the output of the commands.


[nagios@lussvpnagiosdb01 ~]$ netstat -an |grep 5666
tcp 0 0 10.10.83.94:34969 10.10.83.94:5666 TIME_WAIT
tcp 0 0 10.10.83.94:34988 10.10.83.94:5666 TIME_WAIT
tcp 0 0 10.10.83.94:34971 10.10.83.94:5666 TIME_WAIT
tcp 0 0 :::5666 :::* LISTEN

[nagios@lussvpnagiosdb01 ~]$ ps -ef --cols=300
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 2015 ? 00:12:03 /sbin/init
root 2 0 0 2015 ? 00:00:01 [kthreadd]
root 3 2 0 2015 ? 00:07:17 [migration/0]
root 4 2 0 2015 ? 01:01:09 [ksoftirqd/0]
root 5 2 0 2015 ? 00:00:00 [stopper/0]
root 6 2 0 2015 ? 00:01:51 [watchdog/0]
root 7 2 0 2015 ? 00:06:58 [migration/1]
root 8 2 0 2015 ? 00:00:00 [stopper/1]
root 9 2 0 2015 ? 01:02:26 [ksoftirqd/1]
root 10 2 0 2015 ? 00:01:59 [watchdog/1]
root 11 2 0 2015 ? 00:21:57 [events/0]
root 12 2 0 2015 ? 00:36:48 [events/1]
root 13 2 0 2015 ? 00:00:00 [cgroup]
root 14 2 0 2015 ? 00:00:00 [khelper]
root 15 2 0 2015 ? 00:00:00 [netns]
root 16 2 0 2015 ? 00:00:00 [async/mgr]
root 17 2 0 2015 ? 00:00:00 [pm]
root 18 2 0 2015 ? 00:01:41 [sync_supers]
root 19 2 0 2015 ? 00:01:55 [bdi-default]
root 20 2 0 2015 ? 00:00:00 [kintegrityd/0]
root 21 2 0 2015 ? 00:00:00 [kintegrityd/1]
root 22 2 0 2015 ? 00:33:18 [kblockd/0]
root 23 2 0 2015 ? 00:34:55 [kblockd/1]
root 24 2 0 2015 ? 00:00:00 [kacpid]
root 25 2 0 2015 ? 00:00:00 [kacpi_notify]
root 26 2 0 2015 ? 00:00:00 [kacpi_hotplug]
root 27 2 0 2015 ? 00:00:00 [ata_aux]
root 28 2 0 2015 ? 00:00:00 [ata_sff/0]
root 29 2 0 2015 ? 00:00:00 [ata_sff/1]
root 30 2 0 2015 ? 00:00:00 [ksuspend_usbd]
root 31 2 0 2015 ? 00:00:00 [khubd]
root 32 2 0 2015 ? 00:00:00 [kseriod]
root 33 2 0 2015 ? 00:00:00 [md/0]
root 34 2 0 2015 ? 00:00:00 [md/1]
root 35 2 0 2015 ? 00:00:00 [md_misc/0]
root 36 2 0 2015 ? 00:00:00 [md_misc/1]
root 37 2 0 2015 ? 00:00:00 [linkwatch]
root 39 2 0 2015 ? 00:00:09 [khungtaskd]
root 40 2 0 2015 ? 00:00:20 [kswapd0]
root 41 2 0 2015 ? 00:00:00 [ksmd]
root 42 2 0 2015 ? 00:10:26 [khugepaged]
root 43 2 0 2015 ? 00:00:00 [aio/0]
root 44 2 0 2015 ? 00:00:00 [aio/1]
root 45 2 0 2015 ? 00:00:00 [crypto/0]
root 46 2 0 2015 ? 00:00:00 [crypto/1]
root 54 2 0 2015 ? 00:00:00 [kthrotld/0]
root 55 2 0 2015 ? 00:00:00 [kthrotld/1]
root 56 2 0 2015 ? 00:00:00 [pciehpd]
root 58 2 0 2015 ? 00:00:00 [kpsmoused]
root 59 2 0 2015 ? 00:00:00 [usbhid_resumer]
root 60 2 0 2015 ? 00:00:00 [deferwq]
root 92 2 0 2015 ? 00:00:00 [kdmremove]
root 93 2 0 2015 ? 00:00:00 [kstriped]
root 177 2 0 2015 ? 00:15:00 [mpt_poll_0]
root 178 2 0 2015 ? 00:00:00 [mpt/0]
root 179 2 0 2015 ? 00:00:00 [scsi_eh_0]
root 182 2 0 2015 ? 00:00:00 [scsi_eh_1]
root 183 2 0 2015 ? 00:00:00 [scsi_eh_2]
root 315 2 0 2015 ? 00:00:00 [kdmflush]
root 317 2 0 2015 ? 00:00:00 [kdmflush]
root 335 2 0 2015 ? 01:26:12 [jbd2/dm-0-8]
root 336 2 0 2015 ? 00:00:00 [ext4-dio-unwrit]
root 345 2 0 2015 ? 07:00:47 [flush-253:0]
root 609 2 0 2015 ? 00:07:49 [vmmemctl]
root 635 11472 0 Oct19 ? 00:00:00 /sbin/udevd -d
root 636 11472 0 Oct19 ? 00:00:00 /sbin/udevd -d
root 768 2 0 2015 ? 00:00:00 [jbd2/sda1-8]
root 769 2 0 2015 ? 00:00:00 [ext4-dio-unwrit]
