Provided by: snmpd_5.4.2.1~dfsg0ubuntu1-0ubuntu2_i386 bug

NAME

       snmpd.conf - configuration file for the Net-SNMP SNMP agent

DESCRIPTION

       The  Net-SNMP agent uses one or more configuration files to control its
       operation  and  the  management  information  provided.   These   files
       (snmpd.conf  and  snmpd.local.conf)  can  be  located in one of several
       locations, as described in the snmp_config(5) manual page.

       The (perl) application snmpconf can be used to  generate  configuration
       files  for  the  most  common  agent requirements.  See the snmpconf(1)
       manual page for more information, or try running the command:

              snmpconf -g basic_setup

       There are a large number of directives that can be specified, but these
       mostly fall into four distinct categories:

       ·      those controlling who can access the agent

       ·      those configuring the information that is supplied by the agent

       ·      those controlling active monitoring of the local system

       ·      those concerned with extending the functionality of the agent.

       Some directives don’t fall naturally into any of these four categories,
       but this covers the majority of the contents of  a  typical  snmpd.conf
       file.   A full list of recognised directives can be obtained by running
       the command:

              snmpd -H

AGENT BEHAVIOUR

       Although most configuration  directives  are  concerned  with  the  MIB
       information  supplied  by  the agent, there are a handful of directives
       that control the behaviour of  snmpd  considered  simply  as  a  daemon
       providing a network service.

       agentaddress [<transport-specifier>:]<transport-address>[,...]
              defines  a  list  of  listening  addresses,  on which to receive
              incoming SNMP requests.  See the section LISTENING ADDRESSES  in
              the  snmpd(8)  manual page for more information about the format
              of listening addresses.

              The default behaviour is to listen on UDP port 161 on  all  IPv4
              interfaces.

       agentgroup {GROUP|#GID}
              changes  to  the  specified  group  after  opening the listening
              port(s).  This may refer to  a  group  by  name  (GROUP),  or  a
              numeric group ID starting with ’#’ (#GID).

       agentuser {USER|#UID}
              changes  to  the  specified  user  after  opening  the listening
              port(s).  This may refer to a user by name (USER), or a  numeric
              user ID starting with ’#’ (#UID).

       leave_pidfile yes
              instructs  the  agent  to  not  remove its pid file on shutdown.
              Equivalent to specifying "-U" on the command line.

       maxGetbulkRepeats NUM
              Sets the maximum  number  of  responses  allowed  for  a  single
              variable  in  a getbulk request.  Set to 0 to enable the default
              and set it  to  -1  to  enable  unlimited.   Because  memory  is
              allocated  ahead  of  time,  sitting  this  to  unlimited is not
              considered safe if your user population can not be  trusted.   A
              repeat number greater than this will be truncated to this value.

              This is set by default to -1.

       maxGetbulkResponses NUM
              Sets the maximum number  of  responses  allowed  for  a  getbulk
              request.  This is set by default to 100.  Set to 0 to enable the
              default and set it to -1 to enable unlimited.  Because memory is
              allocated  ahead  of  time,  sitting  this  to  unlimited is not
              considered safe if your user population can not be trusted.

              In general, the total number of responses will not be allowed to
              exceed  the  maxGetbulkResponses  number  and  the  total number
              returned will be an integer multiple of the number of  variables
              requested  times  the  calculated number of repeats allow to fit
              below this number.

              Also not that processing of maxGetbulkRepeats is handled  first.

   SNMPv3 Configuration
       SNMPv3  requires  an SNMP agent to define a unique "engine ID" in order
       to respond to SNMPv3 requests.  This ID  will  normally  be  determined
       automatically,   using   two  reasonably  non-predictable  values  -  a
       (pseudo-)random number and the current uptime in seconds. This  is  the
       recommended  approach.  However  the  capacity  exists  to  define  the
       engineID in other ways:

       engineID STRING
              specifies that the engineID should be built from the given  text
              STRING.

       engineIDType 1|2|3
              specifies  that  the  engineID  should  be  built  from the IPv4
              address (1), IPv6 address (2) or MAC  address  (3).   Note  that
              changing  the  IP  address  (or  switching the network interface
              card) may cause problems.

       engineIDNic INTERFACE
              defines which interface to use when determining the MAC address.
              If  engineIDType  3 is not specified, then this directive has no
              effect.

              The default is to use eth0.

ACCESS CONTROL

       snmpd supports the View-Based Access Control Model (VACM) as defined in
       RFC  2575,  to control who can retrieve or update information.  To this
       end, it recognizes  various  directives  relating  to  access  control.
       These fall into four basic groups.

   SNMPv3 Users
       createUser  [-e  ENGINEID]  username (MD5|SHA) authpassphrase [DES|AES]
       [privpassphrase]

              MD5  and  SHA  are the authentication types to use.  DES and AES
              are the privacy protocols to use.  If the privacy passphrase  is
              not   specified,   it   is   assumed  to  be  the  same  as  the
              authentication passphrase.  Note that the users created will  be
              useless  unless  they  are also added to the VACM access control
              tables described above.

              SHA authentication and DES/AES privacy  require  OpenSSL  to  be
              installed  and  the agent to be built with OpenSSL support.  MD5
              authentication may be used without OpenSSL.

              Warning: the minimum pass phrase length is 8 characters.

              SNMPv3 users can be created  at  runtime  using  the  snmpusm(1)
              command.

              Instead  of  figuring out how to use this directive and where to
              put  it  (see  below),  just  run   "net-snmp-config   --create-
              snmpv3-user"  instead,  which will add one of these lines to the
              right place.

              This     directive     should     be     placed     into     the
              /var/lib/snmp/snmpd.conf   file  instead  of  the  other  normal
              locations.  The reason is that the information is read from  the
              file  and  then  the line is removed (eliminating the storage of
              the master password for that user) and  replaced  with  the  key
              that  is  derived from it.  This key is a localized key, so that
              if it is stolen it can not be used to access other  agents.   If
              the password is stolen, however, it can be.

              If  you need to localize the user to a particular EngineID (this
              is useful mostly in the similar snmptrapd.conf  file),  you  can
              use  the  -e argument to specify an EngineID as a hex value (EG,
              "0x01020304").

              If you want to generate either your  master  or  localized  keys
              directly, replace the given password with a hexstring (preceeded
              by a "0x") and precede the hex  string  by  a  -m  or  -l  token
              (respectively).  EGs:

              [these keys are *not* secure but are easy to visually parse for
              counting purposes.  Please generate random keys instead of using
              these examples]

              createUser myuser SHA -l 0x0001020304050607080900010203040506070809 AES -l 0x00010203040506070809000102030405
              createUser myuser SHA -m 0x0001020304050607080900010203040506070809 AES -m 0x0001020304050607080900010203040506070809

              Due  to the way localization happens, localized privacy keys are
              expected to be the length needed by the algorithm (128 bits  for
              all supported algorithms).  Master encryption keys, though, need
              to be the length required by the  authentication  algorithm  not
              the  length required by the encrypting algorithm (MD5: 16 bytes,
              SHA: 20 bytes).

