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RedHat 6.2(Zoot) |
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snmpd.conf(5) |
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/usr/share/snmp/snmpd.conf - configuration file for the ucd-snmp SNMP agent.
snmpd.conf is the configuration file which defines how the ucd-smnp SNMP agent operates. These files may contain any of the directives found in the DIRECTIVES section below. This file is not required for the agent to operate and report mib entries.
First, make sure you have read the snmp_config(5) manual page that describes how the ucd-snmp configuration files operate, where they are located and how they all work together.
The ucd-snmp
SNMP agent reports much of its information through queries
to the 1.3.6.1.4.1.2021 section of the mib tree. Every mib
in this section has the following table entries in it.
.1 -- index
This is the table’s index numbers for each of the DIRECTIVES listed below.
.2 -- name
The name of the given table entry. This should be unique, but is not required to be.
.100 -- errorFlag
This is a flag returning either the integer value 1 or 0 if an error is detected for this table entry.
.101 -- errorMsg
This is a DISPLAY-STRING describing any error triggering the errorFlag above.
.102 -- errorFix
If this entry is SNMPset 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.
Directives
proc NAME
proc NAME MAX
proc NAME MAX MIN
Checks to see if the NAME’d processes are running on the agent’s machine. An error flag (1) and a description message are then passed to the 1.3.6.1.4.1.2021.2.100 and 1.3.6.1.4.1.2021.2.101 mib tables (respectively) if the NAME’d program is not found in the process table as reported by "/bin/ps -e".
If MAX and MIN are not specified, MAX is assumed to be infinity and MIN is assumed to be 1.
If MAX is specified but MIN is not specified, MIN is assumed to be 0.
procfix NAME PROG ARGS
This registers a command that knows how to fix errors with the given process NAME. When 1.3.6.1.4.1.2021.2.102 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.
exec NAME PROG ARGS
exec MIBNUM NAME PROG ARGS
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 1.3.6.1.4.1.2021.8.100 and 1.3.6.1.4.1.2021.8.101 mib tables (respectively). All STDOUT output beyond the first line is silently truncated.
If MIBNUM is specified, it acts as above but returns the exit status to MIBNUM.100.0 and the entire STDOUT output to the table MIBNUM.101 in a mib table. In this case, the MIBNUM.101 mib contains the entire STDOUT output, one mib table entry per line of output (ie, the first line is output as MIBNUM.101.1, the second at MIBNUM.101.2, etc...).
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Note: |
The MIBNUM must be specified in dotted-integer notation and can not be specified as ".iso.org.dod.internet..." (should instead be | ||
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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 1.3.6.1.4.1.2021.100.VERCLEARCACHE. |
execfix NAME PROG ARGS
This registers a command that knows how to fix errors with the given exec or sh NAME. When 1.3.6.1.4.1.2021.8.102 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.
disk PATH
disk PATH [ MINSPACE | MINPERCENT% ]
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 1.3.6.1.4.1.2021.9.100 mib table will be set to (1) and a descriptive error message will be returned to queries of 1.3.6.1.4.1.2021.9.101.
load MAX1
load MAX1 MAX5
load MAX1 MAX5 MAX15
Checks the load average of the machine and returns an error flag (1), and an text-string error message to queries of 1.3.6.1.4.1.2021.10.100 and 1.3.6.1.4.1.2021.10.101 (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.
file FILE [MAXSIZE]
Monitors file sizes and makes sure they don’t grow beyond a certain size. MAXSIZE defaults to infinite if not specified, and only monitors the size without reporting errors about it.
Errors
Any errors in obtaining the above information are reported
via the 1.3.6.1.4.1.2021.101.100 flag and the
1.3.6.1.4.1.2021.101.101 text-string description.
To enable and
SMUX based sub-agent, such as gated, use the
smuxpeer configuration entry
smuxpeer OID PASS
For gated a sensible entry might be
.1.3.6.1.4.1.4.1.3
snmpd supports
the View-Based Access Control Model (vacm) as defined in RFC
2275. To this end, it recognizes the following keywords in
the configuration file: com2sec, group,
access, and view as well as some easier-to-use
wrapper directives: rocommunity, rwcommunity,
rouser, rwuser.
rocommunity COMMUNITY [SOURCE] [OID]
rwcommunity COMMUNITY [SOURCE] [OID]
These create read-only and read-write communities that can be used to access the agent. They are a quick method of using the following com2sec, group, access, and view 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.