root 852 2 0 2015 ? 00:05:50 [kauditd]
root 1190 1 0 2015 ? 07:44:13 /usr/sbin/vmtoolsd
root 1360 1 0 2015 ? 01:50:21 irqbalance --pid=/var/run/irqbalance.pid
dbus 1509 1 0 2015 ? 00:00:28 dbus-daemon --system
68 1526 1 0 2015 ? 00:02:31 hald
root 1527 1526 0 2015 ? 00:00:00 hald-runner
root 1559 1527 0 2015 ? 00:00:00 hald-addon-input: Listening on /dev/input/event2 /dev/input/event0
68 1569 1527 0 2015 ? 00:14:19 /usr/libexec/hald-addon-acpi
root 1632 1 0 2015 ? 00:11:59 /opt/storix/bin/lighttpd -f /storix/config/sthttpd.conf
root 1688 1 0 2015 ? 1-01:24:04 /opt/storix/tcl/bin/tcl /opt/storix/bin/stqdaemon
root 1972 1 0 2015 ? 00:00:24 rhnsd
root 2026 1 0 2015 tty1 00:00:00 /sbin/mingetty /dev/tty1
root 2028 1 0 2015 tty2 00:00:00 /sbin/mingetty /dev/tty2
root 2030 1 0 2015 tty3 00:00:00 /sbin/mingetty /dev/tty3
root 2032 1 0 2015 tty4 00:00:00 /sbin/mingetty /dev/tty4
root 2034 1 0 2015 tty5 00:00:00 /sbin/mingetty /dev/tty5
root 2036 1 0 2015 tty6 00:00:00 /sbin/mingetty /dev/tty6
nagios 2050 1 0 Nov06 ? 00:02:24 /usr/local/nagios/bin/nagios -d /usr/local/nagios/etc/nagios.cfg
nagios 2053 2050 0 Nov06 ? 00:00:15 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
nagios 2054 2050 0 Nov06 ? 00:00:15 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
nagios 2055 2050 0 Nov06 ? 00:00:15 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
nagios 2056 2050 0 Nov06 ? 00:00:15 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
nagios 2069 30569 0 Nov06 ? 00:01:46 /usr/local/nagios//bin/ndo2db -c /usr/local/nagios//etc/ndo2db.cfg
nagios 2070 2069 0 Nov06 ? 00:06:38 /usr/local/nagios//bin/ndo2db -c /usr/local/nagios//etc/ndo2db.cfg
nagios 2073 2050 0 Nov06 ? 00:00:06 /usr/local/nagios/bin/nagios -d /usr/local/nagios/etc/nagios.cfg
apache 3587 8867 0 Nov06 ? 00:06:26 /usr/sbin/httpd
ajaxterm 4015 1 0 Jun14 ? 00:48:03 python /usr/share/ajaxterm/ajaxterm.py --daemon --port=8022 --uid=ajaxterm
postfix 4092 19914 0 00:22 ? 00:00:00 pickup -l -t fifo -u
apache 4282 8867 0 Nov07 ? 00:06:06 /usr/sbin/httpd
apache 4568 8867 0 Nov07 ? 00:06:11 /usr/sbin/httpd
nagios 7506 2055 0 00:25 ? 00:00:00 /usr/local/nagios/libexec/check_icmp -H 10.138.31.254 -w 3000.0 80 -c 5000.0 100 -p 5 -t 60
nagios 7526 2054 0 00:25 ? 00:00:00 /usr/local/nagios/libexec/check_icmp -H 10.50.1.5 -w 3000.0 80 -c 5000.0 100 -p 5 -t 60
root 7546 31529 0 00:26 ? 00:00:00 CROND
root 7547 31529 0 00:26 ? 00:00:00 CROND
root 7548 31529 0 00:26 ? 00:00:00 CROND
root 7549 31529 0 00:26 ? 00:00:00 CROND
root 7550 31529 0 00:26 ? 00:00:00 CROND
root 7551 31529 0 00:26 ? 00:00:00 CROND
nagios 7567 7546 0 00:26 ? 00:00:00 /bin/sh -c /usr/bin/php -q /usr/local/nagiosxi/cron/perfdataproc.php > /usr/local/nagiosxi/var/perfdataproc.log 2>&1
nagios 7568 7550 0 00:26 ? 00:00:00 /bin/sh -c /usr/bin/php -q /usr/local/nagiosxi/cron/cmdsubsys.php > /usr/local/nagiosxi/var/cmdsubsys.log 2>&1
nagios 7569 7551 0 00:26 ? 00:00:00 /bin/sh -c /usr/bin/php -q /usr/local/nagiosxi/cron/sysstat.php > /usr/local/nagiosxi/var/sysstat.log 2>&1
