Manually install net-snmpd on Gentoo

Recently we’ve moved from an aged Opsview instance to Zabbix for our system health monitoring, which in turn facilitated moving data collector agents from Nagios to snmp.

Many of our PBX’s were deployed from the vendors ISO and so run atop of Gentoo, and it has a couple of issues:

  1. We’ve been told not to “emerge” anything by the vendor, as the base OS on the image is not maintained.
  2. Portage (Gentoo’s package manager) has fallen out of date, meaning even if emerge is attempted, it’ll fail as all repository links are broke.

If faced with the same issue, this is how to install net-snmpd from source, add it a startup service and be able to monitor via snmp…

Installation

On the Gentoo box, move to your home directory

cd ~

Download the source .tar.gz file

wget https://sourceforge.net/projects/net-snmp/files/net-snmp/5.9.4/net-snmp-5.9.4.tar.gz

Visit http://www.net-snmp.org/download.html for the latest version. When I was downloading SourceForge’s SSL cert had expired, if this happens add –no-check-certificate after wget in the command above.

Untar the file to your home directory, and change into it

tar -xzvf net-snmp-5.9.4.tar.gz
cd net-snmp-5.9.4

Run the configuration script

./configure

This allows you to set snmp version, file installation locations and snmp details, with exception of snmp version these can be left as default (Hit enter at the prompt). snmp details will look like this if left default…

Compile and install snmpd

make
make install

The make process is quite CPU intensive, may want to do this during a quiet period for the server.

Some libraries are not where they need to be, namely:
libnetsnmpagent.so.40
libnetsnmpmibs.so.40
libnetsnmp.so.40

Find where they were installed

find / -name libnetsnmpagent.so.40

Pick the result that is not in your current working folder (the install setup) and link it to /usr/lib

ln -s /usr/local/lib64/libnetsnmpagent.so.40 /usr/lib/

Repeat this process with the other two files

ln -s /usr/local/lib64/libnetsnmpmibs.so.40 /usr/lib/
ln -s /usr/local/lib64/libnetsnmp.so.40 /usr/lib/

Now can test to see if snmpd can run

snmpd -v

Configuration

Create a configuration file, the “snmpconf” command can be used but I found it easier to create from scratch

nano /usr/local/share/snmp/snmpd.conf

For my needs, only this line is needed

rocommunity {community} {ip address}

Save and exit the editor.

Testing

If you’d like to test your configuration, run snmpd

snmpd

Test on the snmp target machine, for quick results snmpwalk can be run

snmpwalk -c {community} -v 2c {ip address}

When run, snmpd automatically switches to a background process. To stop the process ID needs to be found and killed

ps aux | grep snmpd

Here the process ID (PID) is 5716, use this with the kill command

kill -9 {PID}

Add Service

Create the new service file

nano /etc/init.d/snmpd

Paste the following

#!/sbin/openrc-run
 
depend() {
    after modules
}
 
start() {
    ebegin "Starting snmpd"
    start-stop-daemon --background --start --exec /usr/local/sbin/snmpd --pidfile /var/run/snmpd.pid \
    -- -p /var/run/snmpd.pid -c /usr/local/share/snmp/snmpd.conf
    eend $?
}
 
stop() {
    ebegin "Stopping snmpd"
    start-stop-daemon --stop --exec /usr/local/sbin/snmpd \
    --pidfile /var/run/snmpd.pid
    eend $?
}
restart() {
    ebegin "Restarting snmpd"
    start-stop-daemon --stop --exec /usr/local/sbin/snmpd
    start-stop-daemon --background --start --exec /usr/local/sbin/snmpd --pidfile /var/run/snmpd.pid \
    -- -p /var/run/snmpd.pid -c /usr/local/share/snmp/snmpd.conf
    eend $?
}

Save and exit the text editor, then make the file executable

chmod +x /etc/init.d/snmpd

Start the service, and check its running

/etc/init.d/snmpd start

/etc/init.d/snmpd status

Finally, to make snmpd start with the system, run

rc-update add snmpd default

References

Help Creating init.d file

https://big-elephants.com/2013-01/writing-your-own-init-scripts/
https://tecadmin.net/startup-shutdown-script-on-gentoo/

Experienced issue where the process-id in the PID file was not matching the PID of process. With help of below found flag for snmpd to specify PID file, and match that to init.d

https://forums.gentoo.org/viewtopic-t-886230-start-0.html