Installing and Configuring Net-SNMP for Linux

The following sections describe how to install Net-SNMP on a Linux device and how to configure Net-SNMP:

Use the following menu options to navigate the SL1 user interface:

To view a pop-out list of menu options, click the menu icon ().
To view a page containing all of the menu options, click the Advanced menu icon ().

For detailed descriptions of Net-SNMP for each supported operating system, see http://www.net-snmp.org.

Installing Net-SNMP on Linux Devices

For each Linux device that you want to monitor with Net-SNMP, you must install and configure Net-SNMP. If you want to monitor multiple devices with Net-SNMP, you must install Net-SNMP and create the snmpd.conf file on each device to be monitored.

NOTE: Most Linux distributions will require the same installation and configuration as described in this section.

If Net-SNMP is correctly installed and configured on a Linux device, SL1 can automatically query the device and collect data. SL1 includes multiple default Dynamic Applications for the Net-SNMP agent. These Dynamic Applications allow SL1 to collect selected data-points from Net-SNMP devices. The data is then used to create reports and graphs, accessible via the graphical user-interface.

By querying Net-SNMP data-points, SL1 can collect and present at least the following about a device:

System name, operating system, operating system version, and uptime
File-system configuration and usage
Memory size and usage
CPU usage
Installed software
Running processes
Network interface details, including name, speed, and MAC address
Bandwidth usage

Installing and Configuring Net-SNMP on a Linux computer includes the following steps:

Verifying and Installing Net-SNMP using free RPM Packages.
Stopping snmpd.
Creating the snmpd.conf file. This file defines how the Net-SNMP agent will behave and includes information on the physical location and the contact information for the server, access control for the Net-SNMP agent, and trap destinations for the agent.
Starting snmpd and testing connectivity to Net-SNMP.

Step 1: Verifying and Installing Net-SNMP with RPM Packages

The operating system for SL1 ships with the following RPM packages for Net-SNMP:

net-snmp-5.7.2-24.silo.el7.x86_64
net-snmp-libs-5.7.2-24.silo.el7.x86_64
net-snmp-utils--5.7.2-24.silo.el7.x86_64

To continue with the steps in this section, you must verify the presence of these RPMs on the server that SL1 will monitor. To do this:

Open a shell session
Enter one of the following at the prompt:

rpm -qa | grep net-snmp

yum list net-snmp

Ensure that the output of this command includes each RPM listed above.

If one or more of these packages are missing you can run the appropriate command from the following commands:

yum install net-snmp

yum install net-snmp-libs

yum install net-snmp-utils

After you have verified and installed all the packages, you can create the net-snmp configuration file and start the snmp service (agent).

Step 2: Stopping snmpd

The Linux RPM for net-snmp includes the snmpd (Net-SNMP agent) binary as follows:

The snmpd binary is installed in the directory /usr/sbin/snmpd.
The configuration file for the snmpd agent is installed in /etc/snmp/snmpd.conf

NOTE: You should configure the snmpd.conf file before you start the snmpd daemon.

You must check if the snmpd agent is running. If it is, you must stop the snmpd agent so you can create the configuration file.

To check the snmpd agent and stop it (if necessary):

Open a shell session.

To see if the snmpd agent is running, enter the following at the prompt:

/etc/init.d/snmpd status

If snmpd is running, you will see a message like "snmpd is running".
If the snmpd agent is running, enter the following command to stop the agent:

/etc/init.d/snmpd stop

Step 3: Creating the snmpd.conf file

The snmpd.conf. file defines how the Net-SNMP daemon will behave and includes information about the physical location and contact information for the server, access control for the Net-SNMP agent, and trap destinations for the Net-SNMP agent.

In most cases, your computer(s) will already have an existing /etc/snmp/snmpd.conf file that includes the default settings. Because we want to create a new, clean snmpd.conf file, you must replace the existing file. You must move, not copy, the file, to ensure that you are creating a new file and not simply append new settings to the default settings in the snmpd.conf file. After stopping the snmpd agent, you must move the existing config file.

To move the existing configuration file, open a shell session and enter the following at the command line:

mv /etc/snmp/snmpd.conf /etc/snmp/snmpd.conf.orig

To create the/etc/snmp/snmpd.conf file:

You can replace your snmpd.conf file with one of the examples in the following sections. There is an example configuration file for Net-SNMP for SNMPv2 and another for SNMPv3 on Linux.
The example configuration files contain the basic settings that SL1 will need to communicate successfully with the Net-SNMP agent on the Linux server.
For basic compatibility, you should edit your file to include only the entries from the selected example.

NOTE: Net-SNMP is highly customizable, and SL1 can fully take advantage of these customizations. If you are interested in extending your Net-SNMP agent, please contact ScienceLogic Professional Services.

Example snmpd.conf file for SNMPv2:

The following is a working example of a snmpd.conf file for SNMPv2. You should edit your snmpd.conf file to include only the entries from this example file.