nagios 7571 7549 0 00:26 ? 00:00:00 /bin/sh -c /usr/bin/php -q /usr/local/nagiosxi/cron/eventman.php > /usr/local/nagiosxi/var/eventman.log 2>&1
nagios 7572 7547 0 00:26 ? 00:00:00 /bin/sh -c /usr/bin/php -q /usr/local/nagiosxi/cron/feedproc.php > /usr/local/nagiosxi/var/feedproc.log 2>&1
nagios 7573 2056 0 00:26 ? 00:00:00 /usr/local/nagios/libexec/check_icmp -H 10.138.31.50 -w 3000.0 80 -c 5000.0 100 -p 5 -t 60
nagios 7575 7572 0 00:26 ? 00:00:00 /usr/bin/php -q /usr/local/nagiosxi/cron/feedproc.php
nagios 7576 7567 0 00:26 ? 00:00:00 /usr/bin/php -q /usr/local/nagiosxi/cron/perfdataproc.php
nagios 7577 7548 0 00:26 ? 00:00:00 /bin/sh -c /usr/bin/php -q /usr/local/nagiosxi/cron/event_handler.php > /usr/local/nagiosxi/var/event_handler.log 2>&1
nagios 7580 7571 0 00:26 ? 00:00:00 /usr/bin/php -q /usr/local/nagiosxi/cron/eventman.php
nagios 7582 7577 0 00:26 ? 00:00:00 /usr/bin/php -q /usr/local/nagiosxi/cron/event_handler.php
nagios 7583 7568 0 00:26 ? 00:00:00 /usr/bin/php -q /usr/local/nagiosxi/cron/cmdsubsys.php
nagios 7584 7569 0 00:26 ? 00:00:00 /usr/bin/php -q /usr/local/nagiosxi/cron/sysstat.php
nagios 7707 2054 0 00:26 ? 00:00:00 /usr/local/nagios/libexec/check_icmp -H 10.40.224.10 -w 3000.0 80 -c 5000.0 100 -p 5 -t 60
nagios 7708 2055 0 00:26 ? 00:00:00 /usr/local/nagios/libexec/check_icmp -H 10.134.32.35 -w 3000.0 80 -c 5000.0 100 -p 5 -t 60
nagios 7731 2054 0 00:26 ? 00:00:00 /usr/local/nagios/libexec/check_icmp -H 10.64.3.30 -w 3000.0 80 -c 5000.0 100 -p 5 -t 60
nagios 7748 2053 0 00:26 ? 00:00:00 /usr/local/nagios/libexec/check_icmp -H 10.138.31.255 -w 3000.0 80 -c 5000.0 100 -p 5 -t 60
nagios 7773 2054 0 00:26 ? 00:00:00 /usr/bin/perl /usr/local/nagios/libexec/check_uptime_fossil -H 10.146.35.2 -C *N4gi0s* -p 161
nagios 7834 2053 0 00:26 ? 00:00:00 /usr/bin/perl /usr/local/nagios/libexec/check_uptime_fossil -H 10.81.128.3 -C *N4gi0s* -p 161
nagios 7865 2056 1 00:26 ? 00:00:00 /usr/bin/perl -w /usr/local/nagios/libexec/check_snmp_env.pl -H 10.64.0.11 -C cr3ativ3 -2 -T cisco
nagios 7875 2054 3 00:26 ? 00:00:00 /usr/bin/perl -w /usr/local/nagios/libexec/check_snmp_env.pl -H 10.50.1.1 -C cr3ativ3 -2 -T cisco
nagios 7917 7584 0 00:26 ? 00:00:00 sh -c /usr/bin/iostat -c 5 2 | tail --lines=2 | head --lines=1 | awk '{ print $1,$2,$3,$4,$5,$6 }'
nagios 7918 7917 0 00:26 ? 00:00:00 /usr/bin/iostat -c 5 2
nagios 7919 7917 0 00:26 ? 00:00:00 tail --lines=2
nagios 7920 7917 0 00:26 ? 00:00:00 head --lines=1
nagios 7921 7917 0 00:26 ? 00:00:00 awk { print $1,$2,$3,$4,$5,$6 }
nagios 7922 2055 2 00:26 ? 00:00:00 /usr/bin/perl /usr/local/nagios/libexec/check_uptime_fossil -H 10.144.0.1 -C *N4gi0s* -p 161
nagios 7937 23989 6 00:26 pts/0 00:00:00 ps -ef --cols=300
root 8867 1 0 Oct25 ? 00:00:36 /usr/sbin/httpd
root 11472 1 0 Sep26 ? 00:00:00 /sbin/udevd -d
root 11800 1 0 Jun29 ? 00:35:05 /usr/sbin/snmpd -LS0-6d -Lf /dev/null -p /var/run/snmpd.pid
root 11943 1 0 Jun29 ? 00:06:23 /usr/sbin/snmptrapd -Lsd -p /var/run/snmptrapd.pid
root 13381 1 0 Oct25 ? 00:00:00 /bin/sh /usr/bin/mysqld_safe --datadir=/var/lib/mysql --socket=/var/lib/mysql/mysql.sock --pid-

