Tag Archives: snmpd

Setup SNMP v3 on Debian or Ubuntu

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All the following commands should work on Ubuntu, or just about any other Debian based Linux distro.  If you have a firewall on the server, you’ll need to allow UDP on port 161.

Install SNMP

Install snmp, snmpd, and libsnmp.

sudo apt-get -y install snmp snmpd libsnmp-dev

Stop the snmpd service so we can add a user

sudo service snmpd stop

Add SNMP v3 user

  • Change AuthPassword to your Authentication password
  • Change CryptoPassword to your Crypto Password
  • Change privUser to your private users username
sudo net-snmp-config --create-snmpv3-user -ro -A AuthPassword -X CryptoPassword -a MD5 -x AES privUser

Change System Location, System Contact, and allow SNMP on all interfaces

Open up the SNMP config file usually in /etc/snmp/snmpd.conf

vi /etc/snmp/snmpd.conf

Search for “sysLocation”  and change to whatever your system location is.

Search for “sysContact” and change it.  It should be right underneath sysLocation.

Now allow SNMP on all interfaces.  Find the following line and comment it out.

agentAddress udp:127.0.0.1:161

Add a # to the beginning.

#agentAddress udp:127.0.0.1:161

Now find this line (should be a couple lines down from the line you just commented out)

#agentAddress udp:161,udp6:[::1]:161

and uncomment it

agentAddress udp:161,udp6:[::1]:161

That will enable it so you can read the SNMP info using the servers IP address, as opposed to being limited to localhost.

Start the SNMP service and Test

Start the SNMP service

service snmpd start

Test with

snmpwalk -v3 -a MD5 -A AuthPassword -X CryptoPassword -l authNoPriv -u privUser localhost

 

Setting up SNMP V3 on CentOS

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Install SNMP.

yum install net-snmp net-snmp-utils

Configure the SNMP V3 user by running the following command and then following the prompts it gives you.

net-snmp-create-v3-user

Example: The username is “snmpadmin” and the password is”r123456″

[root@localhost ~]# net-snmp-create-v3-user
Enter a SNMPv3 user name to create:
snmpadmin
Enter authentication pass-phrase:
r123456
Enter encryption pass-phrase:
  [press return to reuse the authentication pass-phrase]

adding the following line to /var/lib/net-snmp/snmpd.conf:
   createUser snmpadmin MD5 "r123456" DES
adding the following line to /etc/snmp/snmpd.conf:
   rwuser snmpadmin
[root@localhost ~]#

Change the syslocation and syscontact in the /etc/snmp/snmpd.conf file.

vi /etc/snmp/snmpd.conf

Start snmpd service

service snmpd start

Configure snmp to start on system boot.

chkconfig snmpd on

Test and make sure snmp is working

replace “password” and “username” with the ones you setup when you created the SNMP V3 user.

snmpwalk -v3 -a MD5 -A password -x DES -X password -l authPriv -u privuser localhost

If you receive something like “snmpwalk: Timeout” then something is not working correctly.  Check to make sure the service is started, and make sure that your firewall is not blocking SNMP.

If you are running a firewall, run the following commands to allow it through.

firewall-cmd --zone=public --add-port=161/udp --permanent
semanage port -a -t snmp_port_t -p udp 161
firewall-cmd --reload

On iptables you should be able to do

 iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 161 -j ACCEPT

or add it to /etc/sysconfig/iptables and then restart iptables

SNMP and Shell Script

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First you will need to make sure SNMP is installed.

apt-get install snmpd snmp snmp-mibs-downloader

You’ll need to configure a new snmpd.conf file with

snmpconf

Run through the steps and when your done replace your current snmpd.conf file in /etc/snmp/ with the new one.

Now open up your new snmpd.conf file

vi /etc/snmp/snmpd.conf

and add the following to the bottom of the file.

extend myshscript /path/to/your.sh

Save and close the file and restart the snmpd service.

service snmpd restart

Now we need to find the OID of our new data point.  Do this by running

snmpwalk -v2c -c public localhost .1.3.6.1.4.1.8072.1.3.2

It should display something similar to the following.

root@localhost:/etc/snmp# snmpwalk -v2c -c public localhost .1.3.6.1.4.1.8072.1.3.2
iso.3.6.1.4.1.8072.1.3.2.1.0 = INTEGER: 1
iso.3.6.1.4.1.8072.1.3.2.2.1.2.4.118.111.108.116 = STRING: "/etc/snmp/volt.sh"
iso.3.6.1.4.1.8072.1.3.2.3.1.4.4.118.111.108.116 = INTEGER: 0
iso.3.6.1.4.1.8072.1.3.2.4.1.2.4.118.111.108.116.1 = STRING: "14.3"
root@localhost:/etc/snmp#

The OID we are interested in is the one on the last line.  If you run a snmpwalk command with the OID you should get your data point.

root@localhost:/etc/snmp# snmpwalk -v2c -c public localhost 1.3.6.1.4.1.8072.1.3.2.4.1.2.4.118.111.108.116.1
iso.3.6.1.4.1.8072.1.3.2.4.1.2.4.118.111.108.116.1 = STRING: "14.3"
root@localhost:/etc/snmp#

All that’s left is to add the OID to your SNMP monitor.  If You run into issues with your SNMP server not monitoring the OID, you might need do what I did in the above command, replace the beginning of the OID “iso.” with a “1”.