NOTE: This snmpd.conf file does not include encrypting SNMP access to the Linux client.

The file should be located in /etc/snmp/snmpd.conf:

# snmpd.conf

# - created by the snmpconf configuration program

##############################################################

# SECTION: System Information Setup

# This section defines some of the information reported in

# the "system" mib group in the mibII tree.

# syslocation: The [typically physical] location of the system.

# Note that setting this value here means that when trying to

# perform an snmp SET operation to the sysLocation.0 variable will make

# the agent return the "notWritable" error code. IE, including

# this token in the snmpd.conf file will disable write access to

# the variable.

# arguments: location_string

syslocation "Reston, Virginia"

# syscontact: The contact information for the administrator

# Note that setting this value here means that when trying to

# perform an snmp SET operation to the sysContact.0 variable will make

# the agent return the "notWritable" error code. IE, including

# this token in the snmpd.conf file will disable write access to

# the variable.

# arguments: contact_string

syscontact "ScienceLogic Support 1-703-354-1010”

##############################################################

# SECTION: Access Control Setup

# This section defines who is allowed to talk to your running

# snmp agent

# rocommunity: a SNMPv1/SNMPv2c read-only access community name

# arguments: community [default|hostname|network/bits] [oid]

rocommunity public

# rwcommunity: a SNMPv1/SNMPv2c read-write access community name

# arguments: community [default|hostname|network/bits] [oid]

# rwcommunity private

##############################################################

# SECTION: Trap Destinations

# Here we define who the agent will send traps to.

# trap2sink: A SNMPv2c trap receiver

# arguments: host [community] [portnum]

trap2sink 192.168.10.71 public

# End of File

NOTE: The example snmpd.conf file for SNMPv2 uses the default community string ("public") and ScienceLogic-specific examples of Contact and Location information and Trap Destinations. You will need to change these settings to match your local environment.

Adding Read/Write Access to the snmpd.conf File for SNMPv2

The example snmpd.conf file provides only Read Only access to your Linux system from SL1 (using the default "SNMP public" credential that is included in SL1). If you require SL1 to have Read/Write access to your Linux system, you will need to perform the following steps.

In the snmpd.conf file, uncomment the line for rwcommunity. To do this:

Change this line:

# rwcommunity private

To:

rwcommunity private

Save your changes and exit the file.

Example snmpd.conf file for SNMPv3:

The following is a working example of a snmpd.conf file for SNMPv3. For operation with SL1, you should edit your snmpd.conf file to include only entries from this example file.

This example snmpd.conf file includes read and write community strings and encrypts all Net-SNMP access to your Linux system from SL1.

The file should reside in /etc/snmp/snmpd.conf:

# snmpd.conf

# - created by the snmpconf configuration program

#################################################################

# SECTION: System Information Setup

# This section defines some of the information reported in

# the "system" mib group in the mibII tree.

# syslocation: The [typically physical] location of the system.

# Note that setting this value here means that when trying to

# perform an snmp SET operation to the sysLocation.0 variable will make

# the agent return the "notWritable" error code. IE, including

# this token in the snmpd.conf file will disable write access to

# the variable.

# arguments: location_string

syslocation "Reston, Virginia”

# syscontact: The contact information for the administrator

# Note that setting this value here means that when trying to

# perform an snmp SET operation to the sysContact.0 variable will make

# the agent return the "notWritable" error code. IE, including

# this token in the snmpd.conf file will disable write access to

# the variable.

# arguments: contact_string

syscontact "ScienceLogic Support: 1-703-354-1010"

#################################################################

# SECTION: Access Control Setup

# This section defines who is allowed to talk to your running

# snmp agent.

# rwuser: a SNMPv3 read-write user

# arguments: user [noauth|auth|priv] [restriction_oid]

rouser linuser priv

createUser linuser SHA linuserpass DES linprivpass

rwuser linadmin priv

createUser linadmin SHA linauthpass DES linprivpass

#################################################################

# SECTION: Trap Destinations

# Here we define who the agent will send traps to.

# trap2sink: A SNMPv2c trap receiver

# arguments: host [community] [portnum]

trap2sink 192.168.10.71 public

# End of File

NOTE: The example snmpd.conf file for SNMPv3 uses ScienceLogic-specific examples of Contact and Location information and Trap Destinations. You will need to change these settings to match your local environment. In SL1, you must create a Read-Only credential for SNMPv3 and a Read/Write credential for SNMPv3 that match the credentials specified in the snmpd.conf file.

Step 4: Starting snmpd and Testing connectivity to Net-SNMP

These sections describe how to start the snmpd agent and how to test connectivity to Net-SNMP.

If you use SNMPv2 and used the example snmpd.conf file for SNMPv2, follow the steps in the section on SNMPv2.
If you use SNMPv3 and used the example snmpd.conf file for SNMPv3, follow the steps in the section on SNMPv3.

