1SNMPD(8) Net-SNMP SNMPD(8)
2
6 snmpd - daemon to respond to SNMP request packets.
7
9 snmpd [OPTIONS] [LISTENING ADDRESSES]
10
12 snmpd is an SNMP agent which binds to a port and awaits requests from
13 SNMP management software. Upon receiving a request, it processes the
14 request(s), collects the requested information and/or performs the re‐
15 quested operation(s) and returns the information to the sender.
16
18 -a Log the source addresses of incoming requests.
19 -A Append to the log file rather than truncating it.
21 -c FILE Read FILE as a configuration file (or a comma-separated list of
23 configuration files). Note that the loaded file will only un‐
24 derstand snmpd.conf tokens, unless the configuration type is
25 specified in the file as described in the snmp_config man page
26 under SWITCHING CONFIGURATION TYPES IN MID-FILE.
27 -C Do not read any configuration files except the ones optionally
29 specified by the -c option. Note that this behaviour also cov‐
30 ers the persistent configuration files. This may result in dy‐
31 namically-assigned values being reset following an agent
32 restart, unless the relevant persistent config files are ex‐
33 plicitly loaded using the -c option.
34 -d Dump (in hexadecimal) the sent and received SNMP packets.
36 -D[TOKEN[,...]]
38 Turn on debugging output for the given TOKEN(s). Without any
39 tokens specified, it defaults to printing all the tokens (which
40 is equivalent to the keyword "ALL"). You might want to try ALL
41 for extremely verbose output. Note: You can not put a space
42 between the -D flag and the listed TOKENs.
43 -f Do not fork() from the calling shell.
45 -g GID Change the group ID of the snmpd process into GID after opening
47 listening sockets. This overrides the agentgroup configuration
48 file parameter.
49 -h, --help
51 Display a brief usage message and then exit.
52 -H Display a list of configuration file directives understood by
54 the agent and then exit.
55 -I [-]INITLIST
57 Specifies which modules should (or should not) be initialized
58 when the agent starts up. If the comma-separated INITLIST is
59 preceded with a '-', it is the list of modules that should not
60 be started. Otherwise this is the list of the only modules
61 that should be started.
62 To get a list of compiled modules, run the agent with the argu‐
64 ments -Dmib_init -H (assuming debugging support has been com‐
65 piled in).
66 -L[eEfFoOsSnN]
68 Specify where logging output should be directed (standard error
69 or output, to a file or via syslog). See LOGGING OPTIONS in
70 snmpcmd(1) for details.
71 -m MIBLIST
73 Specifies a colon separated list of MIB modules to load for
74 this application. This overrides the environment variable
75 MIBS. See snmpcmd(1) for details.
76 -M DIRLIST
78 Specifies a colon separated list of directories to search for
79 MIBs. This overrides the environment variable MIBDIRS. See
80 snmpcmd(1) for details.
81 -n NAME Set an alternative application name (which will affect the con‐
83 figuration files loaded). By default this will be snmpd, re‐
84 gardless of the name of the actual binary.
85 -p FILE Save the process ID of the daemon in FILE.
87 -q Print simpler output for easier automated parsing.
89 -r Do not require root access to run the daemon. Specifically, do
91 not exit if files only accessible to root (such as /dev/kmem
92 etc.) cannot be opened.
93 -u UID Change the user ID of the snmpd process into UID (which can be
95 given in numerical or textual form) after opening listening
96 sockets. This overrides the agentuser configuration file param‐
97 eter.
98 -U Instructs the agent to not remove its pid file (see the -p op‐
100 tion) on shutdown. Overrides the leave_pidfile token in the sn‐
101 mpd.conf file, see snmpd.conf(5).
102 -v, --version
104 Print version information for the agent and then exit.
105 -V Symbolically dump SNMP transactions.
107 -x ADDRESS
109 Listens for AgentX connections on the specified address rather
110 than the default "/var/agentx/master". The address can either
111 be a Unix domain socket path, or the address of a network in‐
112 terface. The format is the same as the format of listening ad‐
113 dresses described below.
114 -X Run as an AgentX subagent rather than as an SNMP master agent.
116 --name="value"
118 Allows one to specify any token ("name") supported in the sn‐
119 mpd.conf file and sets its value to "value". Overrides the cor‐
120 responding token in the snmpd.conf file. See snmpd.conf(5) for
121 the full list of tokens.
122
124 By default, snmpd listens for incoming SNMP requests on UDP port 161 on
125 all IPv4 interfaces. However, it is possible to modify this behaviour
126 by specifying one or more listening addresses as arguments to snmpd. A
127 listening address takes the form:
128 [<transport-specifier>:]<transport-address>
130 At its simplest, a listening address may consist only of a port number,
132 in which case snmpd listens on that UDP port on all IPv4 interfaces.