   Traditional Access Control
       Most simple access control requirements  can  be  specified  using  the
       directives  rouser/rwuser  (for SNMPv3) or rocommunity/rwcommunity (for
       SNMPv1 or SNMPv2c).

       rouser USER [noauth|auth|priv [OID | -V VIEW [CONTEXT]]]

       rwuser USER [noauth|auth|priv [OID | -V VIEW [CONTEXT]]]
              specify an SNMPv3 user that will be allowed read-only  (GET  and
              GETNEXT)   or   read-write   (GET,   GETNEXT   and  SET)  access
              respectively.  By default, this will provide access to the  full
              OID   tree   for   authenticated  (including  encrypted)  SNMPv3
              requests, using the default  context.   An  alternative  minimum
              security   level   can  be  specified  using  noauth  (to  allow
              unauthenticated  requests),  or  priv   (to   enforce   use   of
              encryption).   The  OID  field restricts access for that user to
              the subtree rooted at the given OID,  or  the  named  view.   An
              optional  context can also be specified, or "context*" to denote
              a context prefix.  If no context  field  is  specified  (or  the
              token  "*"  is  used),  the  directive  will  match all possible
              contexts.

       rocommunity COMMUNITY [SOURCE [OID | -V VIEW [CONTEXT]]]

       rwcommunity COMMUNITY [SOURCE [OID | -V VIEW [CONTEXT]]]
              specify an SNMPv1 or SNMPv2c  community  that  will  be  allowed
              read-only (GET and GETNEXT) or read-write (GET, GETNEXT and SET)
              access respectively.  By default, this will  provide  access  to
              the  full  OID  tree for such requests, regardless of where they
              were sent from. The SOURCE token can be used to restrict  access
              to  requests  from the specified system(s) - see com2sec for the
              full details.  The OID field restricts access for that community
              to the subtree rooted at the given OID, or named view.  Contexts
              are typically less relevant to  community-based  SNMP  versions,
              but the same behaviour applies here.

       rocommunity6 COMMUNITY [SOURCE [OID | -V VIEW [CONTEXT]]]

       rwcommunity6 COMMUNITY [SOURCE [OID | -V VIEW [CONTEXT]]]
              are  directives relating to requests received using IPv6 (if the
              agent supports such transport domains).  The  interpretation  of
              the SOURCE, OID, VIEW and CONTEXT tokens are exactly the same as
              for the IPv4 versions.

       In each case, only one directive should be specified for a given SNMPv3
       user,  or  community  string.   It  is  not appropriate to specify both
       rouser and rwuser directives referring to  the  same  SNMPv3  user  (or
       equivalent  community  settings). The rwuser directive provides all the
       access of rouser (as well as allowing SET  support).   The  same  holds
       true for the community-based directives.

       More  complex  access  requirements  (such  as  access  to  two or more
       distinct OID subtrees, or different views for  GET  and  SET  requests)
       should  use  one  of the other access control mechanisms.  Note that if
       several distinct communities or SNMPv3 users need  to  be  granted  the
       same  level  of access, it would also be more efficient to use the main
       VACM configuration directives.

   VACM Configuration
       The full flexibility of the VACM is available using four  configuration
       directives  -  com2sec,  group,  view and access.  These provide direct
       configuration of the underlying VACM tables.

       com2sec  [-Cn CONTEXT] SECNAME SOURCE COMMUNITY

       com2sec6 [-Cn CONTEXT] SECNAME SOURCE COMMUNITY
              map an SNMPv1 or SNMPv2c community string to a security  name  -
              either  from a particular range of source addresses, or globally
              ("default").  A restricted  source  can  either  be  a  specific
              hostname  (or  address),  or  a  subnet - represented as IP/MASK
              (e.g.    10.10.10.0/255.255.255.0),     or     IP/BITS     (e.g.
              10.10.10.0/24), or the IPv6 equivalents.

              The  same  community string can be specified in several separate
              directives (presumably with different source  tokens),  and  the
              first  source/community  combination  that  matches the incoming
              request will be selected.  Various source/community combinations
              can also map to the same security name.

              If a CONTEXT is specified (using -Cn), the community string will
              be mapped to a  security  name  in  the  named  SNMPv3  context.
              Otherwise the default context ("") will be used.

       com2secunix [-Cn CONTEXT] SECNAME SOCKPATH COMMUNITY
              is the Unix domain sockets version of com2sec.

       group GROUP {v1|v2c|usm} SECNAME
              maps  a  security  name (in the specified security model) into a
              named group.  Several group  directives  can  specify  the  same
              group name, allowing a single access setting to apply to several
              users and/or community strings.

              Note that groups must be set  up  for  the  two  community-based
              models  separately  - a single com2sec (or equivalent) directive
              will typically be accompanied by two group directives.

       view VNAME TYPE OID [MASK]
              defines a named "view" - a subset of the overall OID tree.  This
              is  most  commonly a single subtree, but several view directives
              can be given with the same view name (VNAME), to build up a more
              complex   collection  of  OIDs.   TYPE  is  either  included  or
              excluded, which can again define a more  complex  view  (e.g  by
              excluding certain sensitive objects from an otherwise accessible
              subtree).

              MASK is a list of hex octets (optionally  separated  by  ’.’  or
              ’:’)  with  the  set bits indicating which subidentifiers in the
              view OID to match against.  If not specified, this  defaults  to
              matching  the OID exactly (all bits set), thus defining a simple
              OID subtree.  So:
                     view iso1 included .iso  0xf0
                     view iso2 included .iso
                     view iso3 included .iso.org.dod.mgmt  0xf0

              would all define the  same  view,  covering  the  whole  of  the
              ’iso(1)’   subtree   (with   the   third  example  ignoring  the
              subidentifiers not covered by the mask).

              More usefully, the mask can be used to define a view covering  a
              particular  row  (or  rows)  in a table, by matching against the
              appropriate  table  index  value,  but   skipping   the   column
              subidentifier:

                     view ifRow4 included .1.3.6.1.2.1.2.2.1.0.4  0xff:a0

              Note that a mask longer than 8 bits must use ’:’ to separate the
              individual octets.

       access GROUP CONTEXT {any|v1|v2c|usm} LEVEL PREFX READ WRITE NOTIFY
              maps from  a  group  of  users/communities  (with  a  particular
              security  model  and  minimum  security level, and in a specific
              context) to one of three views, depending on the  request  being
              processed.

              LEVEL  is  one  of  noauth,  auth, or priv.  PREFX specifies how
              CONTEXT should be matched against the context  of  the  incoming
              request,  either  exact  or  prefix.   READ,  WRITE  and  NOTIFY
              specifies the view to be used  for  GET*,  SET  and  TRAP/INFORM
              requests (althought the NOTIFY view is not currently used).  For
              v1 or v2c access, LEVEL will need to be noauth.

   Typed-View Configuration
       The final group of directives extend the  VACM  approach  into  a  more
       flexible  mechanism,  which  can  be  applied  to  other access control
       requirements. Rather than the fixed three views of  the  standard  VACM
       mechanism,  this can be used to configure various different view types.
       As far as the main SNMP agent is concerned, the two main view types are
       read  and  write, corresponding to the READ and WRITE views of the main
       access directive.  See the ’snmptrapd.conf(5)’ man page for  discussion
       of other view types.

       authcommunity TYPES  COMMUNITY   [SOURCE [OID | -V VIEW [CONTEXT]]]
              is  an  alternative  to  the rocommunity/rwcommunity directives.
              TYPES will usually be read or read,write respectively.  The view
              specification  can  either  be  an OID subtree (as before), or a
              named view  (defined  using  the  view  directive)  for  greater
              flexibility.  If this is omitted, then access will be allowed to
              the  full  OID  tree.   If  CONTEXT  is  specified,  access   is
              configured  within  this  SNMPv3 context.  Otherwise the default
              context ("") is used.

       authuser   TYPES [-s MODEL] USER  [LEVEL [OID | -V VIEW [CONTEXT]]]
              is an alternative to the rouser/rwuser directives.   The  fields
              TYPES,  OID,  VIEW  and  CONTEXT  have  the  same meaning as for
              authcommunity.

