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.TH SNMPD.CONF 5 "28 Feb 2003" VVERSIONINFO "Net-SNMP"
.UC 4
.SH NAME
SYSCONFDIR/snmp/snmpd.conf - configuration file for the Net-SNMP SNMP agent.
.SH DESCRIPTION
.B snmpd.conf
is the configuration file which defines how the Net-SNMP SNMP agent
operates.  These files may contain any of the directives found in the
.B DIRECTIVES
section below.  This file is not required for the agent to
operate and respond to requests.
.SH PLEASE READ FIRST
First, make sure you have read the
.I snmp_config(5) 
manual page that describes how the Net-SNMP configuration files
operate, where they are located and how they all work together.
.PP
Also, you might consider looking into the
.B snmpconf
application (perl script) which can help you build an snmpd.conf file
by prompting you for information.  You should try it.  Really.  Go
ahead.  Right now.  Run:
.RS
.IP "snmpconf -g basic_setup"
.RE
.PP
to get you started. See the
.I snmpconf(1)
manual page for more information.
.SH EXTENSIBLE-MIB
.PP
The Net-SNMP SNMP agent reports much of its information through
queries to the EXTENSIBLEDOTMIB section of the MIB tree.  Every MIB in
this section has the following table entries in it.
.IP ".MIBINDEX -- index"
This is the table's index numbers for each of the DIRECTIVES listed below.
.IP ".ERRORNAME -- name"
The name of the given table entry.  This should be unique, but is not
required to be.
.IP ".ERRORFLAG -- errorFlag"
This is a flag returning either the integer value 1 or 0 if an error
is detected for this table entry.
.IP ".ERRORMSG -- errorMsg"
This is a DISPLAY-STRING describing any error triggering the errorFlag above.
.IP ".ERRORFIX -- errorFix"
If this entry is set to the integer value of 1 AND the errorFlag
defined above is indeed a 1, a program or script will get executed
with the table entry name from above as the argument.  The program to
be executed is configured in the config.h file at compile time.
.SS Directives
.IP "proc NAME"
.IP "proc NAME MAX"
.IP "proc NAME MAX MIN"
.IP
Checks to see if processes called NAME are running on the agent
machine.  An error flag (1) and a description message are then passed
to the EXTENSIBLEDOTMIB.PROCMIBNUM.1.ERRORFLAG and
EXTENSIBLEDOTMIB.PROCMIBNUM.1.ERRORMSG MIB columns (respectively) if
the NAME'd program is not found in the process table as reported by
PSCMD.
.IP
If MAX and MIN are not specified, MAX is assumed to be 
.B infinity
and MIN is assumed to be 1.
.IP
If MAX is specified but MIN is not specified, MIN is assumed to be 0.
.IP "procfix NAME PROG ARGS"
This registers a command that knows how to fix errors with the given
process NAME.  When EXTENSIBLEDOTMIB.PROCMIBNUM.1.ERRORFIX for a given
NAMEd program is set to the integer value of 1, this command will be
called.  It defaults to a compiled value set using the PROCFIXCMD
definition in the config.h file.
.IP "exec NAME PROG ARGS"
.IP "exec MIBNUM NAME PROG ARGS"
.IP
If MIBNUM is not specified, the agent executes the named PROG with
arguments of ARGS and returns the exit status and the first line of
the STDOUT output of the PROG program to queries of the
EXTENSIBLEDOTMIB.SHELLMIBNUM.1.ERRORFLAG and
EXTENSIBLEDOTMIB.SHELLMIBNUM.1.ERRORMSG mib columns (respectively).  All
STDOUT output beyond the first line is silently truncated.
.IP
If MIBNUM is specified, it acts as above but returns the exit status
to MIBNUM.ERRORFLAG.0 and the entire STDOUT output to the table
MIBNUM.ERRORMSG in a MIB table.  In this case, the MIBNUM.ERRORMSG mib
contains the entire STDOUT output, one MIB table entry per line of
output (ie, the first line is output as MIBNUM.ERRORMSG.1, the second
at MIBNUM.ERRORMSG.2, etc...).
.RS
.IP Note:
The MIBNUM must be specified in dotted-integer notation and can
not be specified as ".iso.org.dod.internet..." (should instead
be .1.3.6.1...).
