Provided by: libsnmp-base_5.4.1~dfsg-4ubuntu4_all bug

NAME

       snmpd.examples - example configuration for the Net-SNMP agent

DESCRIPTION

       The  snmpd.conf(5)  man  page  defines  the syntax and behaviour of the
       various configuration directives  that  can  be  used  to  control  the
       operation  of  the  Net-SNMP  agent,  and the management information it
       provides.

       This companion man page  illustrates  these  directives,  showing  some
       practical examples of how they might be used.

AGENT BEHAVIOUR

   Listening addresses
       The  default  agent behaviour (listing on the standard SNMP UDP port on
       all interfaces) is equivalent to the directive:
              agentaddress udp:161
       or simply
              agentaddress 161
       The agent can be configured to only accept requests sent to  the  local
       loopback interface (again listening on the SNMP UDP port), using:
              agentaddress localhost:161     # (udp implicit)
       or
              agentaddress 127.0.0.1     # (udp and standard port implicit)
       It  can  be  configured  to accept both UDP and TCP requests (over both
       IPv4 and IPv6), using:
              agentaddress udp:161,tcp:161,udp6:161,tcp6:161
       Other combinations are also valid.

   Run-time privileges
       The agent can be configured to relinquish any privileged access once it
       has  opened the initial listening ports.  Given a suitable "snmp" group
       (defined in /etc/group), this could be done using the directives:
              agentuser  nobody
              agentgroup snmp
       A similar effect could be achieved using numeric UID and/or GID values:
              agentuser  #10
              agentgroup #10

   SNMPv3 Configuration
       Rather  than  being  generated  pseudo-randomly,  the engine ID for the
       agent could be calculated based  on  the  MAC  address  of  the  second
       network interface (eth1), using the directives:
              engineIDType 3 engineIDNic  eth1
       or it could be calculated from the (first) IP address, using:
              engineIDType 1
       or it could be specified explicitly, using:
              engineID "XXX - WHAT FORMAT"

ACCESS CONTROL

   SNMPv3 Users
       The following directives will create three users, all using exactly the
       same authentication and encryption settings:
              createUser me     MD5 "single pass phrase"
              createUser myself MD5 "single pass phrase" DES
              createUser andI   MD5 "single pass phrase" DES "single pass phrase"
       Note that this defines three  distinct  users,  who  could  be  granted
       different  levels  of  access.   Changing the passphrase for any one of
       these would not affect the other two.

       Separate  pass  phrases  can  be  specified  for   authentication   and
       encryption:
              createUser onering SHA "to rule them all" AES "to bind them"
       Remember  that  these  createUser  directives  should be defined in the
       /var/lib/snmp/snmpd.conf file, rather than the usual location.

   Traditional Access Control
       The SNMPv3 users defined above can be granted access to  the  full  MIB
       tree using the directives:
              rouser me
              rwuser onering
       Or selective access to individual subtrees using:
              rouser myself   .1.3.6.1.2
              rwuser andI     system

       Note that a combination repeating the same user, such as:
              rouser onering
              rwuser onering
       should  not  be  used. This would configure the user onering with read-
       only access (and ignore the rwuser entry altogether).  The  same  holds
       for the community-based directives.

       The directives:
              rocommunity public
              rwcommunity private
       would define the commonly-expected read and write community strings for
       SNMPv1 and SNMPv2c requests.   This  behaviour  is  not  configured  by
       default, and would need to be set up explicitly.

              Note:  It  would  also  be a very good idea to change private to
                     something a little less predictable!

       A  slightly  less  vulnerable   configuration   might   restrict   what
       information could be retrieved:
              rocommunity public   default system
       or the management systems that settings could be manipulated from:
              rwcommunity private  10.10.10.0/24
       or a combination of the two.

   VACM Configuration
       This last pair of settings are equivalent to the full VACM definitions:
              #         sec.name  source        community
              com2sec   public    default       public
              com2sec   mynet     10.10.10.0/24 private
              com2sec6  mynet     fec0::/64     private

              #                  sec.model  sec.name
              group  worldGroup  v1         public
              group  worldGroup  v2c        public
              group  myGroup     v1         mynet
              group  myGroup     v2c        mynet

              #              incl/excl   subtree     [mask]
              view   all     included    .1
              view   sysView included    system

              #              context model level   prefix  read    write  notify (unused)
              access  worldGroup  ""  any  noauth  exact   system  none   none
              access  myGroup     ""  any  noauth  exact   all     all    none

       There are several points to note in this example:

       The group directives must be  repeated  for  both  SNMPv1  and  SNMPv2c
       requests.

