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SNMPUSM(1)			   Net-SNMP			    SNMPUSM(1)

       snmpusm - creates and maintains SNMPv3 users on a network entity

       snmpusm [COMMON OPTIONS]	[-Cw] AGENT create USER	[CLONEFROM-USER]
       snmpusm [COMMON OPTIONS]	AGENT delete USER
       snmpusm	[COMMON	 OPTIONS] [-Ca]	[-Cx] AGENT passwd OLD-PASSPHRASE NEW-
       snmpusm [COMMON OPTIONS]	<-Ca  |	 -Cx>  -Ck  AGENT  passwd  OLD-KEY-OR-
       snmpusm [COMMON OPTIONS]	[-Ca] [-Cx] AGENT changekey [USER]

       snmpusm	is  an	SNMP application that can be used to do	simple mainte-
       nance on	the users known	to an SNMP agent, by manipulating the  agent's
       User-based Security Module (USM)	table.	The user needs write access to
       the usmUserTable	MIB table.  This tool can be used to  create,  delete,
       clone,  and change the passphrase of users configured on	a running SNMP

       Common options for all snmpusm commands:

       -CE ENGINE-ID
	      Set usmUserEngineID to be	used as	part of	the index of  the  us-
	      mUserTable.   Default  is	to use the contextEngineID (set	via -E
	      or probed) as the	usmUserEngineID.

       -Cp STRING
	      Set the usmUserPublic value of the (new) user to	the  specified

       Options for the passwd and changekey commands:

       -Ca    Change the authentication	key.

       -Cx    Change the privacy key.

       -Ck    Allows  one to use localized key (must start with	0x) instead of
	      passphrase.  When	this option is used, either the	-Ca or -Cx op-
	      tion (but	not both) must also be used.

       An unauthenticated SNMPv3 user can be created using the command

	      snmpusm [COMMON OPTIONS] AGENT create USER

       This  constructs	 an  (inactive)	entry in the usmUserTable, with	no au-
       thentication or privacy settings.  In principle,	this  user  should  be
       useable for 'noAuthNoPriv' requests, but	in practise the	Net-SNMP agent
       will not	allow such an entry to be made active.	The user can  be  cre-
       ated  via  the  createAndWait  operation	instead	by using the -Ca flag.
       This will prevent the user from being marked as active in any agent un-
       til explicitly activated	later via the activate command.

       In order	to activate this entry,	it is necessary	to "clone" an existing
       user, using the command


       The USER	entry then inherits the	same authentication and	 privacy  set-
       tings (including	pass phrases) as the CLONEFROM user.

       These two steps can be combined into one, by using the command


       The  two	 forms	of  the	create sub-command require that	the user being
       created does not	already	exist.	 The  cloneFrom	 sub-command  requires
       that the	user being cloned to does already exist.

       Cloning	is  the	 only  way to specify which authentication and privacy
       protocols to use	for a given user, and it is only possible to  do  this
       once.  Subsequent attempts to reclone onto the same user	will appear to
       succeed,	but will be silently ignored.  This (somewhat unexpected)  be-
       haviour	is  mandated  by the SNMPv3 USM	specifications (RFC 3414).  To
       change the authentication and privacy settings for a given user,	it  is
       necessary to delete and recreate	the user entry.	 This is not necessary
       for simply changing the pass phrases (see below).  This means that  the
       agent  must  be initialized with	at least one user for each combination
       of authentication and privacy protocols.	 See the snmpd.conf(5)	manual
       page for	details	of the createUser configuration	directive.

       A user can be deleted from the usmUserTable using the command

	      snmpusm [COMMON OPTIONS] AGENT delete USER

       User  profiles contain private keys that	are never transmitted over the
       wire in clear text (regardless of whether the  administration  requests
       are encrypted or	not).  To change the secret key	for a user, it is nec-
       essary to specify the user's old	passphrase as well  as	the  new  one.
       This uses the command

	      snmpusm [COMMON OPTIONS] [-Ca] [-Cx] AGENT passwd	OLD-PASSPHRASE

       After cloning a new user	 entry	from  the  appropriate	template,  you
       should immediately change the new user's	passphrase.

       If  USER	 is  not specified, this command will change the passphrase of
       the (SNMPv3) user issuing the command.  If the -Ca or -Cx  options  are
       specified,  then	 only  the authentication or privacy keys are changed.
       If these	options	are not	specified, then	both  the  authentication  and
       privacy keys are	changed.

	      snmpusm [COMMON OPTIONS] [-Ca] [-Cx] AGENT changekey [USER]

       This command changes the	key in a perfect-forward-secrecy compliant way
       through a diffie-helman exchange.  The remote agent  must  support  the
       SNMP-USM-DH-OBJECTS-MIB	for  this command to work.  The	resulting keys
       are printed to the console and may be then set in future	command	 invo-
       cations	using  the --defAuthLocalizedKey and --defPrivLocalizedKey op-
       tions or	in your	snmp.conf file using the defAuthLocalizedKey and  def-
       PrivLocalizedKey	keywords.

       Note  that  since  these	 keys are randomly generated based on a	diffie
       helman exchange,	they are no longer derived from	a  more	 easily	 typed
       password.  They are, however, much more secure.

       To  change from a localized key back to a password, the following vari-
       ant of the passwd sub-command is	used:

	      snmpusm [COMMON OPTIONS] <-Ca | -Cx> -Ck AGENT  passwd  OLD-KEY-

       Either  the  -Ca	 or the	-Cx option must	be specified.  The OLD-KEY-OR-
       PASSPHRASE and/or  NEW-KEY-OR-PASSPHRASE	 arguments  can	 either	 be  a
       passphrase  or  a localized key starting	with "0x", e.g.	as printed out
       by the changekey	sub-command.

       Note that snmpusm REQUIRES  an argument specifying the agent  to	 query
       as described in the .I snmpcmd(1) manual	page.

       Let's  assume for our examples that the following VACM and USM configu-
       rations lines were in the snmpd.conf file for a Net-SNMP	agent.	 These
       lines  set  up  a default user called "initial" with the	authentication
       passphrase "setup_passphrase" 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_passphrase DES

       Note:  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: passphrases must be 8 characters minimum in length.

   Create a new	user
       snmpusm	-v3  -u	initial	-n "" -l authNoPriv -a MD5 -A setup_passphrase
       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 in-
	      herits that user's passphrase ("setup_passphrase").

   Change the user's passphrase
       snmpusm -v 3 -u wes -n "" -l authNoPriv -a MD5 -A setup_passphrase  lo-
       calhost passwd setup_passphrase new_passphrase

	      After  creating  the  user "wes" with the	same passphrase	as the
	      "initial"	user, we need to change	his passphrase for  him.   The
	      above  command changes it	from "setup_passphrase", which was in-
	      herited from the initial user, to	"new_passphrase".

   Test	the new	user
       snmpget -v 3 -u wes -n "" -l authNoPriv -a MD5 -A new_passphrase	local-
       host sysUpTime.0

	      If  the above commands were successful, this command should have
	      properly performed an authenticated SNMPv3 GET  request  to  the

       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  transac-
       tions instead of	initial.

       Manipulating the	usmUserTable using this	command	can only be done using
       SNMPv3.	This command will not work with	the community-based  versions,
       even if they have write access to the table.

       snmpd.conf(5), snmp.conf(5), RFC	3414

V5.7.3				  11 Dec 2009			    SNMPUSM(1)


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