Go to main content

man pages section 1: User Commands

Exit Print View

Updated: Wednesday, February 9, 2022

snmpusm (1)


snmpusm - creates and maintains SNMPv3 users on a network entity


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


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
              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

       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  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
       until explicitly activated later via the activate command.

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

              snmpusm [COMMON OPTIONS] AGENT cloneFrom USER CLONEFROM-USER

       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

              snmpusm [COMMON OPTIONS] AGENT create USER CLONEFROM-USER

       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
              NEW-PASSPHRASE [USER]

       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
       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 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
              inherits that user's passphrase ("setup_passphrase").

   Change the user's passphrase
       snmpusm -v 3 -u wes -n "" -l  authNoPriv  -a  MD5  -A  setup_passphrase
       localhost 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
              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 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.

       See attributes(7) for descriptions of the following attributes:

       |ATTRIBUTE TYPE |        ATTRIBUTE VALUE          |
       |Availability   | system/management/snmp/net-snmp |
       |Stability      | Volatile                        |

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

       Source  code  for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-

       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source   was   downloaded  from   https://sourceforge.net/projects/net-

       Further information about this software can be found on the open source
       community website at http://www.net-snmp.org/.

V5.8                              11 Dec 2009                       SNMPUSM(1)