       The com2sec security name is distinct from the community string that is
       mapped  to  it.  They  can  be  the  same   ("public")   or   different
       ("mynet"/"private")  -  but  what appears in the group directive is the
       security name, regardless of the original community string.

       Both of the view  directives  are  defining  simple  OID  subtrees,  so
       neither  of  these  require  an  explicit mask.  The same holds for the
       "combined subtree2 view defined below.  In fact, a mask field  is  only
       needed  when defining row slices across a table (or similar views), and
       can almost always be omitted.

       In general, it is advisible  not  to  mix  traditional  and  VACM-based
       access  configuration  settings,  as these can sometimes interfere with
       each other in unexpected ways.  Choose a  particular  style  of  access
       configuration, and stick to it.

   Typed-View Configuration
       A similar configuration could also be configured as follows:
              view   sys2View included    system
              view   sys2View included    .1.3.6.1.2.1.25.1

              authcommunity read       public  default      -v sys2View
              authcommunity read,write private 10.10.10.0/8

       This  mechanism  allows multi-subtree (or other non-simple) views to be
       used with the one-line rocommunity style of configuration.

       It would also support configuring "write-only" access, should  this  be
       required.

SYSTEM INFORMATION

   System Group
       The  full  contents  of  the  ’system’  group  (with  the  exception of
       sysUpTime) can be explicitly configured using:
              # Override uname -a and hardcoded system OID - inherently read-only values
              sysDescr     Universal Turing Machine mk I
              sysObjectID  .1.3.6.1.4.1.8072.3.2.1066

              # Override default values from configure - makes these objects read-only
              sysContact   Alan.Turing@pre-cs.man.ac.uk
              sysName      tortoise.turing.com
              sysLocation  An idea in the mind of AT

              # Standard end-host behaviour
              sysServices  72

   Host Resources Group
       The  list  of  devices  probed   for   potential   inclusion   in   the
       hrDiskStorageTable  (and hrDeviceTable) can be amended using any of the
       following directives:
              ignoredisk /dev/rdsk/c0t2d0
       which prevents the device /dev/rdsk/c0t2d0 from being scanned,
              ignoredisk /dev/rdsk/c0t[!6]d0
              ignoredisk /dev/rdsk/c0t[0-57-9a-f]d0
       either  of  which  prevents  all   devices   /dev/rdsk/c0tXd0   (except
       .../c0t6d0) from being scanned,
              ignoredisk /dev/rdsk/c1*
       which  prevents  all devices whose device names start with /dev/rdsk/c1
       from being scanned, or
              ignoredisk /dev/rdsk/c?t0d0
       which prevents all devices /dev/rdsk/cXt0d0 (where ’X’  is  any  single
       character) from being scanned.

   Process Monitoring
       The  list  of  services  running  on  a  system  can  be monitored (and
       provision made for correcting any problems), using:
              # At least one web server process must be running at all times
              proc    httpd
              procfix httpd  /etc/rc.d/init.d/httpd restart

              # There should never be more than 10 mail processes running
              #    (more implies a probable mail storm, so shut down the mail system)
              proc    sendmail   10
              procfix sendmail  /etc/rc.d/init.d/sendmail stop

              # There should be a single network management agent running
              #   ("There can be only one")
              proc    snmpd    1  1
       Also see the "DisMan Event MIB" section later on.

   Disk Usage Monitoring
       The state of disk storage can be monitored using:
              includeAllDisks 10%
              disk /var 20%
              disk /usr  3%
              #  Keep 100 Mb free for crash dumps
              disk /mnt/crash  100000

   System Load Monitoring
       A simple check for an overloaded system might be:
              load 10
       A more refined  check  (to  allow  brief  periods  of  heavy  use,  but
       recognise sustained medium-heavy load) might be:
              load 30 10 5

   Log File Monitoring
       TODO
              file FILE [MAXSIZE]
              logmatch NAME PATH CYCLETIME REGEX

ACTIVE MONITORING

   Notification Handling
       Configuring  the  agent to report invalid access attempts might be done
       by:
              authtrapenable 1
              trapcommunity  public
              trap2sink      localhost
       Alternatively, the second and third directives could be  combined  (and
       an acknowledgement requested) using:
              informsink     localhost  public
       A configuration with repeated sink destinations, such as:
              trapsink       localhost
              trap2sink      localhost
              informsink     localhost
       should  NOT be used, as this will cause multiple copies of each trap to
       be sent to the same trap receiver.

