s9y testdrive

With at least OpenWRT 15.05, the NRPE package appears to be unmaintained. We could should build the package manually, but before we do this, let's install an older version from our backups. For example:

$ ( cd ../backup/router/ && find . -name "*nrpe*" -o -name "check_*" | xargs tar -cf - ) | \
    ssh router "tar -C / -xvf -"

This should restore the NRPE binary, its configuration files and init scripts and all the check_* monitoring plugins. Did I mention that backups are important? :-)
With that, we're almost there:

 $ ldd /usr/sbin/nrpe
        libssl.so.1.0.0 => not found
        libcrypto.so.1.0.0 => not found
        libwrap.so.0 => not found
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x77a64000)
        libc.so.0 => /lib/libc.so.0 (0x779f7000)
        ld-uClibc.so.0 => /lib/ld-uClibc.so.0 (0x77a88000)

Let's install the dependencies:

opkg install libopenssl libwrap

Add the nagios user:

echo 'nagios:x:50:' >> /etc/group
echo 'nagios:x:50:50:nagios:/var/run/nagios:/bin/false' >> /etc/passwd
echo 'nagios::16874:0:99999:7:::' >> /etc/shadow

Configure nrpe:

 $ grep ^[a-z] /etc/nrpe.cfg
 pid_file=/var/run/nrpe.pid
 server_port=5666
 server_address=192.168.0.1
 nrpe_user=nagios
 nrpe_group=nagios
 allowed_hosts=192.168.0.10,192.168.0.11
 dont_blame_nrpe=0
 debug=0
 command_timeout=60
 connection_timeout=300
 
 command[check_dummy]=/usr/libexec/nagios/check_dummy 0
 command[check_dns]=/usr/libexec/nagios/check_dns -H test.example.net -s localhost -w 0.1 -c 0.5
 command[check_entropy]=/root/bin/check_entropy.sh -w 1024 -c 512
 command[check_http]=/usr/libexec/nagios/check_http -H localhost -w 0.1 -c 0.5
 command[check_load]=/usr/libexec/nagios/check_load -w 4,3,2 -c 5,4,3
 command[check_ntp_time]=/usr/libexec/nagios/check_ntp_time -H 0.openwrt.pool.ntp.org -w 0.5 -c 1.0
 command[check_ssh]=/usr/libexec/nagios/check_ssh -4 router
 command[check_softwareupdate_opkg]=/root/bin/check_softwareupdate.sh opkg
 command[check_users]=/usr/libexec/nagios/check_users -w 3 -c 5

Let's try to start it, and enable it if it works:

 $ /etc/init.d/nrpe start
 $ ps | grep nrp[e]
 5320 nagios    2908 S    /usr/sbin/nrpe -c /etc/nrpe.cfg -d
 
 $ /etc/init.d/nrpe enable

And that's about it. Of course: since we're using an outdated NRPE version, we won't receive any (security) updates - so this setup should only be used in a trusted environment, i.e. not over the internet.