The format of the SOURCE is token is described in the com2sec directive section below. The OID token restricts access for that community to everything below that given OID.
rouser USER [noauth|auth|priv]
[OID]
rwuser USER [noauth|auth|priv] [OID]
Creates a SNMPv3 USM user in the VACM access configuration tables. Again, its more efficient (and powerful) to use the combined com2sec, group, access, and view directives instead.
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.
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 "default". A subnet can be specified as IP/MASK or IP/BITS. The first source/community combination that matches the incoming packet is selected.
group NAME MODEL SECURITY
This directive defines the mapping from securitymodel/securityname to group. MODEL is one of v1, v2c, or usm.
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 any, v1, v2c, or usm. LEVEL is one of noauth, auth, or priv. PREFX specifies how CONTEXT should be matched against the context of the incoming pdu, either exact or prefix. 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.
view NAME TYPE SUBTREE [MASK]
The defines the named view. TYPE is either included or excluded. MASK is a list of hex octets, separated by ’.’ or ’:’. The MASK defaults to "ff" if not specified.
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:
view cust1
included interfaces.ifTable.ifEntry.ifIndex.1 ff.a0
view cust2 included interfaces.ifTable.ifEntry.ifIndex.2
ff.a0
(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)
VACM Examples:
# sec.name source community
com2sec local localhost private
com2sec mynet 10.10.10.0/24 public
com2sec public default 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
Default VACM model
The default configuration of
the agent, as shipped, is functionally
equivalent to the following entries:
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com2sec |
public |
default |
public |
||||||||||
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group |
public |
v1 |
|||||||||||
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public |
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group |
public |
v2c |
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public |
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group |
public |
usm |
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public |
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view |
all |
included |
.1 |
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access |
public |
"" |
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any |
noauth |
exact |
all | ||||||||||
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none | |||||||||||||
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none |
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.
createUser username (MD5|SHA) authpassphrase [DES] [privpassphrase]
This directive should be placed into the "/var/ucd-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.
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.
Warning: the minimum pass phrase length is 8 characters.
SNMPv3 users can be created at runtime using the snmpusm command.
syslocation
STRING
syscontact STRING
Sets the system location and the system contact for the agent. This information is reported by the ’system’ table in the mibII tree.
authtrapenable NUMBER
Setting authtrapenable to 1 enables generation of authentication failure traps. The default value is 2 (disable).
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.
trapsink HOST [COMMUNITY
[PORT]]
trap2sink HOST [COMMUNITY [PORT]]
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 trapsink, trap2sink and informsink lines may be specified to specify multiple destinations. Use trap2sink to send SNMPv2 traps and informsink to send inform notifications. If COMMUNITY is not specified, the string from a preceding trapcommunity directive will be used. If PORT is not specified, the well known SNMP trap port (162) will be used.
pass MIBOID EXEC
Passes entire control of MIBOID
to the EXEC program. The EXEC program is called in one of
the following three ways:
EXEC -g MIBOID
EXEC -n MIBOID
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.
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: string, integer, unsigned, objectid, timeticks, ipaddress, counter, or gauge. The third line of stdout should be the VALUE corresponding with the returned TYPE.
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:
.1.3.6.1.4.100
integer
42
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. A snmp error will be generated corresponding to the SNMP NO-SUCH-NAME response.
EXEC -s MIBOID TYPE VALUE
For SNMP set requests, the above call method is used. The TYPE passed to the EXEC program is one of the text strings: integer, counter, gauge, timeticks, ipaddress, objid, or string, indicating the type of value passed in the next argument.
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: not-writable, or wrong-type and the appropriate error response will be generated instead.
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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. |
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.
The ucd-snmp agent can be forced to re-read its configuration files. It can be told to do so by one of two ways:
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1. |
An snmpset of integer(1) to 1.3.6.1.4.1.2021.100.VERUPDATECONFIG. | ||
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2. |
A "kill -HUP" signal sent to the snmpd agent process. |
/usr/share/snmp/snmpd.conf
snmp_config(5), snmpd(1), EXAMPLE.conf, read_config(3).
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snmpd.conf(5) | |