       authgroup  TYPES [-s MODEL] GROUP [LEVEL [OID | -V VIEW [CONTEXT]]]
              is a companion to the authuser directive, specifying access  for
              a particular group (defined using the group directive as usual).
              Both authuser and authgroup default to authenticated requests  -
              LEVEL  can  also  be  specified  as  noauth  or  priv  to  allow
              unauthenticated requests, or  require  encryption  respectively.
              Both   authuser   and   authgroup  directives  also  default  to
              configuring access for SNMPv3/USM requests - use the  ’-s’  flag
              to  specify an alternative security model (using the same values
              as for access above).

       authaccess TYPES [-s MODEL] GROUP VIEW [LEVEL [CONTEXT]]
              also configures the access for a  particular  group,  specifying
              the  name  and type of view to apply. The MODEL and LEVEL fields
              are interpreted in the same way as for authgroup.  If CONTEXT is
              specified,  access  is configured within this SNMPv3 context (or
              contexts with this prefix if the CONTEXT field ends  with  ’*’).
              Otherwise the default context ("") is used.

       setaccess GROUP CONTEXT MODEL LEVEL PREFIX VIEW TYPES
              is  a  direct  equivalent  to  the  original  access  directive,
              typically listing the  view  types  as  read  or  read,write  as
              appropriate.     (or    see    ’snmptrapd.conf(5)’   for   other
              possibilities).  All other fields have the  same  interpretation
              as with access.

SYSTEM INFORMATION

       Most  of  the  information  reported by the Net-SNMP agent is retrieved
       from the underlying system, or  dynamically  configured  via  SNMP  SET
       requests  (and  retained  from  one  run  of  the  agent  to the next).
       However, certain MIB objects can be configured or  controlled  via  the
       snmpd.conf(5) file.

   System Group
       Most  of  the scalar objects in the ’system’ group can be configured in
       this way:

       sysLocation STRING

       sysContact STRING

       sysName STRING
              set  the  system  location,  system  contact  or   system   name
              (sysLocation.0,   sysContact.0  and  sysName.0)  for  the  agent
              respectively.   Ordinarily  these  objects  are  writeable   via
              suitably  authorized SNMP SET requests.  However, specifying one
              of these directives makes the  corresponding  object  read-only,
              and  attempts  to  SET  it  will  result  in a notWritable error
              response.

       sysServices NUMBER
              sets the value of the sysServices.0 object.  For a host  system,
              a  good  value is 72 (application + end-to-end layers).  If this
              directive is not specified, then no value will be  reported  for
              the sysServices.0 object.

       sysDescr STRING

       sysObjectID OID
              sets  the  system  description  or  object  ID  for  the  agent.
              Although  these  MIB  objects  are  not   SNMP-writable,   these
              directives  can  be used by a network administrator to configure
              suitable values for them.

   Interfaces Group
       interface NAME TYPE SPEED
              can be used to provide appropriate type and speed  settings  for
              interfaces  where  the agent fails to determine this information
              correctly.  TYPE is a type value as given in the IANAifType-MIB,
              and  can  be specified numerically or by name (assuming this MIB
              is loaded).

   Host Resources Group
       This requires that the agent was built with support for the host module
       (which  is  now  included as part of the default build configuration on
       the major supported platforms).

       ignoreDisk STRING
              controls which disk devices are scanned as  part  of  populating
              the   hrDiskStorageTable   (and   hrDeviceTable).   The  HostRes
              implementation code includes a  list  of  disk  device  patterns
              appropriate  for the current operating system, some of which may
              cause the agent to block when trying to open  the  corresponding
              disk  devices.   This might lead to a timeout when walking these
              tables, possibly  resulting  in  inconsistent  behaviour.   This
              directive  can  be  used  to  specify particular devices (either
              individually or wildcarded) that should not be checked.

              Note:  Please consult the source (host/hr_disk.c) and check  for
                     the Add_HR_Disk_entry calls relevant for a particular O/S
                     to determine the list of devices that will be scanned.

              The pattern can include one or more wildcard  expressions.   See
              snmpd.examples(5) for illustration of the wildcard syntax.

       skipNFSInHostResources true
              controls whether NFS and NFS-like file systems should be omitted
              from the hrStorageTable (true or 1) or not (false or 0, which is
              the  default).   If  the Net-SNMP agent gets hung on NFS-mounted
              filesystems, you can try setting this to ’1’.

       storageUseNFS [1|2]
              controls how NFS and NFS-like file systems should be reported in
              the hrStorageTable.  as ’Network Disks’ (1) or ’Fixed Disks’ (2)
              Historically, the Net-SNMP agent has reported such file  systems
              as  ’Fixed  Disks’,  and  this  is  still the default behaviour.
              Setting this directive to  ’1’  reports  such  file  systems  as
              ´Network Disks’, as required by the Host Resources MIB.

   Process Monitoring
       The  hrSWRun group of the Host Resources MIB provides information about
       individual processes running on the local system.  The prTable  of  the
       UCD-SNMP-MIB  complements this by reporting on selected services (which
       may involve multiple processes).  This  requires  that  the  agent  was
       built  with  support for the ucd-snmp/proc module (which is included as
       part of the default build configuration).

       proc NAME [MAX [MIN]]
              monitors the number of processes called  NAME  (as  reported  by
              "/bin/ps -e") running on the local system.

              If  the  number  of  NAMEd processes is less than MIN or greater
              than MAX, then the corresponding prErrorFlag  instance  will  be
              set  to  1,  and a suitable description message reported via the
              prErrMessage instance.

              Note:  This situation will not automatically trigger a  trap  to
                     report  the  problem  -  see the DisMan Event MIB section
                     later.

              If neither MAX nor MIN are specified (or are both 0), they  will
              default  to  infinity  and  1 respectively ("at least one").  If
              only MAX is specified, MIN will default  to  0  ("no  more  than
              MAX").

       procfix NAME PROG ARGS
              registers a command that can be run to fix errors with the given
              process NAME.  This  will  be  invoked  when  the  corresponding
              prErrFix instance is set to 1.

              Note:  This command will not be invoked automatically.

              The  procfix directive must be specified after the matching proc
              directive, and cannot be used on its own.

       If no proc directives are defined, then walking the prTable  will  fail
       (noSuchObject).

   Disk Usage Monitoring
       This  requires  that  the  agent  was  built  with support for the ucd-
       snmp/disk module (which is  included  as  part  of  the  default  build
       configuration).

       disk PATH [ MINSPACE | MINPERCENT% ]
              monitors the disk mounted at PATH for available disk space.

              The  minimum  threshold can either be specified in Kb (MINSPACE)
              or as a percentage of the total disk  (MINPERCENT%  with  a  ’%’
              character),  defaulting  to  100Kb if neither are specified.  If
              the free  disk  space  falls  below  this  threshold,  then  the
              corresponding  dskErrorFlag  instance  will  be  set to 1, and a
              suitable  description  message  reported  via  the   dskErrorMsg
              instance.

              Note:  This  situation  will not automatically trigger a trap to
                     report the problem - see the  DisMan  Event  MIB  section
                     later.

       includeAllDisks MINPERCENT%
              configures  monitoring  of  all disks found on the system, using
              the  specified  (percentage)  threshold.   The   threshold   for
              individual  disks can be adjusted using suitable disk directives
              (which can come  either  before  or  after  the  includeAllDisks
              directive).

              Note:  Whether   disk   directives   appears   before  or  after
                     includeAllDisks may affect the indexing of the  dskTable.

              Only  one  includeAllDisks  directive  should be specified - any
              subsequent copies will be ignored.