file=/var/run/mysqld/mysqld.pid --basedir=/usr --user=mysql
mysql 13484 13381 0 Oct25 ? 02:32:40 /usr/libexec/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --log-error=/var/log/mysqld.log --pid-

file=/var/run/mysqld/mysqld.pid --socket=/var/lib/mysql/mysql.sock
apache 13689 8867 0 Nov06 ? 00:07:24 /usr/sbin/httpd
apache 13690 8867 0 Nov06 ? 00:07:24 /usr/sbin/httpd
apache 13692 8867 0 Nov06 ? 00:07:26 /usr/sbin/httpd
apache 13693 8867 0 Nov06 ? 00:07:29 /usr/sbin/httpd
apache 13695 8867 0 Nov06 ? 00:07:18 /usr/sbin/httpd
apache 13696 8867 0 Nov06 ? 00:07:30 /usr/sbin/httpd
root 13707 1 0 Sep26 ? 00:00:01 /usr/bin/rhsmcertd
root 14425 1 0 Sep26 ? 00:00:00 /usr/sbin/certmonger -S -p /var/run/certmonger.pid
root 14541 1 0 Sep26 ? 00:03:03 /usr/sbin/sshd
root 14930 1 0 Oct06 ? 00:01:36 /usr/sbin/sssd -f -D
root 14931 14930 0 Oct06 ? 00:17:24 /usr/libexec/sssd/sssd_be --domain modern.local --uid 0 --gid 0 --debug-to-files
root 14932 14930 0 Oct06 ? 00:06:11 /usr/libexec/sssd/sssd_nss --uid 0 --gid 0 --debug-to-files
root 14933 14930 0 Oct06 ? 00:00:52 /usr/libexec/sssd/sssd_sudo --uid 0 --gid 0 --debug-to-files
root 14934 14930 0 Oct06 ? 00:08:51 /usr/libexec/sssd/sssd_pam --uid 0 --gid 0 --debug-to-files
root 14935 14930 0 Oct06 ? 00:00:18 /usr/libexec/sssd/sssd_ssh --uid 0 --gid 0 --debug-to-files
root 14936 14930 0 Oct06 ? 00:00:18 /usr/libexec/sssd/sssd_pac --uid 0 --gid 0 --debug-to-files
298 15955 1 0 Jun28 ? 00:04:00 memcached -d -p 11211 -u memcached -m 64 -c 1024 -P /var/run/memcached/memcached.pid
apache 16527 8867 0 Nov07 ? 00:05:48 /usr/sbin/httpd
root 17580 1 19 Nov03 ? 23:01:50 splunkd -p 8089 start
root 17592 17580 0 Nov03 ? 00:00:24 [splunkd pid=17580] splunkd -p 8089 start [process-runner]
rpc 19773 1 0 Sep26 ? 00:00:03 rpcbind -w
root 19914 1 0 Sep26 ? 00:01:27 /usr/libexec/postfix/master
postfix 19917 19914 0 Sep26 ? 00:00:52 qmgr -l -t fifo -u
root 19966 1 0 Sep26 ? 00:07:54 auditd
ntp 20029 1 0 Sep26 ? 00:03:04 ntpd -x -u ntp:ntp -p /var/run/ntpd.pid
root 20059 1 0 Sep26 ? 00:00:00 /usr/sbin/oddjobd -p /var/run/oddjobd.pid -t 300
root 20230 1 0 Sep26 ? 00:00:00 /sbin/portreserve
root 20274 1 0 Sep26 ? 00:00:03 /usr/sbin/atd
root 20579 1 0 Sep26 ? 00:00:13 /usr/sbin/abrtd
root 20599 1 0 Sep26 ? 00:03:03 abrt-dump-oops -d /var/spool/abrt -rwx /var/log/messages
root 23744 14541 0 Nov07 ? 00:00:00 sshd: nagios [priv]
nagios 23988 23744 0 Nov07 ? 00:00:00 sshd: nagios@pts/0
nagios 23989 23988 0 Nov07 pts/0 00:00:00 -bash
root 24214 1 0 Feb01 ? 20:56:37 /usr/local/tripwire/te/agent/bin/../sup/rtm/tesvc -port 1169
root 24285 1 0 Feb01 ? 02:33:03 ./wrapper ./agent.conf wrapper.pidfile=../tmp/teagent.pid wrapper.daemonize=TRUE
root 24290 24285 0 Feb01 ? 06:00:46 /usr/local/tripwire/te/agent/jre/bin/java -da -server -Dtw.server=false -

