Skip to content

CentOS8 で SNMP Trap を受信出来るように設定する

以前に CentOS7 で SNMP Trap を受信出来るように設定するというメモを書きました。 今回は CentOS8 用に、メモを改めて書き直しておきます。 但し、内容はほぼ全く同じです。

インストールする

dnf で SNMP デーモンをインストールします。

1
dnf -y install net-snmp net-snmp-utils

Poll を許可する

snmpd を有効化することで SNMP Poll に応答出来るようになります。 /etc/snmp/snmpd.conf に以下を追記します。

1
2
3
4
5
6
7
cat >> /etc/snmp/snmpd.conf << "EOF"
com2sec LocalNetwork      172.16.0.0/12  public
group   LocalGroup        v1              LocalNetwork
group   LocalGroup        v2c             LocalNetwork
view    AllView        included        .1
access  LocalGroup        ""      any     noauth  exact   AllView         none    none
EOF

設定修正が完了したらサービスを開始します。 併せて自動起動の設定もしておきます。

1
2
systemctl enable snmpd.service
systemctl start snmpd.service

別 PC から snmpwalk し、値が返ってくれば成功です。

1
snmpwalk -c public -v 2c 192.0.2.1 .1.3.6.1.2.1.

Trap を受信出来るようにする

/etc/sysconfig/snmptrapd を以下のように書き換えます。 SNMP Trap を Local6 で Syslog に出力するようにします。

1
2
3
cat >> /etc/sysconfig/snmptrapd << "EOF"
OPTIONS="-Ls6 -p /var/run/snmptrapd.pid"
EOF

また、SNMP Trap 受信時に No access configuration – dropping trap. エラーが出ないよう、/etc/snmp/snmptrapd.conf に下記の行を追加し、Community Name を指定しておきます。

1
authCommunity log,execute,net public

設定修正が完了したらサービスを開始します。 併せて自動起動の設定もしておきます。

1
2
systemctl enable snmptrapd.service
systemctl start snmptrapd.service

rsyslog の設定変更

ここまでの変更で SNMP Trap が Local6 で記録されるようになっているはずです。 次は rsyslog の設定を変更し、Local6 を /var/log/snmptrapd.log に記録するようにします。 この設定をしないと SNMP Trap が /var/log/messages に記録されてしまい、他のログと混ざってしまいます。 /etc/rsyslog.conf へ以下のように Local6 に関する処理を追記します。

1
2
3
cat >> /etc/rsyslog.conf << "EOF"
local6.*                                                /var/log/snmptrapd.log
EOF

設定変更を反映する為、サービスを再起動します。

1
systemctl restart rsyslog.service

これで /var/log/snmptrapd.log に SNMP Trap が記録されているはずです。

参考

初期状態の /etc/snmp/snmpd.conf

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
###############################################################################
#
# snmpd.conf:
#   An example configuration file for configuring the ucd-snmp snmpd agent.
#
###############################################################################
#
# This file is intended to only be as a starting point.  Many more
# configuration directives exist than are mentioned in this file.  For
# full details, see the snmpd.conf(5) manual page.
#
# All lines beginning with a '#' are comments and are intended for you
# to read.  All other lines are configuration commands for the agent.

###############################################################################
# Access Control
###############################################################################

# As shipped, the snmpd demon will only respond to queries on the
# system mib group until this file is replaced or modified for
# security purposes.  Examples are shown below about how to increase the
# level of access.

# By far, the most common question I get about the agent is "why won't
# it work?", when really it should be "how do I configure the agent to
# allow me to access it?"
#
# By default, the agent responds to the "public" community for read
# only access, if run out of the box without any configuration file in
# place.  The following examples show you other ways of configuring
# the agent so that you can change the community names, and give
# yourself write access to the mib tree as well.
#
# For more information, read the FAQ as well as the snmpd.conf(5)
# manual page.

####
# First, map the community name "public" into a "security name"

#       sec.name  source          community
com2sec notConfigUser  default       public

####
# Second, map the security name into a group name:

#       groupName      securityModel securityName
group   notConfigGroup v1           notConfigUser
group   notConfigGroup v2c           notConfigUser

####
# Third, create a view for us to let the group have rights to:

# Make at least  snmpwalk -v 1 localhost -c public system fast again.
#       name           incl/excl     subtree         mask(optional)
view    systemview    included   .1.3.6.1.2.1.1
view    systemview    included   .1.3.6.1.2.1.25.1.1

####
# Finally, grant the group read-only access to the systemview view.

#       group          context sec.model sec.level prefix read   write  notif
access  notConfigGroup ""      any       noauth    exact  systemview none none

# -----------------------------------------------------------------------------

# Here is a commented out example configuration that allows less
# restrictive access.

# YOU SHOULD CHANGE THE "COMMUNITY" TOKEN BELOW TO A NEW KEYWORD ONLY
# KNOWN AT YOUR SITE.  YOU *MUST* CHANGE THE NETWORK TOKEN BELOW TO
# SOMETHING REFLECTING YOUR LOCAL NETWORK ADDRESS SPACE.