              The list of mounted disks will  be  determined  when  the  agent
              starts  using the setmntent(3) and getmntent(3), or fopen(3) and
              getmntent(3),  or setfsent(3)  and  getfsent(3) system calls. If
              none  of  the  above  system  calls  are available then the root
              partition  "/" (which  is  assumed to exist on  any  UNIX  based
              system)  will  be  monitored.  Disks mounted after the agent has
              started will not be monitored.

       If neither any disk directives or  includeAllDisks  are  defined,  then
       walking the dskTable will fail (noSuchObject).

   System Load Monitoring
       This requires that the agent was built with support for either the ucd-
       snmp/loadave module or the ucd-snmp/memory module respectively (both of
       which are included as part of the default build configuration).

       load MAX1 [MAX5 [MAX15]]
              monitors  the  load  average  of  the  local  system, specifying
              thresholds for the 1-minute, 5-minute  and  15-minute  averages.
              If  any of these loads exceed the associated maximum value, then
              the corresponding laErrorFlag instance will be set to 1,  and  a
              suitable  description  message  reported  via  the  laErrMessage
              instance.

              Note:  This situation will not automatically trigger a  trap  to
                     report  the  problem  -  see the DisMan Event MIB section
                     later.

              If the MAX15 threshold is omitted, it will default to  the  MAX5
              value.  If both MAX5 and MAX15 are omitted, they will default to
              the MAX1 value.  If this directive is not specified,  all  three
              thresholds will default to a value of DEFMAXLOADAVE.

              If  a  threshold  value of 0 is given, the agent will not report
              errors via the relevant laErrorFlag or  laErrMessage  instances,
              regardless of the current load.

       Unlike  the  proc  and disk directives, walking the walking the laTable
       will succeed (assuming the ucd-snmp/loadave module was configured  into
       the agent), even if the load directive is not present.

       swap MIN
              monitors the amount of swap space available on the local system.
              If this falls below the specified threshold (MIN Kb),  then  the
              memErrorSwap object will be set to 1, and a suitable description
              message reported via memSwapErrorMsg.

              Note:  This situation will not automatically trigger a  trap  to
                     report  the  problem  -  see the DisMan Event MIB section
                     later.
       If this directive is not specified, the default threshold is 16 Mb.

   Log File Monitoring
       This requires that the agent was built with support for either the ucd-
       snmp/file  or ucd-snmp/logmatch modules respectively (both of which are
       included as part of the default build configuration).

       file FILE [MAXSIZE]
              monitors the size of the specified file (in Kb).  If MAXSIZE  is
              specified, and the size of the file exceeds this threshold, then
              the corresponding fileErrorFlag instance will be set to 1, and a
              suitable  description  message  reported  via  the  fileErrorMsg
              instance.

              Note:  This situation will not automatically trigger a  trap  to
                     report  the  problem  -  see the DisMan Event MIB section
                     later.

              A maximum of 20 files can be monitored.

       If no file directives are defined, then walking the fileTable will fail
       (noSuchObject).

       logmatch NAME PATH CYCLETIME REGEX
              monitors  the  specified  file  for  occurances of the specified
              pattern REGEX.

              A maximum of 50 files can be monitored.

       If no logmatch directives are defined, then walking  the  logMatchTable
       will fail (noSuchObject).

ACTIVE MONITORING

       The  usual  behaviour  of  an  SNMP  agent is to wait for incoming SNMP
       requests and respond to them - if no requests are  received,  an  agent
       will typically not initiate any actions. This section describes various
       directives that can configure snmpd to take a more active role.

   Notification Handling
       trapcommunity STRING
              defines the default community string to  be  used  when  sending
              traps.   Note  that  this  directive  must  be used prior to any
              community-based trap destination directives that need to use it.

       trapsink HOST [COMMUNITY [PORT]]

       trap2sink HOST [COMMUNITY [PORT]]

       informsink HOST [COMMUNITY [PORT]]
              define  the  address  of  a notification receiver that should be
              sent  SNMPv1   TRAPs,   SNMPv2c   TRAP2s,   or   SNMPv2   INFORM
              notifications respectively.  See the section LISTENING ADDRESSES
              in the snmpd(8) manual  page  for  more  information  about  the
              format  of  listening addresses.  If COMMUNITY is not specified,
              the most recent trapcommunity string will be used.

              If the transport address  does  not  include  an  explicit  port
              specification,   then  PORT  will  be  used.   If  this  is  not
              specified, the well known SNMP trap port (162) will be used.

              Note:  This mechanism is being  deprecated,  and  the  listening
                     port  should be specified via the transport specification
                     HOST instead.

              If several sink directives are  specified,  multiple  copies  of
              each   notification   (in   the  appropriate  formats)  will  be
              generated.

              Note:  It is not normally appropriate to list two (or all three)
                     sink directives with the same destination.

       trapsess [SNMPCMD_ARGS] HOST
              provides  a  more  generic  mechanism  for defining notification
              destinations.  SNMPCMD_ARGS should be the  command-line  options
              required  for  an equivalent snmptrap (or snmpinform) command to
              send the desired notification.  The option -Ci can be used (with
              -v2c  or  -v3) to generate an INFORM notification rather than an
              unacknowledged TRAP.

              This is the  appropriate  directive  for  defining  SNMPv3  trap
              receivers.                   See                 http://www.net-
              snmp.org/tutorial/tutorial-5/commands/snmptrap-v3.html for  more
              information about SNMPv3 notification behaviour.

       authtrapenable {1|2}
              determines  whether  to  generate  authentication  failure traps
              (enabled(1)) or not (disabled(2) - the default).  Ordinarily the
              corresponding  MIB  object  (snmpEnableAuthenTraps.0)  is  read-
              write, but specifying this directive  makes  this  object  read-
              only, and attempts to set the value via SET requests will result
              in a notWritable error response.

   DisMan Event MIB
       The previous directives can be used to configure where traps should  be
       sent, but are not concerned with when to send such traps (or what traps
       should be generated).  This is the domain of the Event MIB -  developed
       by the Distributed Management (DisMan) working group of the IETF.

       This   requires   that  the  agent  was  built  with  support  for  the
       disman/event module (which is now included as part of the default build
       configuration for the most recent distribution).

              Note:  The  behaviour  of  the  latest implementation differs in
                     some minor respects from the previous code - nothing  too
                     significant,  but existing scripts may possibly need some
                     minor adjustments.

       iquerySecName NAME

       agentSecName NAME
              specifies the default SNMPv3 username, to be  used  when  making
              internal  queries  to retrieve any necessary information (either
              for  evaluating  the  monitored  expression,   or   building   a
              notification   payload).   These  internal  queries  always  use
              SNMPv3, even if normal querying  of  the  agent  is  done  using
              SNMPv1 or SNMPv2c.

              Note that this user must also be explicitly created (createUser)
              and  given  appropriate  access  rights  (e.g.  rouser).    This
              directive is purely concerned with defining which user should be
              used - not with actually setting this user up.

       monitor [OPTIONS] NAME EXPRESSION
              defines a MIB object to monitor.  If  the  EXPRESSION  condition
              holds  (see  below),  then  this  will trigger the corresponding
              event, and either send a notification or apply a SET  assignment
              (or  both).   Note  that  the event will only be triggered once,
              when the expression first matches.  This monitor entry will  not
              fire  again  until  the monitored condition first becomes false,
              and then matches again.  NAME is an administrative name for this
              expression,  and  is  used for indexing the mteTriggerTable (and
              related tables).  Note also that such monitors use  an  internal
              SNMPv3  request  to retrieve the values being monitored (even if
              normal agent queries typically use SNMPv1 or SNMPv2c).  See  the
              iquerySecName token described above.