Djava.security.manager=com.tripwire.kernel.ext.security.TripwireSecurityManager -

Djava.security.properties=/usr/local/tripwire/te/agent/data/security/security.properties -Djava.se
root 25416 1 0 Oct27 ? 00:10:24 xinetd -stayalive -pidfile /var/run/xinetd.pid
root 27941 1 0 Jul12 ? 00:41:50 /usr/local/bin/python bin/carbon-cache.py --instance=a start
postgres 28611 1 0 Jun27 ? 00:01:23 /usr/bin/postmaster -p 5432 -D /var/lib/pgsql/data
postgres 28613 28611 0 Jun27 ? 00:03:15 postgres: logger process
postgres 28615 28611 0 Jun27 ? 00:18:32 postgres: writer process
postgres 28616 28611 0 Jun27 ? 00:16:09 postgres: wal writer process
postgres 28617 28611 0 Jun27 ? 00:05:16 postgres: autovacuum launcher process
postgres 28618 28611 0 Jun27 ? 00:05:04 postgres: stats collector process
root 29682 1 0 Oct06 ? 01:03:09 python /usr/bin/goferd
nagios 30569 1 0 Oct06 ? 00:00:00 /usr/local/nagios//bin/ndo2db -c /usr/local/nagios//etc/ndo2db.cfg
apache 31119 8867 0 Nov06 ? 00:06:31 /usr/sbin/httpd
nagios 31152 1 0 Oct06 ? 00:16:16 /usr/local/nagios/bin/npcd -d -f /usr/local/nagios/etc/pnp/npcd.cfg
root 31529 1 0 Oct06 ? 00:03:59 crond
root 31752 1 0 Oct20 ? 00:04:25 /sbin/rsyslogd -i /var/run/syslogd.pid -c 5

I tried to debug by giving these commands for check_disk in the nrpe.cfg but it still shows the same error

command[check_disk]=/usr/local/nagios/libexec/check_disk -w 80% -c 85% -p /opt/data
command[check_disk]=/usr/local/nagios/libexec/check_disk $ARG1$

Looking forward to hearing from you.

The NRPE agent runs from the xinetd daemon and it looks like it hasn't been restarted.
Whenever you edit the nrpe.cfg file, you need to restart xinetd to reload the changes.
Try running the following on the remote server Then test to see if the check_disk command works. You may have to edit the check_disk command to get the options to match up with the options in the XI server's command.