       TODO - discuss SNMPv3 traps
              trapsess  snmpv3 options  localhost:162

       TODO - mention trapd access configuration

   DisMan Event MIB
       The simplest configuration for active self-monitoring of the agent,  by
       the agent, for the agent, is probably:
              # Set up the credentials to retrieve monitored values
              createUser    _internal MD5 "the first sign of madness"
              iquerySecName _internal
              rouser        _internal

              # Active the standard monitoring entries
              defaultMonitors         yes
              linkUpDownNotifications yes

              # If theres a problem, then tell someone!
              trap2sink localhost

       The  first block sets up a suitable user for retrieving the information
       to by monitored, while  the  following  pair  of  directives  activates
       various built-in monitoring entries.

       Note  that  the  DisMan  directives  are  not  themselves sufficient to
       actively  report  problems  -  there  also  needs  to  be  a   suitable
       destination configured to actually send the resulting notifications to.

       A more detailed monitor example is given by:
              monitor   -u   me   -o   hrSWRunName   "high   process   memory"
              hrSWRunPerfMem > 10000

       This defines an explicit boolean monitor entry, looking for any process
       using more than 10Mb of active memory.  Such processes will be reported
       using  the  (standard) DisMan trap mteTriggerFired, but adding an extra
       (wildcarded) varbind hrSWRunName.

       This entry also specifies an explicit user (me, as defined earlier) for
       retrieving the monitored values, and building the trap.

       Objects that could potentially fluctuate around the specified level are
       better monitored using a threshold monitor entry:
              monitor -D -r 10 "network traffic" ifInOctets 1000000 5000000

       This will send a mteTriggerRising trap whenever  the  incoming  traffic
       rises  above  (roughly)  500  kB/s  on  any  network  interface,  and a
       corresponding mteTriggerFalling trap  when  it  falls  below  100  kB/s
       again.

       Note  that  this  monitors  the  deltas between successive samples (-D)
       rather than the actual sample values themselves.  The same effect could
       be obtained using:
              monitor -r 10 "network traffic" ifInOctets - - 1000000 5000000

       The linkUpDownNotifications directive above is broadly equivalent to:
              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

       This  defines  the  traps  to  be  sent  (using notificationEvent), and
       explicitly references the relevant notification  in  the  corresponding
       monitor entry (rather than using the default DisMan traps).

       The  defaultMonitors  directive  above  is  equivalent  to  a series of
       (boolean) monitor entries:
              monitor   -o prNames      -o prErrMessage  "procTable" 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
       and will send a trap whenever any of these entries indicate a  problem.

       An   alternative   approach   would  be  to  automatically  invoke  the
       corresponding "fix" action:
              setEvent   prFixIt  prErrFix = 1
              monitor -e prFixIt "procTable" prErrorFlag   != 0
       (and similarly for any of the other defaultMonitor entries).

   DisMan Schedule MIB
       The agent could be configured to reload its configuration once an hour,
       using:
              repeat 3600 versionUpdateConfig.0 = 1

       Alternatively  this  could be configured to be run at specific times of
       day (perhaps following rotation of the logs):
              cron 10 0 * * * versionUpdateConfig.0 = 1

       The one-shot style of scheduling is rather less common, but the  secret
       SNMP  virus  could  be  activated  on the next occurance of Friday 13th
       using:
              at   13 13 13 * 5 snmpVirus.0 = 1

EXTENDING AGENT FUNCTIONALITY

   Arbitrary Extension Commands
       Old Style
              exec [MIBOID] NAME PROG ARGS"
              sh   [MIBOID] NAME PROG ARGS"
              execfix NAME PROG ARGS"
       New Style
              extend [MIBOID] NAME PROG ARGS"
              extendfix [MIBOID] NAME PROG ARGS"