       EXPRESSION
              There  are  three  types  of monitor expression supported by the
              Event MIB - existence, boolean and threshold tests.

              OID | ! OID | != OID
                     defines  an  existence(0)  monitor  test.   A  bare   OID
                     specifies  a  present(0)  test,  which will fire when (an
                     instance of) the monitored OID is created.  An expression
                     of the form ! OID specifies an absent(1) test, which will
                     fire when the monitored OID is delected.   An  expression
                     of  the  form  !=  OID specifies a changed(2) test, which
                     will fire whenever the monitored value(s)  change.   Note
                     that there must be whitespace before the OID token.

              OID OP VALUE
                     defines  a  boolean(1) monitor test.  OP should be one of
                     the defined comparison operators (!=, ==, <, <=,  >,  >=)
                     and  VALUE should be an integer value to compare against.
                     Note that there must be whitespace around the  OP  token.
                     A  comparison  such  as  OID  !=0  will  not  be  handled
                     correctly.

              OID MIN MAX [DMIN DMAX]
                     defines a threshold(2) monitor test.   MIN  and  MAX  are
                     integer  values,  specifying  lower and upper thresholds.
                     If the value of the monitored OID falls below  the  lower
                     threshold (MIN) or rises above the upper threshold (MAX),
                     then the monitor entry  will  trigger  the  corresponding
                     event.

                     Note  that  the  rising  threshold event will only be re-
                     armed when the monitored  value  falls  below  the  lower
                     threshold  (MIN).  Similarly, the falling threshold event
                     will be re-armed by the upper threshold (MAX).

                     The optional parameters DMIN and DMAX configure a pair of
                     similar  threshold  tests,  but  working  with  the delta
                     differences between successive sample values.

       OPTIONS
              There are various  options  to  control  the  behaviour  of  the
              monitored expression.  These include:

              -D     indicates  that  the expression should be evaluated using
                     delta differences between sample values (rather than  the
                     values themselves).

              -d OID

              -di OID
                     specifies  a  discontinuity  marker  for validating delta
                     differences.  A -di object instance will be used  exactly
                     as   given.    A   -d   object  will  have  the  instance
                     subidentifiers  from   the   corresponding   (wildcarded)
                     expression object appended.  If the -I flag is specified,
                     then there is no difference between these two options.

                     This option also implies -D.

              -e EVENT
                     specifies the event to be invoked when this monitor entry
                     is  triggered.   If this option is not given, the monitor
                     entry will generate one  of  the  standard  notifications
                     defined in the DISMAN-EVENT-MIB.

              -I     indicates that the monitored expression should be applied
                     to the specified OID as a single instance.   By  default,
                     the  OID  will be treated as a wildcarded object, and the
                     monitor expanded to cover all matching instances.

              -i OID

              -o OID define  additional  varbinds   to   be   added   to   the
                     notification  payload  when  this  monitor trigger fires.
                     For a wildcarded expression, the suffix  of  the  matched
                     instance  will  be  added to any OIDs specified using -o,
                     while OIDs specified using -i will be  treated  as  exact
                     instances.  If the -I flag is specified, then there is no
                     difference between these two options.

                     See  strictDisman  for  details  of   the   ordering   of
                     notification payloads.

              -r FREQUENCY
                     monitors  the  given  expression every FREQUENCY seconds.
                     By default, the expression will be evaluated  every  600s
                     (10 minutes).

              -S     indicates  that  the  monitor  expression  should  not be
                     evaluated when the agent  first  starts  up.   The  first
                     evaluation  will  be  done once the first repeat interval
                     has expired.

              -s     indicates that the monitor expression should be evaluated
                     when  the  agent  first  starts  up.  This is the default
                     behaviour.

                      Note:  Notifications   triggered   by    this    initial
                             evaluation  will  be  sent  before  the coldStart
                             trap.

              -u SECNAME
                     specifies a security name to use for scanning  the  local
                     host,  instead of the default iquerySecName.  Once again,
                     this user must be explicitly created and  given  suitable
                     access rights.

       notificationEvent ENAME NOTIFICATION [-n] [-i OID | -o OID ]*
              defines a notification event named ENAME.  This can be triggered
              from a given monitor entry by specifying  the  option  -e  ENAME
              (see   above).    NOTIFICATION   should   be   the  OID  of  the
              NOTIFICATION-TYPE  definition  for  the   notification   to   be
              generated.

              If the -n option is given, the notification payload will include
              the standard varbinds as specified in the OBJECTS clause of  the
              notification  MIB  definition.   This option must come after the
              NOTIFICATION OID (and the relevant MIB file  must  be  available
              and  loaded  by  the  agent).  Otherwise, these varbinds must be
              listed explicitly (either here or in the  corresponding  monitor
              directive).

              The  -i OID and -o OID options specify additional varbinds to be
              appended to the notification payload, after the  standard  list.
              If  the  monitor  entry  that  triggered  this  event involved a
              wildcarded expression, the suffix of the matched  instance  will
              be  added  to  any OIDs specified using -o, while OIDs specified
              using -i will be treated as exact instances.  If the -I flag was
              specified  to the monitor directive, then there is no difference
              between these two options.

       setEvent ENAME [-I] OID = VALUE
              defines a set event named ENAME, assigning the  (integer)  VALUE
              to  the  specified  OID.   This  can  be  triggered from a given
              monitor entry by specifying the option -e ENAME (see above).

              If the monitor  entry  that  triggered  this  event  involved  a
              wildcarded  expression,  the suffix of the matched instance will
              normally be added to the OID.  If the -I flag was  specified  to
              either  of the monitor or setEvent directives, the specified OID
              will be regarded as an exact single instance.

       strictDisman yes
              The definition of SNMP notifications states  that  the  varbinds
              defined  in  the  OBJECT  clause should come first (in the order
              specified),  followed  by  any   "extra"   varbinds   that   the
              notification  generator feels might be useful.  The most natural
              approach would be to associate these mandatory varbinds with the
              notificationEvent entry, and append any varbinds associated with
              the monitor entry that triggered the notification to the end  of
              this  list.  This is the default behaviour of the Net-SNMP Event
              MIB implementation.

              Unfortunately, the  DisMan  Event  MIB  specifications  actually
              state  that  the  trigger-related  varbinds  should  come first,
              followed by the event-related ones.  This directive can be  used
              to  restore this strictly-correct (but inappropriate) behaviour.

              Note:  Strict DisMan ordering may result in  generating  invalid
                     notifications  payload  lists if the notificationEvent -n
                     flag is used together with monitor  -o  (or  -i)  varbind
                     options.

              If no monitor entries specify payload varbinds, then the setting
              of this directive is irrelevant.

       linkUpDownNotifications yes
              will configure the Event MIB tables to monitor the  ifTable  for
              network  interfaces  being  taken  up  or down, and triggering a
              linkUp or linkDown notification as appropriate.

              This is exactly equivalent to the configuration:

                     notificationEvent  linkUpTrap    linkUp   ifIndex ifAdminStatus ifOperStatus
                     notificationEvent  linkDownTrap  linkDown ifIndex ifAdminStatus ifOperStatus

                     monitor  -r 60 -e linkUpTrap   "Generate linkUp" ifOperStatus != 2
                     monitor  -r 60 -e linkDownTrap "Generate linkDown" ifOperStatus == 2

       defaultMonitors yes
              will configure the Event MIB tables to monitor the various  UCD-
              SNMP-MIB  tables  for  problems (as indicated by the appropriate
              xxErrFlag column objects).