.IP Note: 
The agent caches the exit status and STDOUT of the executed program
for 30 seconds after the initial query.  This is to increase speed and
maintain consistency of information for consecutive table queries.
The cache can be flushed by a snmp-set request of integer(1) to
EXTENSIBLEDOTMIB.VERSIONMIBNUM.VERCLEARCACHE.
.RE
.IP "execfix NAME PROG ARGS"
This registers a command that knows how to fix errors with the given
exec or sh NAME.  When EXTENSIBLEDOTMIB.SHELLMIBNUM.1.ERRORFIX for a
given NAMEd entry is set to the integer value of 1, this command will
be called.  It defaults to a compiled value set using the EXECFIXCMD
definition in the config.h file.
.IP "disk PATH"
.IP "disk PATH [ MINSPACE | MINPERCENT% ]"
.IP
Checks the named disks mounted at PATH for available disk space.  If
the disk space is less than MINSPACE (kB) if specified or less than
MINPERCENT (%) if a % sign is specified, or DEFDISKMINIMUMSPACE (kB)
if not specified, the associated entry in the
EXTENSIBLEDOTMIB.DISKMIBNUM.1.ERRORFLAG MIB table will be set to (1) and
a descriptive error message will be returned to queries of
EXTENSIBLEDOTMIB.DISKMIBNUM.1.ERRORMSG.
.IP "load MAX1"
.IP "load MAX1 MAX5"
.IP "load MAX1 MAX5 MAX15"
.IP
Checks the load average of the machine and returns an error flag (1),
and an text-string error message
to queries of EXTENSIBLEDOTMIB.LOADAVEMIBNUM.1.ERRORFLAG and
EXTENSIBLEDOTMIB.LOADAVEMIBNUM.1.ERRORMSG (respectively) when the
1-minute, 5-minute, or 15-minute averages exceed the associated
maximum values.  If any of the MAX1, MAX5, or MAX15 values are
unspecified, they default to a value of DEFMAXLOADAVE.
.IP "file FILE [MAXSIZE]"
Monitors file sizes and makes sure they don't grow beyond a certain
size (in kilobytes).  MAXSIZE defaults to infinite if not specified,
and only monitors the size without reporting errors about it.
A maximum of 20 files can be monitored.
.SS "Errors"
.PP
Any errors in obtaining the above information are reported via the
EXTENSIBLEDOTMIB.ERRORMIBNUM.1.ERRORFLAG flag and the
EXTENSIBLEDOTMIB.ERRORMIBNUM.1.ERRORMSG text-string description.
.SH AGENTX SUB-AGENTS
To enable AgentX support in the SNMP master agent, put the following
line in your snmpd.conf file:
.IP "master agentx"
See README.agentx for further details.
.IP "AgentXSocket addr"
This defines the address the master agent listens at.
The default is /var/agentx/master. Another possibility is localhost:705
.IP "AgentXTimeout addr"
Defines the timeout period for an AgentX request.
Default is 1 second.
.IP "AgentXRetries addr"
Defines the number of retries for an AgentX request.
Default is 5 retries.
.P
You can also put the following in your subagent.conf file (where
"subagent" is the name you used in your init_snmp("subagent") api call:
.IP "agentPingInterval NUM"
This makes the subagent try and reconnect every NUM seconds to the
master if it ever becomes (or starts) disconnected.
>>>>>>> 5.4.2.3
.SH SMUX SUB-AGENTS
To enable and SMUX based sub-agent, such as
.IR gated ,
use the
.I smuxpeer
configuration entry
.IP "smuxpeer OID PASS"
For 
.I gated
a sensible entry might be
.I smuxpeer .1.3.6.1.4.1.4.1.3 secret
.SH DYNAMICALLY LOADABLE MODULES
If the agent is built with support for the UCD-DLMOD-MIB it is capable
of loading agent MIB modules dynamically at startup through
the \fIdlmod\fR directive and during runtime through use of the UCD-DLMOD-MIB.
The following directive loads the shared object module file PATH which
uses the module name prefix NAME.