   MIB-Specific Extension Commands
       One-Shot
              "pass [-p priority] MIBOID PROG"

              Persistent
              "pass_persist [-p priority] MIBOID PROG"

   Embedded Perl Support
       If  embedded  perl  support  is  enabled  in  the  agent,  the  default
       initialisation is equivalent to the directives:
              disablePerl  false
              perlInitFile /usr/share/snmp/snmp_perl.pl
       The  main  mechanism  for  defining  embedded  perl scripts is the perl
       directive.  A very simple (if somewhat pointless) MIB handler could  be
       registered using:
              perl use Data::Dumper;
              perl sub myroutine  { print "got called: ",Dumper(@_),"\n"; }
              perl $agent->register(’mylink’, ’.1.3.6.1.8765’, \&myroutine);

       This  relies  on the $agent object, defined in the example snmp_perl.pl
       file.

       A more realistic MIB handler might be:
              XXX - WHAT ???
       Alternatively, this code could be  stored  in  an  external  file,  and
       loaded using:
              perl ’do /usr/share/snmp/perl_example.pl’;

   Dynamically Loadable Modules
       TODO
              dlmod NAME PATH"

   Proxy Support
       A  configuration for acting as a simple proxy for two other SNMP agents
       (running on remote systems) might be:
              com2sec -Cn rem1context  rem1user default  remotehost1
              com2sec -Cn rem2context  rem2user default  remotehost2

              proxy -Cn rem1context  -v 1 -c public  remotehost1  .1.3
              proxy -Cn rem2context  -v 1 -c public  remotehost2  .1.3
       (plus suitable access control entries).

       The same proxy  directives  would  also  work  with  (incoming)  SNMPv3
       requests,  which  can specify a context directly.  It would probably be
       more sensible to use contexts of  remotehost1  and  remotehost2  -  the
       names above were chosen to indicate how these directives work together.

       Note that the administrative  settings  for  the  proxied  request  are
       specified  explicitly,  and  are  independent  of the settings from the
       incoming request.

       An alternative use for the proxy directive is to pass part of  the  OID
       tree  to  another  agent  (either  on  a  remote host or listening on a
       different port on the same system), while handling the rest internally:
              proxy -v 1 -c public  localhost:6161  .1.3.6.1.4.1.99
       This mechanism can be used to link together two separate SNMP agents.

       A  less  usual  approach is to map one subtree into a different area of
       the overall MIB tree (either locally or on a remote system):
              # uses SNMPv3 to access the MIB tree .1.3.6.1.2.1.1 on remotehost
              # and maps this to the local tree .1.3.6.1.3.10
              proxy -v 3 -l noAuthNoPriv -u user remotehost .1.3.6.1.3.10 .1.3.6.1.2.1.1

   SMUX Sub-Agents
              smuxsocket 127.0.0.1
              smuxpeer .1.3.6.1.2.1.14 ospf_pass

   AgentX Sub-Agents
       The Net-SNMP agent could be configured to operate as an  AgentX  master
       agent  (listening on a non-standard named socket, and running using the
       access privileges defined earlier), using:
              master agentx
              agentXSocket /tmp/agentx/master
              agentXPerms  0660 0550 nobody snmp
       A sub-agent wishing to connect to this master agent would need the same
       agentXSocket directive, or the equivalent code:
              netsnmp_ds_set_string(NETSNMP_DS_APPLICATION_ID, NETSNMP_DS_AGENT_X_SOCKET,
                                    "/tmp/agentx/master");

       A loopback networked AgentX configuration could be set up using:
              agentXSocket   tcp:localhost:705
              agentXTimeout  5
              agentXRetries  2
       on the master side, and:
              agentXSocket   tcp:localhost:705
              agentXTimeout  10
              agentXRetries  1
              agentXPingInterval 600
       on the client.

       Note  that the timeout and retry settings can be asymmetric for the two
       directions, and the sub-agent can poll  the  master  agent  at  regular
       intervals  (600s = every 10 minutes), to ensure the connection is still
       working.

OTHER CONFIGURATION

              override sysDescr.0 octet_str "my own sysDescr"
              injectHandler stash_cache NAME table_iterator

FILES

       /etc/snmp/snmpd.conf

SEE ALSO

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