              This is exactly equivalent to the configuration:

                     monitor   -o prNames -o prErrMessage "process table" prErrorFlag != 0
                     monitor   -o memErrorName -o memSwapErrorMsg "memory" memSwapError != 0
                     monitor   -o extNames -o extOutput "extTable" extResult != 0
                     monitor   -o dskPath -o dskErrorMsg "dskTable" dskErrorFlag != 0
                     monitor   -o laNames -o laErrMessage  "laTable" laErrorFlag != 0
                     monitor   -o fileName -o fileErrorMsg  "fileTable" fileErrorFlag != 0

       In both  these  latter  cases,  the  snmpd.conf  must  also  contain  a
       iquerySecName directive, together with a corresponding createUser entry
       and suitable access control configuration.

   DisMan Schedule MIB
       The DisMan working group  also  produced  a  mechanism  for  scheduling
       particular  actions  (a specified SET assignment) at given times.  This
       requires that the agent was built with support for the  disman/schedule
       module  (which  is  included as part of the default build configuration
       for the most recent distribution).

       There are three ways of specifying the scheduled action:

       repeat FREQUENCY OID = VALUE
              configures a SET assignment of the (integer) VALUE  to  the  MIB
              instance OID, to be run every FREQUENCY seconds.

       cron MINUTE HOUR DAY MONTH WEEKDAY  OID = VALUE
              configures  a  SET  assignment of the (integer) VALUE to the MIB
              instance OID, to be run at the times  specified  by  the  fields
              MINUTE  to  WEEKDAY.   These  follow  the  same  pattern  as the
              equivalent crontab(5) fields.

              Note:  These fields should be specified as  a  (comma-separated)
                     list  of  numeric values.  Named values for the MONTH and
                     WEEKDAY fields are not supported, and neither  are  value
                     ranges. A wildcard match can be specified as ’*’.

              The  DAY field can also accept negative values, to indicate days
              counting backwards from the end of the month.

       at MINUTE HOUR DAY MONTH WEEKDAY  OID = VALUE
              configures a one-shot SET assignment, to be  run  at  the  first
              matching time as specified by the fields MINUTE to WEEKDAY.  The
              interpretation of these fields is exactly the same  as  for  the
              cron directive.

EXTENDING AGENT FUNCTIONALITY

       One  of the first distinguishing features of the original UCD suite was
       the ability to extend the functionality of the  agent  -  not  just  by
       recompiling  with code for new MIB modules, but also by configuring the
       running agent to report additional information. There are a  number  of
       techniques to support this, including:

       ·      running external commands (exec, extend, pass)

       ·      loading new code dynamically (embedded perl, dlmod)

       ·      communicating with other agents (proxy, SMUX, AgentX)

   Arbitrary Extension Commands
       The  earliest  extension  mechanism  was  the  ability to run arbitrary
       commands or shell scripts. Such commands do not need  to  be  aware  of
       SNMP  operations,  or  conform  to  any  particular behaviour - the MIB
       structures are designed to accommodate any form of command output.  Use
       of  this  mechanism  requires that the agent was built with support for
       the ucd-snmp/extensible and/or agent/extend  modules  (which  are  both
       included as part of the default build configuration).

       exec [MIBOID] NAME PROG ARGS

       sh [MIBOID] NAME PROG ARGS
              invoke  the  named  PROG with arguments of ARGS.  By default the
              exit status and first line of output from the  command  will  be
              reported via the extTable, discarding any additional output.

              Note:  Entries  in  this table appear in the order they are read
                     from the configuration file.  This means that adding  new
                     exec  (or  sh)  directives  and restarting the agent, may
                     affect the indexing of other entries.

              The PROG argument for exec directives must be a full path  to  a
              real  binary,  as it is executed via the exec() system call.  To
              invoke a shell script, use the sh directive instead.

              If MIBOID is specified, then the results will be rooted at  this
              point   in  the  OID  tree,  returning  the  exit  statement  as
              MIBOID.100.0 and the entire command  output  in  a  pseudo-table
              based at MIBNUM.101 - with one ’row’ for each line of output.

              Note:  The  layout  of  this  "relocatable" form of exec (or sh)
                     output does not strictly  form  a  valid  MIB  structure.
                     This  mechanism  is  being  deprecated  -  please see the
                     extend directive (described below) instead.

              The agent does not cache  the  exit  status  or  output  of  the
              executed program.

       execfix NAME PROG ARGS
              registers a command that can be invoked on demand - typically to
              respond to or fix errors  with  the  corresponding  exec  or  sh
              entry.   When  the extErrFix instance for a given NAMEd entry is
              set to the integer value of 1, this command will be called.

              Note:  This directive can only be used  in  combination  with  a
                     corresponding exec or sh directive, which must be defined
                     first.  Attempting to  define  an  unaccompanied  execfix
                     directive will fail.

       exec  and sh extensions can only be configured via the snmpd.conf file.
       They cannot be set up via SNMP SET requests.

       extend [MIBOID] NAME PROG ARGS
              works in a similar manner to the  exec  directive,  but  with  a
              number  of  improvements.   The  MIB tables (nsExtendConfigTable
              etc) are indexed by the NAME token, so  are  unaffected  by  the
              order  in  which  entries are read from the configuration files.
              There  are  two  result  tables  -  one   (nsExtendOutput1Table)
              containing the exit status, the first line and full output (as a
              single  string)  for  each   extend   entry,   and   the   other
              (nsExtendOutput2Table)  containing  the  complete  output  as  a
              series of separate lines.

              If MIBOID is specified, then the configuration and result tables
              will  be rooted at this point in the OID tree, but are otherwise
              structured in exactly the same  way.  This  means  that  several
              separate  extend  directives  can  specify the same MIBOID root,
              without conflicting.

              The  exit  status  and  output  is   cached   for   each   entry
              individually,  and  can  be  cleared  (and the caching behaviour
              configured) using the nsCacheTable.

       extendfix NAME PROG ARGS
              registers a command that can be invoked on  demand,  by  setting
              the  appropriate  nsExtendRunType  instance  to  the  value run-
              command(3).  Unlike the equivalent execfix, this directive  does
              not need to be paired with a corresponding extend entry, and can
              appear on its own.

       Both extend and extendfix directives  can  be  configured  dynamically,
       using SNMP SET requests to the NET-SNMP-EXTEND-MIB.

   MIB-Specific Extension Commands
       The  first group of extension directives invoke arbitrary commands, and
       rely on the MIB structure  (and  management  applications)  having  the
       flexibility  to  accommodate  and  interpret  the  output.   This  is a
       convenient way to make information available quickly and simply, but is
       of  no  use when implementing specific MIB objects, where the extension
       must conform to the structure of the MIB (rather than vice versa).  The
       remaining extension mechanisms are all concerned with such MIB-specific
       situations  -  starting  with  "pass-through"  scripts.   Use  of  this
       mechanism  requires  that the agent was built with support for the ucd-
       snmp/pass and ucd-snmp/pass_persist modules (which are both included as
       part of the default build configuration).

       pass [-p priority] MIBOID PROG
              will  pass  control  of  the  subtree  rooted  at  MIBOID to the
              specified PROG command.   GET  and  GETNEXT  requests  for  OIDs
              within this tree will trigger this command, called as:

                     PROG -g OID

                     PROG -n OID

              respectively,  where OID is the requested OID.  The PROG command
              should return the  response  varbind  as  three  separate  lines
              printed  to  stdout  -  the  first line should be the OID of the
              returned value, the second should be its TYPE (one of  the  text
              strings integer, gauge, counter, timeticks, ipaddress, objectid,
              or string ), and the third should be the value itself.