Testing the Example snmpd.conf file for SNMPv2

Now that you have created the new snmpd.conf file for SNMPv2 on your Linux system, you can start the snmpd service (agent) and test that the new file is working. To do this:

You must first restart the snmpd agent. To do this, open a shell session and enter the following at the command prompt:

/etc/init.d/snmpd start

The snmpd agent should now start running.
To test the snmpd agent and the new configuration file, enter the following at the command prompt:

snmpwalk –v 2c –c public localhost system

You should see output similar to:

SNMPv2-MIB::sysDescr.0 = STRING: Linux ps-centos-lnx 2.6.18-92.el5 #1 SMP Tue Jun 10 18:49:47 EDT 2008 i686

SNMPv2-MIB::sysObjectID.0 = OID: NET-SNMP-MIB::netSnmpAgentOIDs.10

DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (437) 0:00:04.37

SNMPv2-MIB::sysContact.0 = STRING: "ScienceLogic Support 1-703-354-1010"

SNMPv2-MIB::sysName.0 = STRING: ps.centos-lnx

SNMPv2-MIB::sysLocation.0 = STRING: "Reston, Virginia"

SNMPv2-MIB::sysORLastChange.0 = Timeticks: (0) 0:00:00.00

SNMPv2-MIB::sysORID.1 = OID: SNMPv2-MIB::snmpMIB

SNMPv2-MIB::sysORID.2 = OID: TCP-MIB::tcpMIB

SNMPv2-MIB::sysORID.3 = OID: IP-MIB::ip

SNMPv2-MIB::sysORID.4 = OID: UDP-MIB::udpMIB

SNMPv2-MIB::sysORID.5 = OID: SNMP-VIEW-BASED-ACM-MIB::vacmBasicGroup

SNMPv2-MIB::sysORID.6 = OID: SNMP-FRAMEWORK-MIB::snmpFrameworkMIBCompliance

SNMPv2-MIB::sysORID.7 = OID: SNMP-MPD-MIB::snmpMPDCompliance

SNMPv2-MIB::sysORID.8 = OID: SNMP-USER-BASED-SM-MIB::usmMIBCompliance

SNMPv2-MIB::sysORDescr.1 = STRING: The MIB module for SNMPv2 entities

SNMPv2-MIB::sysORDescr.2 = STRING: The MIB module for managing TCP implementations

SNMPv2-MIB::sysORDescr.3 = STRING: The MIB module for managing IP and ICMP implementations

SNMPv2-MIB::sysORDescr.4 = STRING: The MIB module for managing UDP implementations

SNMPv2-MIB::sysORDescr.5 = STRING: View-based Access Control Model for SNMP.

SNMPv2-MIB::sysORDescr.6 = STRING: The SNMP Management Architecture MIB.

SNMPv2-MIB::sysORDescr.7 = STRING: The MIB for Message Processing and Dispatching.

SNMPv2-MIB::sysORDescr.8 = STRING: The management information definitions for the SNMP User-based Security Model.

SNMPv2-MIB::sysORUpTime.1 = Timeticks: (0) 0:00:00.00

SNMPv2-MIB::sysORUpTime.2 = Timeticks: (0) 0:00:00.00

SNMPv2-MIB::sysORUpTime.3 = Timeticks: (0) 0:00:00.00

SNMPv2-MIB::sysORUpTime.4 = Timeticks: (0) 0:00:00.00

SNMPv2-MIB::sysORUpTime.5 = Timeticks: (0) 0:00:00.00

SNMPv2-MIB::sysORUpTime.6 = Timeticks: (0) 0:00:00.00

SNMPv2-MIB::sysORUpTime.7 = Timeticks: (0) 0:00:00.00

SNMPv2-MIB::sysORUpTime.8 = Timeticks: (0) 0:00:00.00

Testing the Example snmpd.conf file for SNMPv3

Now that you have created the new snmpd.conf file for SNMPv3 on your Linux system, you can start the snmpd service (agent) and test that the new file is working. To do this:

You must first restart the snmpd agent. To do this, open a shell session and enter the following at the command prompt:

/etc/init.d/snmpd start

The snmpd agent should now start running.
To test the snmpd agent and the new configuration file, enter the following at the command prompt. We are using the credentials from the example snmpd.conf file for SNMPv3 (linuser, linuserpass, and linprivpass); if you used different credentials, please substitute them in the command:

snmpwalk -v 3 -u linuser -l authPriv -a SHA -A linuserpass -x DES -X linprivpass localhost system

You should see output similar to:

SNMPv2-MIB::sysDescr.0 = STRING: Linux ps-centos-lnx 2.6.18-92.el5 #1 SMP Tue Jun 10 18:49:47 EDT 2008 i686

SNMPv2-MIB::sysObjectID.0 = OID: NET-SNMP-MIB::netSnmpAgentOIDs.10

DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (327207) 0:54:32.07

SNMPv2-MIB::sysContact.0 = STRING: "ScienceLogic Support 1-703-354-1010"

SNMPv2-MIB::sysName.0 = STRING: ps-centos-lnx