.IP "dlmod NAME PATH"
.IP
.SH ACCESS CONTROL
.B snmpd
supports the View-Based Access Control Model (VACM) as defined in RFC
2575.  To this end, it recognizes the following keywords in the
configuration file: \fIcom2sec\fR, \fIgroup\fR, \fIaccess\fR, and
\fIview\fR as well as some easier-to-use wrapper directives:
\fIrocommunity\fR, \fIrwcommunity\fR, \fIrouser\fR, \fIrwuser\fR.  If
IPv6 support has been enabled, the \fIrocommunity6\fR and
\fIrwcommunity6\fR tokens will also be available.  This section
defines how to configure the snmpd program to accept various types and
levels of access.
.IP "rouser USER [noauth|auth|priv] [OID]"
.IP "rwuser USER [noauth|auth|priv] [OID]"
Creates a SNMPv3 USM user in the VACM access configuration tables.  It
is more efficient (and powerful) to use the combined \fIgroup\fR,
\fIaccess\fR, and \fIview\fR directives instead, but these wrapper
directives are much simpler.
.IP
The minimum level of authentication and privacy the user must use is
specified by the first token (which defaults to "auth").  The OID
parameter restricts access for that user to everything below the given
OID.
.IP "rocommunity COMMUNITY [SOURCE] [OID]"
.IP "rwcommunity COMMUNITY [SOURCE] [OID]"
These create read-only and read-write communities that can be used to
access the agent.  They are a quick wrapper around the more complex
and powerful \fIcom2sec\fR, \fIgroup\fR, \fIaccess\fR, and \fIview\fR
directive lines.  They are not as efficient either, as groups aren't
created so the tables are possibly larger.  In other words: don't use
these if you have complex situations to set up.  If your setup is
simple or you don't mind a small performance hit, use these
directives.
.IP
The format of the SOURCE is token is described in the \fIcom2sec\fR
directive section below.  The OID token restricts access for that
community to everything below that given OID.
.IP "rocommunity6 COMMUNITY [SOURCE] [OID]"
.IP "rwcommunity6 COMMUNITY [SOURCE] [OID]"
They are the alternative directives to the \fIrocommunity\fR,
\fIrwcommunity\fR for the transport domain UDPIPv6. They are only
valid in specifing \fIUDPIPv6\fR as transport domain.
.IP
The format of the SOURCE is token is described in the \fIcom2sec6\fR
directive section below.  The OID token restricts access for that
community to everything below that given OID.
.IP "com2sec NAME SOURCE COMMUNITY"
This directive specifies the mapping from a source/community pair to
a security name. SOURCE can be a hostname, a subnet, or the word
\fI"default"\fR.
A subnet can be specified as IP/MASK or IP/BITS.
The first source/community combination that matches the incoming packet
is selected.
.IP "com2sec6 NAME SOURCE COMMUNITY"
This directive is the IPv6 version of \fIcom2sec\fR.
A subnet can be specified as IPv6/IPv6MASK or IPv6/BITS.
It is only valid in specifing \fIUDPIPv6\fR as transport domain.
.IP "group NAME MODEL SECURITY"
This directive defines the mapping from securitymodel/securityname to group.
MODEL is one of \fIv1\fR, \fIv2c\fR, or \fIusm\fR.
.IP "access NAME CONTEXT MODEL LEVEL PREFX READ WRITE NOTIFY"
The access directive maps from group/security model/security level to
a view. 
MODEL is one of \fIany\fR, \fIv1\fR, \fIv2c\fR, or \fIusm\fR.
LEVEL is one of \fInoauth\fR, \fIauth\fR, or \fIpriv\fR.
PREFX specifies how CONTEXT should be matched against the context of
the incoming pdu, either \fIexact\fR or \fIprefix\fR.
READ, WRITE and NOTIFY specifies the view to be used for the corresponding 
access.
For v1 or v2c access, LEVEL will be noauth, and CONTEXT will be empty.
.IP "view NAME TYPE SUBTREE [MASK]"
This defines the named view. TYPE is either \fIincluded\fR or \fIexcluded\fR.
MASK is a list of hex octets, separated by '.' or ':'.  The MASK
defaults to "ff" if not specified.