              If the command cannot return an appropriate varbind  -  e.g  the
              specified  OID  did not correspond to a valid instance for a GET
              request, or there were no following instances for  a  GETNEXT  -
              then  it  should  exit  without producing any output.  This will
              result  in  an  SNMP  noSuchName  error,  or  a   noSuchInstance
              exception.

                      Note:  The  SMIv2 type counter64 and SNMPv2 noSuchObject
                             exception are not supported.

              A SET request will result in the command being called as:

                     PROG -s OID TYPE VALUE

              where TYPE is one of the tokens  listed  above,  indicating  the
              type of the value passed as the third parameter.

              If  the  assignment  is successful, the PROG command should exit
              without producing any output.  Errors  should  be  indicated  by
              writing  one  of  the  strings  not-writable,  or  wrong-type to
              stdout, and  the  agent  will  generate  the  appropriate  error
              response.

                      Note:  The other SNMPv2 errors are not supported.

              In  either  case,  the  command should exit once it has finished
              processing.  Each request (and  each  varbind  within  a  single
              request) will trigger a separate invocation of the command.

              The  default  registration priority is 127.  This can be changed
              by  supplying  the  optional  -p  flag,  with   lower   priority
              registrations  being  used  in  preference  to  higher  priority
              values.

       pass_persist [-p priority] MIBOID PROG
              will also pass control of the subtree rooted at  MIBOID  to  the
              specified  PROG  command.  However this command will continue to
              run after the initial request has been answered,  so  subsequent
              requests can be processed without the startup overheads.

              Upon  initialization, PROG will be passed the string "PING\n" on
              stdin, and should respond by printing "PONG\n" to stdout.

              For GET and GETNEXT requests, PROG will be passed two  lines  on
              stdin,  the  command (get or getnext) and the requested OID.  It
              should respond by printing three lines to stdout - the  OID  for
              the  result  varbind, the TYPE and the VALUE itself - exactly as
              for the pass directive above.  If the command cannot  return  an
              appropriate  varbind,  it  should print print "NONE\n" to stdout
              (but continue running).

              For SET requests, PROG will be passed three lines on stdin,  the
              command  (set)  and  the requested OID, followed by the type and
              value (both on the same line).  If the assignment is successful,
              the  command  should print "DONE\n" to stdout.  Errors should be
              indicated by writing one of  the  strings  not-writable,  wrong-
              type, wrong-length, wrong-value or inconsistent-value to stdout,
              and the agent will generate the appropriate error response.   In
              either case, the command should continue running.

              The  registration  priority can be changed using the optional -p
              flag, just as for the pass directive.

       pass and  pass_persist  extensions  can  only  be  configured  via  the
       snmpd.conf file.  They cannot be set up via SNMP SET requests.

   Embedded Perl Support
       Programs  using the previous extension mechanisms can be written in any
       convenient programming language - including perl,  which  is  a  common
       choice for pass-through extensions in particular.  However the Net-SNMP
       agent also includes support for embedded perl  technology  (similar  to
       mod_perl  for  the  Apache  web  server).   This  allows  the  agent to
       interpret perl scripts directly, thus avoiding the overhead of spawning
       processes  and initializing the perl system when a request is received.

       Use of this mechanism requires that the agent was  built  with  support
       for the embedded perl mechanism, which is not part of the default build
       environment.  It  must  be  explicitly  included  by   specifying   the
       ’--enable-embedded-perl’  option  to  the  configure  script  when  the
       package is first built.

       If enabled, the following directives will be recognised:

       disablePerl true
              will turn off embedded perl support entirely (e.g. if there  are
              problems with the perl installation).

       perlInitFile FILE
              loads the specified initialisation file (if present) immediately
              before the first perl directive is parsed.   If  not  explicitly
              specified,  the  agent  will look for the default initialisation
              file /usr/share/snmp/snmp_perl.pl.

              The  default  initialisation  file  creates  an  instance  of  a
              NetSNMP::agent  object  - a variable $agent which can be used to
              register perl-based MIB handler routines.

       perl EXPRESSION
              evaluates the given expression.  This would typically register a
              handler  routine to be called when a section of the OID tree was
              requested:
                     perl use Data::Dumper;
                     perl sub myroutine  { print "got called: ",Dumper(@_),"\n"; }
                     perl $agent->register(’mylink’, ’.1.3.6.1.8765’, \&myroutine);

              This expression could also source an external file:
                     perl ’do /path/to/file.pl’;

              or  perform  any  other  perl-based  processing  that  might  be
              required.

   Dynamically Loadable Modules
       Most  of  the MIBs supported by the Net-SNMP agent are implemented as C
       code modules, which were compiled and linked into the  agent  libraries
       when  the  suite was first built.  Such implementation modules can also
       be compiled independently and loaded into the running agent once it has
       started.   Use of this mechanism requires that the agent was built with
       support for the ucd-snmp/dlmod module (which is included as part of the
       default build configuration).

       dlmod NAME PATH
              will  load  the  shared  object  module  from  the file PATH (an
              absolute  filename),  and  call   the   initialisation   routine
              init_NAME.

              Note:  If  the specified PATH is not a fully qualified filename,
                     it will be interpreted relative  to  /usr/lib/snmp/dlmod,
                     and .so will be appended to the filename.

       This  functionality  can  also be configured using SNMP SET requests to
       the UCD-DLMOD-MIB.

   Proxy Support
       Another mechanism for extending the functionality of the  agent  is  to
       pass  selected  requests  (or selected varbinds) to another SNMP agent,
       which can be running on  the  same  host  (presumably  listening  on  a
       different  port),  or on a remote system.  This can be viewed either as
       the main agent delegating requests to the remote one, or  acting  as  a
       proxy  for it.  Use of this mechanism requires that the agent was built
       with support for the ucd-snmp/proxy module (which is included  as  part
       of the default build configuration).

       proxy [-Cn CONTEXTNAME] [SNMPCMD_ARGS] HOST OID [REMOTEOID]
              will pass any incoming requests under OID to the agent listening
              on the port specified by the transport address  HOST.   See  the
              section LISTENING ADDRESSES in the snmpd(8) manual page for more
              information about the format of listening addresses.

              Note:  To proxy the entire MIB tree, use the OID .1.3  (not  the
                     top-level .1)

       The  SNMPCMD_ARGS  should provide sufficient version and administrative
       information to generate a valid SNMP request (see snmpcmd(1)).

       Note:  The proxied request will not  use  the  administrative  settings
              from the original request.

       If  a CONTEXTNAME is specified, this will register the proxy delegation
       within the named context in the local agent.  Defining  multiple  proxy
       directives for the same OID but different contexts can be used to query
       several remote  agents  through  a  single  proxy,  by  specifying  the
       appropriate  SNMPv3  context in the incoming request (or using suitable
       configured community strings - see the com2sec directive).

       Specifying the REMOID parameter will map the local MIB tree  rooted  at
       OID to an equivalent subtree rooted at REMOID on the remote agent.

   SMUX Sub-Agents
       The Net-SNMP agent supports the SMUX protocol (RFC 1227) to communicate
       with SMUX-based subagents (such as gated, zebra  or  quagga).   Use  of
       this  mechanism  requires that the agent was built with support for the
       smux module, which is not part of the default  build  environment,  and
       must be explicitly included by specifying the ’--with-mib-modules=smux’
       option to the configure script when the package is first built.

              Note:  This extension protocol has been officially deprecated in
                     favour of AgentX (see below).

       smuxpeer OID PASS
              will  register  a  subtree  for  SMUX-based  processing,  to  be
              authenticated using  the  password  PASS.   If  a  subagent  (or
              "peer")  connects  to  the agent and registers this subtree then
              requests for OIDs within it will be passed to that SMUX subagent
              for processing.

