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# Snmpd

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SNMP is a standard Internet protocol (RFC 1157) designed for the management and monitoring of network devices. Arch Linux offers Net-SNMP, among other `SNMP` implementations. This article discusses configuration and testing of the `snmpd` daemon which is part of the net-snmp package.

## Installation

There is a single package for net-snmp in Arch Linux which contains both the snmpd daemon, and the accompanying utilities.

Install the net-snmp package.

## Configuration

Note: If `/var/net-snmp/snmpd.conf` is modified while snmpd is running, any changes will be lost when the daemon is restarted. It is therefore crucial that the snmpd service is stopped while editing the configuration file.

### SNMP 1 and 2c

There are three versions of SNMP which are supported by net-snmp: 1, 2c and 3. Versions 1 and 2c start with the same basic configuration, using `/etc/snmp/snmpd.conf`.

    # mkdir /etc/snmp/
    # echo rocommunity read_only_community_string >> /etc/snmp/snmpd.conf

The above commands will add a community string that can be used for monitoring. Optionally, you can add another community string used for management. This is not recommended unless you have a specific reason to do so.

    # echo rwcommunity read_write_community_string >> /etc/snmp/snmpd.conf

### SNMP 3

SNMP v3 adds security and encrypted authentication/communication. It uses a different configuration scheme in `/etc/snmp/snmpd.conf` and additional configuration in `/var/net-snmp/snmpd.conf`.

For the former configuration file in `/etc/`, write directly to it or use the snmpconf wizard:

    # mkdir /etc/snmp/
    # echo rouser read_only_user >> /etc/snmp/snmpd.conf

    $ snmpconf -g basic_setup

For the latter configuration file in `/var/`, write directly to it or use net-snmp-create-v3-user:

    # mkdir -p /var/net-snmp/
    # echo createUser read_only_user SHA password1 AES password2 > /var/net-snmp/snmpd.conf

    # net-snmp-create-v3-user -ro -a SHA -x AES

Note that once snmpd is (re)started, `/var/net-snmp/snmpd.conf` will be rewritten, and the clear-text passwords that you have entered will be encrypted.

### Daemon

Start/enable `snmpd.service`.

## Testing

If using SNMP 1 or 2c, use one of the following commands to test configuration:

    # snmpwalk -v 1 -c read_only_community_string localhost | less
    # snmpwalk -v 2c -c read_only_community_string localhost | less

If using SNMP 3, use the following command to test configuration:

    # snmpwalk -v 3 -u read_only_user -a SHA -A password1 -x AES -X password2 -l authNoPriv localhost | less

Either way, you should see several lines of data looking something like:

    SNMPv2-MIB::sysDescr.0 = STRING: Linux myhost 2.6.37-ARCH #1 SMP PREEMPT Sat Jan 29 20:00:33 CET 2011 x86_64
    SNMPv2-MIB::sysObjectID.0 = OID: ccitt.1
    DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (307772) 0:51:17.72
    SNMPv2-MIB::sysContact.0 = STRING: root@localhost
    SNMPv2-MIB::sysName.0 = STRING: myhost
    ...SNIP...

Category:

- Network monitoring