##       sec.name  source          community
#com2sec local     localhost       COMMUNITY
#com2sec mynetwork NETWORK/24      COMMUNITY

##     group.name sec.model  sec.name
#group MyRWGroup  any        local
#group MyROGroup  any        mynetwork
#
#group MyRWGroup  any        otherv3user
#...

##           incl/excl subtree                          mask
#view all    included  .1                               80

## -or just the mib2 tree-

#view mib2   included  .iso.org.dod.internet.mgmt.mib-2 fc


##                context sec.model sec.level prefix read   write  notif
#access MyROGroup ""      any       noauth    0      all    none   none
#access MyRWGroup ""      any       noauth    0      all    all    all


###############################################################################
# Sample configuration to make net-snmpd RFC 1213.
# Unfortunately v1 and v2c don't allow any user based authentification, so
# opening up the default config is not an option from a security point.
#
# WARNING: If you uncomment the following lines you allow write access to your
# snmpd daemon from any source! To avoid this use different names for your
# community or split out the write access to a different community and
# restrict it to your local network.
# Also remember to comment the syslocation and syscontact parameters later as
# otherwise they are still read only (see FAQ for net-snmp).
#

# First, map the community name "public" into a "security name"
#       sec.name        source          community
#com2sec notConfigUser   default         public

# Second, map the security name into a group name:
#       groupName       securityModel   securityName
#group   notConfigGroup  v1              notConfigUser
#group   notConfigGroup  v2c             notConfigUser

# Third, create a view for us to let the group have rights to:
# Open up the whole tree for ro, make the RFC 1213 required ones rw.
#       name            incl/excl       subtree mask(optional)
#view    roview          included        .1
#view    rwview          included        system.sysContact
#view    rwview          included        system.sysName
#view    rwview          included        system.sysLocation
#view    rwview          included        interfaces.ifTable.ifEntry.ifAdminStatus
#view    rwview          included        at.atTable.atEntry.atPhysAddress
#view    rwview          included        at.atTable.atEntry.atNetAddress
#view    rwview          included        ip.ipForwarding
#view    rwview          included        ip.ipDefaultTTL
#view    rwview          included        ip.ipRouteTable.ipRouteEntry.ipRouteDest
#view    rwview          included        ip.ipRouteTable.ipRouteEntry.ipRouteIfIndex
#view    rwview          included        ip.ipRouteTable.ipRouteEntry.ipRouteMetric1
#view    rwview          included        ip.ipRouteTable.ipRouteEntry.ipRouteMetric2
#view    rwview          included        ip.ipRouteTable.ipRouteEntry.ipRouteMetric3
#view    rwview          included        ip.ipRouteTable.ipRouteEntry.ipRouteMetric4
#view    rwview          included        ip.ipRouteTable.ipRouteEntry.ipRouteType
#view    rwview          included        ip.ipRouteTable.ipRouteEntry.ipRouteAge
#view    rwview          included        ip.ipRouteTable.ipRouteEntry.ipRouteMask
#view    rwview          included        ip.ipRouteTable.ipRouteEntry.ipRouteMetric5
#view    rwview          included        ip.ipNetToMediaTable.ipNetToMediaEntry.ipNetToMediaIfIndex
#view    rwview          included        ip.ipNetToMediaTable.ipNetToMediaEntry.ipNetToMediaPhysAddress
#view    rwview          included        ip.ipNetToMediaTable.ipNetToMediaEntry.ipNetToMediaNetAddress
#view    rwview          included        ip.ipNetToMediaTable.ipNetToMediaEntry.ipNetToMediaType
#view    rwview          included        tcp.tcpConnTable.tcpConnEntry.tcpConnState
#view    rwview          included        egp.egpNeighTable.egpNeighEntry.egpNeighEventTrigger
#view    rwview          included        snmp.snmpEnableAuthenTraps

# Finally, grant the group read-only access to the systemview view.
#       group          context sec.model sec.level prefix read   write  notif
#access  notConfigGroup ""      any       noauth    exact  roview rwview none