              A  suitable  entry  for  an  OSPF routing daemon (such as gated,
              zebra or quagga) might be something like
                     smuxpeer .1.3.6.1.2.1.14 ospf_pass

       smuxsocket <IPv4-address>
              defines the IPv4 address for SMUX peers to communicate with  the
              Net-SNMP agent.  The default is to listen on all IPv4 interfaces
              ("0.0.0.0"),  unless  the  package  has  been  configured   with
              "--enable-local-smux"  at  build  time,  which causes it to only
              listen on 127.0.0.1 by default. SMUX  uses  the  well-known  TCP
              port 199.

       Note  the  Net-SNMP  agent will only operate as a SMUX master agent. It
       does not support acting in a SMUX subagent role.

   AgentX Sub-Agents
       The Net-SNMP agent supports the AgentX  protocol  (RFC  2741)  in  both
       master  and  subagent  roles.   Use of this mechanism requires that the
       agent was built with support for the agentx module (which  is  included
       as part of the default build configuration), and also that this support
       is explicitly enabled (e.g. via the snmpd.conf file).

       There are two directives specifically relevant to running as an  AgentX
       master agent:

       master agentx
              will  enable  the  AgentX  functionality  and cause the agent to
              start listening for incoming  AgentX  registrations.   This  can
              also be activated by specifying the ’-x’ command-line option (to
              specify an alternative listening socket).

       agentXPerms SOCKPERMS [DIRPERMS [USER|UID [GROUP|GID]]]
              Defines the permissions and ownership of the AgentX Unix  Domain
              socket,  and  the  parent directories of this socket.  SOCKPERMS
              and DIRPERMS must be octal digits (see chmod(1)  ).  By  default
              this  socket will only be accessible to subagents which have the
              same userid as the agent.

       There is one directive specifically relevant to running  as  an  AgentX
       sub-agent:

       agentXPingInterval NUM
              will  make  the  subagent try and reconnect every NUM seconds to
              the master if it ever becomes (or starts) disconnected.

       The remaining directives are relevant to both AgentX  master  and  sub-
       agents:

       agentXSocket [<transport-specifier>:]<transport-address>[,...]
              defines the address the master agent listens at, or the subagent
              should connect to.   The  default  is  the  Unix  Domain  socket
              "/var/agentx/master".     Another    common    alternative    is
              tcp:localhost:705.  See the section LISTENING ADDRESSES  in  the
              snmpd(8)  manual  page  for more information about the format of
              addresses.

              Note:  Specifying an AgentX socket does not automatically enable
                     AgentX   functionality   (unlike  the  ’-x’  command-line
                     option).

       agentXTimeout NUM
              defines the timeout period (NUM seconds) for an AgentX  request.
              Default is 1 second.

       agentXRetries NUM
              defines the number of retries for an AgentX request.  Default is
              5 retries.

       net-snmp ships with both C and Perl APIs to  develop  your  own  AgentX
       subagent.

OTHER CONFIGURATION

       override [-rw] OID TYPE VALUE
              This  directive  allows  you to override a particular OID with a
              different value (and possibly a different type of  value).   The
              -rw  flag  will  allow  snmp  SETs to modify it’s value as well.
              (note that if you’re  overriding  original  functionality,  that
              functionality  will be entirely lost.  Thus SETS will do nothing
              more than modify the internal  overridden  value  and  will  not
              perform  any  of  the  original  functionality  intended  to  be
              provided by the  MIB  object.   It’s  an  emulation  only.)   An
              example:

                     override sysDescr.0 octet_str "my own sysDescr"

              That  line will set the sysDescr.0 value to "my own sysDescr" as
              well as make it modifiable with SNMP  SETs  as  well  (which  is
              actually illegal according to the MIB specifications).

              Note  that  care must be taken when using this.  For example, if
              you try to override a property  of  the  3rd  interface  in  the
              ifTable  with  a  new  value  and later the numbering within the
              ifTable changes it’s index ordering you’ll end up with  problems
              and  your  modified value won’t appear in the right place in the
              table.

              Valid  TYPEs  are:  integer,  uinteger,  octet_str,   object_id,
              counter,  null (for gauges, use "uinteger"; for bit strings, use
              "octet_str").  Note that setting an object to "null" effectively
              delete’s  it as being accessible.  No VALUE needs to be given if
              the object type is null.

              More types should be available in the future.

       If you’re trying to figure out  aspects  of  the  various  mib  modules
       (possibly  some that you’ve added yourself), the following may help you
       spit out some useful debugging information.  First off, please read the
       snmpd  manual  page  on  the -D flag.  Then the following configuration
       snmpd.conf token, combined with the -D flag, can produce useful output:

       injectHandler HANDLER modulename
              This  will  insert new handlers into the section of the mib tree
              referenced by "modulename".  The types of handlers available for
              insertion are:

              stash_cache
                     Caches  information  returned from the lower level.  This
                     greatly help the performance of the agent, at the cost of
                     caching  the  data  such that its no longer "live" for 30
                     seconds (in this  future,  this  will  be  configurable).
                     Note  that  this means snmpd will use more memory as well
                     while the information is  cached.   Currently  this  only
                     works  for  handlers  registered using the table_iterator
                     support, which is only a few mib tables.  To use it,  you
                     need to make sure to install it before the table_iterator
                     point in the chain, so to do this:

                                       injectHandler     stash_cache      NAME
                     table_iterator

                     If  you  want  a  table  to  play  with,  try walking the
                     nsModuleTable with and without this injected.

              debug  Prints  out  lots  of  debugging  information  when   the
                     -Dhelper:debug flag is passed to the snmpd application.

              read_only
                     Forces turning off write support for the given module.

              serialize
                     If  a  module  is  failing  to  handle  multiple requests
                     properly (using the new 5.0 module API), this will  force
                     the module to only receive one request at a time.

              bulk_to_next
                     If  a module registers to handle getbulk support, but for
                     some reason is failing to  implement  it  properly,  this
                     module  will  convert  all  getbulk  requests  to getnext
                     requests before the final module receives it.

       dontLogTCPWrappersConnects
              If the snmpd was compiled with  TCP  Wrapper  support,  it  logs
              every  connection  made  to the agent. This setting disables the
              log messages for accepted connections. Denied  connections  will
              still be logged.

       Figuring out module names
              To  figure  out  which  modules  you can inject things into, run
              snmpwalk on the nsModuleTable which will  give  a  list  of  all
              named modules registered within the agent.

   Internal Data tables
       table NAME

       add_row NAME INDEX(ES) VALUE(S)

NOTES

       o      The  Net-SNMP  agent  can  be  instructed to re-read the various
              configuration  files,  either  via  an  snmpset  assignment   of
              integer(1)         to        UCD-SNMP-MIB::versionUpdateConfig.0
              (.1.3.6.1.4.1.2021.100.11.0), or by sending a kill  -HUP  signal
              to the agent process.

       o      All  directives  listed  with a value of "yes" actually accept a
              range of boolean values.  These will accept any  of  1,  yes  or
              true  to  enable the corresponding behaviour, or any of 0, no or
              false to disable it.  The  default  in  each  case  is  for  the
              feature to be turned off, so these directives are typically only
              used to enable the appropriate behaviour.

EXAMPLE CONFIGURATION FILE

       See the EXAMPLE.CONF file in the top level source directory for a  more
       detailed example of how the above information is used in real examples.

FILES

       /etc/snmp/snmpd.conf

SEE ALSO

       snmpconf(1),  snmpusm(1),   snmp.conf(5),   snmp_config(5),   snmpd(8),
       EXAMPLE.conf, read_config(3).