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CentOS 7.0 - man page for snmpusm (centos section 1)

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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> -Ck AGENT passwd OLD-KEY-OR-PASSPHRASE NEW-KEY-OR-
       snmpusm [COMMON OPTIONS] [-Ca] [-Cx] AGENT changekey [USER]

       snmpusm is an SNMP application that can be used to do  simple  maintenance  on  the  users
       known  to  an SNMP agent, by manipulating the agent's User-based Security Module (USM) ta-
       ble.  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  usmUserTable.   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 STRING.

       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 option (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 authentication 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  created via the createAndWait operation instead by using the -Ca flag.  This will pre-
       vent the user from being marked as active in any agent until  explicitly  activated  later
       via the activate command.

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


       The USER entry then inherits the same authentication and privacy settings (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 unex-
       pected) behaviour 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 recre-
       ate 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 necessary to specify the user's old passphrase as well as the
       new one.  This uses the command


       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 authentica-
       tion 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  com-
       mand to work.  The resulting keys are printed to the console and may be then set in future
       command invocations using the --defAuthLocalizedKey and --defPrivLocalizedKey  options  or
       in your snmp.conf file using the defAuthLocalizedKey and defPrivLocalizedKey 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

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

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

       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 configurations lines were in
       the  snmpd.conf file for a Net-SNMP agent.  These lines set up a default user called "ini-
       tial" 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

	      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 user's passphrase  ("set-

   Change the user's passphrase
       snmpusm	-v  3 -u wes -n "" -l authNoPriv -a MD5 -A setup_passphrase localhost passwd set-
       up_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 "set-
	      up_passphrase", which was inherited from the initial user, to "new_passphrase".

   Test the new user
       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.

       Manipulating the usmUserTable using this command can only be done using SNMPv3.	This com-
       mand  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

V5.7.2					   11 Dec 2009				       SNMPUSM(1)

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