###############################################################################
# System contact information
#

# It is also possible to set the sysContact and sysLocation system
# variables through the snmpd.conf file:

syslocation Unknown (edit /etc/snmp/snmpd.conf)
syscontact Root <root@localhost> (configure /etc/snmp/snmp.local.conf)

# Example output of snmpwalk:
#   % snmpwalk -v 1 localhost -c public system
#   system.sysDescr.0 = "SunOS name sun4c"
#   system.sysObjectID.0 = OID: enterprises.ucdavis.ucdSnmpAgent.sunos4
#   system.sysUpTime.0 = Timeticks: (595637548) 68 days, 22:32:55
#   system.sysContact.0 = "Me <me@somewhere.org>"
#   system.sysName.0 = "name"
#   system.sysLocation.0 = "Right here, right now."
#   system.sysServices.0 = 72


###############################################################################
# Logging
#

# We do not want annoying "Connection from UDP: " messages in syslog.
# If the following option is commented out, snmpd will print each incoming
# connection, which can be useful for debugging.

dontLogTCPWrappersConnects yes

# -----------------------------------------------------------------------------


###############################################################################
# Process checks.
#
#  The following are examples of how to use the agent to check for
#  processes running on the host.  The syntax looks something like:
#
#  proc NAME [MAX=0] [MIN=0]
#
#  NAME:  the name of the process to check for.  It must match
#         exactly (ie, http will not find httpd processes).
#  MAX:   the maximum number allowed to be running.  Defaults to 0.
#  MIN:   the minimum number to be running.  Defaults to 0.

#
#  Examples (commented out by default):
#

#  Make sure mountd is running
#proc mountd

#  Make sure there are no more than 4 ntalkds running, but 0 is ok too.
#proc ntalkd 4

#  Make sure at least one sendmail, but less than or equal to 10 are running.
#proc sendmail 10 1

#  A snmpwalk of the process mib tree would look something like this:
#
# % snmpwalk -v 1 localhost -c public .1.3.6.1.4.1.2021.2
# enterprises.ucdavis.procTable.prEntry.prIndex.1 = 1
# enterprises.ucdavis.procTable.prEntry.prIndex.2 = 2
# enterprises.ucdavis.procTable.prEntry.prIndex.3 = 3
# enterprises.ucdavis.procTable.prEntry.prNames.1 = "mountd"
# enterprises.ucdavis.procTable.prEntry.prNames.2 = "ntalkd"
# enterprises.ucdavis.procTable.prEntry.prNames.3 = "sendmail"
# enterprises.ucdavis.procTable.prEntry.prMin.1 = 0
# enterprises.ucdavis.procTable.prEntry.prMin.2 = 0
# enterprises.ucdavis.procTable.prEntry.prMin.3 = 1
# enterprises.ucdavis.procTable.prEntry.prMax.1 = 0
# enterprises.ucdavis.procTable.prEntry.prMax.2 = 4
# enterprises.ucdavis.procTable.prEntry.prMax.3 = 10
# enterprises.ucdavis.procTable.prEntry.prCount.1 = 0
# enterprises.ucdavis.procTable.prEntry.prCount.2 = 0
# enterprises.ucdavis.procTable.prEntry.prCount.3 = 1
# enterprises.ucdavis.procTable.prEntry.prErrorFlag.1 = 1
# enterprises.ucdavis.procTable.prEntry.prErrorFlag.2 = 0
# enterprises.ucdavis.procTable.prEntry.prErrorFlag.3 = 0
# enterprises.ucdavis.procTable.prEntry.prErrMessage.1 = "No mountd process running."
# enterprises.ucdavis.procTable.prEntry.prErrMessage.2 = ""
# enterprises.ucdavis.procTable.prEntry.prErrMessage.3 = ""
# enterprises.ucdavis.procTable.prEntry.prErrFix.1 = 0
# enterprises.ucdavis.procTable.prEntry.prErrFix.2 = 0
# enterprises.ucdavis.procTable.prEntry.prErrFix.3 = 0
#
#  Note that the errorFlag for mountd is set to 1 because one is not
#  running (in this case an rpc.mountd is, but thats not good enough),
#  and the ErrMessage tells you what's wrong.  The configuration
#  imposed in the snmpd.conf file is also shown.
#
#  Special Case:  When the min and max numbers are both 0, it assumes
#  you want a max of infinity and a min of 1.
#


# -----------------------------------------------------------------------------


###############################################################################
# Executables/scripts
#