.IP
The reason for the mask is, that it allows you to control access to
one row in a table, in a relatively simple way. As an example, as an ISP
you might consider giving each customer access to his or her own interface:
.IP
.nf
view cust1 included interfaces.ifTable.ifEntry.ifIndex.1 ff.a0
view cust2 included interfaces.ifTable.ifEntry.ifIndex.2 ff.a0
.IP
(interfaces.ifTable.ifEntry.ifIndex.1 == .1.3.6.1.2.1.2.2.1.1.1,
ff.a0 == 11111111.10100000. which nicely covers up and including
the row index, but lets the user vary the field of the row)
.IP "VACM Examples:"
.nf
#        sec.name  source          community
com2sec  local     localhost       private
com2sec  mynet     10.10.10.0/24   public
com2sec  public    default         public
com2sec6 mynet     fec0::/64       public

#             sec.model  sec.name
group mygroup v1         mynet
group mygroup v2c        mynet
group mygroup usm        mynet
group local   v1         local
group local   v2c        local
group local   usm        local
group public  v1         public
group public  v2c        public
group public  usm        public

#           incl/excl subtree                          mask
view all    included  .1                               80
view system included  system                           fe
view mib2   included  .iso.org.dod.internet.mgmt.mib-2 fc

#              context sec.model sec.level prefix read   write notify
access mygroup ""      any       noauth    exact  mib2   none  none
access public  ""      any       noauth    exact  system none  none
access local   ""      any       noauth    exact  all    all   all
.IP "Default VACM model"
The default configuration of the agent, as shipped, is functionally
equivalent to the following entries:
.nf
com2sec public  default public
group   public  v1      public
group   public  v2c     public
group   public  usm     public
view    all     included        .1
access  public  ""      any     noauth  exact   all     none    none
.SH SNMPv3 CONFIGURATION
.PP
.IP "engineID STRING"
The snmpd agent needs to be configured with an engineID to be able to
respond to SNMPv3 messages.  With this configuration file line, the
engineID will be configured from STRING.  The default value of the
engineID is configured with the first IP address found for the
hostname of the machine.
.IP "createUser username (MD5|SHA) authpassphrase [DES] [privpassphrase]"
.IP
MD5 and SHA are the authentication types to use, but you must have
built the package with openssl installed in order to use SHA.  The
only privacy protocol currently supported is DES.  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.
.IP
Warning: the minimum pass phrase length is 8 characters.
.IP
SNMPv3 users can be created at runtime using the
.I snmpusm(1)
command.
.IP
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.
.IP
This directive should be placed into the
PERSISTENT_DIRECTORY/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.
.IP
.SH SETTING SYSTEM INFORMATION
.IP "syslocation STRING"
.IP "syscontact STRING"
.IP "sysname STRING"
Sets the system location, system contact or system name for the agent.
This information is reported in the 'system' group the mibII tree.
Ordinarily these objects (sysLocation.0, sysContact.0 and sysName.0)
are read-write.  However, specifying the value for one of these
objects by giving the appropriate token makes the corresponding object
read-only, and attempts to set the value of the object will result in
a notWritable error response.
.IP "sysservices NUMBER"
Sets the value of the system.sysServices.0 object.
For a host, a good value is 72.
.IP "sysdescr STRING"
.IP "sysobjectid OID"
Sets the system description or object ID for the agent.
Although these values are not SNMP-writable, it is conceivable
that a network administrator may wish to configure them to something
other than the default values.
.IP "agentaddress [<transport-specifier>:]<transport-address>[,...]"
Makes the agent list on the specified comma-separated list of
listening addresses instead of the default behaviour, which is to
listen on UDP port 161 on all IPv4 interfaces.  See the section 
.B LISTENING ADDRESSES
in the
.I snmpd(8)
manual page for more information about the format of listening
addresses.  For example, specifying
.I "agentaddress 161,tcp:161,localhost:9161"
will make the agent listen on UDP port 161 on all IPv4 interfaces, TCP
port 161 on all IPv4 interfaces and UDP port 9161 only on the interface
associated with the localhost address.
.IP "agentgroup groupid"
Change to this gid after opening port. The groupid may refer to a group
by name or a number if the group number starts with '#'. For example,
specifying
.I agentgroup snmp
will cause the agent to run as the snmp group or
.I agentgroup #10
will cause the agent to run as the group with groupid 10.
.IP "agentuser uid"
Change to this uid after opening port. The userid may refer to a user
by name or a number if the user number starts with '#'. For example,
specifying
.I agentuser snmp
will cause the agent to run as the snmp user or
.I agentuser #10
will cause the agent to run as the user with userid 10.