133 Otherwise, the <transport-address> part of the specification is parsed
134 according to the following table:
135 <transport-specifier> <transport-address> format
137 udp (default) hostname[:port] or IPv4-address[:port]
139 tcp hostname[:port] or IPv4-address[:port]
141 unix pathname
143 ipx [network]:node[/port]
145 aal5pvc or pvc [interface.][VPI.]VCI
147 udp6 or udpv6 or udpipv6 hostname[:port] or IPv6-address[:port]
149 tcp6 or tcpv6 or tcpipv6 hostname[:port] or IPv6-address[:port]
151 ssh hostname:port
153 dtlsudp hostname:port
155 Note that <transport-specifier> strings are case-insensitive so that,
157 for example, "tcp" and "TCP" are equivalent. Here are some examples,
158 along with their interpretation:
159 127.0.0.1:161 listen on UDP port 161, but only on the loop‐
161 back interface. This prevents snmpd being
162 queried remotely. The port specification
163 ":161" is not strictly necessary since that is
164 the default SNMP port.
165 TCP:1161 listen on TCP port 1161 on all IPv4 interfaces.
167 ipx:/40000 listen on IPX port 40000 on all IPX interfaces.
169 unix:/tmp/local-agent listen on the Unix domain socket /tmp/lo‐
171 cal-agent.
172 /tmp/local-agent is identical to the previous specification,
174 since the Unix domain is assumed if the first
175 character of the <transport-address> is '/'.
176 PVC:161 listen on the AAL5 permanent virtual circuit
178 with VPI=0 and VCI=161 (decimal) on the first
179 ATM adapter in the machine.
180 udp6:10161 listen on port 10161 on all IPv6 interfaces.
182 ssh:127.0.0.1:22 Allows connections from the snmp subsystem on
184 the ssh server on port 22. The details of us‐
185 ing SNMP over SSH are defined below.
186 dtlsudp:127.0.0.1:9161 Listen for connections over DTLS on UDP port
188 9161. The snmp.conf file must have the
189 serverCert, configuration tokens defined.
190 Note that not all the transport domains listed above will always be
192 available; for instance, hosts with no IPv6 support will not be able to
193 use udp6 transport addresses, and attempts to do so will result in the
194 error "Error opening specified endpoint". Likewise, since AAL5 PVC
195 support is only currently available on Linux, it will fail with the
196 same error on other platforms.
197
199 ssh The SSH transport, on the server side, is actually just a unix
200 named pipe that can be connected to via a ssh subsystem config‐
201 ured in the main ssh server. The pipe location (configurable
202 with the sshtosnmpsocket token in snmp.conf) is
203 /var/net-snmp/sshtosnmp. Packets should be submitted to it via
204 the sshtosnmp application, which also sends the user ID as well
205 when starting the connection. The TSM security model should be
206 used when packets should process it.
207 The sshtosnmp command knows how to connect to this pipe and
209 talk to it. It should be configured in the OpenSSH sshd con‐
210 figuration file (which is normally /etc/ssh/sshd_config using
211 the following configuration line:
212 Subsystem snmp /usr/local/bin/sshtosnmp
215 The sshtosnmp command will need read/write access to the
217 /var/net-snmp/sshtosnmp pipe. Although it should be fairly
218 safe to grant access to the average user since it still re‐
219 quires modifications to the ACM settings before the user can
220 perform operations, paranoid administrators may want to make
221 the /var/net-snmp directory accessible only by users in a par‐
222 ticular group. Use the sshtosnmpsocketperms snmp.conf config‐
223 ure option to set the permissions, owner and group of the cre‐
224 ated socket.
225 Access control can be granted to the user "foo" using the fol‐
227 lowing style of simple snmpd.conf settings:
228 rouser -s tsm foo authpriv
231 Note that "authpriv" is acceptable assuming as SSH protects ev‐
233 erything that way (assuming you have a non-insane setup). sn‐
234 mpd has no notion of how SSH has actually protected a packet
235 and thus the snmp agent assumes all packets passed through the
236 SSH transport have been protected at the authpriv level.
237 dtlsudp The DTLS protocol, which is based off of TLS, requires both
239 client and server certificates to establish the connection and
240 authenticate both sides. In order to do this, the client will
241 need to configure the snmp.conf file with the clientCert con‐
242 figuration tokens. The server will need to configure the
243 snmp.conf file with the serverCert configuration tokens de‐
244 fined.
245 Access control setup is similar to the ssh transport as the TSM
247 security model should be used to protect the packet.
248
250 snmpd checks for the existence of and parses the following files:
251 /etc/snmp/snmp.conf
253 Common configuration for the agent and applications. See
254 snmp.conf(5) for details.
255 /etc/snmp/snmpd.conf
257 /etc/snmp/snmpd.local.conf
259 Agent-specific configuration. See snmpd.conf(5) for details.
260 These files are optional and may be used to configure access con‐
261 trol, trap generation, subagent protocols and much else besides.
262 In addition to these two configuration files in /etc/snmp, the
264 agent will read any files with the names snmpd.conf and snmpd.lo‐
265 cal.conf in a colon separated path specified in the SNMPCONFPATH
266 environment variable.
267 /usr/share/snmp/mibs/
269 The agent will also load all files in this directory as MIBs. It
270 will not, however, load any file that begins with a '.' or de‐
271 scend into subdirectories.
272
274 (in recommended reading order)
275 snmp_config(5), snmp.conf(5), snmpd.conf(5)
277V5.9.3 30 Jun 2010 SNMPD(8)