#
#  You can also have programs run by the agent that return a single
#  line of output and an exit code.  Here are two examples.
#
#  exec NAME PROGRAM [ARGS ...]
#
#  NAME:     A generic name. The name must be unique for each exec statement.
#  PROGRAM:  The program to run.  Include the path!
#  ARGS:     optional arguments to be passed to the program

# a simple hello world

#exec echotest /bin/echo hello world

# Run a shell script containing:
#
# #!/bin/sh
# echo hello world
# echo hi there
# exit 35
#
# Note:  this has been specifically commented out to prevent
# accidental security holes due to someone else on your system writing
# a /tmp/shtest before you do.  Uncomment to use it.
#
#exec shelltest /bin/sh /tmp/shtest

# Then,
# % snmpwalk -v 1 localhost -c public .1.3.6.1.4.1.2021.8
# enterprises.ucdavis.extTable.extEntry.extIndex.1 = 1
# enterprises.ucdavis.extTable.extEntry.extIndex.2 = 2
# enterprises.ucdavis.extTable.extEntry.extNames.1 = "echotest"
# enterprises.ucdavis.extTable.extEntry.extNames.2 = "shelltest"
# enterprises.ucdavis.extTable.extEntry.extCommand.1 = "/bin/echo hello world"
# enterprises.ucdavis.extTable.extEntry.extCommand.2 = "/bin/sh /tmp/shtest"
# enterprises.ucdavis.extTable.extEntry.extResult.1 = 0
# enterprises.ucdavis.extTable.extEntry.extResult.2 = 35
# enterprises.ucdavis.extTable.extEntry.extOutput.1 = "hello world."
# enterprises.ucdavis.extTable.extEntry.extOutput.2 = "hello world."
# enterprises.ucdavis.extTable.extEntry.extErrFix.1 = 0
# enterprises.ucdavis.extTable.extEntry.extErrFix.2 = 0

# Note that the second line of the /tmp/shtest shell script is cut
# off.  Also note that the exit status of 35 was returned.

# -----------------------------------------------------------------------------


###############################################################################
# disk checks
#

# The agent can check the amount of available disk space, and make
# sure it is above a set limit.

# disk PATH [MIN=100000]
#
# PATH:  mount path to the disk in question.
# MIN:   Disks with space below this value will have the Mib's errorFlag set.
#        Default value = 100000.

# Check the / partition and make sure it contains at least 10 megs.

#disk / 10000

# % snmpwalk -v 1 localhost -c public .1.3.6.1.4.1.2021.9
# enterprises.ucdavis.diskTable.dskEntry.diskIndex.1 = 0
# enterprises.ucdavis.diskTable.dskEntry.diskPath.1 = "/" Hex: 2F
# enterprises.ucdavis.diskTable.dskEntry.diskDevice.1 = "/dev/dsk/c201d6s0"
# enterprises.ucdavis.diskTable.dskEntry.diskMinimum.1 = 10000
# enterprises.ucdavis.diskTable.dskEntry.diskTotal.1 = 837130
# enterprises.ucdavis.diskTable.dskEntry.diskAvail.1 = 316325
# enterprises.ucdavis.diskTable.dskEntry.diskUsed.1 = 437092
# enterprises.ucdavis.diskTable.dskEntry.diskPercent.1 = 58
# enterprises.ucdavis.diskTable.dskEntry.diskErrorFlag.1 = 0
# enterprises.ucdavis.diskTable.dskEntry.diskErrorMsg.1 = ""

# -----------------------------------------------------------------------------


###############################################################################
# load average checks
#

# load [1MAX=12.0] [5MAX=12.0] [15MAX=12.0]
#
# 1MAX:   If the 1 minute load average is above this limit at query
#         time, the errorFlag will be set.
# 5MAX:   Similar, but for 5 min average.
# 15MAX:  Similar, but for 15 min average.