.IP "interface NAME TYPE SPEED"
For interfaces where the agent fails to guess correctly on the type and
speed, this directive can supply additional information.
TYPE is a type value as given in the IANAifType-MIB.
.IP "ignoredisk STRING"
When scanning for available disk devices the agent might block in trying
to open all possible disk devices. This might lead to a timeout when
walking the device tree. Sometimes the next walk will run without timeout,
sometimes it will timeout every time you try it.
.IP
If you experience such behaviour you might add this directive and give all
device names not to be checked (i.e. opened). You might have more than one
such directive in your configuration file stating all devices not to be
opened. You might also specify those devices using wildcards similar to
the syntax you can use in a bourne shell (see examples below).
.IP
.B Note:
For a list of devices scanned for every system please consult the sources
(host/hr_disk.c) and check for the Add_HR_Disk_entry() calls relevant for
your type of OS.
.IP
Examples:
.IP
ignoredisk /dev/rdsk/c0t2d0
.IP
This directive prevents the device /dev/rdsk/c0t2d0 from being scanned.
.IP
ignoredisk /dev/rdsk/c0t[!6]d0
.IP
This directive prevents all devices /dev/rdsk/c0tXd0 except .../c0t6d0
from being scanned. For most systems similar is the following directive:
.IP
ignoredisk /dev/rdsk/c0t[0-57-9a-f]d0
.IP
ignoredisk /dev/rdsk/c1*
.IP
This directive prevents all devices whose device names start with /dev/rdsk/c1
from being scanned.
.IP
ignoredisk /dev/rdsk/c?t0d0
.IP
This directive prevents all devices /dev/rdsk/cXt0d0 ('X' might be any char)
from being scanned.
.IP
You might use more than one such wildcard expression in any such directive.
.IP "storageUseNFS NUMBER"
Setting storageUseNFS to 1 causes all NFS and NFS-like file systems to be
marked as 'Network Disks' in the hrStorageTable. This is according to RFC 2790.
Not setting storageUseNFS or setting it to 2 causes NFS and NFS-like file
systems to be marked as 'Fixed Disks' as it has been in previous versions of
the ucd-snmp SNMP agent.
.IP "authtrapenable NUMBER"
Setting authtrapenable to 1 enables generation of authentication failure
traps.  The default value is disabled(2).  Ordinarily the corresponding
object (snmpEnableAuthenTraps.0) is read-write, but setting its value
via this token makes the object read-only, and attempts to set the
value of the object will result in a notWritable error response.
.IP "override 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.
An example:
.IP
override sysDescr.0 octet_str "my own sysDescr"
.IP
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).
.IP
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.
.IP
Valid TYPEs are: integer, uinteger, octet_str, bit_str, object_id,
counter, gauge, null.  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.
.IP
More types should be available in the future, as well as writable
object support.
.SH "SETTING UP TRAP AND/OR INFORM DESTINATIONS"
.IP "trapcommunity STRING"
This defines the default community string to be used when sending traps.
Note that this command must be used prior to any of the following three
commands that are intended use this community string.
.IP "trapsink HOST [COMMUNITY [PORT]]"
.IP "trap2sink HOST [COMMUNITY [PORT]]"
.IP "informsink HOST [COMMUNITY [PORT]]"
These commands define
the hosts to receive traps (and/or inform notifications). The
daemon sends a Cold Start trap when it starts up. If enabled, it also sends
traps on authentication failures.  Multiple \fItrapsink\fR, \fItrap2sink\fR
and \fIinformsink\fR lines may be specified to specify multiple destinations.
Use \fItrap2sink\fR to send SNMPv2 traps and \fIinformsink\fR to send
inform notifications.
If COMMUNITY is not specified, the string from a preceding \fItrapcommunity\fR
directive will be used. If PORT is not specified, the well known SNMP trap
port (162) will be used.
.IP "trapsess [SNMPCMD_ARGS] HOST"
This is a more generic trap configuration token that allows any type
of trap destination to be specified with any version of SNMP.  See the 
.I snmpcmd(1)
manual page for further details on the arguments that can be passed as
.I "SNMPCMD ARGS".
