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ISBN : 978-2-7460-9712-4
EAN : 9782746097124
(Editions ENI)


CentOS 2.1AS







snmpusm - creates and maintains SNMPv3 user’s on a remote entity.


snmpusm [ common arguments ] create username [cloneFromUser]
snmpusm [ common arguments ] delete username
snmpusm [ common arguments ] cloneFrom username cloneFromUser
snmpusm [ common arguments ] passwd [-Co] [-Ca] [-Cx] old_passphrase new_passphrase


Snmpusm is an SNMP application that can be used to do simple maintenance on a SNMP agent’s User based Security Module (USM) table. You can create, delete, clone, and change the password of users configured on a running SNMP agent.

The SNMPv3 USM specifications (see RFC2574) dictate that users are created and maintained by adding and modifying rows to the usmUser MIB table. To create a new user you simply create the row using an snmpset. User’s profiles contain private keys that are never transmitted over the wire in clear text (regardless of whether the administration requests are in encrypted or not).

The secret key for a user is initially set by cloning another user in the table, so that a new user inherits the cloned user’s secret key. A user can only be cloned once, however, after which they must be deleted and re-created to be re-cloned. The authentication and privacy security types are also inherited during this cloning (E.G., MD5 vs SHA1). To change the secret key for a user, you must know the user’s old passphrase as well as the new one. The passwd sub-command of the snmpusm command, therefore, requires both the new and the old password to be supplied. After cloning from the appropriate template, you should immediately change the new users password.

The ucd-snmp agent must first be initialized so that at least one user is setup in it before you can use this command to clone new ones. See the snmpd.conf(5) manual page on the createUser configuration parameter.


Lets assume for our examples that the following VACM and USM configurations lines were in the snmpd.conf file for a ucd-snmp agent, which sets up a default user called "initial" with the passphrase "setup_password" so that we can perform the initial setup of an agent:

# VACM configuration entries
rwuser initial
# lets add the new user we’ll create too:
rwuser wes
# USM configuration entries
createUser initial MD5 setup_password DES

Note: that the "initial" user’s setup should be removed after creating a real user that you grant administrative privileges to (like the user "wes" we’ll be creating in this example.

Note: passwords (passphrases really) must be 8 characters minimum in length.
snmpusm -v 3 -u initial -n " -l authNoPriv -a MD5 -A setup_password
localhost create wes initial

Creates a new user, here named "wes" using the user "initial" to do it. "wes" is cloned from "initial" in the process, so he inherits that users password ("setup_password").

snmpusm -v 3 -u wes -n " -l authNoPriv -a MD5 -A setup_password
localhost passwd -setup_password new_passphrase

After creating the user "wes" with the same password as the "initial" user, we need to change his passphrase for him. The above command changed it from "setup_password", which was inherited from the initial user, to "new_passphrase".

snmpget -v 3 -u wes -n " -l authNoPriv -a MD5 -A new_passphrase
localhost sysUpTime.0

If the above commands were successful, this command should have properly performed an authenticated snmpv3 GET request to the agent.

Now, go remove the vacm "group" snmpd.conf entry for the "initial" user and you have a valid user ’wes’ that you can use for future transactions instead of initial.


snmpd.conf(5), snmp.conf(5)