# Check for loads:
#load 12 14 14

# % snmpwalk -v 1 localhost -c public .1.3.6.1.4.1.2021.10
# enterprises.ucdavis.loadTable.laEntry.loadaveIndex.1 = 1
# enterprises.ucdavis.loadTable.laEntry.loadaveIndex.2 = 2
# enterprises.ucdavis.loadTable.laEntry.loadaveIndex.3 = 3
# enterprises.ucdavis.loadTable.laEntry.loadaveNames.1 = "Load-1"
# enterprises.ucdavis.loadTable.laEntry.loadaveNames.2 = "Load-5"
# enterprises.ucdavis.loadTable.laEntry.loadaveNames.3 = "Load-15"
# enterprises.ucdavis.loadTable.laEntry.loadaveLoad.1 = "0.49" Hex: 30 2E 34 39
# enterprises.ucdavis.loadTable.laEntry.loadaveLoad.2 = "0.31" Hex: 30 2E 33 31
# enterprises.ucdavis.loadTable.laEntry.loadaveLoad.3 = "0.26" Hex: 30 2E 32 36
# enterprises.ucdavis.loadTable.laEntry.loadaveConfig.1 = "12.00"
# enterprises.ucdavis.loadTable.laEntry.loadaveConfig.2 = "14.00"
# enterprises.ucdavis.loadTable.laEntry.loadaveConfig.3 = "14.00"
# enterprises.ucdavis.loadTable.laEntry.loadaveErrorFlag.1 = 0
# enterprises.ucdavis.loadTable.laEntry.loadaveErrorFlag.2 = 0
# enterprises.ucdavis.loadTable.laEntry.loadaveErrorFlag.3 = 0
# enterprises.ucdavis.loadTable.laEntry.loadaveErrMessage.1 = ""
# enterprises.ucdavis.loadTable.laEntry.loadaveErrMessage.2 = ""
# enterprises.ucdavis.loadTable.laEntry.loadaveErrMessage.3 = ""

# -----------------------------------------------------------------------------


###############################################################################
# Extensible sections.
#

# This alleviates the multiple line output problem found in the
# previous executable mib by placing each mib in its own mib table:

# Run a shell script containing:
#
# #!/bin/sh
# echo hello world
# echo hi there
# exit 35
#
# Note:  this has been specifically commented out to prevent
# accidental security holes due to someone else on your system writing
# a /tmp/shtest before you do.  Uncomment to use it.
#
# exec .1.3.6.1.4.1.2021.50 shelltest /bin/sh /tmp/shtest

# % snmpwalk -v 1 localhost -c public .1.3.6.1.4.1.2021.50
# enterprises.ucdavis.50.1.1 = 1
# enterprises.ucdavis.50.2.1 = "shelltest"
# enterprises.ucdavis.50.3.1 = "/bin/sh /tmp/shtest"
# enterprises.ucdavis.50.100.1 = 35
# enterprises.ucdavis.50.101.1 = "hello world."
# enterprises.ucdavis.50.101.2 = "hi there."
# enterprises.ucdavis.50.102.1 = 0

# Now the Output has grown to two lines, and we can see the 'hi
# there.' output as the second line from our shell script.
#
# Note that you must alter the mib.txt file to be correct if you want
# the .50.* outputs above to change to reasonable text descriptions.

# Other ideas:
#
# exec .1.3.6.1.4.1.2021.51 ps /bin/ps
# exec .1.3.6.1.4.1.2021.52 top /usr/local/bin/top
# exec .1.3.6.1.4.1.2021.53 mailq /usr/bin/mailq

# -----------------------------------------------------------------------------


###############################################################################
# Pass through control.
#

# Usage:
#   pass MIBOID EXEC-COMMAND
#
# This will pass total control of the mib underneath the MIBOID
# portion of the mib to the EXEC-COMMAND.
#
# Note:  You'll have to change the path of the passtest script to your
# source directory or install it in the given location.
#
# Example:  (see the script for details)
#           (commented out here since it requires that you place the
#           script in the right location. (its not installed by default))

# pass .1.3.6.1.4.1.2021.255 /bin/sh /usr/local/local/passtest

# % snmpwalk -v 1 localhost -c public .1.3.6.1.4.1.2021.255
# enterprises.ucdavis.255.1 = "life the universe and everything"
# enterprises.ucdavis.255.2.1 = 42
# enterprises.ucdavis.255.2.2 = OID: 42.42.42
# enterprises.ucdavis.255.3 = Timeticks: (363136200) 42 days, 0:42:42
# enterprises.ucdavis.255.4 = IpAddress: 127.0.0.1
# enterprises.ucdavis.255.5 = 42
# enterprises.ucdavis.255.6 = Gauge: 42
#
# % snmpget -v 1 localhost public .1.3.6.1.4.1.2021.255.5
# enterprises.ucdavis.255.5 = 42
#
# % snmpset -v 1 localhost public .1.3.6.1.4.1.2021.255.1 s "New string"
# enterprises.ucdavis.255.1 = "New string"
#

# For specific usage information, see the man/snmpd.conf.5 manual page
# as well as the local/passtest script used in the above example.

###############################################################################
# Further Information
#
#  See the snmpd.conf manual page, and the output of "snmpd -H".