In addition to the arguments listed there, the special argument
\fI-Ci\fR specifies that you want inform notifications to be used
instead of unacknowledged traps (this requires that you also specify a 
version number of v2c or v3 as well).
.SH "PROXY SUPPORT"
.IP "proxy [-Cn CONTEXTNAME] [SNMPCMD ARGS] HOST OID [REMOTEOID]"
.IP
This token specifies that any incoming requests under OID should be
proxied on to another HOST instead.  If a CONTEXTNAME is specified, it
assigns the proxied tree to a particular context name within the local
agent.  This is the proper way to query multiple agents through a
single proxy.  Assign each remote agent to a different context name.
Then you can use "snmpwalk -n contextname1" to walk one remote proxied
agent and "snmpwalk -n contextname2" to walk another, assuming you are
using SNMPv3 to talk to the proxy (snmpv1 and snmpv2c context mappings
aren't currently supported but might be in the future).  Optionally,
relocate the local OID tree to the new location at the REMOTEOID.  To
authenticate to HOST you should use the appropriate set of
.I "SNMPCMD ARGS."
See the
.I snmpcmd(1)
manual page for details.
.IP
Examples:
.RS
.IP
.nf
# assigns the entire mib tree on remotehost1 to the context of the
# same name:
proxy -Cn remotehost1 -v 1 -c public remotehost1 .1.3
# ditto, but for remotehost 2
proxy -Cn remotehost2 -v 1 -c public remotehost2 .1.3
# proxies only the ucdavis enterprises tree to the remote host using snmpv1
proxy -v 1 -c public remotehost .1.3.6.1.4.1.2021
# uses v3 to access remotehost and converts the remote .1.3.6.1.2.1.1
# oid to local .1.3.6.1.3.10 oid (another way to access mulitple hosts
# without using contexts)
proxy -v 3 -l noAuthNoPriv -u user remotehost .1.3.6.1.3.10 .1.3.6.1.2.1.1
.SH "PASS-THROUGH CONTROL"
.IP "pass MIBOID EXEC"
(If you're writing perl scripts, please see the embedded perl support
information later in this manual page).  Passes entire control of
MIBOID to the EXEC program.  The EXEC program is called in one of the
following three ways:
.RS
.IP "EXEC -g MIBOID"
.IP "EXEC -n MIBOID"
.IP
These call lines match to SNMP get and getnext requests.  It is
expected that the EXEC program will take the arguments passed to it
and return the appropriate response through it's stdout.  
.IP
The first line of stdout should be the MIB OID of the returning value.
The second line should be the TYPE of value returned, where TYPE is
one of the text strings:
.B string, integer, unsigned, objectid, timeticks, ipaddress, counter, 
or
.B gauge.
The third line of stdout should be the VALUE corresponding with the
returned TYPE.
.IP
For instance, if a script was to return the value integer value "42"
when a request for .1.3.6.1.4.100 was requested, the script should
return the following 3 lines:
.br
.RS
  .1.3.6.1.4.100
.br
  integer
.br
  42
.RE
.IP
To indicate that the script is unable to comply with the request due
to an end-of-mib condition or an invalid request, simple exit and
return no output to stdout at all.  An SNMP error will be generated
corresponding to the SNMP noSuchName response.
.IP "EXEC -s MIBOID TYPE VALUE"
.IP 
For SNMP set requests, the above call method is used.  The TYPE passed
to the EXEC program is one of the text strings:
.B integer, counter, gauge, timeticks, ipaddress, objid,
or 
.B string,
indicating the type of value passed in the next argument.
.IP
Return nothing to stdout, and the set will assumed to have been
successful.  Otherwise, return one of the following error strings to
signal an error:
.B not-writable, 
or 
.B wrong-type
and the appropriate error response will be generated instead.
.RS
.IP Note:
By default, the only community allowed to write (ie snmpset) to your
script will be the "private" community,or community #2 if defined
differently by the "community" token discussed above.  Which
communities are allowed write access are controlled by the RWRITE
definition in the snmplib/snmp_impl.h source file.
.RE
.RE
.IP
Example (in snmpd.conf):
.IP
pass .1.3.6.1.4.1.2021.255 /path/to/local/passtest
.RE
.IP "pass_persist MIBOID EXEC"
Passes entire control of MIBOID to the EXEC program.  
Similar to pass, but the EXEC program continues to run after the initial
request is answered.
.IP
Upon initialization, EXEC is passed the string "PING\\n" in stdin,
and it should respond by printing "PONG\\n" to stdout.
.IP
For get and getnext requests, EXEC program is passed two lines,
the command (get or getnext) and the MIB OID.  It should return
three lines, the MIB OID, the TYPE of value returned,
the VALUE corresponding with the returned TYPE.
.IP
For example, if the value for .1.3.6.1.4.100 was requested, the following
2 lines would be passed in to stdin:
.br
.RS
  get
.br
  .1.3.6.1.4.100  
.RE
.IP
To return the value, say, 42, the script would write to stdout:
.br
.RS
  .1.3.6.1.4.100
.br
  integer
.br
  42
.RE
.IP
To indicate that the script is unable to comply with the request due
to an end-of-mib condition or an invalid request, print "NONE\\n" to
stdout.
.IP
Example (in snmpd.conf):
.IP
pass_persist .1.3.6.1.4.1.2021.255 /path/to/local/pass_persisttest
.RE
.SH "EMBEDDED PERL SUPPORT"
.PP
Warning: though embedded perl is working, not much functionality has
been implemented yet and thus writing mib module pieces for the agent
within perl is not trivial at this point.  It should get better in
future releases.
.PP
The net-snmp package has ability to call perl scripts directly inside
the agent through embedded perl technology (similar to mod_perl for
the apache web server).  This must be turned on at compile time by
passing --enable-embedded-perl to the configure script when the
package is built.  To see if your package was built with embedded
perl, run "net-snmp-config --configure-options" and see if that flag
was used.
.PP
If compiled in, it defines the following snmpd.conf configuration
directives:
.IP "disablePerl true"
This will turn off perl support entirely.  If the embedded perl
support stops working due to a change in perl, etc, this will stop any
calls to the perl core.

.IP "perlInitFile FILE"
Use FILE as the initialization file.  This file is normally
DATADIR/snmp/snmp_perl.pl but this token can override that default.
This file performs any in-perl initialization that is needed before
the rest of the perl directives (below) are called.  It is sourced
once just before the first perl directive is parsed.  See the default
file for an example of the initialization it performs.
.IP "perl EXPRESSION"
Calls perl to evaluate an expression.  Normally you'd want to do
something like register a function to call when an OID is requested,
but you can really do anything perl related you want.  For example:
.IP
.RS
perl print "hello world\\n";
.RE
.IP
is the most basic hello world example.
.IP
The init script by default initializes a $agent variable which
is a pointer to a NetSnmp::agent object through which you can register
callbacks when a section of the OID tree is hit:
.IP
.RS
.nf
perl use Data::Dumper;
perl sub myroutine  { print "got called: ",Dumper(@_),"\\n"; }
perl $agent->register('mylink', '.1.3.6.1.8765', \\&myroutine);
.fi
.RE
.IP
Sourcing an external file:
.IP
.RS
.nf
perl 'do /path/to/file.pl';
.fi
.RE
.IP
No better examples exist at the moment, unfortunately.  Look for
improved support in future releases.  Comments on how this looks as an
architecture are certainly appreciated now.
.SH "DISMAN-EVENT-MIB SUPPORT (READ: SENDING TRAPS ON ERRORS)"
.PP
Warning: this implementation has not been extensively tested and is
additionally not known to be entirely complete.  The concepts defined
here should function appropriately, however, but no promises are made
at this time.
.PP
If your agent was compiled with support for the DISMAN-EVENT-MIB (you
can enable this by running the net-snmp configure script with the
--with-mib-modules=disman/event-mib argument) you have support for
having the agent check its own data at regular intervals and to send
out traps when certain conditions occur.  Traps are sent when
expressions are first noticed, not once per evaluation.  Once a test
expression fires a trap, the test will have to fail again before a new
trap is sent.  See the DISMAN-EVENT-MIB documentation for more
details. This can be configured either using the MIB tables themselves
or by using these special key words:
.IP "agentSecName NAME"
The DISMAN-EVENT-MIB support requires a valid user name for which to
scan your agent with.  This can either be specified using the
agentSecName token or by explicitly list one on the "monitor" lines
described below using the -u switch.  Either way, a "rouser" line (or
equivalent access control settings) must also be specified with the
same security name name.  If you need an example, just do something
like this:
.RS
.IP
.nf
agentSecName internal
rouser internal
.fi
.RE
.IP
And everything below should work just fine.
.IP "monitor [OPTIONS] NAME EXPRESSION"
This token tells the agent to monitor itself for problems based on
EXPRESSION.  Expression is a simple expression based on an oid, a
comparison operator (!=, ==, <, <=, >, >=) and an integer value (see
the examples below).  NAME is merely an arbitrary name of your
choosing for administrative purposes only.  OPTIONS include the
following possibilities:
.RS
.IP "-r FREQUENCY"
Monitors the given expression every FREQUENCY seconds.  The default is
600 (10 minutes). 
.IP "-u SECNAME"
Use the SECNAME security name for scanning the local host.
Specifically, this SECNAME must then be given access control rights
via something like the "rouser" snmpd.conf token for this expression
to be valid at all.  If not specified, it uses the default security
name specified by the agentsecname snmpd.conf token.  Either the -u
flag or a valid agentsecname token must be specified (and that name
must be given proper access control rights via a "rouser" token).
.IP "-o OID"
Specifies additional object values to be delivered with in the
resulting trap in addition to the normal trap objects.  This is useful
for obtaining other columns in the table for the row that triggered
the expression.  See the examples below for more details.
.RE
.IP
The following example configuration checks the hrSWRunPerfTable table
(listing running processes) for any process which is consuming > 10Mb
of memory.  It performs this check every 600 seconds (the default).
For every process it finds exceeding the limit, it will end out
exactly one notification.  In addition to the normal hrSWRunPerfMem
oid and value sent in the trap, the hrSWRunName object will also be
sent.  Note that the hrSWRunName object actually occurs in a different
table, but since the indexes to the two tables are the same this works
out alright.
.RS
.IP
.nf
rouser me
monitor -u me -o sysUpTime.0 -o hrSWRunName "high process memory" hrSWRunPerfMem > 10000
.RE
.fi
.IP
The above line would produce a trap which, when formated by snmptrapd, would
look like:
.RS
.IP
.nf
2002-04-05 13:33:53 localhost.localdomain [udp:127.0.0.1:32931]:
        sysUpTimeInstance = Timeticks: (1629) 0:00:16.29        snmpTrapOID.0 = OID: mteTriggerFired    mteHotTrigger = high process memory     mteHotTargetName =      mteHotContextName =     mteHotOID = OID: hrSWRunPerfMem.1968    mteHotValue = 28564     hrSWRunName.1968 = "xemacs"
.RE
.fi
.IP
This shows my xemacs process using 28Mb of resident memory.  Which,
considering it's xemacs, is not that surprising.
.IP "defaultMonitors yes"
By default, the agent and the DISMAN-EVENT-MIB support do nothing
until configured.  Typically people wish to watch a bunch of tables
within the UCD-SNMP-MIB which are designed specifically for reporting
problems.  If the "defaultMonitors yes" line is put into the
snmpd.conf file (which must be accompanied by an appropriate
agentSecName line and a rouser line), the following monitoring
conditions will be installed:
.RS
.IP
.nf
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
.fi
.RE
.SH "DEBUGGING AND OTHER EXTENSIBILITY NOTES"
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:
.IP "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:
.RS
.nf
debug        - Prints out lots of debugging information when -Dhelper:debug
               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.
.fi
.RE
.IP "Figuring out module names"
To figure out which modules you can inject things into, snmpwalk the
nsModuleTable which will give you a list of all named modules
registered within the agent.
.SH "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.
.SH "RE-READING snmpd.conf AND snmpd.local.conf"
The Net-SNMP agent can be forced to re-read its configuration files.
It can be told to do so by one of two ways:
.IP 1.
An snmpset of integer(1) to UCD-SNMP-MIB::versionUpdateConfig.0
(.1.3.6.1.4.1.2021.100.11.0)
.IP 2.
A "kill -HUP" signal sent to the snmpd agent process.
.SH "FILES"
SYSCONFDIR/snmp/snmpd.conf
.SH "SEE ALSO"
snmpconf(1), snmpusm(1), snmp.conf(5), snmp_config(5), snmpd(8), EXAMPLE.conf, read_config(3).
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